JP2022114272A - Optical device and laser device - Google Patents

Abstract

To provide an optical device and a laser device, which can prevent reliability from being deteriorated by heat generation due to clad mode light.SOLUTION: An optical device 1 includes: a core 10a; a clad 10b that covers the core 10a and has a refractive index lower than that of the core 10a; a protective coating 10c that covers the clad 10b; a slant type FBG 11 that is formed in the core 10a in a removed portion RP obtained by removing the protective coating 10c and couples SRS light propagating the core 10a to the clad 10b. At least a part of an outer peripheral surface of the clad 10b in the removed portion RP is a roughened surface portion 12 obtained by roughening a surface.SELECTED DRAWING: Figure 2

Description

The present invention relates to optical devices and laser devices.

Currently, laser devices are used in various fields such as the processing field, the automobile field, and the medical field. In recent years, for example, in the field of processing, attention has been focused on fiber laser devices, which are superior in beam quality and convergence to conventional laser devices (for example, carbon dioxide laser devices). The maximum output of such a fiber laser device is limited by SRS (Stimulated Raman Scattering) which occurs nonlinearly with respect to the laser output.

Patent Document 1 below discloses an optical device that removes SRS light generated by a fiber laser device or the like. In this optical device, a slant-type FBG (Fiber Bragg Grating) is formed in the core of an optical fiber, and the outer peripheral surface of the clad is covered with a high refractive index resin. According to this optical device, the SRS light is selectively removed from the light propagating in the core, and the cladding mode light including the removed SRS light is emitted to the outside through the high refractive index resin. This makes it possible to stabilize signal light propagating through the core and prevent damage to the excitation light source.

WO2020/171152

By the way, in the optical device disclosed in the above-mentioned Patent Document 1, since the outer peripheral surface of the clad is covered with a high refractive index resin, the clad mode light including the SRS light coupled from the core to the clad by the slant type FBG is efficiently emitted. can be released to the outside. However, depending on the power and NA (Numerical Aperture) of the cladding mode light, the high refractive index resin and protective coating (protective coating of the optical fiber) that covers the outer peripheral surface of the cladding will heat up, reducing reliability. There is a possibility that it will decrease.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical device and a laser apparatus capable of preventing deterioration in reliability due to heat generated by cladding mode light.

In order to solve the above problems, an optical device (1) according to one aspect of the present invention includes a core (10a), a clad (10b) covering the core and having a lower refractive index than the core, and the clad a covering protective coating (10c); and a slant-type FBG (11) formed on the core at a removed portion (RP) where the protective coating is removed to couple SRS light propagating in the core to the cladding. At least part of the outer peripheral surface of the clad in the removed portion is a roughened portion (12).

In the optical device according to one aspect of the present invention, the slant-type FBG is formed in the core in the removed portion from which the protective coating has been removed, and the roughened portion is formed in at least a part of the outer peripheral surface of the clad in the removed portion. there is Then, the SRS light propagating through the core is reflected by the slant type FBG and coupled to the clad, and the clad mode light including the SRS light coupled to the clad is scattered by the roughened portion formed on the outer peripheral surface of the clad. removed by In this way, the clad mode light including the SRS light coupled from the core to the clad is scattered and removed by the roughened portion formed in the clad without using resin. There is an effect that it is possible to prevent deterioration of reliability due to heat generation.

Also, in the optical device according to one aspect of the present invention, the roughened portion is not in contact with the protective coating.

Further, in the optical device according to one aspect of the present invention, the slant FBG is a chirped FBG in which the period of the grating changes so that the reflection position of light differs according to the wavelength of the light.

Further, an optical device according to an aspect of the present invention comprises a housing (20) having a housing portion (21) housing at least the removed portion, and the protective coating on both sides of the removed portion housed in the housing portion. a resin (30) for fixing the portion having the .

A laser device (40) according to one aspect of the present invention includes excitation light sources (41a, 41b) that emit excitation light, and a resonator (43) that generates signal light, which is laser light, by the excitation light emitted from the excitation light source. ), and any one of the above optical devices disposed between the resonator and the output end of the signal light, and (1).

