CN106062600A - Various novel multi-wavelength multiplexers, and novel multi-wavelength light sources using multiplexers - Google Patents

Abstract

The present invention pertains to:a small multiplexer with which it is possible to achieve higher environmental resistance and higher light efficiency as well as low-cost mass production when used in a laser projector for a mobile telephone and in-vehicle use, wherein the multiplexer multiplexes light beams of a plurality of red, green, blue, or near-infrared wavelengths; and a light source using the multiplexer. The present invention makes it possible to produce at low cost the following: multiplexers which have a hollow light guide of claim 1 or a bundle fiber having a thin cladding diameter of 10 mum or less of claim 4, which are not affected by beam vertical and horizontal modes of wavelength and wavelength bandwidth, and with which it is possible to solve the aforementioned problems of improving environmental resistance, light efficiency, productivity, and the like; and multi-wavelength small laser light sources which, with the combined use of the multiplexer and a surface mount chip-type LD, can be realized on a practical level as a fiber output type of claim 3, a thin chip type for LD surface mounting of claim 5, and an outer cylindrical or square type for LD three-dimensional mounting of claim 6.

Description

Various novel multi-wavelength wave combiners and novel multi-wavelength light source using wave combiners

Technical Field

The present invention relates to a light source technology of three primary colors RGB (R, G, and B) used for medical diagnosis and treatment using light, optical communication, MEMS or DMD based scanning type or LCOS based projection type projectors, such as image processing devices, endoscopes, and ophthalmic devices.

Background

In conventional optical communications, an Arrayed Waveguide Grating (AWG) is often used in a multiplexer based on optical fiber wavelength division multiplexing (patent document 1). Recently, in order to use a projector type compact laser display for mobile phones and vehicle-mounted applications, a compact waveguide type RGB three-wavelength multiplexer has also appeared (patent document 2). Further, there are an optical fiber output and a filter type RGB combiner which are low in cost and high in coupling efficiency (patent document 3).

Documents of the prior art

Patent document 1: japanese patent laid-open No. 2005-234245

Patent document 2: japanese patent laid-open publication No. 2013-195603

Patent document 3: japanese patent laid-open No. 2013-228651

Disclosure of Invention

Technical problem to be solved by the invention

Although various multi-wavelength combiners can be produced according to the above-described conventional techniques, in applications other than optical communications, for example, in apparatuses and devices such as projection type projectors using laser light, the following conditions and limitations are imposed on the operation of these conventional combiners in terms of general evaluation criteria, such as optical loss, wavelength band, transverse mode of light beam, productivity, and cost.

Conventionally, optical loss is not negligible including optical coupling efficiency from a light source to a combiner, loss of a combining optical system inside the combiner, and optical transmission loss inside the combiner, and such optical loss increases as the number of combined wavelengths and the number of light sources increase.

In addition, the conventional wave-combining technology depends greatly on the transverse modes of incident and outgoing light beams, regardless of whether the light source is an LD or an LED, and regardless of whether the component on the wave-combiner side is an optical fiber or a waveguide.

In addition, in the conventional multiplexer, the wavelength of each light to be multiplexed is multiplexed based on the wavelength difference, and a transmission or reflection type filter or a diffraction element based on the wavelength is used. On the other hand, when a waveguide-type or optical fiber-type multiplexer is used, the confinement of light in the waveguide or optical fiber is performed by the refractive index difference between the core and the cladding material, and thus, it is also related to the transverse mode of the confined light. Because of their wavelength dependence, a light source of 200nm or more and within 1600nm for a sensor is applied to the blue-green-red wavelength of the three primary colors used for projection television display, and the bandwidth of a light source such as an LD is extended to 1200nm, which has not been able to be handled by conventional optical fiber or waveguide technologies at all. That is, most of the existing combiners have wavelength dependence and beam transverse mode dependence.

In summary, the existing problems of the optical loss of the combiner, and the limitations and dependencies on the transverse mode, wavelength and wavelength bandwidth of the light beam are the main technical problems to be solved by the present invention.

There is a demand for mass production of projection televisions, particularly for vehicle-mounted and mobile phone applications, and there is a need for a production method of a multiplexer that can satisfy the above requirements, such as productivity and product reliability due to the semiconductor process technology, low cost and high performance, and a very small product such as a chip type.

Technical scheme for solving technical problem

One of the main technical problems to be solved by the present invention is the wavelength dependence of the light combined by the existing combiner and the transverse mode dependence of the combined light beam. First, as a method for solving these problems, a hollow light guide having no wavelength dependence in the multiplexer according to claim 1 of the present invention can be used as a medium for transmitting light. As another method for solving these problems, a reflection film made of metal or the like which is hardly dependent on the wavelength is attached to the inner wall surface of the light guide according to claim 1, thereby confining the light beam in the light guide regardless of the wavelength of the incident light. In addition, the light beam transmitted through the light guide can be confined in the light guide by reflection of the film attached to the side surface of the light guide regardless of the transverse mode, that is, regardless of the beam diameter and the beam divergence angle, and thus the dependence of the combiner on the beam transverse mode can be solved by the above-described methods.

In the combiner of claim 4, as a method for solving the above problems, a bundle-shaped optical fiber is used, and the type of each bare optical fiber to be bundled is individually selected on the basis of the wavelength characteristics and the transverse mode characteristics of the light beam of each incident light source, so that the wavelength and the bandwidth of the light source to be combined and the transverse mode of the light beam are not affected by the limiting factors.

Therefore, the combiner manufactured by using the components of the hollow light guide according to claim 2 and the bundle-shaped optical fiber according to claim 4 as technical means can be applied to an LD in a single transverse mode, or a surface light source such as an LED including a higher order mode, and has little dependence on wavelength from ultraviolet to near infrared or wavelength bandwidth.

