JPH1187811A - Laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the energy conversion efficiency of a fiber laser. SOLUTION: To both ends of a light amplification fiber 10 composed of a fluoride fiber to which Pr ions and Yb ions are added, optical fiber gratings 12a and 12b for selectively reflecting 1.02 μm band and the optical fiber gratings 14a and 14b for selectively reflecting 1.3 μm band are respectively connected. A pigtail fiber 16 for excitation light input is connected to the opposite end of the optical fiber grating 14a, and the output laser beam of an excitation light source 18 laser oscillated in 0.98 μm band is converged by a convergence lens 20 and made incident on the pigtail fiber 16. On the other hand, to the opposite end of the optical fiber grating 14b, an output optical fiber 22 for taking out laser oscillation light is connected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a laser device, and more particularly, to a laser device using wavelength conversion.

[0002]

2. Description of the Related Art As a laser device using wavelength conversion, a fiber laser using an optical fiber doped with two or more specific light-emitting elements as an optical amplification medium is known.
For example, an excitation light for exciting the second element is externally introduced into an optical fiber to which a first element emitting at a laser oscillation wavelength and a second element emitting at the excitation wavelength of the first element are added. I do. That is, wavelength conversion is performed in two stages, and laser oscillation is performed at a desired laser oscillation wavelength.

[0003]

However, in a conventional laser device utilizing such a plurality of stages of wavelength conversion, although the selection range of the laser oscillation wavelength is widened, energy loss due to non-light emission transition or the like in each wavelength conversion stage. Also, there is a problem that the energy conversion efficiency is poor due to the large optical coupling loss.

An object of the present invention is to provide a laser device having high energy conversion efficiency even after a plurality of stages of wavelength conversion.

[0005]

According to the present invention, there is provided a second excitation light generating material which is excited by a first excitation light to generate a second excitation light having a wavelength different from the wavelength of the first excitation light and the oscillation wavelength; The first and second wavelengths of the second excitation light and the first and second wavelengths are selectively reflected on both sides of a light-emitting medium having an oscillation wavelength light-emitting material that is excited by the second excitation light and emits light at the oscillation wavelength. A second reflection member is arranged to form a resonator having the second excitation light and the oscillation wavelength. Thereby, the second excitation light is confined in the light emitting medium and efficiently excites the luminescent material of the oscillation wavelength, so that high energy conversion efficiency can be achieved.

[0006] The luminous medium may be divided into a first medium having the second excitation light generating material and a second medium having the oscillating wavelength luminescent material. In this case, a light-emitting medium can be prepared under optimum conditions according to individual light-emitting materials. The light emitting medium is made of, for example, a fluoride fiber.

By setting the second excitation light generating material to Yr, the oscillation wavelength light emitting material to Pr, and the wavelength of the first excitation light to 0.98 μm band, a 1.3 μm band laser device can be realized.

By setting the second excitation light generating material to Er, the oscillation wavelength light emitting material to Tm, and the wavelength of the first excitation light to 1.48 μm band, a 1.9 μm band laser device can be realized.

By separating the reflecting member into a second excitation light reflecting member that selectively reflects the wavelength of the second excitation light and an oscillation wavelength reflecting member that selectively reflects the oscillation wavelength, the reflection of each wavelength is achieved. Rates can be set individually. For example, the reflectance of the first and second excitation light reflecting members included in the first and second reflecting members is substantially 100%, and the reflectance of the oscillation wavelength reflecting member included in the first reflecting member is substantially 100%. A reflectivity of substantially 100
%, The reflectance of the oscillation wavelength reflection member included in the second reflection member can be set to less than 100% for extracting laser oscillation light. Thereby, the second excitation light can be used efficiently.

[0010] By using an optical fiber grating for the second excitation light reflecting member and the oscillation wavelength reflecting member, a fiber laser can be easily realized.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic block diagram of a first embodiment of the present invention in which laser oscillation occurs in a 1.3 μm band. 10
Is an optical amplification fiber composed of a fluoride fiber doped with Pr ions and Yb ions, and has optical fiber gratings 12a and 12b and a 1.3 μm band which selectively reflect the 1.02 μm band at both ends thereof. Optical fiber gratings 14a and 14b that selectively reflect are connected. A pigtail fiber 16 for inputting excitation light is connected to the opposite end of the optical fiber grating 14a, and output laser light of an excitation light source 18 which oscillates laser in a 0.98 μm band is condensed by a condenser lens 20 and pigtailed. The light is incident on the fiber 16. On the other hand, at the opposite end of the optical fiber grating 14b,
An output optical fiber 22 for extracting laser oscillation light is connected.

