CN213782471U - Gain optical fiber and high-power laser - Google Patents

Abstract

The utility model relates to a fiber laser field, concretely relates to gain optic fibre and use its high power laser. The gain fiber is composed of a fiber core and a fiber cladding which is coated outside the fiber core, at least two fiber cladding light stripping sections are arranged inside the fiber cladding along the signal light transmission direction, and the at least two fiber cladding light stripping sections are integrated in the fiber cladding in a laser etching mode. Gain fiber set up a plurality of optical fiber cladding light through the mode with laser sculpture in the optical fiber cladding and strip the section, clear away the signal light that gets into the optical fiber cladding by the optical fiber core stage by stage to reflect out gain fiber with it, can reduce cladding signal light to the absorption of core area pumping energy, increase the efficiency of laser instrument, improve the output beam quality of laser instrument.

Description

Gain optical fiber and high-power laser

Technical Field

The utility model relates to a fiber laser field, concretely relates to a high power laser for stripping gain fiber of covering light and use it.

Background

With the rapid development of fiber laser technology, fiber lasers have been applied to various industries in society. A master oscillator-based power amplifier (MOPA) is a core technology for obtaining high-power laser in kilowatts or even kilowatts. The structure of the oscillator is shown in fig. 1, and comprises an oscillator 1 and an amplifier 2. The oscillator 1 generates low-power laser through the resonant cavity, and the amplifier 2 is responsible for amplifying the low-power laser to obtain the output of the high-power laser. As shown in fig. 5, mode instability effects occur when the amplifier output power reaches the order of several kilowatts or even ten-thousand watts. The mode instability can cause the energy of a low-order mode to be converted into a high-order mode, and the high-order mode is easy to leak from a fiber core to a cladding when being transmitted in the optical fiber, and then the high-order mode passes through the core region again for multiple times to be amplified and absorbed with energy, and finally the high-order mode is stripped by a stripper. The high-order mode of the stripping part is a main factor causing the output laser power of the laser to be reduced, the power to be stagnated and the efficiency to be reduced.

At present, a common mode for suppressing mode instability is to leak a high-order mode into a cladding through bending of an amplifier gain fiber, so that the proportion of cladding light in a core region is reduced, the coupling coefficient of the low-order mode and the high-order mode is reduced, and the threshold value of mode instability is improved. The mode of directly radiating high-order signal light into the cladding layer inherently increases the mode instability threshold to a certain extent, but the signal light entering the cladding layer still passes through the core region for multiple times to be amplified, thereby causing the waste of core region pumping energy. Meanwhile, the signal light power of the cladding layer is continuously increased along with the influence of leakage and amplification, so that the output power of the amplifier is influenced, and the efficiency of laser is reduced. More seriously, there is still coupling between the cladding signal light and the core signal light, which also affects mode instability. This effect, although smaller than that of the core region, is still negligible when the signal light power reaches the order of ten-thousandths of a watt. How to effectively process the signal light in the cladding layer becomes one of the limiting factors for limiting the power of the high-power laser to be further increased. There is no related art to solve this problem.

SUMMERY OF THE UTILITY MODEL

Based on the defect that the high-order mode that exists can't be clear away in the current unstable mode of suppression mode, the utility model aims to solve the technical problem that a gain fiber that can strip the signal light in the fiber cladding to and can effectively improve the high power laser of gain fiber heat dissipation problem is provided.

The utility model provides a technical scheme that above-mentioned technical problem adopted is: a gain optical fiber is composed of an optical fiber core and an optical fiber cladding which is coated and arranged outside the optical fiber core, wherein at least two sections of optical fiber cladding light stripping sections are arranged inside the optical fiber cladding along the signal light transmission direction, and the at least two sections of optical fiber cladding light stripping sections are integrated in the optical fiber cladding in a laser etching mode.

Preferably, the at least two optical fiber cladding light-stripping sections are disposed in the optical fiber cladding at equal intervals.

Preferably, the at least two optical fiber cladding light-stripping sections are arranged in a manner of gradually increasing density along the signal light transmission direction.

Further, the laser etching is ultraviolet laser etching.

Furthermore, the optical fiber cladding light stripping section is a micro-reflection structure with a periodically-changed refractive index, wherein ultraviolet laser is etched in the optical fiber cladding according to a reflection angle of 0-180 degrees.

The utility model also provides a high-power laser, which consists of an oscillator and an amplifier; any gain optical fiber in the scheme is arranged in the amplifier, one end of the gain optical fiber is connected with the second beam combiner, and the other end of the gain optical fiber is connected with the pump light stripper.

Preferably, the gain fiber is arranged in a bent manner.

Preferably, the amplifier further comprises a condensation sleeve, the condensation sleeve is provided with an optical fiber inlet and an optical fiber outlet, the gain optical fiber is introduced into the condensation sleeve through the optical fiber inlet and is led out through the optical fiber outlet, a closed water storage cavity is formed between the condensation sleeve and the gain optical fiber, and the condensation sleeve is provided with a circulating water inlet and a circulating water outlet respectively.