Advantageous Effects of Invention According to the present invention, it is possible to prevent deterioration of reliability due to heat generation caused by cladding mode light.

1 is a cross-sectional view showing the essential configuration of an optical device according to a first embodiment of the present invention; FIG. 1 is a cross-sectional view of an optical fiber included in an optical device according to a first embodiment of the present invention; FIG. 1 is a diagram showing the main configuration of a laser device according to a first embodiment of the present invention; FIG.

Hereinafter, optical devices and laser apparatuses according to embodiments of the present invention will be described in detail with reference to the drawings. In addition, in the drawings used in the following explanation, in order to make the features easier to understand, the characteristic parts may be shown enlarged for convenience, and the dimensional ratios of each component and the like may not be the same as the actual ones. Not exclusively. Moreover, the present invention is not limited to the following embodiments.

[First embodiment]
<Optical device>
FIG. 1 is a cross-sectional view showing the essential configuration of an optical device according to a first embodiment of the present invention. As shown in FIG. 1, the optical device 1 of this embodiment includes an optical fiber 10, a housing 20, and a fiber fixing resin 30 (resin). including ). Such an optical device 1 is also called a so-called clad mode stripper. In the following, the longitudinal direction of the optical fiber 10 (horizontal direction on the paper surface) will be referred to as the "X direction", the right side on the paper surface will be referred to as the "+X side", and the left side on the paper surface will be referred to as the "-X side".

FIG. 2 is a cross-sectional view of an optical fiber included in the optical device according to the first embodiment of the invention. As shown in FIG. 2, the optical fiber 10 includes a core 10a formed with a slant type FBG 11, a clad 10b, and a protective coating 10c. That is, the optical fiber 10 is a single clad fiber having a core 10a formed with a slant FBG 11. FIG. In the optical fiber 10, the clad 10b may be composed of two clads or three clads. That is, the optical fiber 10 may be a double-clad fiber or a triple-clad fiber having a core 10a formed with a slant FBG 11. FIG.

The core 10 a of the optical fiber 10 is an elongated member formed in a cylindrical shape, and propagates light of a predetermined wavelength (hereinafter referred to as signal light) along the longitudinal direction of the optical fiber 10 . For example, silica glass or the like can be used as the core 10a. The cladding 10b covers the core 10a and has a lower refractive index than the core 10a. Silica glass, for example, can be used for the clad 10b, like the core 10a. The protective coating 10c covers the clad 10b and protects the optical fiber 10 from external forces such as lateral pressure. A resin material such as an acrylic resin or a silicone resin can be used as the protective coating 10c. These resin materials used as the protective coating 10c generally absorb light and generate heat.

The slant-type FBG 11 is formed in the core 10a of the optical fiber 10 and is for coupling (mode-coupling) the SRS light propagating through the core 10a to the clad 10b. The slant type FBG 11 is formed by partially irradiating the core 10a of the optical fiber 10 with a processing light beam (such as ultraviolet laser light) to modulate the refractive index of the core 10a in the longitudinal direction. In this embodiment, in order to form the slant-type FBG 11, the protective coating 10c is partially removed, and the core 10a is irradiated with the processing light beam through the removed portion (removed portion RP) of the protective coating 10c. Therefore, the slant type FBG 11 is formed on the core 10a at the removed portion RP where the protective coating 10c is removed.

The slant-type FBG 11 is configured to transmit light in the wavelength band of signal light (for example, 1070 nm) and to allow light in the wavelength band of SRS light (for example, 1125 nm) to escape from the core 10a toward the clad 10b. there is Here, the slant-type FBG 11 transmits most of the signal light propagating through the core 10a, but reflects part of the signal light. The signal light reflected by the slant type FBG 11 is coupled to the clad 10b.

