CN1726414A

CN1726414A - High Power Low Loss Fiber Waveguide

Info

Publication number: CN1726414A
Application number: CN 200380105777
Authority: CN
Inventors: 吉勒斯·贝努瓦; 约尔·芬克; 约翰·D.·琼诺保罗斯; 尚顿·哈特; 布拉克·泰梅尔库兰
Original assignee: Massachusetts Institute of Technology
Current assignee: Massachusetts Institute of Technology
Priority date: 2002-12-10
Filing date: 2003-12-10
Publication date: 2006-01-25
Also published as: CA2504624A1; AU2003297857A1; WO2004052078A3; WO2004052078A2; JP2006509253A; EP1579252A2

Abstract

In general, in one aspect, the invention features an article comprising a high-power, low-loss fiber optic waveguide (100) comprising various dielectric Alternating layers of materials (130, 140), the different dielectric materials including polymer (130) and glass (140).

Description

High-power low-loss optically fiber wave guide

The cross reference of related application

The application requires to enjoy the 60/432nd, No. 059 unsettled U.S. Provisional Application No. of submitting on Dec 10th, 2002.Here the disclosed full content of above-mentioned application is incorporated among the application as a reference.

Technical field

The method that the present invention relates to fibre-optic waveguide and make waveguide.

Background technology

Important effect is being brought into play in waveguide in many industries.For example, optical waveguide is widely used in the telecommunication communication network, wherein is used to transmission information between different regions such as fibre-optic fibre-optic waveguide.This waveguide fully limits light signal along a certain or some preferred propagated.Other application of optical waveguide comprise imaging applications, as endoscope and optical detection.

Modal fibre-optic waveguide type is an optical fiber, and it utilizes refractive-index-guiding restriction light signal to transmit along preferred path.This fiber comprises the central core region that extends along the waveguide axis direction, and the cladding zone along waveguide axis around the axle center, and wherein the refractive index in cladding zone is lower than central core region.Owing to there is refringence, total reflection (TIR) can take place at the interface place of axle center and cladding layer in light, thereby propagates in having the axle center of high index along waveguide axis basically.Therefore, bootable single mode of optical fiber or multimode electromagnetic wave (EM) are propagated in the axle center along waveguide axis.The quantity of bootmode increases with axis diameter.Notably, for being parallel to the axial given wave vector of waveguide, this refractive-index-guiding mechanism stops and any cladding pattern occurs under the low-limit frequency bootmode.The refractive-index-guiding optical fiber of nearly all commercialization all is to be principal ingredient with silicon dioxide, and wherein one of axle center and cladding layer or both all mix impurity, to produce refringence and to form the axle center and the interface of cladding layer.For example, according to practical application, for the wavelength in 1.5 mu m ranges, the fibre-optic refractive index of normally used silicon dioxide is about 1.45, and its refringence is in about scope of 0.2% to 3%.

Becoming optical fiber by preform bar stretching, is the most frequently used method for preparing fibre-optic waveguide.Prefabricated rods is a stub (for example 10 to 20 inches long), and it has the accurate shape and the composition of required optical fiber.Yet the diameter of this prefabricated rods is much larger than the diameter (for example 100 to 1000 times big) of optical fiber.When the stretching optical fiber, the material of prefabricated rods is formed and is typically comprised single glass, and it provides one or more alloys of different brackets in the prefabricated rods axle center, thereby improves the axle center refractive index with respect to the cladding layer refractive index.This material that has guaranteed to form axle center and cladding layer is with rheology and chemically be stretched to similarity, and the while still provides enough refringence keeping the bootmode in the axle center.For making prefabricated rods form optical fiber, with the furnace heats prefabricated rods to the temperature that makes glass viscosity fully low (for example being lower than 108Poise), thereby preform bar stretching is become optical fiber.During stretching, the optical fiber that the prefabricated rods constriction forms has the xsect The Nomenclature Composition and Structure of Complexes identical with prefabricated rods.Fibre diameter is to be determined by the special flow change nature of optical fiber and rate of extension.

Prefabricated rods can be utilized many those skilled in the art to know technology and make, and comprising: modified chemical vapor deposition process (MCVD) (MCVD), outside vapour deposition process (OVD), plasma-activated chemical vapour deposition technique (PCVD) and axial vapor deposition method (VAD).The whole bag of tricks comprises that typically the starting material form with cigarette ash on the wall of prefabricated pipe or rod that makes vaporization forms sedimentary deposit.Each soot layer immediate fusion after deposition.This makes prefabricated pipe melt subsequently and shortens the solid bar with surrounding layer into, is drawn into optical fiber then.

Fibre-optic application can be subjected to optical wavelength and signal power limitations.Optical fiber preferably should be formed by the material that has low-yield degree of absorption in the guide wave strong point, and should have minimum defective.For the situation through long-distance optical fiber transmission, if the degree of absorption height, signal intensity can weaken to the degree that can't differentiate with noise.Even for the low relatively material of degree of absorption, the absorption of axle center and/or surrounding layer can make optical fiber generate heat.Defective can make the radiating scattering of guiding beyond the axle center, and this also can make the optical fiber heating.More than certain power density, the heating meeting causes expendable infringement to optical fiber.Therefore, in many application scenarios, utilize high-power radiation source, use the equipment except that optical fiber that radiation is guided to its destination from the source.

Summary of the invention

In some aspects, the photon crystal wave-guide (for example Bragg optical fiber) that comprises polymer moieties and glass part (for example chalcogenide glass part) that is characterized as of the present invention.In some specific embodiments, photon crystal wave-guide comprises the axle center of a hollow.The photon band gap that forms by multi-stage alternate layer (for example a continuous polymeric layer and a continuous glassy layer being wound in spiral fashion) by polymkeric substance and glass with radiation limitations in the axle center of hollow.Generally speaking, glassy layer has high index of refraction, and polymeric layer has low-refraction.Basis and high-order spectral transmissions window depend on the optical thickness of alternating layer, and scope is from visible radiation (wavelength is 0.35～0.75 μ m) to infrared radiation (wavelength be 0.75 to about 15 μ m or bigger).

Another feature of the present invention is for making the method for photon crystal fiber guide.Polymer substrate is covered with one deck glass to form the plane multilayer film.Then multilayer film are rolled into hollow multilayer pipe with spiral fashion xsect.Then hollow tube is merged, and obtain the preform of the hollow of drawing optical fiber waveguide by the heating and fusing spiral layers.

Can obtain high index-contrast between the photon crystal wave-guide different piece by selecting material.High index-contrast can make optical fiber have big photon band gap and omnidirectional's reflectivity.Big photon band gap can make in the waveguide part in axle center transmission depth little, reduces the absorption loss by the radiation of fiber guides.

If thermodynamic behaviour, rheological properties and the physicochemical characteristics of various fiber optic materials are compatible, dissimilar material can make optical fiber have fabricating low-defect-density on the optics that then stretches altogether.Therefore, in some aspects, of the present inventionly be characterized as the glass that can stretch altogether and the combination of polymkeric substance, and select the glass that can stretch altogether and the standard of polymkeric substance.

The optical fiber of low-loss, fabricating low-defect-density can be used for guiding powerful radiation, and to the damage of optical fiber very little or not damaged.

Generally speaking, in first aspect, of the present inventionly be characterized as a kind of method, it comprises: sandwich construction is rolled into helical structure, and forms fibre-optic waveguide, wherein said forming process comprises the preform of stretching from helical structure.

The specific embodiments of the inventive method comprises the feature of one or more following features and/or others.

Described sandwich construction can comprise at least two layers that contain the different refractivity material.Described layer can comprise one deck first material and two-layer first material layer is clipped in wherein second material.Described layer can be the plane basically.Described different material can comprise: first material and second material that comprises polymkeric substance that comprise glass.In some specific embodiments, described different materials comprises a kind of high-index material and a kind of low-index material, and wherein high-index material and the ratio of the refractive index of low-index material are greater than 1.5 (for example greater than 1.8).

The inventive method also can comprise to the ground floor of major general's first material (for example glass, as chalcogenide glass) and being placed on the second layer of second material that is different from first material (for example polymkeric substance, as PES or PEI), thereby form described sandwich construction.First material can be placed in two faces of the second layer.Described instrumentation can comprise sputter or evaporation.Extra play can be placed on the ground floor and the second layer to form multi-layer product.

Described sandwich construction can be rolled to form described helical structure around a plug (for example hollow bar).The inventive method can comprise merges to form prefabricated rods helical structure.The process of described merging can comprise the heating helical structure.In some specific embodiments, the process of described merging is included under the vacuum and heats helical structure.The inventive method can be included in to stretch removes plug (for example chemical corrosion) before from prefabricated rods.

