HUNDRED-KILOWATTS-LEVEL MONOLITHIC FIBER LASER BASED ON AUXILIARY LASERS AND HYBRID CLADDING PUMPING SCHEME

Abstract

The present disclosure discloses a hundred-kilowatts-level monolithic fiber laser based on auxiliary lasers and hybrid cladding pumping scheme. Multi-wavelength auxiliary lasers and a signal laser are simultaneously coupled into a core of a gain fiber, and the gain fiber provides gains for the auxiliary lasers and the signal laser under multi-wavelength cladding pumping. The multi-wavelength auxiliary lasers and the signal laser are sequentially amplified under the action of gain competition, and the amplification of signal laser is suppressed at a front segment of the gain fiber, while the signal laser is effectively amplified at a rear segment of the gain fiber after the multi-wavelength auxiliary lasers are reabsorbed; quantum defects generated are reduced, and uniformly distributed thermal loads will be achieved, and the bearing capacity of laser power is improved, thereby further achieving inhibition on the transverse mode instability effect.

Claims

1. A hundred-kilowatts-level monolithic fiber laser based on multi-wavelength auxiliary lasers and hybrid cladding pumping, comprising the following operations: outputting, by a signal laser seed source, a signal laser with a central wavelength of ?.sub.s, outputting, by a first auxiliary laser source, a second auxiliary laser source, . . . , and an Nth auxiliary laser source, auxiliary lasers with central wavelengths of ?.sub.P1, ?.sub.P2, ?.sub.P3, . . . and ?.sub.PN respectively; the signal laser seed source, the first auxiliary laser source, the second auxiliary laser source, . . . and the Nth auxiliary laser source are coupled into the core of gain fiber through a signal port of a cladding pumping combiner; outputting, by a first cladding pumping laser, a second cladding pumping laser, a third cladding pumping laser, . . . and an Nth cladding pumping laser, cladding pumping lasers with gradually-increased central wavelengths of ?.sub.PC1, ?.sub.PC2, . . . and ?.sub.PCN respectively, and the cladding pumping lasers enter the cladding of gain fiber of power amplifier stage through the cladding pumping combiner; sequentially amplifying the first auxiliary laser source, the second auxiliary laser source, . . . and the Nth auxiliary laser source and the signal laser seed source in the gain fiber; and the amplification of signal laser is suppressed at a front segment of the gain fiber; and with the power decreasing of cladding pumping lasers, the first auxiliary laser source, the second auxiliary laser, . . . and the Nth auxiliary laser source in the fiber core will be gradually reabsorbed by gain fiber; then the 1090 nm single-mode laser can be effectively amplified at a rear segment of the gain fiber, and hundred-kilowatts-level near-diffraction-limited 1090 nm single-mode laser is achieved after the end cap.

2. The hundred-kilowatts-level monolithic fiber laser based on multi-wavelength auxiliary lasers and hybrid cladding pumping according to claim 1, wherein the central wavelengths of ?.sub.P1, ?.sub.P2, ?.sub.P3 . . . and ?.sub.PN of the auxiliary laser sources should be located in laser emission band width of rare-earth ions of the gain fiber, and absorption sections and emission sections of the rare-earth ions at the central wavelengths of ?.sub.P1, ?.sub.P2, ?.sub.P3, . . . and ?.sub.PN are higher than those of the signal laser at the central wavelength of ?.sub.s.

3. The hundred-kilowatts-level monolithic fiber laser based on multi-wavelength auxiliary lasers and hybrid cladding pumping according to claim 1, wherein the auxiliary lasers with the central wavelengths of ?.sub.P1, ?.sub.P2, . . . and ?.sub.PN and the signal laser with the central wavelength of ?.sub.s are sequentially amplified at the power amplifier stage, and thermal loads at an input end of the amplifier are reduced due to a smaller wavelength difference between the auxiliary lasers with the central wavelength of ?.sub.P1 and the cladding pumping lasers; and when the auxiliary lasers with the central wavelengths of ?.sub.P2, . . . and ?.sub.PN and the signal laser with the central wavelength of ?.sub.s are sequentially amplified, quantum defects generated are reduced, and uniformly distributed thermal loads will be achieved.

