JP2002171017A - Control method of oscillation wavelength in polymer optical fiber laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve diversity in oscillation wavelength for a polymer optical fiber laser. SOLUTION: In this polymer optical fiber laser, using an active medium for the polymer optical fiber laser formed in an optical fiber shape by mixing an photoactive medium into a matrix using a polymer material for stimulated emission, a low-molecular weight substance having a different polarity to a matrix polymer is mixed into the matrix with the photoactive medium, and the oscillation wavelength is changed according to the degree of difference in the polarity between the low-molecular weight substance and matrix polymer, and the amount of mixture of the low-molecular weight substance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for controlling an oscillation wavelength in a polymer optical fiber laser.

[0002]

2. Description of the Related Art In a polymer optical fiber laser (POF laser), an active medium formed by mixing a photoactive medium (fluorescent substance) in an optical waveguide having an optical fiber structure formed of a polymer material is used as a stimulated emission portion. Then, the stimulated emission is caused by irradiating the stimulated emission portion with the excitation light, thereby performing laser oscillation. This eliminates the need for elaborate alignment adjustments like Fabry-Perot cavity lasers,
When a signal light source for an optical fiber communication network using a polymer optical fiber (POF) is used, it can be directly connected to a POF. Has many advantages, such as being able to select the oscillation wavelength in a wide range from near ultraviolet to far infrared. Such a P
Regarding the OF laser, for example, “Polymer Optical Fiber Laser”, edited by POF Consortium, Kyoritsu Shuppan, 1997
Described in the year.

[0003]

SUMMARY OF THE INVENTION As described above, POF
The use of various organic dyes as a photoactive medium in a laser has the advantage that the oscillation wavelength can be selected in a wide range. However, if one type of organic dye can oscillate at one wavelength, the variety of oscillating wavelengths is naturally limited even if various organic dyes can be used. This is insufficient, for example, when used as a light source for wavelength division multiplexing optical fiber communication using POF. In other words, in the wavelength division multiplexing method, it is desirable to be able to use signal light of more wavelengths in a specific wavelength region where transmission can be efficiently performed by the POF. Can't respond enough.

Accordingly, it is an object of the present invention to provide a method of controlling an oscillation wavelength which enables a variety of oscillation wavelengths other than the means of selecting an organic dye.

[0005]

An organic dye laser which has been used as an active medium by dissolving an organic dye in a liquid has been already widely used. In the field of this existing organic dye laser, the shift between the absorption wavelength peak and the stimulated emission wavelength peak, that is, the Stokes shift, of the organic dye is different depending on the polarity of the active medium. It is known that the wavelength can be controlled.

In the present invention, by utilizing this principle, the PO
Also in the F laser, it is possible to control the oscillation wavelength in a narrower wavelength range. In order to make use of the difference in Stokes shift in a POF laser, the present invention incorporates a low molecular substance having a different polarity with respect to the matrix polymer into a polymer forming a matrix of the active medium, and mixes the low molecular substance with the matrix polymer. The polarity of the composite matrix composed of the low-molecular substance and the polymer is controlled depending on the degree of the difference in the polarity and the amount of the low-molecular substance mixed. That is, the present invention relates to a method for controlling an oscillation wavelength in a polymer optical fiber laser using an active medium formed into an optical fiber by mixing a photoactive medium into a matrix using a polymer material for stimulated emission, A low-molecular substance having a different polarity to the polymer is mixed into the matrix together with the photoactive medium, and if the oscillation wavelength differs depending on the degree of the difference in polarity between the low-molecular substance and the matrix polymer and the amount of the low-molecular substance mixed therein. I try to make it.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In an embodiment of the present invention, a step index type (SI type) having a uniform refractive index in a core portion and a refractive index in a core portion having, for example, a quadratic curve are described. A graded index type (refractive index distribution type: GI type) that forms a distribution is possible. More preferably, G having a large effect of confining oscillation light
I type.