Described helical structure can comprise an axle center that is centered on by the alternating layer of sandwich construction.Described fibre-optic waveguide can comprise a hollow axle center that is centered on by a plurality of layers that conform to described sandwich construction.

Generally speaking, on the other hand, of the present inventionly be characterized as a kind of goods that comprise fibre-optic waveguide, the alternating layer of the different materials that described fibre-optic waveguide comprises around the axle center, extend along waveguide axis, wherein alternating layer limits helical structure.

The specific embodiments of goods of the present invention can comprise the feature of one or more following features and/or others.

Described helical structure can comprise a sandwich construction, and this sandwich construction comprises the two-layer at least different materials around the axle center multi-turn.Described different materials can comprise a kind of high index of refraction dielectric substance and a kind of low index dielectric material, and wherein high-index material and the ratio of the refractive index of low-index material are greater than 1.5 (for example greater than 1.8).Described different materials can comprise polymkeric substance (for example PES) and chalcogenide glass (As for example ₂Se ₃).

The thickness of alternating layer innermost layer can be less than the postorder layer of same material.The optional thickness of selecting alternating layer is propagated along waveguide axis with the electromagnetic radiation of guide wavelength in about 8～12 μ m (for example wavelength is about 10.6 μ m) scope.In some specific embodiments, select the thickness of alternating layer to propagate along waveguide axis with the electromagnetic radiation of guide wavelength in about 2～5 mu m ranges.

Described axle center can be hollow.Described fibre-optic waveguide can be less than about 1dB/m for the loss of optical fiber straight length under selected wavelength (for example at about 0.75 wavelength to the scope of about 10.6 μ m).In some specific embodiments, selected wavelength is about 10.6 μ m.

When optical fiber is turned when crooked around 90 degree of radius-of-curvature in about 4～10cm scope, the loss of fibre-optic waveguide under selected wavelength (for example at about 0.75 wavelength to about 10.6 mu m ranges) can be less than about 1.5dB.

For selected wavelength (for example at about 0.75 wavelength to about 10.6 mu m ranges), fibre-optic waveguide can be more than or equal to about 300W/cm ²Power density along the waveguide axis direct electromagnetic radiation.In some specific embodiments, selected wavelength is about 10.6 μ m.Even when fibre-optic waveguide with the radius-of-curvature of 0.3m at least during around the turning smooth curved of 90 degree, for selected wavelength, fibre-optic waveguide still can be more than or equal to about 300W/cm ²Power density along the waveguide axis direct electromagnetic radiation.

For selected wavelength (for example at about 0.75 wavelength to about 10.6 mu m ranges), fibre-optic waveguide can be more than or equal to the power of about 25W along the waveguide axis direct electromagnetic radiation.In some specific embodiments, selected wavelength is about 10.6 μ m.

Generally speaking, on the other hand, of the present inventionly be characterized as a kind of goods high-power, low-loss fibre-optic waveguide that comprise, the alternating layer of the different dielectric substances that this fibre-optic waveguide comprises around the axle center, extend along waveguide axis, described different dielectric substances comprise polymkeric substance and glass.

Described alternating layer can limit helical structure.Described helical structure can comprise a sandwich construction, and this sandwich construction comprises the two-layer at least different materials around the axle center multi-turn.Described different materials can comprise a kind of high index of refraction dielectric substance and a kind of low index dielectric material, and wherein high-index material and the ratio of the refractive index of low-index material are greater than 1.5.Described different materials can comprise a kind of high index of refraction dielectric substance and a kind of low index dielectric material, and wherein high-index material and the ratio of the refractive index of low-index material are greater than 1.8.Described glass can comprise chalcogenide glass (As for example ₂Se ₃).Described polymkeric substance can comprise PES or PEI.The thickness of alternating layer innermost layer can be less than the postorder layer of same material.The optional thickness of selecting alternating layer is propagated along waveguide axis with the electromagnetic radiation of guide wavelength in about 8～12 μ m (for example wavelength is about 10.6 μ m) scope.In some specific embodiments, select the thickness of alternating layer to propagate along waveguide axis with the electromagnetic radiation of guide wavelength in about 2～5 mu m ranges.

The axle center can be hollow.

Described fibre-optic waveguide can be less than about 1dB/m for the loss of fibre-optic waveguide straight length under selected wavelength (for example at about 0.75 wavelength to about 10.6 mu m ranges).Selected wavelength can be about 10.6 μ m.

When optical fiber is turned when crooked around 90 degree of radius-of-curvature in about 4～10cm scope, the loss of fibre-optic waveguide under selected wavelength (for example at about 0.75 wavelength to about 10.6 mu m ranges) can be less than about 1.5dB.Selected wavelength can be about 10.6 μ m.

For selected wavelength (for example at about 0.75 wavelength to about 10.6 mu m ranges), fibre-optic waveguide can be more than or equal to about 300W/cm ²Power density along the waveguide axis direct electromagnetic radiation.Selected wavelength can be about 10.6 μ m.

Even when fibre-optic waveguide with the radius-of-curvature of 0.3m at least during around the turning smooth curved of 90 degree, for selected wavelength, fibre-optic waveguide still can be more than or equal to about 300W/cm ²Power density along the waveguide axis direct electromagnetic radiation.

For selected wavelength (for example at about 0.75 wavelength to about 10.6 mu m ranges), fibre-optic waveguide can be more than or equal to the power of about 25W along the waveguide axis direct electromagnetic radiation.Selected wavelength can be about 10.6 μ m.

Specific embodiments of the present invention has one or more following advantages.

Photon crystal fiber guide all has the low transmission loss for the straight length or the bending length of optical fiber.It can be used for guiding the large power, electrically magnetic radiation.It can be used for guiding the electromagnetic radiation of high power density.It can be used for guiding the electromagnetic radiation of infrared wavelength (for example 0.75 to about 12 μ m or bigger).

Below in conjunction with Figure of description and explanation sets forth in detail one or more specific embodiments of the present invention.Other features, objects and advantages of the present invention will be by instructions and Figure of description, and is illustrated by claims.

Description of drawings

Figure 1A is a kind of viewgraph of cross-section of specific embodiments of photon crystal fiber guide.

Figure 1B is the figure of the refractive index profile of photon crystal fiber guide shown in a part of Figure 1A.

Fig. 2 A～2D is the synoptic diagram of step in the method for making photon crystal fiber guide.

Fig. 3 A is a kind of viewgraph of cross-section of restricted area of specific embodiments of photon crystal fiber guide.

Fig. 3 B is the figure of the refractive index profile of restricted area shown in Fig. 3 A.

Fig. 4 A and 4B are the SEM microphoto of a kind of embodiment of photon crystal fiber guide.

Fig. 5 is the transmission spectrum figure of two different embodiment of photon crystal fiber guide.Article two, the highest transmission peak is corresponding with the basic mode photon band gap in the curve, and the arrow indication is than the higher mode band gap.

Fig. 6 A is the transmission spectrum figure of a kind of embodiment of photon crystal fiber guide.

Fig. 6 B is the function relation figure of the logarithm of the fiber lengths of embodiment of a photon crystal fiber guide that is truncated into different length and through-put power.The unit of rate of curve is dB/m.

Fig. 7 is the transmission spectrum figure with the optical fiber of different curvature radius bending.

Fig. 8 is by CO ₂Laser instrument is by the transmission curvature of the electromagnetic radiation of photon crystal fiber guide and the function relation figure of bending loss.The numerical value of loss is to be obtained by the overall transmission power with same fibre by keeping straight line of the optical fiber by bending relatively.

Identical mark is represented components identical in the different accompanying drawings.

Embodiment

With reference to Figure 1A, photon crystal fiber guide 100 comprises along the axle center 120 that waveguide axis extends and the dielectric restricted area 110 (high refractive index layer that for example replaces and low-index layer) that centers on this axle center.Restricted area 110 is centered on by the supporting layer 150 that mechanical support is provided for restricted area.

Restricted area 110 comprises the successive layers 130 and 140 of the dielectric substance (for example polymkeric substance, glass) with different refractivity, and this situation with multiple discontinuous concentric layer is opposite, and described concentric layer forms restricted area in other specific embodiments.Successive layers 130 and 140 forms around the helical structure of axle 199, and photon crystal fiber guide is along this direct electromagnetic radiation.Such as wherein one deck of layer 140 for having refractive index n _HAnd thickness d _HHigh refractive index layer; And such as layer 130 the layer for having refractive index n _LAnd thickness d _LLow-index layer, n wherein _H＞n _L(n for example _H-n _LCan more than or equal to or greater than 0.01,0.05,0.1,0.2,0.5 or bigger).Because layer 130 and 140 centers on axle 199 shape in the shape of a spiral, intersect more than once from radial cross section 160 and each layer that axle 199 extends, thereby acquisition comprises the high refractive index layer alternately and the radial section of low-index layer.