4. The hundred-kilowatts-level monolithic fiber laser based on multi-wavelength auxiliary lasers and hybrid cladding pumping according to claim 1, wherein the signal laser with the central wavelength of ?.sub.s is in-band pumped by the auxiliary lasers with the central wavelengths of ?.sub.P1, ?.sub.P2, . . . and ?.sub.PN on a rear segment of the power amplifier, thereby reducing waste heat generated by the quantum defects, and improving gain saturation of a system to increase the threshold of a TMI effect.

5. The hundred-kilowatts-level monolithic fiber laser based on multi-wavelength auxiliary lasers and hybrid cladding pumping according to claim 1, wherein the auxiliary lasers with the central wavelengths of ?.sub.P1, ?.sub.P2, . . . and ?.sub.PN are introduced to inhibit gain of the signal laser with the central wavelength of ?.sub.s on a front segment of the amplifier, so as to modulate the gain distribution of the signal laser at the power amplifier stage and reduce the effective a nonlinear length, therefore the nonlinear effect can be suppressed.

6. The hundred-kilowatts-level monolithic fiber laser based on multi-wavelength auxiliary lasers and hybrid cladding pumping according to claim 1, wherein output power of the signal laser seed source, the first auxiliary laser source, the second auxiliary laser source, . . . and the Nth auxiliary laser source is independently controlled, and the energy transfer among the auxiliary lasers and the signal laser in the power amplifier stage can be controlled.

7. The hundred-kilowatts-level monolithic fiber laser based on multi-wavelength auxiliary lasers and hybrid cladding pumping according to claim 1, wherein the first auxiliary laser source, the second auxiliary laser source, . . . and the Nth auxiliary laser source are solid lasers, fiber lasers, or semiconductor lasers; the first auxiliary laser source, the second auxiliary laser source, . . . and the Nth auxiliary laser source are single-longitudinal-mode lasers or multi-longitudinal-mode lasers; and the first auxiliary laser source, the second auxiliary laser source, . . . and the Nth auxiliary laser source are single-transverse-mode lasers or high-order transverse-mode lasers.

8. The hundred-kilowatts-level monolithic fiber laser based on multi-wavelength auxiliary lasers and hybrid cladding pumping according to claim 1, wherein the first cladding pumping laser, the second cladding pumping laser, the third cladding pumping laser, . . . and the Nth cladding pumping laser are semiconductor lasers, solid lasers or fiber lasers.

9. The hundred-kilowatts-level monolithic fiber laser based on multi-wavelength auxiliary lasers and hybrid cladding pumping according to claim 1, wherein the signal laser seed source and the auxiliary laser sources are oscillators or amplifiers.

10. The hundred-kilowatts-level monolithic fiber laser based on multi-wavelength auxiliary lasers and hybrid cladding pumping according to claim 1, wherein the end cap is a laser transmission device used for reducing power density of a laser output end face.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG. 1 is a schematic structural diagram of a hundred-kilowatts-level monolithic fiber laser based on multi-wavelength auxiliary lasers and hybrid cladding pumping. In which:

[0027]

TABLE-US-00001 1: signal laser seed source; 2: first auxiliary laser source; 3: second auxiliary laser source; 4: Nth auxiliary laser source; 5: laser signal combiner; 6: first cladding pumping laser; 7: second cladding pumping laser; 8: third cladding pumping laser; 9: Nth cladding pumping laser; 10: cladding pumping combiner; 11: gain fiber; 12: cladding laser stripper; and 13: end cap.

DETAILED DESCRIPTION OF THE PRESENT DISCLOSURE

[0028] To make the objectives, technical schemes and advantages of the present disclosure clearer, the implementations of the present disclosure will be described below in detail.

[0029] A hundred-kilowatts-level fiber laser based on multi-wavelength auxiliary lasers and hybrid pumping scheme based on MOPA structure includes: a signal laser seed source 1, a first auxiliary laser source 2, a second auxiliary laser source 3, . . . an Nth auxiliary laser source 4, a laser signal combiner 5, a first cladding pumping laser 6, a second cladding pumping laser 7, a third cladding pumping laser 8, . . . an Nth cladding pumping laser 9, a cladding pumping combiner 10, a gain fiber 11, a cladding laser stripper 12 and an end cap 13.