Preferably, the optical fiber inlet and the optical fiber outlet on the condensation sleeve are sealed with the gain optical fiber through optical cement.

Compared with the prior art, the utility model have following advantage and effect:

1. the gain fiber of the utility model is provided with a plurality of fiber cladding light stripping sections in the fiber cladding by laser etching, removes the signal light entering the fiber cladding from the fiber core by stages, reflects the signal light out of the gain fiber, and can reduce the absorption of the cladding signal light to the core region pumping energy and increase the efficiency of the laser; on the other hand, the reduction of the cladding signal light also reduces the coupling effect of the cladding signal light and the low-order mode of the optical fiber core region, thereby improving the unstable threshold of the mode, increasing the upper limit of the output power of the laser and improving the quality of the output beam of the laser.

2. Gain fiber through strip the section with at least two optic fibre claddings light and carry out equidistant setting or set up with the mode that density scales up along light propagation direction, can realize progressively even cladding signal light of peeling off, the cladding light of having avoided the filtering in the cladding is too concentrated, the hot spot appears, guarantees the reliability of optic fibre.

3. The high-power laser of the utility model soaks the gain optical fiber in the sealed water storage cavity formed by the condensation sleeve, so that the heat dissipation problem of the gain optical fiber in the high-power laser amplifier can be effectively solved, and then the quality performance stability and the service life of the gain optical fiber are improved; on the other hand, the circulating flow of the cooling liquid in the sealed water storage cavity can also effectively disperse the heat effect generated by cladding light, so that the problem of local overheating of the optical fiber cladding is avoided.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without inventive exercise.

Fig. 1 is a schematic structural diagram of a conventional master-controlled oscillator-based high-power laser (MOPA).

Fig. 2 is a schematic structural diagram of a master-controlled oscillator-based high power laser (MOPA) according to an embodiment of the present invention.

Fig. 3 is a schematic view of a gain optical fiber according to embodiment 1 of the present invention.

Fig. 4 is a schematic structural diagram of a condensing sleeve disposed outside the gain fiber.

Fig. 5 is a schematic diagram of the transmission principle of laser light in the cladding and core of the gain fiber in the conventional high-power laser amplifier.

Fig. 6 is a schematic diagram illustrating a reflection principle of the optical fiber cladding light stripping section according to the embodiment of the present invention.

Description of reference numerals: an oscillator 1; an amplifier 2; a first pump source 11; a first combiner 12; a grating 13, an oscillator gain fiber 14; a second pump source 21; a second combiner 22; a gain fiber 23; a pump light stripper 24; a QBH linker 25; an optical fiber core 231; a fiber cladding 232; a fiber cladding light-stripping section 233; a condensing sleeve 3; a circulating water inlet 31; a circulating water outlet 32.

Detailed Description

The present invention will be described in further detail with reference to the following examples, which are illustrative of the present invention and are not intended to limit the present invention.

Example 1:

as shown in fig. 3, a gain fiber is composed of a fiber core 231 and a fiber cladding 232 disposed outside the fiber core 231 in a wrapping manner, at least two fiber cladding light stripping sections 233 are disposed inside the fiber cladding 232 along a signal light transmission direction, the at least two fiber cladding light stripping sections 233 are integrated in the fiber cladding 232 in an ultraviolet laser etching manner, and the at least two fiber cladding light stripping sections 233 are disposed in the fiber cladding 232 in an equidistant arrangement manner.

Specifically, in this embodiment 1, the optical fiber cladding light stripping section 233 is a micro-reflective structure with a periodically varying refractive index, in which ultraviolet laser light is etched in the optical fiber cladding 232 at a reflection angle of 0 ° to 180 °.

Example 2:

as shown in fig. 3, a gain fiber is different from embodiment 1 in that the at least two fiber cladding light stripping sections 233 are arranged in a manner of gradually increasing density along the signal light transmission direction, so as to achieve gradual and uniform stripping of cladding signal light in the fiber cladding 232 and avoid overheating spots caused by excessive concentration of cladding light filtered from the cladding.

The gain fiber described in embodiments 1 and 2 has the following advantages compared with the conventional technique for increasing the power and the mode instability threshold of the high-power fiber laser, because at least two sections of fiber cladding light stripping sections 233 are arranged in the fiber cladding to completely strip the high-order mode from the inside of the gain fiber:

(1) the at least two sections of optical fiber cladding light stripping sections 233 are directly written into the gain optical fiber cladding region through ultraviolet laser, so that the integration level is higher; (2) the cladding signal light is reflected from the cladding in a split stage by the mode of interval arrangement or density increasing arrangement of the optical fiber cladding light stripping sections 233, so that the heat effect generated by cladding light is effectively dispersed, and the mode instability threshold of the high-power optical fiber laser is further improved; (3) the cladding signal light is divided into stages and reflected from the cladding, so that the cladding signal laser is effectively prevented from absorbing the pumping energy of the fiber core area, and the conversion efficiency of the high-power fiber laser is improved.