In practicing the present invention, various polymers can be used for the matrix. Considering transparency, which is particularly important, methacrylic acid-based or acrylic acid-based polymers can be mentioned as the main ones. In addition, a fluorine-based polymer is one of the promising ones.
Examples of a monomer that gives these polymers include methacrylic acid-based and acrylic acid-based polymers such as methyl methacrylate (MMA) and methacrylic acid 2,2,2-
Trifluoroethyl (3FMA), benzyl methacrylate (BzMA), ethyl methacrylate (EMA), n-butyl methacrylate (nBMA), n-propyl methacrylate (nPMA), n-hexyl methacrylate (nHMA)
MA), isopropyl methacrylate (iPMA), 1-phenylethyl methacrylate (1PhEMA), 2-phenylethyl methacrylate (2PhEMA), and the like.

Similarly, various photoactive media can be used. For example, a typical example of an organic dye that can be generally used as a photoactive medium is a dye generally called a laser dye. For example, Rhodamine
B, Rhodamine-based organic dyes such as Rhodamine 6G, Rhodamine 19 Perchlorate and coumarin-based organic dyes such as Coumarin 120 and Coumarin 2, or Oxazine 4 Perchlorate
Oxazine-based organic dyes such as Oxazine 170 Perchlorate, and the like.
Carbostyril 124, Fluorescein, Cryptocyanine and the like can also be mentioned.

[0010] Many manufacturing methods are already known for GI-type POF. For example, JP-A-4-97302
No., JP-A-4-97303, WO93 / 08488
JP-A-2-16504, JP-A-8-114714
And Japanese Patent Application Laid-Open No. 8-114715 disclose examples. Among these, WO93 / 0848
No. 8 can be used as a more preferable method. The method disclosed in WO 93/08488 is a method for forming a desired refractive index distribution by diffusing a dopant for the refractive index distribution using a polymerization process of a monomer, and usually includes the following process.

[0011] The whole process is divided into a preform preparation process and a process of obtaining a POF from the preform by hot stretching. The preform is manufactured by charging a monomer, a polymerization initiator, a chain transfer agent, a dopant for refractive index distribution and a photoactive medium into a cylindrical polymerization tube and polymerizing the monomer. Use a glass tube or a polymer tube for the polymerization tube,
When a polymer tube is used, this polymer tube can be used as it is as a cladding layer. When a polymer tube is used, it can be made of a specific polymer material, that is, a polymer material having the same or a similar composition as the polymer material of the POF to be manufactured, so that the interfacial gel effect can be used. It is possible to form the refractive index distribution in a steeper form. That is, when the monomer is polymerized, the polymer in the polymer tube swells with the monomer liquid,
As a result, the polymerization proceeds preferentially at the interface between the polymer tube and the monomer liquid, and as a result, the dopant is easily gathered at the center of the preform, and the refractive index distribution can be formed by a steeper distribution. Become.

In the process of forming a distribution of a dopant as described above, a photoactive medium (eg, an organic dye) having a larger molecular size than a monomer similarly to the dopant undergoes substantially the same behavior as the dopant, and is similar to that of the dopant. A good diffusion distribution. This has the effect of increasing the probability that a dopant having a different polarity compared to the matrix polymer will be present around the photoactive medium, and therefore has the effect of more efficiently exhibiting the matrix polarity effect, that is, wavelength selectivity, due to the dopant. Will bring.

When the polymerization of the monomer in the polymerization tube is performed by thermal polymerization, the viscosity is increased to some extent by first preliminary heating for about several hours in a water bath or an oil bath at about 70 ° C., for example. Then, usually, the polymerization is carried out by heating at about 70 ° C. while rotating the polymerization tube at a speed of, for example, about 2000 rpm in a horizontal state. This rotation polymerization is usually performed over 15 hours or more.

When a preform having a desired thickness is obtained in this manner, the preform is thermally stretched by a stretching apparatus to obtain POF. Heat stretching is usually heated to about 200 ° C., and several to several tens m
Per minute.