In the slant type FBG 11, it is desirable that the intervals between the refractive index modulation portions in the longitudinal direction are non-uniform. For example, the slant FBG 11 is desirably a chirped FBG in which the period of the grating changes so that the reflection position of the light propagating through the core 10a differs according to the wavelength of the light. As a result, the wavelength band of light removed from the core 10a by the slant type FBG 11 is widened. By doing so, the SRS light can more reliably escape toward the clad 10b. By selectively removing the SRS light from the core 10a and coupling it to the clad 10b in this way, the quality of the signal light is stabilized, and problems caused by the propagation of the SRS light through the core 10a are prevented. be able to.

A roughened portion 12 is formed by roughening the outer peripheral surface of the clad 10b on at least a part of the outer peripheral surface of the clad 10b in the removed portion RP from which the protective coating 10c has been removed. This roughened portion 12 is for scattering clad mode light including SRS light coupled from the core 10a of the optical fiber 10 to the clad 10b and removing it from the clad 10b. That is, the roughened portion 12 is a portion that functions as a so-called clad mode stripper. As the clad mode light is scattered by the roughened portion 12, the energy density of the clad mode light is reduced. heat generation) can be suppressed.

For example, as shown in FIG. 2, the roughened portion 12 is formed over the entire outer peripheral surface of the clad 10b in the removed portion RP, except for the vicinity region R1 of the protective coating 10c. Here, the vicinity region R1 of the protective coating 10c is, for example, a region from the end E1 of the protective coating 10c to a position about 5 [mm] or more away from the +X side, and the -X side from the end E2 of the protective coating 10c It is an area up to a position separated by about 5 [mm] or more. That is, the roughened portion 12 is kept out of contact with the protective coating 10c. This is to prevent the cladding mode light scattered by the roughened portion 12 from entering the protective coating 10c and generating heat in the protective coating 10c by keeping the roughened portion 12 away from the protective coating 10c. .

The roughened portion 12 is a region on the -X side from the center position P0 of the slant type FBG 11 in the removed portion RP, and is formed in the whole or a part of the region R21 excluding the neighboring region R1 of the protective coating 10c. Also good. In addition, the roughened portion 12 is a region on the +X side from the center position P0 of the slant type FBG 11 in the removed portion RP, and is formed in the whole or a part of the region R22 excluding the neighboring region R1 of the protective coating 10c. can be Alternatively, the roughened portion 12 may be formed in the regions R21 and R22 so as to sandwich the slant FBG 11 in the longitudinal direction of the optical fiber 10 .

When the roughened portion 12 is formed in the region R21, the cladding mode light including the SRS light that propagates through the core 10a of the optical fiber 10 from the -X side to the +X side and is reflected by the slant type FBG 11 is can be removed. When the roughened portion 12 is formed in the region R22, the cladding mode light including the SRS light that propagates through the core 10a of the optical fiber 10 from the +X side to the -X side and is reflected by the slant type FBG 11 is can be removed.

The surface roughness of the roughened portion 12 (the surface roughness of the outer peripheral surface of the clad 10b) is set in consideration of, for example, the reflection angle of the slant type FBG 11, the energy density of the clad mode light, and the like. The surface roughness of the roughened portion 12 may be uniform or may vary depending on locations. For example, the structure may be such that the surface roughness of the roughened portion 12 increases as the distance from the central position P0 of the slant type FBG 11 increases. In the case of such a configuration, the surface roughness of the roughened portion 12 may increase stepwise or may increase gradually. With such a configuration, heat generation in the longitudinal direction of the optical fiber 10 can be made nearly uniform.

Further, the surface roughness of the roughened portion 12 may be changed according to, for example, whether the portion is likely to generate heat. For example, when the slant FBG 11 is a chirped FBG, the reflected wavelength differs depending on the position of the slant FBG 11 in the longitudinal direction of the optical fiber 10 . Therefore, for example, the portion where the central wavelength of the SRS light is reflected is likely to generate heat, and the portion where the wavelength deviated from the central wavelength of the SRS light is reflected is less likely to generate heat. In such a situation, for example, the surface roughness of the roughened portion 12 may be reduced in the portion where heat is easily generated, and the surface roughness of the roughened portion 12 may be increased in the portion where heat is less likely to be generated. By doing so, heat generation in the longitudinal direction of the optical fiber 10 can be made nearly uniform.