With reference to Figure 1B, optically, the spiral fashion layer makes refractive index present cyclical variation along radial cross section 160, and its cycle, promptly restricted area 110 had double-deck optical cycle n corresponding to the optical thickness of layer 130 and 140 _Hd _H+ n _Ld _L" R " representative among the figure is from the radial position of axle 199 measurements.

Thickness (the d of layer 130 and 140 _HAnd d _L) and optical thickness (n _Hd _HAnd n _Ld _L) can change.In some specific embodiments, layer 130 is identical with the optical thickness of layer 140.The selection of layer thickness is normally based on the expection optical property of optical fiber the wavelength of guiding radiation (for example according to).Relation between following gnu.GNU thickness and the optical property.Typical layer thickness is in the scope of sub-micron to tens micron.For example, the thickness of layer 130 and 140 can be between about 0.1 μ m to 20 μ m (for example about 0.5～5 μ m).

For the specific embodiments shown in Figure 1A, restricted area 110 has the thickness of 5 bilayers.Yet in fact, restricted area 110 can comprise more bilayer (for example more than about 8 bilayers, 10 bilayers, 15 bilayers, 20 bilayers, 25 bilayers, as 40 or more a plurality of bilayer).

Layer 140 comprises the material with high index of refraction, as chalcogenide glass.Layer 130 comprises the refractive index materials that is lower than layer 140 high-index material, and layer 130 typically has mechanical flexibility.For example, layer 130 generally includes polymkeric substance.Preferably the material with cambium layer 130 and layer 140 stretches altogether.The choice criteria that can be total to expanded material is discussed below.

In this specific embodiments, axle center 120 is a hollow.When needing, fluid filled can be used in the axle center of this hollow, as gas (for example air, nitrogen and/or inert gas) or liquid (for example isotropic liquid or liquid crystal).Axle center 120 is optionally contained and the material that forms restricted area 110 compatible any material or combination of material on rheology.In some specific embodiments, one or more dopant materials can be contained in axle center 120, the sequence number that is called " high index-contrast fibre-optic waveguide and application " as the name of submitting on April 12nd, 2002 is 10/121,452, publication number is described in the U.S. Patent application of US-2003-0044158-A1, and its full content is incorporated among the application as a reference.

Axle center and restricted

area

120 and 110 can comprise multiple dielectric substance with different refractivity.In the case, we can be with reference to " mean refractive index " of given area, and this relates to the weighting refractive index sum of this zone ingredient, is weighted and each refractive index is a area fraction by its ingredient zone.Yet the border between the layer 130 and 140 is determined by change of refractive.This variation can cause by the interface of two kinds of different dielectric substances or by the different levels of doping in the same dielectric material (for example different concentration of mixing in the silicon dioxide).

Electromagnetic radiation in dielectric restricted area 110 guiding first wavelength coverage is along propagating in the dielectric axle center 120 of waveguide axis 199.Restriction scheme is based on the photon crystal structure in the zone 110, and zone 110 forms the band gap that comprises first wavelength coverage.Because this restriction scheme is not a refractive-index-guiding, the refractive index in axle center need not to be higher than the refractive index with the restricted area part of axle center direct neighbor.On the contrary, the mean refractive index in axle center 120 can be lower than restricted area 110.For example, axle center 120 can be air, such as other gases of nitrogen or find time substantially.In this case, the electromagnetic radiation that guides in described axle center is compared with the electromagnetic radiation that guides in the silicon dioxide axle center, have much smaller loss and much smaller nonlinear interaction, reveal less absorption and nonlinear interaction constant corresponding to silicon dioxide or the many gas meters of other solid materials.For example in additional specific embodiments, axle center 120 can comprise the porous dielectric material, thereby supports for restricted area on every side provides certain structure, still defines the axle center that is mainly air simultaneously.Therefore axle center 120 needn't have consistent refractive index profile.

The layer 130 and 140 of restricted area 110 has formed Bragg optical fiber as is known.The alternating layer of the reflecting body that the periodicity optical similar of spiral winding layer is piled up in planar dielectric (also Bragg mirror) as is known.The alternate planes layer of the circular layer of restricted area 110 and dielectric stack reflecting body all is the example of photon crystal structure.In " photonic crystal (Photonic Crystals) " (Princeton University publishing house, Princeton NJ, 1995) of people such as John D.Joannopoulos photon crystal structure has been described mainly.

The used photonic crystal of the present invention is to have the dielectric medium structure that produces the index modulation of photon band gap in photonic crystal.The used photon band gap of the present invention is the scope of wavelength (or on the contrary, being frequency), does not wherein have accessible extension (being non-local propagation) state in this dielectric medium structure.This structure is typically a kind of periodic dielectric structure, but it also can comprise for example more complicated " quasicrystal ".Can this band gap be used for restriction, guiding and/or location light by with photonic crystal and " defective " the regional combination of departing from bandgap structure.In addition, for less than with wavelength greater than this band gap, have accessible extension state, thereby even allow light is limited in the lower zone of refractive index (ining contrast to the TIR structure of above-mentioned refractive-index-guiding).This term " accessible " state is meant the state that coupling is not forbidden by some symmetry or the law of conservation of system as yet.For example, polarization is a conservation in two-dimentional system, just need be excluded beyond band gap so only be similar to the state of polarization.In having the waveguide of uniform cross sections (as typical optical fiber), wave vector β is a conservation, just need be excluded beyond band gap so only have the state of given β, to support the bootmode of photonic crystal.In addition, in the waveguide of cylindrosymmetry, " angular momentum " refractive index m is a conservation, just need be excluded beyond band gap so only have the pattern of identical m.In brief, compare with " fully " band gap that wherein no matter symmetric all states all are excluded, high symmetric system is quite loose for the requirement of photon band gap.

Therefore, the dielectric stack reflecting body has the reflectivity of height in photon band gap, and this is to propagate because electromagnetic radiation can not see through stack layer.Circular layer in the restricted area 110 provides restriction equally, and this is because it has highly reflective for the incident ray in the band gap.Strict in fact, photonic crystal only when wherein index modulation has infinite range, just has complete reflectivity in band gap.In addition, incident radiation can " penetrate " photonic crystal by the pattern that consumes gradually that communication mode is coupled in arbitrary of photonic crystal.Yet the speed that in fact, penetrates is index with the increase of photonic crystal thickness (for example number of alternating layer) to be reduced.It also reduces with the increase of refringence in the restricted area.

In addition, photon band gap can only be distributed in the relative small range propagating vector.For example, dielectric stack layers can have highly reflective to vertical incident ray, and the incident ray that tilts is only had the reflectivity of part." complete photonic band gap " is the band gap that spreads all over all possible wave vector and all polarization states.Complete photonic band gap only relates to the photonic crystal that has index modulation along three-dimensional usually.Yet with regard to the electromagnetic radiation that is incident to photonic crystal from adjacent dielectric substance, also definable " omnidirectional's photon band gap ", it is the electromagnetic mode of a photon band gap adjacent dielectric substance all supports to propagate to(for) all possible wave vector and polarization state.Omnidirectional's photon band gap can be defined as the photon band gap of above all electromagnetic modes of light (light line) equally, and wherein said light (light line) has defined the communication mode of the low-limit frequency of being supported by the material adjacent with photonic crystal.For example, airborne light (light line) is roughly given by ω=c β, and wherein ω is the angular frequency of radiation, and β is a wave vector, and c is the light velocity.US 6,130, and 780 disclose the description about omnidirectional's plane reflection body, incorporate its content into the application as a reference here.In addition, people such as Yoel Fink the name be called " omnidirectional's multi-layered devices of the optical waveguide of raising " the 6th, 463, No. 200 U.S. Patent Publications use alternately that dielectric layer provides omnidirectional's reflection (in a plane restriction) as the cylindrical waveguide geometric configuration, incorporate its content into the application as a reference here.

When the alternating layer in the restricted area 110 130 and 140 caused omnidirectional band gap about axle center 120, bootmode was by strong restrictions, and this is because any electromagnetic radiation of injecting restricted area from the axle center is reflected fully in principle.Yet, described reflection fully only just can appear when having infinitely many layers.Layer (for example about 10 bilayers) for limited quantity, omnidirectional's photon band gap can be consistent with the reflection in the Any shape of plane, described reflection accounts at least 95% of all angles from 0 ° to 80 ° of incident scopes, and account for the electromagnetic radiation with this omnidirectional's band gap medium frequency all polarization states at least 95%.In addition, even when the band gap of photon crystal fiber guide 100 restricted areas is non-omnidirectional, it still can support strong bootmode, and for example the radiation loss of band gap medium frequency scope is less than the pattern of 0.1dB/km.Whether band gap is the omnidirectional's size (proportional with two-layer refringence usually) that depends on band gap that alternating layer produces usually and the lowest refractive index ingredient of photonic crystal.