The P for the active medium obtained as described above
For example, the POF laser can be formed by incorporating the OF into the oscillating portion with a structure as shown in FIG. That is, the POF laser shown in FIG. 1 includes a POF 1 for an active medium that forms an oscillation section, a mirror 2 for resonance, a laser 3 for excitation, and cylindrical lenses 4 and 5 for condensing laser light from the laser 3.

Here, the present invention controls the polarity of the composite matrix by controlling the polarity of the composite matrix by using a substance having a different polarity from that of the matrix polymer as the dopant in the matrix of the active medium in a composite structure of a polymer and a dopant. This is to select the oscillation wavelength. Therefore, what is important in the present invention is to appropriately select a substance to be used as a dopant with respect to polarity. The polarity of a substance can be relatively evaluated by, for example, the solubility of the substance in a specific solvent. However, the oscillation wavelength is given by the polarity of the composite matrix composed of the dopant and the polymer, and the addition amount of the dopant also has an effect. Therefore, actually, the correlation with the oscillation wavelength is experimentally obtained including the type of the dopant and the amount of addition.

[0017]

EXPERIMENTAL EXAMPLE 1 An experimental example relating to the type of dopant and the oscillation wavelength will be described below. PMMA is used as the matrix polymer, Rhodamine 6G is used as the photoactive medium, and Triphenyl phosphate (TP
P), Diphenyl sulfoxide (DPSO) and Diphenyl
Sulfide (DPS) was used. The relationship between these polarities is T
PP <DPS <DPSO. The production of the active medium was based on the above-mentioned method for producing GI POF. And Rhodamine
The addition amount of 6G is 0.01 wt%, TPP 20 wt%,
TPP11wt%, DPSO11wt%, DPS11w
For each of the t%, the oscillation wavelength and the laser output intensity were measured. The result is shown in FIG. From this figure, it can be seen that there is a clear shift in the peak of the oscillation wavelength in a narrow wavelength range according to the polarity of the dopant, that is, it is possible to oscillate at a different wavelength in the narrow wavelength range.

[0018]

As described above, according to the present invention, one kind of photoactive medium can oscillate at a plurality of wavelengths in a wavelength range close to each other. As a result, the wavelength selectivity of the POF laser can be greatly increased,
The usefulness of the OF laser can be further enhanced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a POF laser.

FIG. 2 is a graph showing a relationship between an oscillation wavelength and a laser output intensity obtained in an experiment on active media having different dopant conditions.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) H01S 3/16 H01S 3/16 (72) Inventor Akihiro Takaya 6-23- Konandai, Konan-ku, Yokohama-shi, Kanagawa 5 Port Minamidai 6A-2 (72) Inventor Ken Kuriki 2273 Cosmo House B-101 F-term (reference) 2273 Kitsuki Ise-cho, Nakahara-ku, Kawasaki-shi, Kanagawa 2H050 AB43Z AC03 AC05 AD00 5F072 AB20 AK06 JJ20 KK01 PP07

Claims (2)

[Claims] 1. A method for controlling an oscillation wavelength in a polymer optical fiber laser in which a photoactive medium is mixed in a matrix using a polymer material and an active medium formed in the form of an optical fiber is used for stimulated emission. A low-molecular substance having a different polarity to the polymer is mixed into the matrix together with the photoactive medium, and if the oscillation wavelength differs depending on the degree of the difference in polarity between the low-molecular substance and the matrix polymer and the amount of the low-molecular substance mixed therein. A method of controlling the oscillation wavelength. 2. A low-molecular substance having a refractive index different from that of the matrix polymer is used as the low-molecular substance, and a distribution is formed in the matrix by the low-molecular substance, so that the active medium has a refractive index distribution type. 2. The method of controlling an oscillation wavelength according to claim 1, wherein a distribution similar to the low-molecular substance is formed in the photoactive medium.