The roughened portion 12 is formed, for example, by etching the outer peripheral surface of the clad 10b or by performing laser processing using a pulse laser. The method of etching the outer peripheral surface of the clad 10b may be chemical etching using an etchant or physical etching using sandblasting. When the optical fiber 10 is a double-clad fiber or a triple-clad fiber, the roughened portion 12 is formed on the outer peripheral surface of the clad located in the outermost layer.

The removed portion RP from which the protective coating 10c has been removed is not recoated (recoated) with resin. Therefore, in the removed portion RP where the protective coating 10c is removed, the outer peripheral surface of the clad 10b (including the portion where the roughened portion 12 is formed and the portion where the roughened portion 12 is not formed) is exposed to the outside. exposed to

The housing 20 includes an accommodating portion 21 that accommodates at least a portion (removed portion RP) from which the protective coating 10c of the optical fiber 10 has been removed. This housing 20 reinforces the optical fiber 10 from which the protective coating 10c has been removed, prevents heat generation due to adhesion of foreign matter (for example, dust, dirt, etc.) to the clad 10b, and clad mode light removed from the optical fiber 10. provided to absorb

That is, the strength of the removed portion RP of the optical fiber 10 is reduced because the protective coating 10c has been removed. By housing the removed portion RP of the optical fiber 10 whose strength is reduced in this way in the housing portion 21 of the housing 20, the optical fiber 10 from which the protective coating 10c has been removed is reinforced.

Further, when foreign matter adheres to the roughened portion 12 formed on the outer peripheral surface of the clad 10b, the clad mode light scattered by the roughened portion 12 is absorbed by the foreign matter and generates heat. By housing the removed portion RP of the optical fiber 10 in the housing portion 21 of the housing 20, heat generation due to adhesion of foreign matter to the clad 10b is prevented.

Further, when the cladding mode light removed from the optical fiber 10 is emitted to the outside of the optical device 1, the light may enter members other than the optical device 1, causing unintended heat generation. The removed portion RP of the optical fiber 10 is accommodated in the accommodation portion 21 of the housing 20 , and the cladding mode light scattered by the roughening portion 12 is absorbed by the housing 20 , so that the cladding mode light is emitted to the outside of the optical device 1 . to prevent it from being released into the environment.

The housing 20 is, for example, a prismatic or cylindrical member, and is arranged to surround the removed portion RP of the optical fiber 10 housed in the housing portion 21 . The inner surface of the housing 20 (the surface facing the removed portion RP of the optical fiber 10) serves as a light absorbing portion 22. As shown in FIG. Specifically, the housing 20 is made of a metal such as aluminum whose inner surface has undergone black alumite treatment, Raydent treatment (registered trademark), or low-temperature black plating. The reason why the inner surface of the housing 20 is subjected to black alumite treatment or the like is to absorb while preventing reflection of cladding mode light including SRS light incident on the inner surface. As the material of the housing 20, for example, a metal having an emissivity (a measure representing the radiation efficiency of an object) of 0.7 or more can be used.

Note that the housing 20 may be formed of a plurality of (for example, two) members so that the removed portion RP of the optical fiber 10 can be easily accommodated in the accommodating portion 21 . For example, it may be formed of a rectangular tube-shaped first housing with one side open and a flat plate-like second housing covering the one side of the first housing having the opening. Even if the housing 20 is composed of a plurality of members, the surface (inner surface) facing the removed portion RP of the optical fiber 10 accommodated inside must be the light absorbing portion 22. .

The fiber fixing resin 30 is for fixing the optical fiber 10 whose removed portion RP is housed in the housing portion 21 of the housing 20 to the housing 20 . The fiber fixing resin 30 is filled in both ends (−X side end, +X side end) of the housing 20, and protects both sides of the removed portion RP accommodated in the housing portion 21 of the housing 20. The portion having the coating 10c is fixed to the housing 20. As shown in FIG. For example, a silicone resin can be used as the fiber fixing resin 30 . The silicone resin forming the fiber fixing resin 30 may or may not have optical transparency.