[0030] In an embodiment of the present disclosure, the signal laser seed source 1 outputs a signal laser with a central wavelength of ?.sub.s, the first auxiliary laser source 2, the second auxiliary laser source 3, . . . , and the Nth auxiliary laser source 4 output auxiliary lasers with central wavelengths of ?.sub.P1, ?.sub.P2, ?.sub.P3, . . . and ?.sub.PN respectively, the signal laser seed source 1, the first auxiliary laser source 2, the second auxiliary laser source 3, . . . and the Nth auxiliary laser source 4 are coupled into the core of gain fiber 11 through a signal port of the cladding pumping combiner 10; and output power of the signal laser seed source 1, the first auxiliary laser source 2, the second auxiliary laser source 3, . . . and the Nth auxiliary laser source 4 can be independently regulated, so as to control subsequent energy transmission of the auxiliary lasers and the signal laser at a power amplifier stage. The first cladding pumping laser 6, the second cladding pumping laser 7, the third cladding pumping laser 8, . . . and the Nth cladding pumping laser 9 output cladding pumping lasers with gradually-increased central wavelengths of ?.sub.PC1, ?.sub.PC2, . . . and ?.sub.PCN respectively, and the cladding pumping lasers enter claddings of gain fiber 11 at the power amplifier stage through the cladding pumping combiner 10.

[0031] In the embodiment of the present disclosure, the signal laser with the central wavelength of ?.sub.s and the auxiliary lasers with the central wavelengths of ?.sub.P1, ?.sub.P2, . . . and ?.sub.PN respectively are simultaneously amplified at the power amplifier stage firstly with the injection of the cladding pumping lasers with the central wavelengths of ?.sub.PC1, ?.sub.PC2, . . . and ?.sub.PCN respectively. Due to the gain competition effect, the auxiliary laser with the central wavelength of 41 is firstly amplified at the main power amplifier stage, meanwhile, amplification of the auxiliary lasers with the central wavelength of ?.sub.P2, . . . and ?.sub.PN and the signal laser with the central wavelength of ?.sub.s is inhibited; with the propagation of the lasers and the decrease in power of cladding pumping lasers, the auxiliary laser with the wavelength of ?.sub.P1 is reabsorbed, meanwhile, the auxiliary laser with the central wavelength of ?.sub.P2 starts to be amplified, laser energy is transmitted to the auxiliary laser with the central wavelength of ?.sub.P2, then the auxiliary laser with the central wavelength of ?.sub.P2 continues to be reabsorbed, the energy is gradually transmitted to the auxiliary laser with the central wavelength of ?.sub.PN, and the signal laser is always in a state that power amplification is inhibited in this process; and when the auxiliary laser with the central wavelength of ?.sub.PN is reabsorbed, the signal laser starts to be effectively amplified, as the wavelength ?.sub.s of the signal laser is greater than ?.sub.P1, ?.sub.P2, . . . and ?.sub.PN, the laser energy is finally transmitted to the signal laser at the power amplifier stage, and when all the auxiliary lasers are effectively absorbed, the signal laser can be effectively amplified.

[0032] In the embodiment of the present disclosure, the central wavelengths of the auxiliary lasers should be located in laser emission bands of rare-earth ions of the gain fiber, and meanwhile absorption sections and emission sections of the rare-earth ions in an active fiber at these wavelengths should be higher than those of the signal laser at the central wavelength, so as to ensure effective extraction of gains on a front segment of an amplifier to achieve inhibition on the signal laser and ensure that the auxiliary lasers are reabsorbed on a rear segment of the amplifier to enable the laser energy to be transmitted to the signal laser.

[0033] In the embodiment of the present disclosure, specific to the specificity of the high-power fiber amplifier, taking a ytterbium-doped fiber amplifier as an example, the central wavelength ?.sub.s of the signal laser is preferably 1060 nm to 1090 nm. The wavelength range of the auxiliary lasers is 1010 nm to 1090 nm, and the maximum wavelength of the auxiliary lasers should be smaller than the central wavelength of the signal laser.

[0034] In the embodiment of the present disclosure, considering transmission of the cladding pumping lasers in inner claddings, the rare-earth ions in the gain fiber should have high absorption sections at the central wavelengths of the cladding pumping lasers. Taking the ytterbium-doped fiber amplifier as an example, the central wavelengths of the cladding pumping lasers are selected among 915 nm+/?5 nm, 976 nm+/?5 nm and 940 nm+/?5 nm, so as to ensure absorption of the gain fiber for the cladding pumping lasers.