In being similar to the structure of Bragg, the refractive index of high refractive index layer and thickness can change, and/or the refractive index of low-index layer and thickness also can change.Restricted area can comprise weekly that also the phase contains the periodic structure greater than two-layer (for example three layers of phases or more multi-layered) weekly.In addition, index modulation can be used as fiber radius function in restricted area continuously or discontinuous variation.Restricted area usually can be based on the index modulation of any generation photon band gap.

In this specific embodiments, sandwich construction 110 forms the Bragg reflecting body, and this is because the radially axle variation of its periodic refractive index.Suitable refractive index variable quantity is about the condition of 1/4 ripple.As everyone knows, for vertical incidence, the maximum band gap that obtains is " 1/4 ripple " stack layer, and wherein each layer has equal optical thickness λ/4, or is equivalent to d _H/ d _L=n _L/ n _H, wherein d and n are respectively the thickness and the refractive index of high refractive index layer and low-index layer.It corresponds respectively to layer 240 and layer 230.Vertical incidence is equivalent to β=0.For cylindrical waveguide, desired pattern typically is arranged near light (light line) ω=c β place (in the restriction of big axis core radius, it is the plane wave that waveguide axis is propagated that the lowest order mode formula is essentially along the z axle).In the case, the condition of described 1/4 ripple becomes:

\frac{d_{H}}{d_{L}} = \frac{\sqrt{n_{L}^{2} - 1}}{\sqrt{n_{H}^{2} - 1}}

Strict in fact, can be in strict conformity with this equation, this is because the condition of described 1/4 ripple changes by cylindrical geometries, this optical thickness that requires each layer is smooth change with its radial coordinate position.Yet we find that this equation especially under the situation of axle center radius greater than the mid-gap wavelength, provides fabulous method for optimizing the performance of many expectations.

The sequence number that the name that people such as Steven G.Johnson submitted on January 25th, 2002 is called " the low-loss photonic crystal optical fiber with big axis core radius " is 10/057,258, publication number is some specific embodiments of having described photon crystal fiber guide in the U.S. Patent application of US-2002-0164137-A1, and these incorporate its all the elements into the application as a reference.

The radius in axle center 120 can change according to the final use of optical fiber 120.The axle center radius can be depending on the wavelength or the wavelength coverage of optical fiber institute guiding energy, and depends on that described optical fiber is single mode or multimode optical fiber.For example, for the single-mode fiber of guiding visible wavelength (for example in the scope of about 400nm to 800nm), the axle center radius can be in from sub-micron to several microns scope (for example from about 0.5 μ m to 5 μ m).Yet for the multimode optical fiber of guiding IR wavelength (for example from about 2 μ m to 15 μ m, as 10.6 μ m), the axle center radius can be in tens to several thousand microns scope (for example from about 10 μ m to 2,000 μ m, as 500 μ m to 1,000 μ m).The axle center radius can be greater than about 5 λ (for example greater than about 10 λ, 20 λ, 30 λ, 50 λ, 100 λ), and wherein λ is the wavelength of institute's guiding energy.

As previously mentioned, supporting layer 150 provides mechanical support for restricted area 110.The thickness of supporting layer 150 can change as required.In some specific embodiments, supporting layer 150 is much thicker than restriction zone 110.For example, thicker about 10 times or more times (for example thicker 20 times, 30 times, 50 times) of supporting layer 150 comparable restricted areas 110.

Usually select the composition of supporting layer 150 to think that restricted area 110 provides the mechanical support and the protection of expectation.In a lot of specific embodiments, supporting layer 150 is by forming with the material that restricted area 110 stretches altogether.The standard that selection is suitable for the material of common stretching is discussed below.In some specific embodiments, supporting layer can by with form in order to the material identical materials that forms restricted area 110.For example layer 130 is formed by a kind of polymkeric substance, and supporting layer 150 can be formed by identical polymkeric substance.

The composition of the layer 130 and 140 in the restricted area 110 is discussed below, have suitable high index of refraction with the material that forms high index of refraction part (for example layer 140) comprise chalcogenide glass (for example containing glass), heavy metal oxide glass, non-crystaline amorphous metal such as the chalcogen of sulphur, selenium and/or tellurium with and combination.

Except that the chalcogen element, chalcogenide glass can comprise one or more in the following element: boron, aluminium, silicon, phosphorus, sulphur, gallium, germanium, arsenic, indium, tin, antimony, thallium, lead, bismuth, cadmium, lanthanum and halogen (fluorine, chlorine, bromine, iodine).

Chalcogenide glass can be binary or TERNARY GLASS, for example As-S, As-Se, Ge-S, Ge-Se, As-Te, Sb-Se, As-S-Se, S-Se-Te, As-Se-Te, As-S-Te, Ge-S-Te, Ge-Se-Te, Ge-S-Se, As-Ge-Se, As-Ge-Te, As-Se-Pb, As-S-Tl, As-Se-Tl, As-Te-Tl, As-Se-Ga, Ga-La-S, Ge-Sb-Se, or based on the multicomponent glass of the complexity of these elements, as As-Ga-Ge-S, Pb-Ga-Ge-S etc.The ratio of various elements can change in the chalcogenide glass.For example, the chalcogenide glass with suitable high index of refraction can be made of the germanium of the arsenic of 5～30 moles of %, 20～40 moles of % and the selenium of 30～60 moles of %.

Example with heavy metal oxide glass of high index of refraction comprises: contain Bi ₂O ₃Glass, contain PbO glass, contain Tl ₂O ₃Glass, contain Ta ₂O ₃Glass, contain TiO ₂Glass and contain TeO ₂Glass.

Non-crystaline amorphous metal with suitable high index of refraction comprises Al-Te and R-Te (Se) (R=alkaline metal).

Have suitable low-refraction with the material that forms low-refraction part (for example layer 130) comprise oxide glass, halide glass, polymkeric substance with and combination.Following polymkeric substance is the polymkeric substance to be selected that mates well, comprise: the polymkeric substance in carbonates (for example polycarbonate (PC)), sulfone class (for example polyethersulfone (PES)), ether acid imide (for example polyetherimide (PEI)) and the esters of acrylic acid (for example polymethylmethacrylate (PMMA)), and fluoropolymer.

Suitable oxide glass can comprise the glass that contains one or more following compounds: the M of 0～40 mole of % ₂O, wherein M is Li, Na, K, Rb or Cs; M ' O of 0～40 mole of %, wherein M ' is Mg, Ca, Sr, Ba, Zn or Pb; The M of 0～40 mole of % " ₂O ₃, wherein M " is B, Al, Ga, In, Sn or Bi; The P of 0～60 mole of % ₂O ₅And the SiO of 0～40 mole of % ₂

The part of photon crystal fiber guide can randomly comprise other material.For example any part can comprise that one or more change this part refractive index materials.A part can comprise this part refractive index materials of a kind of raising.These materials comprise the germanium oxide that for example can improve the refractive index of the part that contains borosilicate glass.In other words, a part can comprise this part refractive index materials of reduction.For example, boron oxide can reduce the refractive index of the part that contains borosilicate glass.

Each several part with fibre-optic waveguide of high index-contrast can be homogeneous or heterogeneous.For example, one or more parts can comprise a kind of the embedding in the material of main part to form the nanoparticle (for example these particulates are fully little so that the scattered light minimum under institute's guide wavelength) of heterogeneous body material partly.The example is a kind of high refractive index polymer compound by forming in the nanoparticle embedded polymer owner body with the high index of refraction chalcogenide glass.Other examples comprise CdSe and/or the PbSe nanoparticle in the unorganic glass matrix

The part of fibre-optic waveguide can comprise the material of the mechanical property, rheological property and/or the thermodynamic property that change these parts of optical fiber.For example, one or more parts can comprise plastifier.These parts can comprise the material that suppresses the characteristic of other non-expectation phases in crystallization or the optical fiber.For example can be by introducing the crystallization in crosslinking chemical (for example photosensitive crosslinker) the inhibition polymkeric substance.In other examples,, then nucleator can be introduced in material, as TiO if need glass-ceramic material ₂Or ZrO ₂

These parts also can comprise the compound that is used for influencing (for example between low-index layer and the high refractive index layer) interface between the optical fiber adjacent part.These compounds comprise adhesive accelerant and bulking agent.For example can use the organic siliconresin compound to promote the clinging power between silica based glasses part and the polymer moieties.For example phosphorus or P ₂O ₅All compatible with chalcogenide glass and oxide glass, and the clinging power between the part that can promote to form by these glass.

