High-peak power all-fiber femtosecond laser system based on GMN spectrum shaping technology

Abstract

The invention discloses a high-peak power all-fiber femtosecond laser system based on a GMN spectrum shaping technology, and belongs to the field of laser technologies and nonlinear optics. Comprising an all-fiber broadband GMN seed source, an all-fiber anti-gain narrowing spectrum shaping system based on a nonlinear amplification loop mirror, a high-power fiber laser amplifier and a pulse compressor. The optical fiber laser comprises the following optical devices: a pumping source, a wavelength division multiplexer, a gain optical fiber, a 2 * 2 optical fiber coupler, a beam combiner, a filter, a pumping stripper and a grating pair compressor. According to the high-peak-power all-fiber femtosecond laser system based on the GMN spectrum shaping technology, a spectrum shaping anti-gain narrowing technology is introduced while a wide-spectrum light source generated by the GMN technology is further amplified, and the output energy and the peak power of the laser system are improved while ultrashort pulse width femtosecond laser output is guaranteed; and the application prospect of the gain management nonlinear amplification technology is widened.

Description

Technical Field

[0001] The invention belongs to the field of laser technology and nonlinear optics, and in particular relates to a high peak power all-fiber femtosecond laser system based on GMN spectrum shaping technology. Background Art

[0002] With its ultra-short pulse width and ultra-high peak power, femtosecond lasers have shown their important application value in many fields such as precision manufacturing, biomedicine, national defense and aerospace. In particular, femtosecond fiber lasers have made great progress in these fields with their compact system design, excellent beam quality and reliable environmental adaptability.

[0003] At present, fiber lasers mainly rely on mode-locking technology to generate ultrashort pulse lasers. However, the lasers directly output by this technology often have relatively low peak power, which is difficult to meet the diverse application requirements. To solve this problem, power amplification is usually required through a laser amplifier. However, when the laser is directly amplified in the amplifier, it will be restricted by nonlinear effects such as self-phase modulation (SPM) and stimulated Raman scattering (SRS). These nonlinear effects limit the increase in pulse peak power and may lead to a decrease in pulse quality. In order to overcome the limitations of nonlinear effects, chirped pulse amplification (CPA) technology has become a common means to increase pulse peak power. This technology can effectively reduce the impact of nonlinear effects by stretching the pulse before amplification, and ultimately achieve high peak power and narrow pulse width laser output. However, due to dispersion mismatch and the influence of gain narrowing, the compressed pulse width is often difficult to reach less than two hundred femtoseconds, which limits its scope of application.

[0004] In recent years, with the development of laser technology, a gain managed nonlinear (GMN) amplification technology has been proposed. This technology can overcome the limitation of gain narrowing by utilizing the nonlinear effect in the amplification process, greatly broaden the spectral width, and achieve laser output with a pulse width of less than 100 femtoseconds. However, due to the nonlinear characteristics of optical fiber and the limitation of damage threshold, it is difficult to achieve higher peak power output.

[0005] In order to overcome these challenges, the present invention proposes an innovative femtosecond laser system, which not only further amplifies the wide-spectrum light source generated by GMN technology, but also introduces spectrum shaping and anti-gain narrowing technology, aiming to achieve femtosecond laser output with high energy and high peak power below 100 femtoseconds, which has broad application prospects in the fields of high-precision processing and nonlinear optical research. Summary of the invention

[0006] In order to solve the problem of low peak power of existing GMN light sources, the present invention proposes a high peak power femtosecond laser system that further amplifies the GMN wide-spectrum light source and introduces anti-gain narrowing technology. In this system, the anti-gain narrowing technology is achieved through spectrum shaping. The output of the mode-locked seed source in the system is pre-compressed by a bandpass filter and then injected into the GMN amplifier for amplification. After amplification, the laser enters the spectrum shaping system and then enters the laser main amplifier. Finally, this method can achieve a high peak power femtosecond laser output with a pulse width of less than 100 femtoseconds. Compared with the direct output of the GMN amplification system, this method further improves the peak power of the laser while achieving ultrashort pulse output.