[0035] A principle of balancing the thermal loads in the embodiment of the present disclosure is as follows: the auxiliary lasers with the central wavelengths of ?.sub.P1, ?.sub.P2, . . . and ?.sub.PN and the signal laser with the central wavelength of ?.sub.s are sequentially amplified at the power amplifier stage, and the thermal loads at an input end of the amplifier are effectively reduced due to a smaller wavelength difference between the auxiliary laser with the central wavelength of ?.sub.P1 and the cladding pumping lasers; and when the auxiliary lasers with the central wavelengths of ?.sub.P2, . . . and ?.sub.PN and the signal laser with the central wavelength of ?.sub.s are sequentially amplified, as more laser gains are provided in an in-band pumping manner, quantum defects generated can be greatly reduced, and uniformly distributed thermal loads will be achieved.

[0036] A principle of inhibiting the TMI effect in the embodiment of the present disclosure is as follows: when the signal laser with the central wavelength of ?.sub.s is in-band pumping by the auxiliary lasers with the central wavelength of ?.sub.P1, ?.sub.P2, . . . and ?.sub.PN on the rear segment of the power amplifier, thus, the quantum defects generated by amplifying the signal laser are reduced so as to reduce waste heat generated in the amplifier, and the gain saturation effect in the power amplifier can be effectively improved due to weak absorption for the auxiliary lasers in the gain fiber, thereby inhibiting the TMI effect.

[0037] A principle of inhibiting the SRS effect in the embodiment of the present disclosure is as follows: the amplification efficiency of the signal laser is suppressed at the front segment of the gain fiber; so that the effective accumulation length of the nonlinear effect of the signal laser at the power amplifier stage is reduced, thereby inhibiting the SRS effect.

[0038] Wherein, total power of the signal laser seed source 1, the first auxiliary laser source 2, the second auxiliary laser source 3, . . . and the Nth auxiliary laser source 4 needs to meet the condition of effectively extracting ions with energy levels on the gain fiber.

[0039] A power ratio of the signal laser seed source 1 to the first auxiliary laser source 2 to the second auxiliary laser source 3, . . . to the Nth auxiliary laser source 4 can be freely adjusted according to the length of the gain fiber of the amplifier, the doping concentration, target amplification power and the like, as long as it meets the requirement that the auxiliary lasers are effectively absorbed finally.

[0040] Wherein, the end cap 13 is a laser transmission device used for reducing power density of a laser output end face to prevent system damage.

Embodiment 1

[0041] A hundred-kilowatts-level monolithic fiber laser based on auxiliary lasers and hybrid cladding pumping scheme, referring to FIG. 2, includes a signal laser seed source 1 with a central wavelength of 1090 nm, wherein the signal laser seed source is provided in the form of a single-mode fiber amplifier (maximum output power: 50 W), and sizes of output tail fibers are 10/130 m; a first auxiliary laser source 2 with a central wavelength of 1020 nm, wherein the first auxiliary laser source is provided in the form of a single-mode fiber amplifier (maximum output power: 100 W), and sizes of output tail fibers are 10/130 ?m; a second auxiliary laser source 3 with a central wavelength of 1040 nm, wherein the second auxiliary laser source is provided in the form of a single-mode fiber amplifier (maximum output power: 100 W), and sizes of output tail fibers are 10/130 ?m; a third auxiliary laser source 4 with a central wavelength of 1060 nm, wherein the third auxiliary laser source is provided in the form of a single-mode fiber amplifier (maximum output power: 200 W), and sizes of output tail fibers are 10/130 ?m; a laser signal combiner 5, which is a 4?1 signal combiner, wherein sizes of input tail fibers are both 10/130 ?m, and sizes of output tail fibers are 20/130 ?m; a first cladding pumping laser 6 of 981 nm, which is a high-power pumping source for beam combination of a semiconductor laser; a second cladding pumping laser 7 of 976 nm, which is a high-power pumping source for beam combination of the semiconductor laser; a third cladding pumping laser 8 of 940 nm, which is a high-power pumping source for beam combination of the semiconductor laser; a fourth cladding pumping laser 9 of 915 nm, which is a high-power pumping source for beam combination of the semiconductor laser; a (18+1)?1 cladding pumping combiner 10, wherein sizes of input signal fibers are 20/130 ?m, output signal fibers are three-cladding fibers, sizes thereof are 100/400/480 ?m, and a mode field matcher is integrated therein, so as to inhibit the generation of a high-order mode; a gain fiber 11, which is a Yb.sup.3+ doped three-cladding fiber, wherein fiber sizes are 100/400/480 ?m; a cladding laser stripper 12, wherein fiber sizes are 100/400/480 ?m; and an end cap 13, wherein sizes of tail fibers are 100/400/480 ?m.