Further, the problems of the total light efficiency of the combiner include, specifically, improvement of coupling efficiency of incident light beams in the combiner, improvement of combining efficiency of an optical system used when a plurality of light beams incident into the combiner are coupled into one light beam, and overcoming of transmission loss and emission end loss of light in the combiner. The combiner of claim 1, wherein a hollow light guide is used as a means for increasing light efficiency. First, since the hollow light guide is hollow, there is no light absorption, and since a thin film having a high reflectance is attached to the inner wall of the hollow light guide, light can be sealed well, and transmission loss is small. And the shape of the incident end of the light guide can be designed according to the characteristics of the incident light beam, so that the coupling efficiency of the incident light is improved. In the bundle-type optical fiber combiner according to claim 4, since the optical fibers are individually selected according to the wavelength and the beam characteristic of each incident light source, the maximum coupling efficiency can be obtained by the method with the most suitable coupling method for each incident light. Further, since the light coupled to each optical fiber is directly coupled to the output end and output, there is almost no loss in the multiplexer main body except for the loss at the time of coupling the incident light at the input end.

In order to solve the problem of mass production with high reliability, downsizing and low cost, a method for manufacturing a hollow light guide of a combiner according to claim 1, that is, a method for manufacturing a combiner by bonding a substrate having a groove with a reflective film and a cover plate with a reflective film according to claim 2 of the present invention can solve the problem. That is, if the substrate according to claim 2 is made of a general material such as silicon or glass, the light guide groove according to claim 2 can be easily formed with high accuracy by using an etching device for semiconductor processes or a laser beam direct forming device. Further, the metal or dielectric thin film can be coated on both side surfaces and the bottom surface of the groove for light guide engraved on the substrate of claim 2 by plating or evaporation methods such as PVD (Physical Vapor Deposition) and CVD (Chemical Vapor Deposition). The above-described manufacturing method enables mass production at low cost, as in the manufacture of semiconductor components. The method for manufacturing the combiner according to claim 4 by using a bundle fiber is also a method capable of mass production at low cost. Further, according to the multiwavelength light source of any of claims 5 and 6 of the present invention, since the combiner which is low in cost, highly reliable, and mass-producible as described in claims 1 and 4 can be used as a component, and can be independently prepared from the original plurality of N light sources, mass production can be performed at low cost and high reliability in both management and production.

Effects of the invention

The use of a hollow light guide having no wavelength dependence as claimed in claim 1, thereby enabling the multiplexing of multiple wavelengths of light over a wide bandwidth of 1000nm or more from ultraviolet to visible and near infrared. The combiner according to claim 4 is applicable to a wide bandwidth from ultraviolet to near infrared as long as it is in a transmission band of bare glass of an optical fiber because a bundle-shaped optical fiber is used. That is, the two kinds of wave combiners according to claims 1 and 4 of the present invention are almost independent of wavelength and wavelength bandwidth, and have excellent effects in wavelength characteristics.

In addition, since the hollow light guide according to claim 1 can block light almost independently of the divergence angle of an input light beam by the reflection film attached to each side surface with respect to the light transmission direction, the LED of high order multiple transverse modes from the LD of single transverse mode to the surface light source can combine light sources of each wavelength and each transverse mode according to each application almost independently of the transverse mode of the light beam. The bundled optical fiber according to claim 4 can also select the type of each bare optical fiber according to the characteristics of each transverse mode of the incident light source beam. That is, the two wave combiners of claims 1 and 4 of the present invention have excellent applicability in the transverse mode of the incident light source beam.

In view of the basic structure, the optical waveguide according to claim 1 or the bundle-shaped optical fiber according to claim 4 has almost no loss and the efficiency of the combiner main body approaches 100% because the incident light is directly coupled from the light receiving end face to the light emitting end and emitted from the light source of each combined wave without passing through other members. Especially, when the light source is a single transverse mode LD, the total light efficiency from the light exit to the output of the combiner can reach 70% when the combiner of claim 1 is used, and can reach more than 90% when the combiner of claim 4 is used, and the efficiency improvement effect is very significant. In addition, since the two types of wave combiners are made compact, the transmission path of light inside the wave combiner is directly connected between the incident end and the exit end and has a very short distance as described above, and thus spatial coherence of light beams can be maintained to the maximum extent during transmission.

Further, the two types of multiplexers according to claims 1 and 4, which are indispensable key components of a multi-wavelength light source manufactured from the above multi-wavelength multi-surface mount LD light source, have an effect of improving product reliability and practicality because they are compact and thin chip types.

The combiner according to claim 1 can be mass-produced at low cost by using the semiconductor manufacturing method such as etching of the hollow light guide groove and vapor deposition of the reflective film according to claim 2. Further, the chip-type multiplexer using the bundled optical fiber according to claim 4 can be significantly reduced in cost as compared with a conventional waveguide-type or filter-type multiplexer. The two wave combiners of claims 1 and 4 of the present invention are also effective in mass productivity and cost as key components of the multiwavelength light source.

Further, according to claim 3, a multi-wavelength light source of an optical fiber output can be realized by a compact thin chip type combiner. In the case of the glasses-type and vehicle-mounted head-up display type projectors, since the light source transmits light through an optical fiber, the light source and the display device can be separately provided. For example, in a glasses type projector, a light source and a driving power source are placed in a pocket, light is connected through an optical fiber, and only a projector optical system is placed on glasses, so that it is possible to achieve weight reduction and size reduction. In the case of vehicle-mounted use, since the temperature change in the vehicle interior is large as the placement position of the head-up display projector, the operation condition of the device needs to satisfy a temperature range of minus 30 ℃ to minus plus 90 ℃, and it is very difficult to operate the LD light source in such a large temperature range, and by using an optical fiber multiplexer, the RGB three-wavelength LD and a driver are placed in another place where temperature management is easy, and only the optical system is placed in the head-up display projector that transmits light through the optical fiber, and it is possible to withstand an extremely cold or hot environment. When the multiplexer according to the present invention is used in the above-described application fields, it is possible to provide great convenience in manufacturing various devices. Further, the surface mount LD chip according to claim 6 is three-dimensionally mounted to improve heat dissipation, and is formed into a cylindrical shape of about Φ 3mm to Φ 6mm or a cubic rod shape of 3mm to 5mm, and has mountability and can be miniaturized as a multiwavelength laser light source used for Wearable (Wearable) electronic devices.