Fibre-optic waveguide can comprise the additional materials at the special fiber wave guide applications.For example in fiber amplifier, any part all can by can with being combined to form of interactional any doping agent of the optical signalling in the optical fiber or doping agent, to improve one or more wavelength of light by the absorption of optical fiber or emission, for example at least a rare earth ion is as erbium ion, ytterbium ion, neodymium ion, holmium ion, dysprosium ion and/or thulium ion.

The part of high index-contrast waveguide can comprise one or more nonlinear materials.Nonlinear material is for improving the material of waveguide nonlinear response.Especially, the nonlinear response of nonlinear material is higher than silicon dioxide.For example the Kerr nonlinear factor of nonlinear material is n ⁽²⁾, its Kerr nonlinear factor that is higher than silicon dioxide (promptly is higher than 3.5 * 10 ^-20m ²/ W, as be higher than 5 * 10 ^-20m ²/ W, be higher than 10 * 10 ^-20m ²/ W, be higher than 20 * 10 ^-20m ²/ W, be higher than 100 * 10 ^-20m ²/ W, be higher than 200 * 10 ^-20m ²/ W).

When utilizing the thicker fibre-optic waveguide of pulling method manufacturing, be not every kind of combination with expection optical characteristics material all be inevitable suitable.Should typically select material compatible on rheology, thermodynamics and the physical chemistry.Next some standards of selecting compatibility material are discussed.

It is compatible on the rheology selecting first standard of material.In other words, should be chosen in the broad temperature range, promptly under the temperature corresponding to the different phase of the stretching of optical fiber and processing, have the material of similar viscosity.Viscosity is meant and hinders the resistance that fluid flows under the shear stress that is applied.Here the unit of viscosity is pool.Before setting forth the rheology compatibility, be favourable for institute defines the series of features temperature to material, have special viscosity following of characteristic temperature to material.

Annealing point T _aFor the viscosity of material is 10 ¹³Temperature during pool.T _aCan utilize Orton CeramicFoundation (Westerville, SP-2A type systematic survey OH).Typically at T _aTemperature under, the viscosity of a glass is enough low to eliminate unrelieved stress.

Softening point T _sFor the viscosity of material is 10 ^7.65Temperature during pool.T _sCan utilize (Westerville, the softening point instrument measurement of SP-3A type OH) such as OrtonCeramic Foundation.It is relevant that softening point and material stream changes the temperature of viscosity into by plasticity in fact.

Working point T _wFor the viscosity of material is 10 ⁴Temperature during pool.T _wCan utilize (Westerville, the glass viscosity instrument measurement of SP-4A type OH) such as OrtonCeramic Foundation.Working point and glass can easily be drawn into the temperature correlation of optical fiber.For example in some specific embodiments, this material is a unorganic glass, and the working point temperature of this material can be higher than 250 ℃, 300 ℃ according to appointment, 400 ℃, 500 ℃ or higher.

Melting point T _mFor the viscosity of material is 10 ²Temperature during pool.T _mCan utilize (Westerville, SP-4A type glass viscosity instrument measurement OH) such as OrtonCeramic Foundation.The control that melting point and glass become liquid state and keeps the optical fiber drawing process of the fibre geometry very temperature correlation of difficulty that becomes.

For compatible on rheology, two kinds of materials should have close viscosity in broad temperature range, for example can not be again from the temperature of stretching optical fiber to optical fiber can debate the temperature that other speed eliminates stress (T for example _a) or lower temperature.Therefore, the working temperature of two kinds of compatible materials should be close, thereby two kinds of material streams are stretched with close speed.For example, if record the work temperature of first material at second material _W2Under viscosities il ₁(T), η then ₁(T _W2) should be at least 10 ³Pool, for example 10 ⁴Pool or 10 ⁵Pool, and be not higher than 10 ⁶Pool.In addition, when the optical fiber that is stretched cooled off, two kinds of properties of materials all should change elasticity into by viscosity under close temperature.In other words, the softening temperature of two kinds of materials should be close.For example at the softening temperature T of second material _S2Down, the viscosities il of first material ₁(T _S2) should be at least 10 ⁶Pool, for example 10 ⁷Pool or 10 ⁸Pool, and be not higher than 10 ⁹Pool.In preferred specific embodiments, two kinds of materials should be annealed jointly, thereby at the annealing temperature T of second material _A2Down, the viscosities il of first material ₁(T _A2) should be at least 10 ⁸Pool (for example at least 10 ⁹Pool, at least 10 ¹⁰Pool, at least 10 ¹¹Pool, at least 10 ¹²Pool, at least 10 ¹³Pool, at least 10 ¹⁴Pool).

In addition, for compatible on rheology, the function (being the viscosity slope) that the viscosity with temperature of two kinds of materials changes preferably should be approaching as much as possible.

Second choice criteria is that the thermal expansivity (TEC) in the temperature range of various materials between annealing temperature and room temperature should be close.In other words, when optical fiber cooling and its rheological properties are changed into similarly when solid-state by similar liquid state, the volume of two kinds of materials all should change close amount.If the TEC of two kinds of materials conforms to fully, huge volume change difference can cause the accumulation of abundant residues stress between two fiber sections, thereby one or more parts are cracked and/or layering.Even under the stress far below the material faulting stress, unrelieved stress also can cause the fracture that postpones.

TEC is the tolerance of sample length with the subtle change of temperature change.For a kind of given material, this parameter can be calculated by temperature-length (or temperature-volume of equal value) slope of a curve.A kind of temperature-length curve of material can be utilized (Westerville, the dilatometer measurement of 1200D type dilatometer OH) such as Orton Ceramic Foundation.TEC can measure in the chosen temperature scope, or to measure to the transient change under the fixed temperature.Its unit is ℃ ^-1

For many materials, all there are two ranges of linearity in temperature-length curve with Different Slope.There is a zone of transition in the transformation of curve from first to second range of linearity.This zone is relevant with the glass transition process, and the characteristic of glass sample is changed into usually and the relevant characteristic of viscous fluid by the common characteristic relevant with solid material in this transition process.This is a continuous transition process, it is characterized in that, and is opposite with the discontinuous variation of slope, and the slope of temperature-volume curve gradually changes.Glass transformation temperature T _gMay be defined as the glass solid wires of extrapolation and the intersection point of viscous fluid line.Glass transformation temperature is relevant by the temperature that brittle solid is converted to charge of flowable solids with the rheological properties of material.On the physics, the required heat energy of the translation of different molecular and rotation mode is relevant in glass transformation temperature and the excitation material.Usually with glass transformation temperature as approximate annealing point, viscosity at this moment is 10 ¹³Pool, but T in fact _gBe a relative numerical value, and depend on measuring technique.

Also can use dilatometer to measure expansion softening point T _DsDilatometer is by applying a little compressive load and heat this sample and work on sample.When the temperature of sample becomes abundant when high, material begins to soften, and compressive load makes the sample distortion when observing volume or length and reduce.This relative value is called as the expansion softening point, and is 10 in the viscosity of material usually ¹⁰～10 ^12.5Produce during pool.A kind of accurate T of material _DsNumerical value depends on the instrumentation and testing parameter usually.If use approximate instrumentation and testing parameter, then this temperature provides the useful tolerance of different materials rheology compatibility under this viscous state.

As previously mentioned, it is a significant consideration that obtains the optical fiber of no excessive residual stress that TEC is complementary, and described excessive residual stress can develop in optical fiber in drawing process.Typically, when the TEC of two kinds of materials is not when being complementary fully, unrelieved stress produces as elastic stress.This elastic stress component comes from the optical fiber between the different materials difference of volumetric contraction when glass transformation temperature is cooled to room temperature (for example 25 ℃).Volume change is that the change by TEC and temperature is determined.For the specific embodiments that the material in the optical fiber in the drawing process fusion takes place on any interface or bonds, the difference of its TEC will cause stress at the interface.A kind of material is in (normal stress) in the tension stress, and another kind of material is in (negative stress) in the compressive stress, so total stress is zero.Moderate compression stress itself is not the major influence factors of glass optical fiber usually, but tension stress does not expect that it can cause fault in time.Therefore, the TEC difference of composition material being minimized, is desired thereby the elastic stress that produces in the optical fiber in the drawing process is minimized.For example, in the composite fiber that forms by two kinds of different materials, utilize dilatometer with the rate of heat addition of 3 ℃/min in T _gAnd the absolute difference between the various glass TEC that record under the temperature between the room temperature should be not more than 5 * 10 ^-6℃ ^-1(for example be not more than 4 * 10 ^-6℃ ^-1, be not more than 3 * 10 ^-6℃ ^-1, be not more than 2 * 10 ^-6℃ ^-1, be not more than 1 * 10 ^-6℃ ^-1, be not more than 5 * 10 ^-7℃ ^-1, be not more than 4 * 10 ^-7℃ ^-1, be not more than 3 * 10 ^-7℃ ^-1, be not more than 2 * 10 ^-7℃ ^-1).