[0042] Lasers output by the signal laser seed source 1, the first auxiliary laser source 2, the second auxiliary laser source 3, . . . and the third auxiliary laser source 4 are coupled into the cores of the output tail fibers through the laser signal combiner 5; then the lasers are coupled into a core of the gain fiber 11 through the (18+1)?1 cladding pumping combiner 10; and lasers output by the first cladding pumping laser to an 18th cladding pumping laser are coupled into inner claddings of the gain fiber 11 through the (18+1)?1 cladding pumping combiner 10.

[0043] A total length of the gain fiber 11 is 20 m, and a cladding absorption coefficient at 915 nm is 7.5 dB/m. The lasers output by the first auxiliary laser source 2, the second auxiliary laser source 3, . . . and the Nth auxiliary laser source 4 and the signal laser seed source 1 are sequentially amplified in the gain fiber 11. The amplification of the signal laser output by the signal laser seed source 1 is suppressed at a front segment of the gain fiber 11; and with the power decreasing of cladding pumping lasers, the auxiliary lasers are gradually reabsorbed by the gain fiber 11, in turn, the 1090 nm single-mode lasers can be effectively amplified at a rear segment of the gain fiber 11, and therefore a hundred-kilowatts-level near-diffraction-limited 1090 nm single-mode laser is achieved after the end cap 13.

Embodiment 2

[0044] In the embodiment of the present disclosure, rare-earth ions of an active fiber of a gain fiber 11 may be ytterbium ions, thulium ions, holmium ions, neodymium ions or the like.

[0045] In the embodiment of the present disclosure, specific to active fibers doped with different rare-earth ions, the selection of wavelengths of a signal laser and auxiliary lasers thereof is implemented only by following the idea of the present disclosure, which is not limited to the embodiment of the present disclosure.

[0046] In the embodiment of the present disclosure, a first auxiliary laser source 2, a second auxiliary laser source 3, . . . and an Nth auxiliary laser source 4 may be provided in the form of solid lasers, fiber lasers, semiconductor lasers or the like, as long as they can generate lasers with respective wavelengths; the lasers output therefrom may be single-longitudinal-mode lasers or multi-longitudinal-mode lasers; the lasers output therefrom may be single-transverse-mode lasers or high-order transverse-mode lasers, as long as they can be coupled into a fiber laser system to be transmitted, amplified and absorbed; and models, types and the like of the above devices are not limited in the embodiment of the present disclosure.

[0047] In the embodiment of the present disclosure, a signal laser seed source 1 may be provided in the form of a solid laser, a fiber laser, a semiconductor laser or the like, as long as it can generate single-mode lasers with the respective wavelength and the single-mode lasers can be coupled into the whole laser system to be transmitted and amplified.

[0048] In the embodiment of the present disclosure, the signal laser seed source 1, the first auxiliary laser source 2, the second auxiliary laser source 3, . . . and the Nth auxiliary laser source 4 may be provided in the form of oscillators or amplifiers, as long as they can meet the requirements of injection power and wavelengths, which is not limited to the embodiment of the present disclosure.

[0049] In the embodiment of the present disclosure, a first cladding pumping laser 6, a second cladding pumping laser 7, a third cladding pumping laser 8, . . . and an Nth cladding pumping laser 9 may be provided in the form of semiconductor lasers, solid lasers or fiber lasers, as long as they can output pumping lasers with needed wavelengths and power and the pumping lasers can be coupled into claddings of the gain fiber 11, which is not limited in the embodiment of the present disclosure.

[0050] In the embodiment of the present disclosure, the gain fiber 11 only needs to meet the amplification requirement of the laser seed source, and fiber types, doping concentrations and sizes of the gain fiber 11 are not limited in the embodiment of the present disclosure.

[0051] The embodiments of the present disclosure do not limit models of other devices except for those specifically specified, as long as the devices can complete the above functions.

[0052] Those skilled in the art can understand that the drawing is only a schematic diagram of a preferred embodiment. The serial numbers of the above embodiments of the present disclosure are only for description, and do not represent the advantages and disadvantages of the embodiments.

[0053] The above descriptions are merely preferred embodiments of the present disclosure, which are not intended to limit the present disclosure. Any modification, equivalent replacement and improvement made within the spirit and principle of the present disclosure should fall within the scope of protection of the present disclosure.