Drawings

Fig. 1 is a conceptual diagram of the multiplexer structure of claim 1 using N incident and 1 exiting hollow light guides fabricated according to the method of claim 2. The upper layer is a cover plate with a light reflection film attached to the lower surface, the lower layer is a substrate engraved with N +1 grooves for light guide, and the side surfaces and the bottom surface of the grooves are covered with light reflection films. By bonding the two, N incident and 1 outgoing light guides, i.e., N +1 light guides, are formed. The light beams of the respective wavelengths input into the incident light guide are closed before reaching the output end of the exit light guide by the total reflection film of light additionally coated on the lower surface of the cover plate and the respective side surfaces and bottom surfaces of the N +1 grooves for light guide.

Fig. 2 is a diagram showing a cross-sectional structure of a light guide of a combiner manufactured by grooving a substrate as set forth in claim 2, that is, a pattern of forming an incident light guide and an exit light guide on the substrate, in example 1. In fig. 2, the image is enlarged for clarity of the structure of the grooves and the coupling portions for the light guides, but is not drawn to scale. In the single transverse mode LD, the incident and exit light guides of the combiner formed from the substrate and the external dimensions thereof will be described in detail in example 1 below.

Fig. 3 is a spatial combiner of 3-to-1 beams in embodiment 2, using the bundle-shaped optical fiber of claim 4 with a plurality of N-3 beams as input and output.

Fig. 4 is a photomicrograph of the exit end face of 3 optical fibers bundled in a bore of 25 μm inner diameter at the center of a ferrule attached to the output end of the combiner of fig. 3, the 3 optical fibers having a cladding diameter of Φ 10 μ.

Fig. 5 shows a compact thin chip type RGB laser light source in example 2, in which 3 pairs of 1 s shown in fig. 3 are used as the multiplexer, and light sources on the input side of the multiplexer are RGB three-wavelength single transverse mode surface mount type LDs of 638nm, 520nm, and 450 nm.

Fig. 6 is a three-dimensional CAD design drawing showing the configuration of an RGB light source of a cylindrical shape as an example of embodiment 3. In the figure, three surface mount LDs are three-dimensionally mounted in a circle-symmetric manner, and the bundle-shaped optical fiber type 3-to-1 combiner according to claim 4 is used.

Fig. 7 is a three-dimensional CAD design drawing showing a structure of a multiwavelength light source for three-dimensionally mounting an LD, which is another example of embodiment 3. The right part of the figure shows four wavelength light sources of RGB and NIR having a square-bar shape in external form, four surface mount LDs are installed on the faces around the cube in a centrosymmetric manner, and the 4-to-1 combiner uses the bundle-shaped optical fiber type combiner according to claim 4. In addition, the square rod-shaped light source (light source assembled by the parts 711-732 in the figure) on the right side in the figure is placed in a cylindrical metal shell (740 in the figure) which is positioned on the left side in the figure and has the functions of heat dissipation and protection, and the external shape can be changed into a cylinder.

FIG. 8 is a photograph of the outer shape of the test articles of examples 3 and 4. The left photograph 801 is a cylindrical RGB three-wavelength LD light source described in example 3, and the right photograph 802 is an RGB three-wavelength light source using a fiber output type multiplexer in the light guide described in claim 3 as example 4.

Detailed Description

Example 1

Fig. 1 schematically shows the structure of a combiner of hollow light guides according to claim 1, which is manufactured by the method according to claim 2 of the present invention. The detailed shapes and dimensions of the input and output light guides and the coupling portions shown in the figures vary depending on the difference in the transverse modes of the input light source and the associated output side light beam. In addition, the dimensions of the light guide in fig. 1 are not shown to scale with the substrate dimensions, but are shown arbitrarily enlarged for clarity of the basic parts of the respective configurations.

First, the method of forming a hollow light guide according to claim 2 of the present invention is shown in fig. 2 by using a 3-to-1 three-wavelength multiplexer for a single transverse mode LD having a wavelength RGB (red, green, blue). The method for manufacturing light guides by grooving a substrate according to claim 2, wherein 4 grooves in total of 3 input sides and 1 output side on the substrate of fig. 2 form the hollow portions of the light transmission medium of these hollow type light guides. That is, the shape of each groove on the substrate shown in fig. 2 is the shape of the actual light guide itself, and is also the formation pattern of the light guide of the multiplexer. Since the light source in this example is an RGB single transverse mode LD, the cross section of each light guide of the multiplexer, that is, the cross sectional shape of the groove on the substrate is an extremely fine square of about several micrometers (μm) designed in accordance with practical levels. The dimensions of the grooves in fig. 2 are not shown to scale with the substrate dimensions, but are arbitrarily enlarged to show the detailed shape of these light guides.

The light source in this embodiment 1 has three wavelengths of red 660nm, green 520nm, and blue 450nm, and is a high-brightness single-transverse-mode LD. Typical beam characteristics are a spot width on the fast axis fa (fast axis) of 25 ° divergence Angle FAHM (full Angle at Half maximum), about 1.5 μ M, a spot width on the slow axis sa (slow axis) of 10 ° FAHM, about 5 μ M, and a beam quality factor M Λ 2 of about 1.2.