[0007] To achieve the above object, the present invention adopts the following technical solution:

[0008] A high peak power femtosecond laser system based on gain management nonlinear amplification and anti-gain narrowing technology, characterized by comprising an all-fiber GMN seed source, an all-fiber anti-gain narrowing spectrum shaping system based on a nonlinear amplifying ring mirror, a high-power fiber laser amplifier and a pulse compressor.

[0009] The all-fiber GMN seed source includes: a first all-fiber linear cavity CFBG mode-locked laser, a first bandpass filter, a first pump source, a first beam combiner, a first gain fiber, and a first pump light stripper. The output end of the first all-fiber linear cavity CFBG mode-locked laser is connected to the input end of the first bandpass filter, and the output end of the first bandpass filter is connected to the signal end of the first beam combiner, wherein the pump end of the first beam combiner is connected to the output end of the first pump source. The output end of the first beam combiner is connected to the first gain fiber and the first pump stripper in sequence, and the output end of the first pump stripper is connected to the spectrum shaping system.

[0010] The all-fiber anti-gain narrowing spectrum shaping system comprises: a first circulator, a first 2x2 beam splitter, a second pump source, a first wavelength division multiplexer, a second gain fiber, a first passive fiber, and a third gain fiber. The output end of the all-fiber GMN seed source is connected to the first end 1 of the first circulator, the first end 2 of the first circulator is connected to the first 2x2 beam splitter, the output port of the first 2x2 beam splitter is connected to the first wavelength division multiplexing signal end, the pump section of the first wavelength division multiplexer is connected to the second pump source, the output end of the first wavelength division multiplexer is connected to the second gain fiber and the first passive fiber in sequence, the output end of the first passive fiber returns to the first circulator port 2 through the 2x2 beam splitter and then outputs through port 3, the output end of the first circulator port 3 is connected to the third gain fiber, and the output end of the third gain fiber is connected to the high-power laser main amplifier.

[0011] The high-power fiber laser amplifier and pulse compressor include: a second beam combiner, a third pump source, a fourth gain fiber, a second pump stripper, and a first grating pair compressor. The output end of the anti-gain narrowing spectrum shaping system is connected to the signal end of the second beam combiner, the third pump source is connected to the pump end of the second beam combiner, and then the output end of the beam combiner is connected to the fourth gain fiber, the output end of the third gain fiber is connected to the second pump stripper, and the output end of the second pump stripper is connected to the first grating pair compressor.

[0012] Preferably, the first all-fiber linear cavity CFBG mode-locked laser has an output central wavelength of 1000-1050nm, a spectral bandwidth of 1-25nm, a pulse width of 0.1-20ps, a repetition frequency of 0.1-100MHz, a pulse energy of 0.1-10nJ, and a pulse width of less than 2ps after pre-compression by a bandpass filter.

[0013] Preferably, the pump source is a semiconductor laser, the laser type is a continuous laser, and the output optical fiber is a single-mode optical fiber or a multi-mode optical fiber.

[0014] Preferably, the gain optical fiber is a quartz optical fiber doped with ytterbium (Yb) rare earth ions, the optical fiber type may be a single-clad optical fiber or a double-clad optical fiber, and the optical fiber core diameter is between 4-50 μm.

[0015] Preferably, the optical fiber device and the optical fiber are coupled by optical fiber fusion splicing.

[0016] Compared with the prior art, the advantages of the present invention are:

[0017] The present invention provides a high peak power femtosecond laser based on gain management nonlinear amplification technology and anti-gain narrowing technology. The spectrum is modulated by spectrum shaping technology, and a concave shaping effect with an intensity difference of more than 20dB at the gain peak relative to the highest point of the signal spectrum is achieved on the basis of the GMN spectrum, which has an inhibitory effect on the gain narrowing during the amplification process. Finally, after laser compression, the output of less than 100 femtoseconds is successfully achieved. At the same time, the peak power of the GMN amplifier is further improved. The present invention has a significant effect on the improvement of the peak power of the GMN amplifier. It is conducive to expanding the application range of GMN lasers. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic structural diagram of a femtosecond laser system based on gain management nonlinear amplification and anti-gain narrowing technology provided for the implementation of the present invention.