The material that selection has close TEC can make the elastic stress component minimize, and unrelieved stress still can be developed by the viscoelastic stress component.When the difference between composition material strain point temperature or the glass transformation temperature is fully big, then produce the viscoelastic stress component.When material cooled to being lower than T _gThe time, significantly volumetric contraction then takes place.When viscosity changes with cooling procedure in this transition process, discharge the stress required time and increase to a few minutes by zero (moment).For example suppose that a compound prefabricated rods is by having different glass transformation range (and different T _g) glass and polymkeric substance make.In the incipient extension process, glass and polymkeric substance have the characteristic of viscous fluid, and owing to the stress that tensile strain produced can be discharged immediately.Leave after the hottest part of stretching furnace, the rapid release heat of optical fiber causes the viscosity of fiber optic materials to be exponential increase together with the time that discharges stress.Because comparing with rate of extension, the time of release stress becomes very long, when being cooled to its T _gThe time, in fact glass and polymkeric substance can not discharge stress again.So, if the composition material has different T _gNumerical value then is cooled to its T _gFirst material can not reduce stress again, and second material still is higher than its T _gValue, but and the stress that produces between the releasable material.When second material cooled to its T _gThe time, the stress that produces between the material can not be discharged effectively again.In addition, the volumetric contraction of second glass (now is lower than its T much larger than the volumetric contraction of first material under this temperature spot _gAnd the characteristic of the solid that enbrittles).This situation can cause the abundant accumulation of stress between glass and the polymkeric substance, thereby makes one or two part that physical damage all take place.This guides the 3rd choice criteria of selective light fiber material into: make composition material T _gDifference to minimize so that the viscoelastic stress that is produced in the optical fiber in the optical fiber drawing process minimizes be desired.The glass transformation temperature T of first material _G1Glass transformation temperature T with second material _G2Difference preferably should 100 ℃ with interior (for example | T _G1-T _G2| should less than 90 ℃, less than 80 ℃, less than 70 ℃, less than 60 ℃, less than 50 ℃, less than 40 ℃, less than 30 ℃, less than 20 ℃, less than 10 ℃).

Owing to there are the two kinds of mechanism (being elasticity and viscoelasticity mechanism) that develop permanent stress in institute's stretching optical fiber in the difference between the composition material, so can use these mechanism to cancel out each other.For example if the T of material _gDo not match and cause the stress of contrary sign, the material of then forming optical fiber can be offset usually by thermal expansion and do not matched and the stress that causes.On the contrary, if material coefficient of thermal expansion can reduce whole permanent stress, then T between the material _gAllow than big-difference.An approach of the combined effect of assessment thermal expansion and glass transformation temperature difference is by comparing the temperature-length curve of each composition material.Utilize aforementioned slope-tangential method to find the T of each material _gAfterwards, will be wherein a curve along longitudinal axis translation, thereby make curve in low T _gTemperature numerical coincides.If the not combination of each glass, then the difference of y y-intercept produces strain stress under the room temperature.For at T _gHave the material of amount of contraction greatly to the temperature range of room temperature, desired tensile stress sigma can be calculated by following equation simply:

σ＝E·ε，

Wherein E is the elastic modulus of this material.Typical unrelieved stress numerical value is less than 100MPa (for example less than 50MPa, less than 30MPa), and it is fully for a short time to show that two kinds of materials are compatible.

The thermal stability that the 4th choice criteria is material to be selected is complementary.The tolerance of thermal stability is by temperature range (T _x-T _g) provide T wherein _xMaterial slowly cools to when beginning for crystallization is enough to make the temperature that each molecule can be when its lowest energy state.So crystalline state is compared with glassy state, be preferred materials behavior on the energy.But in the application of fibre-optic waveguide, the glassy state of material is compared the advantage that typically has performance and/or manufacturing with crystalline state.Tc and glass transformation temperature are approaching more, and then material more may crystallization in drawing process, and this is (for example introduce the optics nonuniformity in optical fiber, this can increase loss) that is harmful to optical fiber.Thermal stability interval (T _x-T _g) being generally at least 80 ℃ (for example at least 100 ℃), it is enough to by making material fiberization by preform bar stretching optical fiber.In preferred specific embodiments, thermal stability is interval to be at least 120 ℃, as 150 ℃, 200 ℃ or higher.Can utilize thermal-analysis instrumentation to measure T _x, as differential thermal analyzer (DTA) or differential scanning calorimeter (DSC).

Another Consideration when selection can be total to expanded material is the temperature of fusion T of material _MgUnder temperature of fusion, to such an extent as to the viscosity of material is crossed and lowly can't successfully be kept accurate geometric configuration in the optical fiber drawing process.Therefore, in preferred specific embodiments, a kind of temperature of fusion of material is higher than the working temperature of second compatible on the rheology material.In other words, when the heating prefabricated rods, prefabricated rods reaches the temperature that can stretch smoothly before the various therein material melts.

The example of a pair of material that can stretch and obtain to have the photon crystal fiber guide of high index-contrast altogether between the layer of restricted area is As ₂Se ₃With polymer P ES.As ₂Se ₃Glass temperature (T _g) be about 180 ℃, its thermal expansivity (TEC) is about 24 * 10 ^-6/ ℃.When wavelength is 10.6 μ m, As ₂Se ₃Refractive index be 2.7775, as surveyed by people such as Hartouni and Proc.SPIE, described in 505,11 (1984); Its absorption coefficient is 5.8dB/m, as being surveyed by Voigt and Linke and in " physical property and the application (Physics and Applications of Non-Crystalline Semiconductors inOptoelectronics) of amorphous semiconductor in optoelectronics ", Ed.A.Andriesh and M.Bertolotti, NATO ASI Series, 3.High Technology, Vol.36 is p.155 described in (1996).Here incorporate the full content of above-mentioned document into the application as a reference.The TEC of PES is about 55 * 10 ^-6/ ℃, refractive index is about 1.65.

In some specific embodiments, can be by the plane multi-layer product being rolled into helical structure and becoming optical fiber by preform bar stretching from this helical structure, and make photon crystal fiber guide, as waveguide 100.

With reference to Fig. 2 A,, glass 220 is deposited on the surface 211 of polymer film 210 for the preparation prefabricated rods.This glass can deposit by the method that comprises thermal evaporation, chemical vapor deposition or sputter.With reference to Fig. 2 B, this deposition process provides a multi-layer product 240, and it comprises the glassy layer 230 on the polymer film 210.

With reference to Fig. 2 C, after deposition step, multilayer film 240 is rolled into a spiral pipe around plug 255 (for example hollow glass, as borosilicate glass or polymer pipe).Then some (for example about 3～10) polymer films are wrapped in spiral pipe on every side to form the prefabricated rods overcoat.In some specific embodiments, polymer film is to be made by same polymer that is used to form multi-layer product or glass.Under vacuum, the prefabricated rods overcoat is heated above formation multilayer film 240 and is wrapped in the polymkeric substance of spiral pipe film on every side and the glass transformation temperature of glass.So that the fusion mutually of the layer of spiral pipe, and spiral pipe and the polymer film that is wrapped in around it are fused prefabricated rods overcoat heating time enough.The temperature and time of heating depends on the composition of prefabricated rods overcoat.If described multilayer film is by As ₂Se ₃Be made up of PES with the film of PES composition and parcel, it is typically sufficient then for example heating 15～20 minutes (for example about 18 minutes) down at 200～300 ℃ (for example about 250 ℃).Heating process makes the fusion mutually of different layers, thereby the film of spiral pipe and parcel is merged.Structure through merging is shown in Fig. 2 D.Described spiral pipe is merged into the multi-layer area 260 corresponding to the multilayer film 240 that is rolled.The polymer film that is wrapped is merged into whole support cladding layer 270.Structure through merging has kept the hollow axle center 250 of plug 255.

As polymer film being wrapped in around the spiral pipe, spiral pipe can be inserted in the hollow tubular that an internal diameter and spiral pipe external diameter be complementary to obtain to support the replacement of cladding layer 270.