Now, consider a case where signal light including SRS light propagates through the core 10a of the optical fiber 10 from the -X side to the +X side. When signal light including SRS light propagating through the core 10a of the optical fiber 10 enters the slant FBG 11, most of the signal light passes through the slant FBG 11, while part of the signal light and the SRS light pass through the slant FBG 11. It is reflected and coupled to the clad 10b to become clad mode light.

If the roughened portion 12b is not formed on the outer peripheral surface of the clad 10b, this clad mode light travels from the +X side to the −X side in the clad 10b while being reflected by the outer peripheral surface of the clad 10b. . However, in the present embodiment, the roughened portion 12b is formed on the outer peripheral surface of the clad 10b. It is scattered at portion 12 and removed from optical fiber 10 .

Most of the cladding mode light removed from optical fiber 10 is absorbed in housing 20 . As a result, heat generation due to irradiation of the protective coating 10c of the optical fiber 10 and the fiber fixing resin 30 with clad mode light can be suppressed. In this way, it is possible to prevent deterioration of reliability due to heat generation caused by clad mode light.

Here, the case where the signal light including the SRS light propagates through the core 10a of the optical fiber 10 from the -X side to the +X side has been described. Similarly, when signal light including SRS light propagates through the core 10a of the optical fiber 10 from the +X side to the -X side, the cladding mode can Light can be removed.

<Laser device>
FIG. 3 is a diagram showing the main configuration of the laser device according to the first embodiment of the present invention. As shown in FIG. 3, the laser device 40 of this embodiment includes a pumping light source 41a, a pumping light source 41b, a first combiner 42a, a second combiner 42b, a resonator 43, an optical device 1, and an output end 44. Such a laser device 40 is a bidirectionally pumped fiber laser device that includes an excitation light source 41a and an excitation light source 41b.

In the following, when viewed from the amplification fiber 43a of the resonator 43, the pumping light source 41a side may be referred to as "forward" and the pumping light source 41b side may be referred to as "rear". Further, in FIG. 3, the fusion spliced portions of various fibers are indicated by x marks. This fusion splice is actually placed inside a reinforcement (not shown) and protected. The reinforcing part includes, for example, a fiber container formed with a groove capable of accommodating an optical fiber, and a resin for fixing various fibers to the fiber container while the fusion splicing part is contained in the groove of the fiber container. Be prepared.

As shown in FIG. 3, a plurality of excitation light sources 41a and 41b are arranged with the resonator 43 interposed therebetween. The excitation light source 41 a emits excitation light (forward excitation light) toward the resonator 43 , and the excitation light source 41 b emits excitation light (backward excitation light) toward the resonator 43 . Laser diodes, for example, can be used as the excitation light source 41a and the excitation light source 41b.

The first combiner 42 a and the second combiner 42 b are arranged on both sides of the resonator 43 . The first combiner 42 a couples the excitation light emitted from each of the excitation light sources 41 a to one optical fiber and directs it to the resonator 43 . The second combiner 42 b couples the excitation light emitted from each of the excitation light sources 41 b to one optical fiber and directs it to the resonator 43 .

The resonator 43 is composed of an amplification fiber 43a, an HR-FBG (High Reflectivity-Fiber Bragg Grating) 43b and an OC-FBG (Output Coupler-Fiber Bragg Grating) 43c. The resonator 43 generates signal light, which is laser light, by excitation light emitted from the excitation light sources 41a and 41b.

The amplification fiber 43a has a core doped with one or more active elements, a first clad covering the core, a second clad covering the first clad, and a protective coating covering the second clad. . That is, the amplification fiber 43a is a double clad fiber. Rare earth elements such as erbium (Er), ytterbium (Yb), and neodymium (Nd) are used as active elements added to the core. These active elements emit light in an excited state. Silica glass or the like can be used for the core and the first clad. A resin such as a polymer can be used as the second clad. A resin material such as an acrylic resin or a silicone resin can be used as the protective coating.