According to the invention of claim 1, in this example, N is 3, the number of light guides is 3 incident lights N, 1 outgoing light, and 4 in total, and 1 outgoing light is merged with 1 of the 3 incident lights with red wavelength, so that fig. 2 only looks like 3 light guides of three RGB wavelengths.

First, when light is directly coupled between the LD and the light guide without using a lens, the cross-sectional shapes perpendicular to the light transmission direction of the light guide shown in fig. 2 were all 6.5 ± 0.5 μm in the lateral direction (width direction of the groove in fig. 2) and 3.5 ± 0.5 μm in the longitudinal direction (depth direction of the groove), and test pieces were produced based on these values. At this time, the light efficiency of the combiner was examined using 3 single transverse mode LDs of three colors of RGB. By first placing the LDs FA and SA in the longitudinal and transverse directions of the combiner of this example, and then aligning the light emitting points of the LDs with the center positions of the light receiving surfaces of the light guides on the input side of the combiner of this example in both the longitudinal and transverse directions, and aligning the light emitting points with the light receiving surfaces at a distance of about 5 μm in the optical axis direction, the total efficiency of light can be obtained at a ratio of 75% red, 71% green, and 68% blue from the exit of the output side of the combiner of this example, compared to the original output of the LDs. The outgoing light beam emitted by the wave combiner has a value of M & lt2 & gt ═ 1.6 or so, which is much better than the expected value of M & lt2 & gt, 2.1. This result can be obtained because the combiner in this example is a small-sized combiner, and the optical path length of the light guide is only about several mm from the entrance to the exit, and the light beam does not completely diffuse to the desired higher-order transverse mode.

When a light beam is shaped into a substantially square shape and coupled to a combiner by using a cylindrical lens having a magnification of 1 to 2.5 in the FA direction and a magnification of 1 to 1 in the SA direction between the LD and the light guides, the cross-sectional shape of each of the RGB light guides is also adjusted to a square shape of 5 μm in both the lateral direction and the longitudinal direction at the incident side of the combiner in accordance with the shape of the incident light beam. The output of the RGB light source using the combiner is a single transverse mode light beam with M & lt2 & gt & lt1.3, and the comprehensive light efficiency of about 90% is obtained.

In example 1, a process was employed in which a photoresist was applied to the upper surface of a silicon wafer substrate having a thickness of about 1mm or less, trenches having the cross-sectional shapes described above were formed by a dry etching method, and then a gold thin film was deposited on the side surfaces and the bottom surface of the trenches. Fig. 2 is not to scale with the actual size, and the multiplexer in this example has 3 light guides arranged transversely on the incident side with a gap of 1.5mm between each other, and has a length direction of 5mm, and is formed into a chip shape having a width W5mm × a length L5mm × a thickness t1.5mm or so. Then, the multiplexer was mounted in cooperation with the surface-mount RGB three-wavelength LD, and a light source was manufactured in a trial manner. The light source is output in a single transverse mode of three primary colors of RGB, the external shape is W5mm xL 8mm xT 2.5mm when the light source is directly coupled, the external shape is W5mm xL 12mm xT 2.8mm when the light source is coupled by using a lens, and the light source and the lens are both compact chip types.

Example 2

A chip-type multiplexer using a bundled optical fiber according to claim 4 of the present invention, which is suitable for use in a plurality of RGB three-wavelength single transverse mode LDs having N-3, is shown in the CAD drawing of fig. 3 as example 2. Further, the object of the present embodiment 2 is a chip-type light source of RGB three primary colors LD according to claim 5 of the present invention using the multiplexer, and the basic configuration of the light source is as shown in fig. 5.

If the bare optical fibers bundled by the combiner have a single transverse mode, that is, NA is 0.12 to 0.13 and core diameter Φ is 3.5 to 4.0 μm, the transverse mode of the primary light source LD is matched, and spatial coherence of the light beams output from the combiner is not disturbed. However, the commercially available single transverse mode optical fiber is not suitable for use in embodiment 2 because its cladding diameter is Φ 125 μm. The ideal bare optical fiber is a bare optical fiber with a core diameter of phi 4 μm and a cladding diameter of phi 6-8 μm, but the present invention is applied to make a combiner using an existing product of the bare optical fiber with NA of 0.2, a core diameter of phi 7 μm, and a cladding diameter of phi 10 μm according to the practical level. Single transverse mode bare fiber with cladding diameter less than 10 μm is still under development, and low melting point inorganic glass or plastic material is used.

Fig. 4 is a photomicrograph showing the emission end surfaces of 3 optical fibers bundled on the output side of the RGB three-wavelength single-transverse-mode combiner of example 2 configured in fig. 3. The distance between adjacent cores of 3 fibers bundled closely together in a delta shape of an equilateral triangle is about 10 μm. In the manufacturing method shown in the photograph of FIG. 4, since the end faces of the bundled 3 optical fibers were polished, 3 bare wires were inserted into a glass tube-shaped ferrule having a center with a small hole of about 25 μm and an outer diameter of 1mm, and fixed with an adhesive. On the input side of the combiner, the incident end faces of 3 optical fibers were arranged laterally at intervals of 2mm from each other. The RGB combiner of claim 4, wherein the width and length of the RGB combiner are 6mm and the thickness of the RGB combiner is about 2 mm.