Optical fiber gratings 12a, 12
The reflectivity of b and 14a is preferably as high as possible, and ideally 100%. The reflectivity of the optical fiber grating 14b is set to less than 100% in order to extract laser oscillation light in the 1.3 μm band.

The optical amplification fiber 10 and the optical fiber
Between the gratings 12a and 12b, if necessary,
A matching connection member that absorbs the difference between the effective core diameter and the effective refractive index may be provided.

As is well known, Yb ions are 0.98 μm
It has an absorption band in the band, by absorbing the excitation light of 0.98μm band, 1 by the transition from the ⁴ F _5/2 level to the ⁴ F _7/2 level.
02 μm band (more specifically, the band is 1.01 to 1.02 μm, but is referred to as a 1.02 μm band in this specification).
Emits light. The Pr ion has an absorption band in the 1.02 μm band, and is excited by light in the 1.02 μm band,
Light is emitted in the 1.3 μm band due to the transition from the ¹ G ₄ level to the ³ H ₅ level.

The operation of the embodiment will be described. Excitation light source 18
The laser beam of 0.98 μm band output by
And is incident on the pigtail fiber 16. 0.98 μ incident on pigtail fiber 16
The m-band excitation light is supplied to the optical fiber grating 14a,
The light passes through the optical amplification fiber 10 through the optical amplification fiber 10 with almost no loss, and is attenuated while exciting the Yb ions added to the optical amplification fiber 10. That is, the Yb ion is 0.98
It is excited by the excitation light in the μm band, and as described above, 1.
It emits light in the 02 μm band. Optical fiber gratings 12a and 12b that reflect 100% or almost 100% of the 1.02 μm band are connected to both ends of the optical amplification fiber 10, so that the resonator structure of the 1.02 μm band is generated and generated by Yb ions. The 1.02 μm light round-tripped between the optical fiber gratings 12a and 12b is confined in the optical amplification fiber 10, and has a very high light intensity due to stimulated emission.

As described above, Pr ions added to the optical amplification fiber 10 absorb light in the 1.02 μm band and emit light in the 1.3 μm band. Therefore, Pr ions are
It will be excited by 1.02 μ band light generated by Yb ions. On both sides of the optical amplification fiber 10, specifically, outside the optical fiber gratings 12a and 12b that reflect 100% of the 1.02 μm band, optical fiber gratings 14a and 14b that reflect the 1.3 μm band are arranged. Therefore, the resonator structure becomes 1.3 μm band, and P
The 1.3 μm light generated by the r ions round-trips between the optical fiber gratings 14 a and 14 b, and has a very high light intensity due to stimulated emission in the optical amplification fiber 10. If the reflectivity of the optical fiber grating 14a is set to 100% or almost 100% and the reflectivity of the optical fiber grating 14b is sufficiently high, laser oscillation can be caused in the 1.3 μm band.

The laser-oscillated 1.3 μm band light enters the output optical fiber 22 from the optical fiber grating 14b, propagates through the output optical fiber 22, and is extracted outside.

FIG. 2 is a schematic block diagram showing a second embodiment of the present invention in which laser oscillation is performed in the 1.9 μm band. Except for the composition and wavelength characteristics of each element, the structure is basically the same as that of the embodiment shown in FIG. 30 is Tm ion and E
An optical amplifier fiber made of a fluoride fiber doped with r ions, and an optical fiber grating 32 at each end of which selectively reflects the 1.58 μm band.
a and 32b are connected to optical fiber gratings 34a and 34b that selectively reflect the 1.9 μm band. A pigtail fiber 36 for inputting pump light is connected to the opposite end of the optical fiber grating 34a.
The output laser light of the excitation light source 38 that oscillates in the band is condensed by the condenser lens 40 and enters the pigtail fiber 36. On the other hand, optical fiber
An output optical fiber 42 for extracting laser oscillation light is connected to the opposite end of the grating 34b.

As in the embodiment shown in FIG.
The reflectivity of the gratings 32a, 32b, 34a is preferably as high as possible, and ideally 100%. The reflectivity of the optical fiber grating 34b is set to less than 100% in order to extract laser oscillation light in the 1.9 μm band.