The HR-FBG 43b is formed in the core of an optical fiber fusion-spliced to the front end of the amplification fiber 43a. The HR-FBG 43b is adjusted so as to reflect almost 100% of the light having the wavelength of the signal light among the light emitted from the active element of the amplified fiber 43a which is in the pumped state. The HR-FBG 43b has a structure in which high refractive index portions are repeated at a constant period along the longitudinal direction.

The OC-FBG 43c is formed in the core of an optical fiber fused to the rear end of the amplification fiber 43a. The OC-FBG 43c has substantially the same structure as the HR-FBG 43b, but is adjusted to reflect light with a lower reflectance than the HR-FBG 43b. For example, the OC-FBG 43c is adjusted to have a reflectance of about 10 to 20% with respect to the light having the wavelength of the signal light.

In the amplification fiber 43a, the signal light reflected by the HR-FBG 43b and the OC-FBG 43c reciprocates in the longitudinal direction of the amplification fiber 43a. The signal light is amplified as it travels back and forth to become laser light. Thus, the light is amplified in the resonator 43 to generate laser light. A part of the laser light passes through the OC-FBG 43c, reaches the output end 44 via the optical device 1, and is output to the outside.

Here, even if the laser light (signal light) generated by the amplification fiber 43a and transmitted through the OC-FBG 43c contains the SRS light, when the signal light containing the SRS light passes through the optical device 1, The optical device 1 removes the SRS light. Therefore, signal light with stable quality is output from the output end 44 of the laser device 40 . In addition, SRS light caused by return light of the signal light output from the laser device 40 (light input from the output terminal 44 and traveling toward the resonator 43) may also be generated. Such SRS light is also removed by the optical device 1 when the returned light passes through the optical device 1 .

As described above, in the present embodiment, the slant type FBG 11 is formed on the core 10a in the removed portion RP from which the protective coating 10c has been removed, and the roughened portion is formed on at least a part of the outer peripheral surface of the clad 10b in the removed portion RP 12 are formed. Then, the SRS light propagating through the core 10a is reflected by the slant type FBG 11 and coupled to the clad 10b, and the clad mode light including the SRS light coupled to the clad 10b is transferred to the roughened portion formed on the outer peripheral surface of the clad 10b. 12 is removed by scattering.

As described above, in the present embodiment, clad mode light including SRS light coupled from the core to the clad is scattered and removed by the roughened portion 12 formed in the clad 10b without using resin. Therefore, it is possible to prevent deterioration in reliability due to heat generation caused by the cladding mode light. In addition, in the present embodiment, the slant type FBG 11 and the roughened portion 12 functioning as a so-called cladding mode stripper are formed in the device 1, so the number of parts is reduced compared to a configuration in which these are provided separately. can be reduced.

[Second embodiment]
Next, a laser device according to a second embodiment of the invention will be described. The laser device of this embodiment differs in the pumping method of the amplification fiber 43a. The laser device 40 according to the first embodiment described above includes an excitation light source 41a and an excitation light source 41b, and performs excitation using excitation light output from the excitation light source 41a and excitation light output from the excitation light source 41b. It was a bi-directional excitation type laser device.

On the other hand, the laser apparatus of the present embodiment includes either one of the excitation light source 41a and the excitation light source 41b. This is a one-sided pumping type laser device in which one of the two is used for excitation. Specifically, the pumping light source 41b and the second combiner 42b shown in FIG. 3 are omitted, and this is a forward pumping laser device that performs pumping using the pumping light output from the pumping light source 41a. Alternatively, the pumping light source 41a and the first combiner 42a shown in FIG. 3 are omitted, and it is a backward pumping laser device that performs pumping using the pumping light output from the pumping light source 41b.

