JP2002171019A - Active medium of polymer optical fiber laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform simultaneous oscillations, having a plurality of wavelength in one active medium for a polymer optical fiber laser. SOLUTION: In this active medium that is formed in an optical fiber shape, by mixing a photoactive medium into a matrix using a polymer material, and is used for stimulated emission for the polymer optical fiber laser, a plurality of types of photoactive media are mixed, thus achieving simultaneous stimulated emission of light having different wavelengths.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an active medium used for stimulated emission in polymer optical fiber lasers.

[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,
Further, when used as a signal light source for optical fiber communication using a polymer optical fiber (POF), it can be directly connected to a POF, and since a wide variety of photoactive media can be used, it can be used in the near-ultraviolet range. It has many advantages such as the ability to arbitrarily select the oscillation wavelength in a wide range up to infrared. Such a POF laser is described in, for example, "Polymer Optical Fiber Laser", edited by POF Consortium, Kyoritsu Shuppan, 1997.

[0003]

SUMMARY OF THE INVENTION As described above, POF
A variety of photoactive media can be used for the laser, which has the advantage that the oscillation wavelength can be selected over a wide range. However, this only makes it possible to obtain different wavelengths per active medium. This means that the active medium needs to be replaced each time a different wavelength is needed.
On the other hand, if a single active medium can oscillate a plurality of wavelengths, the usefulness of the POF laser can be further enhanced.

The present invention has been made based on such a concept, and it is an object of the present invention to provide a POF laser capable of oscillating a plurality of wavelengths with one active medium.

[0005]

An active medium having an optical fiber structure using a polymer as a matrix has a maximum temperature of about 200 ° C. in the manufacturing process. Therefore, an organic dye can be used as a photoactive medium to be mixed into the active medium, and a chelate compound having an organic molecule as a ligand can be used. These organic dyes and chelate compounds are abundant in types that can be used as a photoactive medium. For example, in the case of an organic dye, from 200 nm to 1100 nm
A photoactive medium having a stimulated emission wavelength peak in such a wide wavelength range can be selected. On the other hand, in the case of a chelate compound, its ligand gives an absorption wavelength peak, and its central atom gives a stimulated emission wavelength peak. Therefore, by combining different central atoms with the same ligand, the Stokes shift between the absorption wavelength peak and the stimulated emission wavelength peak can be increased. That is, a photoactive medium in which the stimulated emission wavelength peak is greatly different from the same absorption wavelength peak is possible.

The present invention focuses on and utilizes the variety of usable photoactive media as described above in a polymer optical fiber active medium. That is, a plurality of types are selected from various photoactive medium materials, and by mixing the plurality of types, a plurality of wavelengths can be oscillated by one active medium. More specifically, a plurality of photoactive media are mixed in an active medium which is formed into an optical fiber by mixing a photoactive medium in a matrix using a polymer material and is used for stimulated emission in a polymer optical fiber laser. This makes it possible to simultaneously stimulate and emit light having different wavelengths.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention relate to an optical fiber structure in which a refractive index in a core portion is uniform, such as a step index type (SI type) in which a refractive index in a core portion is uniform. 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.
ostyril 124, Fluorescein, Cryptocyanine and the like can also be mentioned. On the other hand, as chelating compounds, for example, Europium tristifluoroacetylacetone (Eu (TFA) 3),
Europium trishexafluoroacetylacetone (Eu (HFA) 3), Ne
odymium tristifluoroacetylacetone and the like.

However, the selection range of the photoactive medium is naturally limited according to the intended oscillation wavelength. In addition, in order to oscillate a plurality of wavelengths by mixing a plurality of types of photoactive media, there is also a limitation for obtaining effective oscillation for each wavelength. In this regard, the selection range of the types of photoactive media is also defined.
That is, in order to oscillate a plurality of wavelengths effectively, it is necessary that the stimulated emission spectrum in one photoactive medium and the absorption spectrum in the other photoactive medium do not substantially overlap, and to satisfy this condition It is necessary to select each photoactive medium species. For example, in the case of an organic dye,
In Rhodamine 6G and Rhodamine B, the stimulated emission spectrum and the absorption spectrum overlap in the range of 100 nm or more, and these combinations are not preferable,
Oxazine 4 and Coumarin 4 have a small overlap with the stimulated emission wavelength spectrum and are usable combinations. on the other hand,
In the case of a chelate compound, as described above, the Stokes shift can be increased by combining different central atoms with the same ligand, so that the photoactive medium species for effectively oscillating each wavelength is Relatively high degree of freedom in selection. The feature of the chelate compound that enables oscillation of a plurality of wavelengths with the same ligand has a great advantage that when a laser beam is used as the excitation light, oscillation of a plurality of wavelengths is possible with one type of excitation light.

Many manufacturing methods are already known for GI-type POF. For example, JP-A-4-97302
Gazette, JP-A-4-97303, WO93 / 08
488, JP-A-2-16504, JP-A-8-1
Examples are disclosed in, for example, Japanese Patent Application Laid-Open No. 14714 and Japanese Patent Application Laid-Open No. 8-114715. Among these, WO93
/ 08488 can be used as a more preferable method. The method disclosed in WO 93/08488 is a method of forming a desired refractive index distribution by diffusing a substance (dopant) for the refractive index distribution by utilizing a polymerization process of a monomer. including.

[0012] The whole process is divided into a process of producing a preform and a process of obtaining a POF by hot stretching from the preform. The preform is produced by polymerizing a monomer in a cylindrical polymerization tube under the addition of a polymerization initiator and a chain transfer agent. A glass tube or a polymer tube is used for the polymerization tube. When a polymer tube is used, the 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, during the polymerization of the monomer, the polymer in the polymer tube swells with the monomer solution, whereby the polymerization proceeds preferentially at the interface between the polymer tube and the monomer solution, and as a result, the dopant is gathered at the center of the preform. This makes it possible to form a refractive index distribution with a steeper distribution.

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. 2 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.

[0016]

[Experimental Example 1] An experimental example in which two kinds of organic dyes are mixed as a photoactive medium to obtain oscillation of two wavelengths will be described below. PMMA was used as the matrix polymer, and Coumarin 4 (absorption wavelength peak 372 nm, stimulated emission wavelength peak 445 nm) and Oxazine 4 (absorption wavelength peak 615 nm, stimulated emission wavelength peak 630 nm) were used as the photoactive medium. 0.0005wt%, 0.0005wt%
And Triphenyl phosphate (TP) is used as a dopant for refractive index distribution to make the optical fiber structure GI type.
Using P), an active medium was produced by the above-described method for producing a GI POF. For this active medium, P as shown in FIG.
The oscillation wavelength was measured according to the configuration of the OF laser. As a result, the oscillation wavelength has a peak wavelength of 454 nm and 640 nm.
Are obtained, and their intensities are 0.15mj and 0.10m, respectively.
j.

[0017]

As described above, according to the present invention, one active medium can oscillate a plurality of wavelengths, and the usefulness of a POF laser can be further enhanced.

[Brief description of the drawings]

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

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Akihiro Takaya 6-6-2 Konandai, Konan-ku, Yokohama-shi, Kanagawa 6A-2 Minamidai F-term (reference) 2H050 AB42Z AD00 5F072 AB20 JJ20 KK01 PP07

Claims (1)

[Claims] 1. An active medium which is formed into an optical fiber by mixing a photoactive medium in a matrix using a polymer material and is used for stimulated emission in a polymer optical fiber laser, wherein a plurality of types of the photoactive medium are mixed. An active medium characterized in that light having different wavelengths can be simultaneously stimulatedly emitted.