At present, when the light coupling is directly performed between the LD and the optical fiber without a lens using the RGB three-wavelength chip-type light source using the above-mentioned bundle-type optical fiber combiner having NA0.2, core diameter Φ 7 μm bare wire, and N ═ 3, as shown in fig. 5, the external form thereof is 6mm wide, 8.5mm long, and 1.8mm thick, and the maximum optical coupling efficiency between the LD and the optical fiber of the combiner can be about 65%; when a coupling lens is used between the light source LD and the combiner, the coupling efficiency of light can be increased up to 85%, but the longitudinal direction of the outer shape thereof reaches 11 mm. At present, two end faces of the beam-shaped optical fiber for incidence and emergence are not attached with anti-reflection dielectric films, and if the anti-reflection dielectric films are attached, the light coupling efficiency can be further improved by more than 5%. Basically, the combiner in fig. 5 can be switched from the bundle fiber system according to claim 4 to the hollow optical waveguide system according to claim 1. The characteristics of both are almost the same as described above, and the manufactured RGB light source can also perform single transverse mode output with the same chip-type profile and the same level of coupling efficiency. That is, the RGB light source of claim 5 of the present invention shown in fig. 5, which is the subject matter of embodiment 2, covers the chip-type multiplexer of the two modes described in claims 1 and 4.

In example 2, the transverse mode characteristics of the RGB three-wavelength light beams emitted from the bundle fiber to the output side of the combiner were also examined. Trial calculation is carried out according to the diameter of the bare optical fiber inner core of 7 mu M and the NA of 0.2, and the numerical values of the quality factor M & ltlambada & gt 2 relevant to the transverse mode of the light beam are respectively as follows: the red wavelength was 3.5 at 638nm, the green wavelength was 4.2 at 520nm, and the blue wavelength was 4.9 at 450nm, and the measured values were all 2 or less in red, green, and blue, which are almost close to a single transverse mode. The reason for this is that the length of the bare optical fiber of the combiner in this example is about 6mm, the transmission distance of the light beam in the optical fiber is extremely short, the effect of mixing the higher-order mode is not yet prominent, and the transverse mode of the input light beam reaches the output end without being disturbed.

Further, the coaxiality of the RGB three-wavelength light beams emitted from the light source in example 2 was examined, and a colorless (achromatic) lens having a focal length of 20mm was placed at the exit of the bundle-shaped optical fiber, and the beam diameter at 1m front was calibrated to be the minimum, and the beam spot diameters (FWHM) of the three beams of R, G, and B, which were finally measured, were about Φ 0.5mm or less. Further, the three light beams having three wavelengths are spaced apart from each other by about 0.5mm within a concentric circle of Φ 1.5mm, and therefore, from the practical level, they can be used as one light beam having three wavelengths.

From the above evaluation results, the outputs after using the combiner of example 2 were 135mW for 160mW output at 638nm red, 65mW output at 520nm green, and 62mW output at 450nm blue, respectively, as compared with the output light from the original LD, and the three-wavelength light beams emitted from the combiner fiber were almost all in the single transverse mode, and thus the requirements of high luminance and high output to be provided as projection type projectors for vehicles and mobile phones were satisfied.

Example 3

Since the RGB multiwavelength light sources of embodiments 1 and 2 described above are mounted in parallel with a plurality of LDs on the same plane capable of dissipating heat, even a plurality of surface-mounted LD chips with high output of 100mW or more per wavelength would have a significant problem of heat dissipation due to high current consumption and high-density mounting with extremely small size. The RGB light source of the present embodiment 3 is different from the above-described 2 embodiments in that a plurality of LD chips are mounted on one plane, and the surface mount type LD chip is used as well, but the RGB light source is three-dimensionally mounted by the method according to claim 6, and the external shape thereof is a cylindrical or polygonal bar-shaped three-dimensional shape. In the light source of this example, the plurality of LDs are three-dimensionally mounted in this manner, so that not only is the heat dissipation improved, but also the light source can be formed into a shape that is easy to mount for various applications by changing the outer shape to a cylindrical shape or the like.

As an example, the assembly principle and the structure of the RGB light source are shown in fig. 6, which is obtained by three-dimensionally mounting the chip-type LD, the coupling lens, and the bundle-shaped optical fiber combiner according to claim 4 in the method according to claim 6. Since the light source has a cylindrical shape, three light emitting points from the RGB LD which are three-dimensionally assembled inside a cylindrical metal case and three light receiving end surfaces from the 3 optical fibers which are positioned on the incident side of the combiner are aligned with each other in a manner of 1 to 1 of the light emitting points and the light receiving surfaces, and distributed in an equilateral triangle delta of the same size, and the light output from each of the three LDs is coupled to each of the 3 optical fibers by passing through each of the three optical fiber end surfaces using three coupling lenses. In this FIG. 6, a cylindrical shape with a length of 8mm and a diameter of 5.6mm was designed and trial-produced. If the optical fiber is directly coupled without using a lens, the size can be reduced to 4.8mm in diameter and 6mm in length.

Fig. 7 is an assembly configuration diagram of an assembly of visible RGB and near-infrared four-wavelength LD light source modules mounted in a square shape as another example. As in the example of fig. 6, 4 coupling lenses are used to couple 4-wavelength light beams emitted from four LDs in a three-dimensional distribution to a combiner of 4-to-1-bundle optical fibers in the same three-dimensional distribution. The square 4-color LD module (711-732 set in the figure) on the right side of FIG. 7 can be packaged in a cylindrical housing case (740 in the figure) with an outer diameter of phi 5mm and a length of 8mm on the left side. The left photograph in fig. 8 shows one of the prototype products of the RGB-NIR light source packaged in the past. The module has the size of 6mm outside diameter and 12mm length.

Example 4

Embodiment 4 is an RGB light source using the optical fiber type combiner in a light guide according to claim 3, as shown in the right photograph of fig. 8. Laser emitted by the pot-shaped single transverse mode RGB LD with phi 3.8 is coupled into the input side light guide of the wave combiner by using a lens, in addition, output light of the output light guide is also coupled onto 1 single transverse mode optical fiber by using the lens, and finally, the output of the optical fiber is about 60 percent of the output of the original LD.