[0019] Figure 2 It is a logic process diagram of the laser system of the present invention.

[0020] Among them, 1. all-fiber ultrashort pulse mode-locked laser, 2. first bandpass filter, 3. first pump source, 4. first beam combiner, 5. first gain fiber, 6. first pump stripper, 7. first circulator, 8. first 2x2 beam splitter, 9. second pump source, 10. first wavelength division multiplexer, 11. second gain fiber, 12. first passive fiber, 13. third passive fiber, 14. third pump source, 15. second beam combiner, 16. fourth gain fiber, 17. second pump stripper, 18. first grating pair compressor. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the present invention clearer, the present invention is further described below in conjunction with several drawings and embodiments. It should be noted that, under the premise of no conflict, the embodiments or technical features described below can be arbitrarily combined to form a new embodiment. The specific embodiments described here are only used to explain the present invention, but not to limit the present invention.

[0022] The present invention is a high peak power all-fiber femtosecond laser system based on GMN spectrum shaping technology, comprising: an all-fiber broadband GMN seed source, an all-fiber gain narrowing resistance spectrum shaping system based on a nonlinear amplifying ring mirror, a high power fiber laser amplifier and a pulse compressor; the optical components include: a pump source, a wavelength division multiplexer, a gain fiber, a 2×2 fiber coupler, a beam combiner, a filter, a pump stripper, and a grating pair compressor. The high peak power all-fiber femtosecond laser system based on GMN spectrum shaping technology of the present invention not only further amplifies the wide spectrum light source generated by the GMN technology, but also introduces spectrum shaping resistance gain narrowing technology, thereby improving the output energy and peak power of the laser system while ensuring the ultra-short pulse width femtosecond laser output, and broadening the application prospects of gain management nonlinear amplification technology.

[0023] like Figure 1 As shown, an all-fiber one-second laser system based on gain management nonlinear amplification technology and anti-gain narrowing technology includes: 1. an all-fiber ultrashort pulse mode-locked laser, 2. a first bandpass filter, 3. a first pump source, 4. a first beam combiner, 5. a first gain fiber, 6. a first pump stripper, 7. a first circulator, 8. a first 2x2 beam splitter, 9. a second pump source, 10. a first wavelength division multiplexer, 11. a second gain fiber, 12. a first passive fiber, 13. a third passive fiber, 14. a third pump source, 15. a second beam combiner, 16. a fourth gain fiber, 17. a second pump stripper, and 18. a first grating pair compressor.

[0024] like Figure 2 As shown, the above laser system logic flow chart includes the following steps:

[0025] The ultrashort pulse generated by the all-fiber mode-locked laser 1 is input to the bandpass filter for compression. The pulse is compressed by filtering to ensure that the laser pulse width output by the pre-compressor 2 is within 2 picoseconds and then enters the GMN amplifier 3-6. The spectrum is broadened by nonlinear effects and gain management. The pulse spectrum width supports the output of pulses with a pulse width of tens of femtoseconds after compression. The pulse output by the fiber GMN amplifier 3-6 is then input to the spectrum shaping system 7-13. The GMN output is a wide-spectrum light source. The lasers of different wavelengths correspond to different intensities. The spectrum shaping system has different responses to different laser intensities. Therefore, the spectrum will be modulated to achieve spectrum shaping. At the same time, the system also uses the difference in the absorption coefficient of the gain fiber for different wavelengths to jointly achieve a spectrum depression shaping effect of more than 20dB. Finally, the shaped laser enters the laser main amplifier and compressor 14-18. The laser enters the main amplifier to further increase the energy of the pulse. Due to the anti-gain narrowing effect of the front-end spectrum shaping, the wide spectrum width is still maintained. After entering the compressor 18, the laser output with a pulse width of less than 100 femtoseconds and high peak power is achieved.

[0026] The present invention provides a femtosecond laser with compact structure, stable performance, and ultra-short pulse width and high peak power. Based on gain management nonlinear amplification technology and anti-gain narrowing technology, compared with the pure GMN laser, the anti-gain narrowing technology improves the system output pulse energy while still maintaining a narrow pulse width, further expanding the application range of GMN lasers.