The laser device of the present embodiment differs from the laser device 40 of the first embodiment only in the excitation method, and is arranged between the resonator 43 and the output end 44 in the same manner as the laser device 40 of the first embodiment. An optical device 1 is provided. For this reason, the laser device of this embodiment can prevent a decrease in reliability due to heat generated by the cladding mode light, and can reduce the number of parts, like the laser device 40 of the first embodiment. can.

[Third embodiment]
Next, a laser device according to a third embodiment of the invention will be described. The laser device of this embodiment differs in the method of supplying pumping light to the amplification fiber 43a. In the laser device 40 according to the first embodiment described above, the excitation light output from the excitation light source 41a is supplied by the first combiner 42a, and the excitation light output from the excitation light source 41b is supplied by the second combiner 42b.

On the other hand, the laser device of this embodiment supplies pumping light by side pumping. Here, the side pump means that the side surfaces of the cladding of the supply fiber to which the excitation light is supplied and the cladding of the supply fiber to which the excitation light is to be supplied are partially in contact with each other, or partially fusion-spliced. Then, the excitation light supplied to the supply fiber is supplied to the supplied fiber through the contact portion.

Specifically, in the laser apparatus of this embodiment, the first combiner 42a and the second combiner 42b shown in FIG. 3 are omitted. Then, pumping light output from the pumping light source 41a is supplied by a side pump, for example, between the HR-FBG 43b and the fusion splicing portion located behind the HR-FBG 43b. Pumping light output from the pumping light source 41b is supplied by a side pump, for example, between the OC-FBG 43c and a fusion splicing portion located in front of the OC-FBG 43c.

The laser device of the present embodiment differs from the laser device 40 of the first embodiment only in the method of supplying pumping light to the amplification fiber 43a. It comprises an optical device 1 arranged between the ends 44 . For this reason, the laser device of this embodiment can prevent a decrease in reliability due to heat generated by the cladding mode light, and can reduce the number of parts, like the laser device 40 of the first embodiment. can.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and can be freely modified within the scope of the present invention. For example, although the laser device of the above-described embodiment has one output end 44, an optical fiber or the like may be further connected to the tip of the output end 44. FIG. Also, a beam combiner may be connected to the tip of the output end 44 to bundle laser beams from a plurality of laser devices.

Further, the optical device 1 described above may be employed in a MOPA (Master Oscillator Power Amplifier) type laser apparatus. Furthermore, the optical device 1 is a laser device in which a resonator is constructed of a material other than an optical fiber, such as a semiconductor laser (DDL: Direct Diode Laser) or a disk laser, and in which laser light emitted from the resonator is condensed into the optical fiber. It is also applicable to

DESCRIPTION OF SYMBOLS 1... Optical device 10a... Core 10b... Clad 10c... Protective coating 11... Slant-type FBG 12... Roughening part 20... Housing 21... Accommodating part 22... Light absorption part 30... Fiber Fixing resin 40 Laser device 41a, 41b Excitation light source 43 Resonator 44 Output end RP Removed portion

Claims (5)

a core;
a cladding covering the core and having a lower refractive index than the core;
a protective coating covering the cladding;
a slant-type FBG formed in the core at the removed portion from which the protective coating was removed and coupling SRS light propagating in the core to the cladding;
with
At least part of the outer peripheral surface of the clad in the removed portion is a roughened portion,
optical device. 2. The optical device according to claim 1, wherein said roughened portion is not in contact with said protective coating. 3. The optical device according to claim 1, wherein said slant type FBG is a chirped FBG in which the period of the grating changes so that the reflection position of light differs according to the wavelength of said light. a housing provided with a housing for housing at least the removed portion;
a resin that fixes the portions having the protective coating on both sides of the removed portion accommodated in the accommodating portion to the housing;
further comprising
A surface of the housing facing the removed portion is a light absorbing portion that absorbs at least the SRS light,
4. An optical device according to any one of claims 1 to 3. an excitation light source that emits excitation light;
a resonator for generating signal light, which is laser light, by pumping light emitted from the pumping light source;
5. The optical device according to any one of claims 1 to 4, arranged between the resonator and the output end of the signal light;
a laser device.

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