The key point of the application device of the multi-wavelength LD light source using the combiner according to the embodiment 4 is the optical fiber output. The light transmission is performed between the light source including the LD and the output end of the optical fiber through the optical fiber, so that a desired light can be output to an application device at a place spaced apart from the light source, and the heat dissipation problem can be easily solved by separately placing only the light source main body alone. In the case of the above-described vehicle-mounted projector, even when the ambient temperature of the installation place of the head-up display type projector for outputting light is in a wide range of minus 35 ℃ to minus 90 ℃ or more, the RGB light source main body including the LD is placed alone, and thus the normal operation is possible. That is, such a light source is indispensable for the application in the vehicle.

Industrial applicability of the invention

The thin and compact chip type multiplexer according to claims 1 and 4 is used as a key component, and the mounting technique according to claim 5 is applied, so that a flat-surface mounting type thin and compact multi-wavelength light source can be manufactured, and the chip type multiplexer can be applied to a mobile phone or other wearable display device requiring miniaturization, for example, a laser projector using MEMS, DMD, LCOS, or the like.

Further, in the multiwavelength light source using the optical fiber output type multiplexer according to claim 4, since transmission is performed between the LD light source and the destination "projector" of light via an optical fiber, it is more easily endurable in severe temperature environments such as in-vehicle and field, and thus it is applicable to applications such as in-vehicle fields.

Further, in claim 6, since a plurality of multi-wavelength high-output LDs are three-dimensionally mounted together, and a cylindrical multi-wavelength light source having an outer diameter of Φ 5mm or less can be manufactured, it is possible to improve heat dissipation properties as well as to adopt an external shape that is easy to mount, and it is possible to use the multi-wavelength high-output LD in a wearable type laser display device such as a laser pen or a glasses type.

Further, in regard to the mounting of the small multi-wavelength laser light source, if various component parts of the combiner such as those described in claims 1 and 4 are used, the mounting can be divided into two major works, that is, the mounting work of the combiner itself by the mounting of each internal part and the mounting work of coupling the light emitted from each individual LD to the combiner, and therefore, particularly in mass production, the management and manufacturing are both easier to be performed than the mounting work involving a plurality of LDs in the past, and the reliability of the product can be improved while reducing the cost.

Description of the reference symbols

Relevant reference numbers of fig. 1:

110 the waveguide-grooved substrate of the combiner of claim 1

111 an upper surface of the substrate 110, the upper surface having grooves for light guide engraved thereon

112, N +1 grooves for light guide engraved on the surface 111, where N-1, …, and N denote the nth incident light guide and N-N +1 denotes the 1 outgoing light guide

113 incident and exiting light guide grooves, and metal thin films or dielectric thin films coated on the side surfaces and bottom surfaces thereof for totally reflecting light in order to block the light

120 and a cover plate attached to the upper surface of the substrate 110 for covering the light guide grooves

The lower surface of the cover plate 120 121, that is, the surface where the light guide grooves engraved on the upper surface 111 of the counter substrate 110 bonded to the surface are covered to form a light guide. In order to enclose the light in the formed light guide, the surface is coated with a metal or dielectric film that totally reflects the light

FIG. 2 associated reference numbers:

200 the output end of the channel for the outgoing light guide of the combiner of claim 1 fabricated by the method of claim 2

Input end of light beam of 1 st red wavelength incident light guide of a plurality of 201N-3

202 light beam input end of 2 nd blue wavelength incident light guide

203 beam input end of 3 rd green wavelength incident light guide

210 groove for exit light guide

211 st 1 st red wavelength light guide groove

212 groove for 2 nd blue wavelength incident light guide

213 groove for incident light guide of 3 rd green wavelength

222 incident and outgoing light guide coupling for 2 nd blue wavelength

The coupling of the 223 rd 3 green wavelength entrance and exit lightguides is in color

As shown in fig. 2, the 1 st red wavelength is a straight line from the input end 201 to the output end 200, that is, the input light guide 211 is directly connected to the output light guide 210 without a coupling portion, and the number of the two is 1.

FIG. 3 associated reference numbers:

300 the chip-type board with optical fibers fixed in the bundled optical fiber type combiner of claim 4

301 input side of a multiplexer

Output side of 302 wave combiner

310 outgoing ends of a plurality of N-3 optical fibers tightly bundled at the output side of the wave combiner

31i i ═ 1, 2, 3; incident end face of 3 optical fibers on input side of wave combiner

32j j ═ 1, 2, 3; 3 grooves on the chip template 300 for high-precision positioning and fixing of 3 optical fibers

Fig. 4 (photomicrograph) relevant reference numerals:

400 emission end face of ferrule bundled with optical fibers at output side of wave combiner shown in FIG. 3 after polishing

41i i is 1, 2, 3; the bare wires of 3 optical fibers with the cladding diameter of phi 10 mu m bundled on the end face of the ferrule are tightly bundled together in an equilateral triangle delta shape as can be seen from the photograph

Inner core of 421 optical fiber bare wire

Cladding of 422 optical fiber bare wire

430 micrograph, unit length 10 μm

FIG. 5 associated reference numbers:

501 Blue (Blue)450nm wavelength surface mounting COS type single transverse mode LD

502 Red (Red)638nm wavelength COS type single transverse mode LD

503 Green (Green)520nm wavelength COS type single transverse mode LD

504 RGB three-wavelength LD heat dissipation copper plate

505 the chip-type board with fixed optical fibers of the combiner of claim 1, wherein the combiner is composed of the board 505 and 3 bundle-type optical fibers 51i (i-B, R, G three-color)