Claims

1. A high peak power all-fiber femtosecond laser system based on GMN spectrum shaping technology, characterized in that: Including all-fiber broadband GMN seed source, all-fiber anti-gain narrowing spectrum shaping system based on nonlinear amplifying ring mirror NALM, high-power fiber laser amplifier and pulse compressor; The all-fiber GMN seed source comprises: a first all-fiber linear cavity CFBG mode-locked laser, a first bandpass filter, a first pump source, a first beam combiner, a first gain fiber and a first pump light stripper; the output end of the first all-fiber linear cavity CFBG mode-locked laser is connected to the input end of the first bandpass filter, the output end of the first bandpass filter is connected to the signal end of the first beam combiner, wherein the pump end of the first beam combiner is connected to the output end of the first pump source; the output end of the first beam combiner is connected to the first gain fiber and the first pump stripper in sequence, and the output end of the first pump stripper is connected to the all-fiber anti-gain narrowing spectrum shaping system; The all-fiber anti-gain narrowing spectrum shaping system comprises: a first circulator, a first 2x2 beam splitter, a second pump source, a first wavelength division multiplexer, a second gain fiber, a first passive fiber, and a third gain fiber; the output end of the all-fiber GMN seed source is connected to the first circulator end 1, the first circulator end 2 is connected to the first 2x2 beam splitter, the output port of the first 2x2 beam splitter is connected to the first wavelength division multiplexing signal end, the first wavelength division multiplexer pump section is connected to the second pump source, the output end of the first wavelength division multiplexer is connected to the second gain fiber and the first passive fiber in sequence, the output end of the first passive fiber returns to the first circulator port 2 through the 2x2 beam splitter and then outputs through port 3, the output end of the first circulator port 3 is connected to the third gain fiber, and the output end of the third gain fiber is connected to a high-power laser main amplifier. The high-power fiber laser amplifier and pulse compressor include: a second beam combiner, a third pump source, a fourth gain fiber, a second pump stripper, and a first grating pair compressor; the output end of the anti-gain narrowing spectrum shaping system is connected to the signal end of the second beam combiner, the third pump source is connected to the pump end of the second beam combiner, and then the output end of the beam combiner is connected to the fourth gain fiber, the output end of the third gain fiber is connected to the second pump stripper, and the output end of the second pump stripper is connected to the first grating pair compressor.

2. The high peak power all-fiber femtosecond laser system based on GMN spectrum shaping technology as claimed in claim 1, characterized in that: The central wavelength of the all-fiber linear cavity CFBG mode-locked laser is 1000-1050nm, the spectrum full width at half maximum is 1-20nm, the pulse width is 0.1-20ps, the repetition frequency is 1-100MHz, the pulse energy is 0.1-10nJ, and the pulse width is less than 2ps after pre-compression by a bandpass filter.

3. The high peak power all-fiber femtosecond laser system based on GMN spectrum shaping technology as claimed in claim 1, characterized in that: The central wavelength of the first bandpass filter is 1000-1040nm, and the bandwidth is 1-3nm.

4. The high peak power all-fiber femtosecond laser system based on GMN spectrum shaping technology as claimed in claim 1, characterized in that: The pump source is a semiconductor laser, the laser type is a continuous laser, and the output optical fiber is a single-mode optical fiber or a multi-mode optical fiber.

5. The high peak power all-fiber femtosecond laser system based on GMN spectrum shaping technology as claimed in claim 1, characterized in that: The optical fiber device and the optical fiber are coupled by optical fiber fusion splicing.

6. The high peak power all-fiber femtosecond laser system based on GMN spectrum shaping technology as claimed in claim 1, characterized in that: In the anti-gain narrowing spectrum shaping system based on the nonlinear amplifying ring mirror NALM, the splitting ratio of the first 2x2 beam splitter is between 0-1.

7. The high peak power all-fiber femtosecond laser system based on GMN spectrum shaping technology as claimed in claim 1, characterized in that: The gain optical fiber is a quartz optical fiber doped with ytterbium rare earth ions, the optical fiber type is a single-clad optical fiber or a double-clad optical fiber, and the optical fiber core diameter is between 4-50 μm.

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