Plug 255 is removed from the structure through merging, to obtain to be drawn into subsequently the hollow prefabricated rods of optical fiber.Prefabricated rods has composition identical with final optical fiber and relative size (for example relative size of axle center radius and restricted area middle level thickness).The absolute dimension of optical fiber depends on used extensibility.But the optical fiber (for example the longest is several kms) that tensile elongation is long.The fiber cut of drawn can be become the length of needs then.

Merging process is preferably implemented below the glass transformation temperature of plug, thereby makes plug provide firm support for spiral pipe.This assurance multilayer film can not produce thereon under vacuum and subside.Can select the composition of plug, so that its innermost layer from multilayer pipe after merging discharges.In other words, bonding as if the innermost layer of plug in merging process and multilayer pipe, then it can be removed by chemistry, for example by corrosion.For example, plug is in a kind of specific embodiments of glass capillary, and it can utilize hydrofluorite to corrode, thereby obtains prefabricated rods.

In the specific embodiments in the solid axle center of needs, multilayer pipe can be merged around the solid mandrel, and stretches altogether with the other parts of optical fiber.Optionally, in other specific embodiments, can multilayer film be rolled without plug, thus the spiral pipe of acquisition self-supporting.

In some specific embodiments, can be on two faces of polymer film 210 with vitreous coating.Because each glassy layer only needs to deposit glassy layer thickness half on a face, so this is favourable.Typically, glassy layer is thin more, then is not easy to take place in the process of rolling mechanical stress damage more.

Adopt the photon crystal fiber guide of above-mentioned technology preparation can have fabricating low-defect-density.For example, every 10m optical fiber of waveguide can have less than an about defective (optical fiber of for example every 20m, 50m, 100m has less than an about defective).Defective comprises fault in material (for example impurity) and fault of construction (for example the separating of interlayer, layer breaks), and two kinds of defectives all can make the radiation that is guided from the axle center scattering, thereby cause loss of signal, and can cause the optical fiber local pyrexia.Therefore, in the application to the loss of signal sensitivity (for example in the high-power applications, if radiation can be caused damage to optical fiber by the absorption of optical fiber), the defective that reduces optical fiber is desired.

By being coated in photon crystal fiber guide that the glass-film of substrate on two-sided make and comparing, has slightly different refractive index profile by single coated side former of institute.With reference to Fig. 3 A and 3B, for example the restricted area 310 of the optical fiber of being made by the multilayer film that applies on two-sided has continuous worm-like polymer layer 330 and glassy layer 340.Compare with the bilayer thickness that occurs in other zones, the innermost layer 340A of glassy layer 340 and the zone of outermost layer 340B are corresponding to the single glassy layer that is coated on the polymkeric substance.The gained refractive index profile that passes radial cross section 360 is shown in Fig. 3 B.

In some specific embodiments, before rolling, can prepare two-layer or more multi-layered film, and stack.Can under the situation that does not increase the film size, increase the quantity in restricted area middle level like this.

As previously mentioned, photon crystal fiber guide can be in order to the guiding infrared radiation.The wavelength of infrared radiation is (for example between about 2～5 μ m or between about 8～12 μ m) between about 0.7～20 μ m.In some specific embodiments, photon crystal fiber guide can be the CO of the radiation of about 6.5 μ m or 10.6 μ m as emission wavelength in order to the radiation of guiding infrared laser generation ₂Laser instrument.Other examples that can launch the laser instrument of infrared energy comprise Nd:YAG laser instrument (for example at 1.064 μ m); Er:YAG laser instrument (for example at 2.94 μ m); Er, Cr:YSGG (the yttrium scandium gallium garnet of erbium doped and chromium) laser instrument (for example at 2.796 μ m); Ho:YAG laser instrument (for example at 2.1 μ m); Free electron laser (for example in the scope of 6～7 μ m); Quantum cascade laser (for example in the scope of 3～5 μ m).

In some specific embodiments, photon crystal fiber guide can have the radiation of very high power density in order to guiding.For example, available waveguide conduct power density is greater than about 100W/cm ²Radiation (for example greater than about 300W/cm ², 500W/cm ², 1kW/cm ², 10kW/cm according to appointment ²Or it is higher).Because the absorptivity of the radiation that guides is low in the axle center, so the waveguide in hollow axle center is particularly suitable for this application.By selecting material, can further reduce absorption loss so that the restricted area of waveguide has low absorptivity under the wavelength that is guided.As previously mentioned, for example the absorptivity of chalcogenide glass under infrared wavelength is low, thereby is suitable for the Infrared High-Power waveguide.Radiation loss not only reduces the performance of waveguide, also can make waveguide produce damage, and the material of selecting to have high index-contrast also can reduce radiation loss as restricted area.

Be coupled in the optical fiber by the radiation that high power laser is produced, can in fibre-optic waveguide, produce high power density.For example, the radiation available photon crystal optical fibre waveguide of all device of high power infrared laser as the aforementioned generations is guided.The output power of laser instrument can be greater than about 1W (for example about 5W, 10W, 25W or higher).In some applications, the output of laser instrument energy can be greater than about 100W, as several hectowatts (for example being higher than about 200W, 300W, 500W, 1kW).

In some specific embodiments, photon crystal fiber guide has relatively low loss.For example loss can be lower than about 2dB/m (for example being lower than about 1dB/m, 0.5dB/m, as 0.2dB/m or lower).Fibre-optic waveguide can have the low transmission loss under infrared wavelength, be about 3～5 μ m (for example about 3.5 μ m) or about 10～12 μ m (for example about 10.6 μ m) as wavelength.Compare with the TIR optical fibers of being made by similar material, loss can be quite low (for example low 1～3 or more a plurality of order of magnitude).For example, the photon crystal fiber guide with hollow axle center and chalcogenide glass/polymkeric substance restricted area is compared with the TIR optical fiber with chalcogenide glass axle center and polymkeric substance cladding layer and can be had quite low loss.For example it is said As ₂Se ₃Loss under the wavelength of 10.6 μ m is about 7～10dB/m, and the loss of PES under the wavelength of 10.6 μ m is about 100,000dB/m.As a comparison, has As ₂Se ₃The loss of the photon crystal fiber guide of/PES restricted area can be less than about 1dB/m.Because it is short that the electromagnetic wave that is guided enters the penetration depth of optical fiber restricted area, so can produce quite low loss.Therefore, even the material in the restricted area can have higher relatively absorptivity under the wavelength that is guided, the radiation that is guided and the interaction of storeroom also are minimum.

Turn owing to exist in the optical fiber, photon crystal fiber guide also can have relatively low loss.For example, radius-of-curvature is to turn less than 90 degree of about 10cm (for example less than about 5cm, as 4cm or littler), and producible loss is lower than about 2dB (for example 1.5dB, 1dB, 0.5dB or lower).If the relative intensity of signal of transmission preferably in use be can't help the bending of optical fiber sizable variation is taken place, then relevant with bending relatively low loss is favourable in a lot of fiber optic applications.

Low transmission loss (for example inherent loss and/or the loss that caused by bending) also has typical advantage in high-power applications, if along the power attenuation of fiber lengths except making the power that transmits to its destination by radiation source lower, also can cause damage to optical fiber.

Embodiment

Multiple optical fiber is by utilizing thermal evaporation one 5～10 thick As of μ m of deposition on the thick PES film of one 25～50 μ m ₂Se ₃Layer is rolled the film through applying and made around the hollow glass plug then.On this pipe, apply thick outer PES, and under vacuum, merge by heating.After the merging, introduce hydrofluorite in the heart and this plug is eroded at the quill shaft of plug.Corrosion process provides the prefabricated rods of layering, each prefabricated rods is placed in the optical fibers stretching tower, and is drawn into tens meters optical fiber to hundreds of rice.

The nominal position of each optical fiber photon band gap is to determine by the external diameter (OD) of optical fiber in the monitoring drawing process.The position of photon band gap is determined that by extensibility extensibility is the measurement acquisition by OD.The typical standard deviation of optical fiber OD is about 1% of OD.

With reference to Fig. 4 A and 4B, a kind of scanning electron microscopy of cross section of optic fibre (SEM) the analysis showed that the optical fiber of drawn keeps proportional layer thickness ratios usually, and PES and As ₂Se ₃Film bonds together in thermal cycle relevant with manufacture method and elongation process well.In the sandwich construction shown in Fig. 4 A and the 4B, the thickness of PES layer (ash) is about 900nm, and As ₂Se ₃The thickness of layer (bright) is about 270nm and (removes first and last As ₂Se ₃The thickness of layer is 135nm).

The band optical fiber transmission spectrum records with fourier-transform infrared (FTIR) spectrometer (NicoletMagna 860), utilizes a paraboloidal mirror that light is coupled in optical fiber and the outer locator.Have two kinds of different layers structures optical fiber these measurement results as shown in Figure 5.For every spectrum, light is guided in basic mode and the higher mode photon band gap.