In fig. 51i, three colors i-B, R, G are respectively arranged from the left, the input end of the combiner is a plurality of N-3 optical fibers which are installed in a 1-to-1 direct optical coupling manner with an RGB LD light source, in this embodiment 1, the sizes of the bare wires of the 3 optical fibers are core diameters Φ 7 μm and NA0.2, and the cladding diameter Φ 10 μm

The output side of 514 wave-combiner satisfies the condition of claim 1 and the output end face of a plurality of bundled N-3 optical fibers

FIG. 6 associated reference numbers:

611-i three color i-R, G, B surface mounting type COS type LD (3)

612-j three-color j-R, G, B LD electrodes (3 sets of cathode and anode, total 6)

613-k three-color k-R, G, B radiator for LD heat radiation (3 sets)

621-s coupling lens (3 sets) for optically coupling from LD of three colors(s) R, G, B to combiner

630 combiner body consisting of 3 bundled optical fibers 631-i (i ═ R, G, B)

631-t three bundled optical fibers of a combiner for receiving light from an LD having three colors t-R, G, B

The RGB three-color LD light source main body is composed of the right-hand components in the figure, such as the above-mentioned 611-i LD, 612-j LD electrode, 613-k heat sink, 621-s coupling lens, and 630 wave combiner, and is three-dimensionally mounted in the arrangement relationship in the figure to form one module.

Light beam exit port of 632 bundle optical fiber type wave combiner

640 an outer casing for accommodating the three-color RGB laser light source main body module on the right side of the figure, the outer casing having a cylindrical shape and a size of L8mm × Φ 5.6mm

Relevant reference numbers of fig. 7:

711-i four-color i-R, G, B, NIR near infrared surface mount COS type LD (4)

712a-j four-color j R, G, B, NIR + electrode of LD (4 anodes in total)

712b-j four colors j R, G, B, NIR of LD-electrode (4 cathodes in total)

713 Heat sink for Heat dissipation with four LDs of RGB and NIR bonded together

721-k four sets of coupling lenses coupled from four color k-R, G, B, NIR LDs to a combiner

730-beam optical fiber type 4-to-1 combiner body

731-s four bundle optical fibers of combiner for receiving light from four-color s-R, G, B, NIR LD

The light beam exit port of the bundled optical fiber type combiner of claim 732 claim 4

The RGB + NIR four-color LD light source main body is composed of the right-hand components in the drawings, such as the above-mentioned 711-i LD, 712a-j and 712b-j LD electrodes, 713 heat sink, 721-k coupling lens, 730 combiner, and the like, and is three-dimensionally mounted in the arrangement relationship in the drawings to form one module.

740 an outer case for accommodating a 4-color LD light source main body of RGB + NIR on the right side in the figure, the outer case having a cylindrical shape and a size of L8mm x phi 5mm

Fig. 8 (photo) related reference numerals:

801 photograph of prototype of cylindrical RGB three-wavelength light source module having LD stereoscopically mounted thereon according to example 3 of claim 6

802 photograph of a fiber optic output RGB three-wavelength light source module using a light guide type wave combiner according to embodiment 4 of claim 3

810 RGB three-wavelength light source main body mounted with LD, wave combiner and emergent optical fiber

811 green 520nm wavelength, Can-3.8 package, single transverse mode LD

812 red 638nm wavelength, Can-3.8 package, single transverse mode LD

813 blue 450nm wavelength, Can-3.8 package, single transverse mode LD

821 Single transverse mode fiber for coupling light beams emitted from RGB three-wavelength LD and outputting light from light source 810 to outside

822 optical fiber 821 and light of three RGB wavelengths output from the end face of the ferrule

Claims (6)

1. An N-to-1 optical multiplexer is characterized in that,

in order to combine N incident light beams incident from N incident light guides into which a plurality of N light beams are incident and output the combined light beams to 1 outgoing light guide, N (N is 1, 2, …, N) th light guides of the N incident light beams have N (N is 1, 2, …, N) th terminals as a terminal of a light advancing direction, N coupling parts provided to transfer and output N (N is 1, 2, …, N) th light beams of the N incident light beams from N (N is 1, 2, …, N) th terminals of the N light guides to the outgoing light guides are provided, and in order to combine all the N light beams incident from N incident end surfaces of the N light guides to the 1 outgoing light guide and output the combined light beams, N +1 light guides for transmitting the N incident light beams and the 1 outgoing light beams are formed by forming a hollow body, the entire surface of the inner side wall of the light guide is coated with a metal film or a dielectric film which can totally reflect light, so that the light guide has a structure which can completely seal and transmit light beams in the light guide, and the N lights which are incident into the N incident light guides are efficiently combined to the 1 emergent light guide to be output.

2. A method of fabricating the N +1 light guides on the N-to-1 combiner of claim 1,

in the N-to-1 combiner according to claim 1, as a basic element of the structure, for forming N +1 hollow incident and exit light guides coated with a reflective film, 1 sheet of a substrate made of silicon or metal, or ceramic or glass, or optical crystal is previously provided, patterns for forming the N coupling parts between the N incident light guides and the 1 exit light guides and between the incident and exit light guides are previously designed, grooves for the N +1 light guides are engraved along the patterns of the N +1 light guides formed with the N coupling parts in a depth direction from an upper surface of the substrate by wet etching or dry etching, or by beam fine processing using laser beams or ion beams depending on the substrate material, and the bottom surfaces and all surfaces of both side surfaces of the N +1 grooves for the light guides engraved by the method, coating a metal thin film or a dielectric thin film which totally reflects light is performed, a cover plate (made of the same material as the substrate as much as possible) which covers the N +1 grooves for light guide is provided by opening the upper side of the grooves for light guide engraved on the substrate, the metal thin film or the dielectric thin film which totally reflects light is coated on the lower surface of the cover plate, the upper surface of the substrate where the N +1 grooves for light guide in which the total reflection thin film is coated on the bottom surface and both side surfaces thereof manufactured by the method is aligned with the lower surface of the cover plate in which the total reflection thin film is coated manufactured by the method, and the cover plate is attached, so that the total reflection thin film which totally reflects light is attached to both the side surfaces and the bottom surface of the N +1 grooves for light guide of the substrate and the lower surface of the attached cover plate, that is, all the side surfaces as light guides in the light transmission, thereby enclosing light in the N +1 hollow type trenches.