The need for a matching connection member that absorbs the difference between the effective core diameter and the effective refractive index may be provided between the optical amplification fiber 30 and the optical fiber gratings 32a and 32b, if necessary. This is the same as the embodiment shown in FIG.

Er ions have an absorption band in the 1.48 μm band, absorb excitation light in the 1.48 μm band, and generate ⁴ I
1.58 μm due to transition from _13/2 level to ⁴ I _15/2 level
It emits light in a band. Also, Tm ion has an absorption band in the 1.58μm band is excited by light of 1.58μm band, emitting at 1.9μm band by a transition from ³ H ₄ level to the ³ H ₆ level.

The operation of the embodiment shown in FIG. 2 will be described. Except for the wavelength relationship, it is the same as the embodiment shown in FIG.
The wavelength relationship will be mainly described. 1. Output from the excitation light source 38
The 48 μm band laser light is condensed by the condenser lens 40 and is incident on the pigtail fiber 36, where the optical fiber
The light passes through the gratings 34a and 32a with almost no loss and enters the optical amplification fiber 30. The excitation light in the 1.48 μm band incident on the optical amplification fiber 30 is
It attenuates while exciting the Er ions added to 0. That is, Er ions are excited by the excitation light in the 1.48 μm band, and emit light in the 1.58 μm band as described above. The light in the 1.58 μm band is divided into 1.58 μm band by 10
Due to the resonator structure including the optical fiber gratings 32a and 32b that reflect 0% or almost 100%, the optical fiber gratings 32a and 32b are round-tripped and confined in the optical amplification fiber 30, and are very large due to stimulated emission. Light intensity.

The Tm ions added to the optical amplification fiber 30 absorb light in the 1.58 μm band and emit light in the 1.9 μm band. The light in the 1.9 μm band in which Tm ions are generated is as follows.
Optical fiber grating 14 reflecting 9 μm band
a, round trip in the resonator structure by 14b,
It is mainly confined in the optical amplification fiber 30. As is well known, if the reflectivity of the optical fiber grating 34a is set to 100% or almost 100%, and the reflectivity of the optical fiber grating 34b is made sufficiently high, then:
Laser oscillation can be caused in the 9 μm band, and laser light in the 1.9 μm band can be extracted from the optical fiber grating 34b. 1.9 μm with laser oscillation
The band light enters the output optical fiber 22 from the optical fiber grating 14b, propagates through the output optical fiber 42, and is extracted to the outside.

In each of the above embodiments, although the wavelength conversion is performed in two stages, the intermediate wavelength band is 1.02 μm or 1.58 μm.
Optical fiber gratings 12a,
Since it is configured to be confined in the resonator of 12b or 32a and 32b, the intermediate wavelength light of 1.02 μm band or 1.58 μm band light can be made extremely strong light. Since the element Pr ions or Tm ions emitting at the original laser oscillation wavelength are arranged in substantially the same resonator, incident coupling loss does not occur and Pr ions or Tm ions can be efficiently excited. Therefore, a fiber laser with high energy conversion efficiency can be realized.

In the above embodiment, one optical amplification fiber 1
The two ions Yb, Pr or ions Er, T at 0, 30
Although m is added, a configuration may be adopted in which an optical amplification fiber to which Yb ions or Er ions are added and an optical amplification fiber to which Pr ions or Tm ions are added are serially connected.

The optical fiber gratings 12a and 12a are used as reflecting elements for selectively reflecting specific wavelengths.
b, 14a, 14b; 32a, 32b, 34a, 34b
May be replaced by a multilayer reflection mirror. However, since a desired gain is easily obtained by using a fiber structure as the optical amplifying medium, the optical fiber gratings 12a, 12b, 14a, and 14b are improved in terms of the coupling efficiency of incident light. 32a, 32
b, 34a and 34b are excellent.

In each of the above embodiments, the pumping light is incident from one end. However, the excitation light may be incident into the resonator having the intermediate wavelength and / or the oscillation wavelength by using a wavelength division multiplexing coupler or the like. Further, the pump light is transmitted to the optical amplification fibers 10, 30.
Reflecting elements that selectively reflect the wavelength of the excitation light may be arranged on both sides of the optical amplification fibers 10 and 30 so as to be confined inside. In this case, the excitation light can be effectively used.

[0029]

As can be easily understood from the above description, according to the present invention, an efficient laser device having very high energy conversion efficiency can be realized even in a multi-stage wavelength conversion system.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of a first embodiment of the present invention applied to a 1.3 μm band laser device.