The diameter in the hollow axle center of some made optical fiber is preferably 700～750 μ m, and OD is 1300～1400 μ m, and the basic mode photon band gap is crossed over the wavelength mode of 10～11 μ m.Fig. 6 A is depicted as the wherein FTIR transmission spectrum of an optical fiber, utilizes the fine cross section of the long direct light of about 30cm to record.

For quantizing the loss in these optical fiber, adopt the optical fiber intercept method to measure.These measurements relate to the intensity of transmission radiation by the long direct light fibre of about 4m and the comparison (referring to Fig. 6 B) of the intensity in the same fibre cross section of propagate radiation by being cut into shorter length.This test is to implement on a plurality of cross sections of optical fiber, and the result of different measured sections is approximate identical.Utilize the CO of 25W ₂(the 818T-10 type Newport) is implemented to measure for laser instrument (GEM-25 type, Coherent-DEOS company) and high-power detector.Optical fiber keeps straight line, and a plurality of points between two ends and optical fiber end points are protected, to reduce the variation of input coupling and transmission conditions in the fiber cut process.The guided laser bundle is the aperture of 500 μ m by the diameter that condenser lens and enter before the optical fiber.In addition, with the input end face of optical fiber with metal film coated with reducing the unexpected damage from laser that causes by dislocation.

Record that the loss in the optical fiber basic mode band gap is about 0.95dB/m under the wavelength of about 10.6 μ m, shown in Fig. 6 B, the uncertainty of measurement of estimation is about 0.15dB/m.The band gap mid point shows at the bending analysis (discussing in the back) of about 10.6 μ m optical fiber, is the 90 degree bendings of 4～10cm for radius-of-curvature, and bending loss is less than about 1.5dB/m.

Utilize FTIR source, a broadband and a CO in 10.6 μ m work ₂Laser instrument is measured bending loss.For each measurement, with the metal cylinder crooked an angle of 90 degrees of optical fiber around different radii.The crooked amount of optical fiber afterwards is about 15cm under every kind of situation.Under every kind of situation, this part keeps straight line.Figure 7 shows that long straight line optical fiber of the about 50cm that utilizes the FTIR spectrometer to record and relative intensity with same fibre of different curvature radius.

The FTIR flexural measurement as shown in Figure 7, for the bending of maximum radius, total bending loss numerical value is less than 1dB.For confirming this result, use CO ₂Laser instrument uses the long fiber lengths of about 2.5m to implement similar test.Figure 8 shows that crooked for 90 degree is the average bending loss of unit, wherein CO with dB ₂Laser instrument does not carry out benchmark by there being crooked fiber lengths.

CO ₂The result of laser instrument bending loss is repeatedly the mean value of test, and the level that is changed to about 0.2dB that records loss is inferior.Use CO ₂The result of laser instrument gained compares with result with FTIR equipment gained has identical qualitative features.Notice that used not homology has different coherences, numerical aperture and polarization state.Therefore they should be coupled to pattern with different loss character.

From CO ₂The highest laser power density that laser instrument is coupled in the optical fiber is about 300W/m ², this is enough to paper and PES film (principal ingredient of optical fiber) are burnt.When radiation suitably is coupled in the axle center of hollow optic fibre, then can not observe infringement to optical fiber.Utilize a helium-neon laser calibration CO ₂Laser instrument (GEM-25 type, Coherent-DEOS company).Use helium-neon laser to follow the tracks of CO ₂The path of laser instrument makes the laser calibration of this equipment with relatively low power.Between optical fiber and laser instrument, place a ZnSe optical splitter, so that reference beam separates.Before in being coupled to optical fiber, the light beam that is transmitted by optical splitter passes an aperture by lens subassembly focusing.The Newport binary channels power meter that use has a GPIB/Labview computer software interface is simultaneously from the output image data of the reference beam and the optical fiber of optical splitter.

In the intercept method measuring process, optical fiber utilizes cutter to cut the effect fast shut-off, produces quite reproducible otch.In order to explain that any residue in the cutting process changes, all short fiber sections occur near being recorded in each data point of blocking shown in Fig. 6 B in the measurement data.Though abandoned the data of tangible poor fiber segment, power grade does not significantly change because of fiber segment.The mean value that records data from every part has just constituted the data on the curve of Fig. 6 B.In addition, the power ratio of transmitting beam of measuring after each fiber segment and reference beam is the mean value in a few minutes.

By changing CO ₂Laser instrument keeps the input coupling condition in the long straight line optical fiber of the about 4m with the about 700 μ m axle center of diameter of straight line on paper, also can observe the output pattern of different mode in the optical fiber.Utilize be imaged on optical fiber in the observing pattern output pattern of Spiricon Pyrocam III by output beam.The imaging of different mode pattern shows that fiber work is (for example optical fiber has about 10 or bootmode still less) under the state of less relatively pattern.

Additional embodiment

A lot of specific embodiments of the present invention has been described.Yet be interpreted as, the spirit and scope of the present invention can not be left in different modifications.Therefore, other specific embodiments is in the scope of following claim.

Claims

CLAIMS 1. An article comprising a high power, low loss fiber optic waveguide comprising alternating layers of different dielectric materials including polymers and glass extending along the axis of the waveguide around a core.

2. The article of claim 1, wherein the alternating layers define a helical structure.

3. The article of claim 2, wherein said helical structure comprises a multilayer structure comprising at least two layers of different materials with multiple turns around the axis.

4. The article of claim 1, wherein the different materials comprise a high refractive index dielectric material and a low refractive index dielectric material, and wherein the difference between the high refractive index material and the low refractive index material is The ratio is greater than 1.5.

5. The article of claim 1, wherein the different materials comprise a high-refractive index dielectric material and a low-refractive-index dielectric material, and wherein the difference between the high-refractive index material and the low-refractive index material is The ratio is greater than 1.8.

6. The article of claim 1, wherein the glass comprises chalcogenide glass.

7. The article _of claim 6, wherein the chalcogenide glass comprises _As2Se3 .

8. The article of claim 6, wherein the polymer comprises PES or PEI.

9. The article of claim 1, wherein the innermost layer of alternating layers has a thickness that is less than subsequent layers of the same material.

10. The article of claim 1, wherein the thicknesses of the alternating layers are selected to direct electromagnetic radiation having a wavelength of about 10.6 μm to propagate along the waveguide axis.

11. The article of claim 1, wherein the thicknesses of the alternating layers are selected to direct electromagnetic radiation having a wavelength in the range of about 8-12 [mu]m along the waveguide axis.

12. The article of claim 1, wherein the thicknesses of the alternating layers are selected to direct electromagnetic radiation having a wavelength in the range of about 2-5 [mu]m along the waveguide axis.

13. The article of claim 1, wherein the shaft is hollow.

14. The article of claim 1, wherein the fiber optic waveguide has a transmission loss of less than about 1 dB/m at the selected wavelength for a linear length of the fiber optic waveguide.

15. The article of claim 14, wherein the selected wavelength is in the range of about 0.75 to about 10.6 μm.

16. The article of claim 15, wherein the selected wavelength is about 10.6 μm.

17. The article of claim 1, wherein the fiber optic waveguide has a transmission loss of less than about 1.5 dB at the selected wavelength when the fiber optic waveguide is bent around a 90 degree turn with a radius of curvature in the range of about 4 to 10 cm.

18. The article of claim 17, wherein the selected wavelength is in the range of about 0.75 to about 10.6 μm.

19. The article of claim 18, wherein the selected wavelength is about 10.6 μm.

20. The article of claim 1, wherein the fiber optic waveguide is capable of directing electromagnetic radiation along a waveguide axis at a power density greater than or equal to about 300 W/ ^cm2 for a selected wavelength.

21. The article of claim 20, wherein the selected wavelength is in the range of about 0.75 to about 10.6 μm.

22. The article of claim 21, wherein the selected wavelength is about 10.6 μm.

23. The article of claim 20, wherein the fiber optic waveguide is capable of greater than or equal to about 300 W/cm for selected wavelengths even when the fiber optic waveguide is smoothly bent around a 90 degree turn with a bend length of at least 0.3 m A power density of ² directs electromagnetic radiation to propagate along the waveguide axis.

24. The article of claim 1, wherein the fiber optic waveguide is capable of directing electromagnetic radiation along a waveguide axis at a power greater than or equal to about 25 W for a selected wavelength.

25. The article of claim 24, wherein the selected wavelength is in the range of about 0.75 to about 10.6 μm.

26. The article of claim 24, wherein the selected wavelength is about 10.6 μm.