3. An N-to-1 multiplexer, which is based on the hollow optical waveguide type N-to-1 basic multiplexer of claim 1, and which is interposed in an optical fiber and adopts any one of the following three types:

a type 1 multiplexer including N input light guides and 1 output optical fiber, and coupling output light from an output light guide of the multiplexer to 1 optical fiber provided in advance; or,

a type 2 multiplexer including N input optical fibers and 1 output optical guide, and directly coupling a light beam in a 1-to-1 manner or coupling the light beam using a lens between a plurality of N optical fibers provided in advance and N incident optical guides of the basic multiplexer; or,

the optical coupler includes N input optical fibers and 1 output optical fiber, and couples output light from an exit light guide of the preset type 2 multiplexer to the preset type 3 multiplexer having 1 optical fiber in the same manner as the type 1 multiplexer.

4. A chip type N-to-1 beam space combiner using bundled optical fibers is characterized in that,

for N spatially independent beams of light from a plurality of N point light sources or a plurality of N parallel light output lasers on the input side, in order to converge the optical axes thereof on the output side to become a point light source for multiplexing and outputting,

preparing a chip template 1 made of glass or metal in advance; and N bare optical fibers composed of an inner core and a cladding layer ground for guiding light to an incident end surface and an exit end surface, wherein light input sides and light output sides are arranged on both sides of the chip template, the incident ends of the N bare optical fibers are aligned with the incident positions of N light beams from the N light sources which are independent in space and are desired to be multiplexed along the edge of the input side of the chip template, are transversely arranged in a row at certain intervals and are fixed by an adhesive, and the exit ends of the N bare optical fibers are tightly bundled and fixed by the adhesive at the edge of the output side of the chip template,

the N point light sources or the N parallel light beams 1 are input to the incident end surfaces of the N bare optical fibers on the input side of the chip template by using an optical system such as a lens, so that the N light beams can be directly output from the emergent end surfaces of the N optical fibers bundled on the output side of the chip template as they are,

when the bare N optical fibers each composed of the core and the cladding are prepared in advance, the thickness of the cladding covering the core of the bare fiber is further reduced to a limit (for example, about 1 μm), that is, the outer diameter (that is, the cladding diameter) of the bare N optical fibers is made extremely small (for example, when the core diameter is Φ 4 μm or less in the case of a single transverse mode, and when the cladding thickness is 1 μm or less, the outer diameter of the bare fiber is Φ 6 μm or less),

thus, the N light beams outputted from the outgoing end faces of the N optical fibers, which usually look like N point light sources, are tightly bundled at the outgoing ends of the N optical fibers, and since the inner core and the inner core are very close to each other (when the cladding thickness is 1 μm or less, the interval between the two is 2 μm or less), the light beams are converged and outputted as one point light source, that is, the N light beams from the N spatially independent light sources are spatially combined into one light beam as one point light source at a practical level and outputted to the output end.

5. A multi-wavelength laser light source module is characterized in that,

the multiwavelength laser light source module is a thin and compact chip-type module, in order to manufacture a thin and compact chip-type multiwavelength light source, a plurality of N surface-mounting chip-type LDs are arranged in a row on a preset fixing frame for plane mounting, a plurality of N-to-1 wave combiners of a thin and compact chip type are arranged in advance according to any one method of a hollow light guide type of claim 1 or a bundle-shaped optical fiber type of claim 4, light is directly coupled or coupled by using a lens in a mode of 1 to 1 between the N LDs and N incident end faces for light receiving of the N hollow light guides or N bundle-shaped optical fibers of the wave combiner, and wave combination is carried out by the wave combiner to output as a point light source.

6. A multi-wavelength laser light source module is characterized in that,

in order to manufacture a compact multi-wavelength light source, easily dissipate heat of a plurality of LDs mounted at high density, and design the light source according to the external shape required for mounting application equipment,

a plurality of N chip-type LDs for surface mounting which are installed in a three-dimensional manner are arranged on a fixing frame which is arranged in advance and has a three-dimensional shape such as a cylindrical shape or a cubic shape and is easy to dissipate heat of the LD; and a plurality of N-to-1 combiners produced by the method according to any one of claim 1, wherein the chip LD for surface mounting is a thin chip type, and the plurality of N wavelengths are different from each other,

then, the light guide or the N incident end faces of the bundle-shaped optical fiber arranged in front of the incident side of the combiner for receiving the light emitted from the plurality of N LDs are arranged on the input side of the combiner body in the same three-dimensional distribution as the plurality of N LDs, and a plurality of N coupling lenses are arranged in advance, and the light emitted from each LD is aligned with each incident end face on the input side of the combiner by aligning each lens, is coupled to the combiner, and is combined into one point light source by the action of the combiner to be output to the emission side,

thus, by three-dimensionally assembling a plurality of N LD light sources mounted in a three-dimensional distribution, a combiner having a plurality of N incident ends having the same three-dimensional distribution, and a plurality of N coupling lenses for inputting light from the light sources to the combiner from the structure of each element member, the light is outputted by a point light source having an external shape such as a compact cylindrical shape or a cubic shape which is easy to be mounted for various applications and which is easy to dissipate heat from the LD structurally.