FIG. 2 is a schematic block diagram of a second embodiment of the present invention applied to a 1.9 μm band laser device.

[Explanation of symbols]

10: Optical amplification fiber 12a, 12b: Optical fiber grating 14a, 14b that selectively reflects the 1.02 μm band: Optical fiber grating that selectively reflects the 1.3 μm band 16: Pigtail fiber 18: 0. 98 μm band excitation light source 20: condenser lens 22: output optical fiber 30: optical amplification fiber 32 a, 32 b: optical fiber grating 34 a, 34 b for selectively reflecting 1.58 μm band selectively reflecting 1.9 μm band Optical fiber grating 36: pigtail fiber 38: 1.48 μm excitation light source 40: condenser lens 42: output optical fiber

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tetsuya Nakai 2-3-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Inside the International Telegraph and Telephone Corporation (72) Inventor Toshio Tani 2-3-3 Nishi-Shinjuku, Shinjuku-ku, Tokyo No. 2 International Telegraph and Telephone Corporation (72) Inventor Tomomi Sudo 2-7-12 Omorikita, Ota-ku, Tokyo Inside Furuuchi Chemical Corporation (72) Inventor Shunichi Ohno 2-chome Omorikita, Ota-ku, Tokyo No. 12 Furuuchi Chemical Co., Ltd.

Claims (11)

[Claims] 1. A laser device which is excited by a first pumping light and oscillates with a laser having an oscillation wavelength different from the first pumping light, comprising: a pumping light source for generating the first pumping light; A second pumping light generating material which is excited by the second pumping light and generates a second pumping light having a wavelength different from the wavelength of the first pumping light and the oscillation wavelength, and is excited by the second pumping light and emits light at the oscillation wavelength A light-emitting medium comprising a light-emitting material having an oscillation wavelength that is arranged on both sides of the light-emitting medium so as to form a resonator, and a first and a second light that selectively reflect at least the wavelength of the second excitation light and the oscillation wavelength. A laser device comprising: a second reflection member. 2. The laser device according to claim 1, wherein the light-emitting medium includes a first medium including the second excitation light generating material and a second medium including the oscillation wavelength light-emitting material. 3. The laser device according to claim 1, wherein said light emitting medium is made of a fluoride fiber. 4. The second excitation light generating material is Yr, the oscillation wavelength light emitting material is Pr, and the wavelength of the first excitation light is 0.9.
2. An 8 μm band, and the oscillation wavelength is a 1.3 μm band.
The laser device according to any one of claims 1 to 3. 5. The second excitation light generating material is Er, the oscillation wavelength light emitting material is Tm, and the first excitation light has a wavelength of 1.4.
2. An 8 .mu.m band, and said oscillation wavelength is a 1.9 .mu.m band.
The laser device according to any one of claims 1 to 3. 6. The reflection member comprises a second excitation light reflection member for selectively reflecting the wavelength of the second excitation light, and an oscillation wavelength reflection member for selectively reflecting the oscillation wavelength. 3. The laser device according to claim 1. 7. The reflectance of both the first and second excitation light reflecting members included in the first and second reflecting members is substantially 100%, and is included in the first reflecting member. 7. The reflectance of the oscillation wavelength reflecting member included in the second reflecting member is set to substantially 100%, and the reflectance of the oscillation wavelength reflecting member included in the second reflecting member is set to less than 100% for extracting laser oscillation light. 3. The laser device according to claim 1. 8. The laser device according to claim 6, wherein each of said second excitation light reflecting member and said oscillation wavelength reflecting member comprises an optical fiber grating. 9. A laser device which is excited by a first pumping light and oscillates at an oscillation wavelength different from the pumping light via one or more intermediate wavelengths, wherein the laser device emits laser light at the one or more intermediate wavelengths and the oscillation wavelength, respectively. A light-emitting medium comprising a plurality of light-emitting materials that emit light; first and second light-emitting media disposed on both sides of the light-emitting medium to form a resonator and selectively reflecting at least the one or more intermediate wavelengths and the oscillation wavelength. 2. A laser device comprising: two reflection members. 10. The laser device according to claim 9, wherein the light-emitting medium includes a plurality of media each individually including the plurality of light-emitting materials. 11. The laser device according to claim 9, wherein the reflecting member includes a plurality of reflectors that individually reflect the one or more intermediate wavelengths and the oscillation wavelength.