Example 3: as shown in fig. 2, the high power laser includes an oscillator 1 and an amplifier 2. The oscillator 1 is composed of a first pump source 11, a first beam combiner 12, a grating 13 and an oscillator gain fiber 14; the amplifier 2 is composed of a second pump source 21, a second beam combiner 22, a gain fiber 23, a pump stripper 24 and a QBH connector 25, wherein one end of the gain fiber 23 is connected with the second beam combiner 22, and the other end is connected with the pump stripper 24.

Specifically, the structural arrangement of the gain fiber 23 is the same as that of embodiment 1 or embodiment 2.

Example 4:

as shown in fig. 2, a high power laser differs from that described in embodiment 3 in that the gain fiber 23 is disposed in a curved shape.

The working principle of the high-power laser described in this embodiment 4 is as follows:

first, the first pump source 11 pumps energy into the oscillator gain fiber 14 through the first beam combiner 12, and the laser starts oscillation in the resonant cavity formed by the grating 13 and the oscillator gain fiber 14 to form low-power laser. The low power laser enters an amplifier for further amplification to obtain high power laser. A second pump source 21 powers the amplifier through a second combiner 22. High order modes are generated during amplification of the low power signal light in the gain fiber 23. The high-order mode radiation enters the optical fiber cladding 232 through the optical fiber bending, and the multi-section optical fiber cladding light stripping section 233 arranged in the gain optical fiber 23 strips the cladding signal light in stages and reflects the cladding signal light out of the gain optical fiber, so that the ratio of the signal light in the cladding is reduced. (the principle of stripping the cladding signal light is shown in fig. 6). on one hand, the above effects can reduce the absorption of the cladding signal light to the pumping energy of the fiber core region, and increase the efficiency of the laser; on the other hand, the interaction between the cladding signal light and the low-order mode of the core is reduced due to the reduction of the cladding signal light, so that the mode instability threshold is improved, and the upper limit of the output power of the laser can be increased.

Example 5: as shown in fig. 4:

the high-power laser is different from the embodiments 3 and 4 in that the amplifier further includes a condensation sleeve 3, the condensation sleeve 3 is provided with an optical fiber inlet and an optical fiber outlet, the gain optical fiber 23 is introduced into the condensation sleeve 3 through the optical fiber inlet and is led out through the optical fiber outlet, a closed water storage cavity is formed between the condensation sleeve 3 and the gain optical fiber 23, the condensation sleeve 3 is respectively provided with a circulating water inlet 31 and a circulating water outlet 32, and the optical fiber inlet and the optical fiber outlet on the condensation sleeve 3 are sealed with the gain optical fiber 23 through optical cement.

In the high-power laser described in this embodiment 5, the arrangement of the condensation sleeve 3 can effectively solve the problem that the gain fiber 23 in the amplifier is large in laser energy transmitted during operation and needs to dissipate heat in time; on the other hand, the circulating flow of the cooling liquid in the water storage cavity can also effectively disperse the heat effect generated by the optical fiber cladding signal light, and the problem of local overheating of the optical fiber cladding is avoided.

The high power laser described in this embodiment 5 has high reliability and stability.

In addition, it should be noted that the specific embodiments described in the present specification may differ in the shape of the components, the names of the components, and the like. All equivalent or simple changes made according to the structure, characteristics and principle of the utility model are included in the protection scope of the utility model. Various modifications, additions and substitutions may be made by those skilled in the art without departing from the scope of the invention as defined in the accompanying claims.

Claims (9)

1. The gain optical fiber is characterized in that at least two sections of optical fiber cladding light stripping sections are arranged in the optical fiber cladding along the signal light transmission direction, and are integrated in the optical fiber cladding in a laser etching mode.

2. The gain optical fiber of claim 1, wherein the at least two fiber cladding light-stripped sections are disposed in the fiber cladding at equal intervals.

3. The gain optical fiber of claim 1, wherein the at least two fiber cladding light-stripped sections are arranged in a density increasing manner along the direction of signal light transmission.

4. A gain optical fiber according to claim 2 or 3, wherein said laser etching is uv laser etching.

5. The gain optical fiber according to claim 4, wherein the optical fiber cladding light stripping section is a micro-reflective structure with a periodically-changing refractive index, in which the ultraviolet laser is etched in the optical fiber cladding according to a reflection angle of 0-180 °.

6. A high power laser, characterized in that the laser consists of an oscillator and an amplifier; the amplifier is provided with any one of the gain fibers of claims 1 to 5, one end of the gain fiber is connected with the second beam combiner, and the other end of the gain fiber is connected with the pump light stripper.

7. The high power laser according to claim 6, wherein the gain fiber is arranged in a bend.

8. The high power laser according to claim 6 or 7, wherein the amplifier further comprises a condensation sleeve, the condensation sleeve is provided with an optical fiber inlet and an optical fiber outlet, the gain optical fiber is introduced into the condensation sleeve from the optical fiber inlet and is led out from the optical fiber outlet, a closed water storage cavity is formed between the condensation sleeve and the gain optical fiber, and the condensation sleeve is provided with a circulating water inlet and a circulating water outlet respectively.

9. The high power laser according to claim 8, wherein the optical fiber inlet and the optical fiber outlet on the condensation sleeve are sealed with the gain fiber by optical cement.

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