Method and system for generating mid-infrared laser based on soliton self-frequency shift

Abstract

The invention belongs to the technical field of laser, and discloses a method and system for generating mid-infrared laser based on soliton self-frequency shift, and the method comprises the steps: obtaining a 2 [mu] m ultrashort pulse laser pumping source, a forward pumping source and a reverse pumping source; coupling the obtained 2-micron ultrashort pulse laser pumping source and the forward pumping source to a first end of a gain fiber, and coupling the obtained reverse pumping source to a second end of the gain fiber; adjusting the ratio of the pumping power of the forward pumping source in the first end of the gain optical fiber to the pumping power of the reverse pumping source in the second end of the gain optical fiber, and exciting the 2-micron ultra-short pulse laser pumping source in the gain optical fiber to generate soliton self-frequency shift to obtain wide-spectrum ultra-short pulse laser; and inputting the broad-spectrum ultrashort pulse laser into a filter for wavelength filtering treatment to obtain 2.8 [mu] m intermediate infrared laser. By adjusting the pumping power of the pumping sources at the two ends of the gain fiber, various different soliton self-frequency shift effects can be obtained.

Description

Technical Field

[0001] The present invention belongs to the field of laser technology, and in particular relates to a method and system for generating mid-infrared laser based on soliton self-frequency shift. Background Art

[0002] Mid-infrared pulsed laser sources are widely used in laser remote sensing, weapons and other fields due to their strong transmittance in the atmosphere. In addition, since their wavelengths cover many gas absorption peaks, infrared pulsed laser sources also play a vital role in gas analysis and environmental monitoring. In particular, 2.8μm mid-infrared pulsed laser sources are widely used in medical, military, gas detection and other fields and have great potential. At present, the common method to achieve wide-spectrum tunable output of mid-infrared pulsed laser sources is to add a section of fluoride fiber of appropriate length after the ultrashort pulse laser to stimulate the soliton self-frequency shift effect to produce wide-spectrum frequency-shifted pulses. However, the method of selecting the appropriate fiber length requires experimental measurement by continuously changing the length of the fiber. The experimental process is relatively complicated and soliton splitting may occur. Moreover, for single-ended pumped fiber amplifiers, only a fixed "nonlinear phase shift-pump power" correspondence can be achieved, so only a single soliton self-frequency shift effect can be produced.

[0003] In view of this, how to achieve wide-spectrum tunable output of mid-infrared pulse laser source, obtain a variety of different soliton self-frequency shift effects or output different laser powers while maintaining a certain soliton self-frequency shift state is a technical problem that needs to be solved urgently. Summary of the invention

[0004] The present invention provides a method and system for generating mid-infrared laser based on soliton self-frequency shift, which is used to solve the technical problem that only a single soliton self-frequency shift effect can be generated when realizing the wide-spectrum tunable output of the existing mid-infrared pulse laser source.

[0005] In a first aspect, the present invention provides a method for generating a mid-infrared laser based on soliton self-frequency shift, the method for generating a mid-infrared laser based on soliton self-frequency shift comprising:

[0006] Obtain 2μm ultrashort pulse laser pump source, forward pump source and reverse pump source;

[0007] The obtained 2 μm ultrashort pulse laser pump source and the forward pump source are coupled to the first end of the gain fiber through a first pump combiner, and the obtained reverse pump source is coupled to the second end of the gain fiber through a second pump combiner;

[0008] Adjusting the ratio between the pump power of the forward pump source in the first end of the gain fiber and the pump power of the reverse pump source in the second end of the gain fiber, and exciting the 2 μm ultrashort pulse laser pump source in the gain fiber to generate soliton self-frequency shift, thereby obtaining ultrashort pulse laser with a wide spectrum;

[0009] The generated wide-spectrum ultrashort pulse laser is input into a filter for wavelength filtering to obtain a 2.8μm mid-infrared laser.

[0010] Furthermore, the ratio between the pump power of the forward pump source in the first end of the gain fiber and the pump power of the reverse pump source in the second end of the gain fiber is adjusted to excite the 2 μm ultrashort pulse laser pump source in the gain fiber to generate soliton self-frequency shift, thereby obtaining ultrashort pulse laser with a wide spectrum, including:

[0011] The peak power of the 2 μm ultrashort pulse laser in the gain fiber is set to a fixed value to obtain a fixed nonlinear phase shift or a fixed soliton self-frequency shift state in the gain fiber;

[0012] The ratio between the pump power of the forward pump source in the first end of the gain fiber and the pump power of the reverse pump source in the second end of the gain fiber is adjusted, and the high-frequency component of the 2μm ultrashort pulse laser in the gain fiber is excited to be pumped toward the low-frequency component to generate ultrashort pulse lasers with a wide spectrum of different powers.

[0013] Furthermore, the method further comprises adjusting the ratio between the pump power of the forward pump source in the first end of the gain optical fiber and the pump power of the reverse pump source in the second end of the gain optical fiber to excite the 2 μm ultrashort pulse laser pump source in the gain optical fiber to generate soliton self-frequency shift, thereby obtaining ultrashort pulse laser with a wide spectrum, and further comprising:

[0014] The peak power of the ultrashort pulse laser with a wide spectrum in the gain fiber is set to a fixed value, and the ratio between the pump power of the forward pump source in the first end of the gain fiber and the pump power of the reverse pump source in the second end of the gain fiber is adjusted;

[0015] The high-frequency component of the 2μm ultrashort pulse laser in the exciting gain fiber is pumped toward the low-frequency component to obtain different nonlinear phase shifts or different soliton self-frequency shift states in the gain fiber.

[0016] Furthermore, after the generated wide spectrum ultrashort pulse laser is input into a filter for wavelength filtering to obtain a 2.8 μm mid-infrared laser, the method further comprises:

[0017] The 2.8 μm mid-infrared laser is input into an optical fiber amplifier to amplify the laser power, thereby obtaining a 2.8 μm mid-infrared laser after laser power amplification.

[0018] Furthermore, the forward pump source is a 793nm forward pump source, and the reverse pump source is a 793nm reverse pump source.

[0019] Furthermore, the gain fiber is a thulium-doped gain fiber with a fixed length.

[0020] In a second aspect, the present invention provides a system for generating mid-infrared laser based on soliton self-frequency shift, comprising:

[0021] 2 μm ultrashort pulse laser and fixed-length thulium-doped gain fiber, wherein the fixed-length thulium-doped gain fiber is used to excite the 2 μm ultrashort pulse laser pump source to generate soliton self-frequency shift, thereby obtaining ultrashort pulse laser with a wide spectrum;

[0022] A 793nm forward pump source and a first pump combiner, wherein the first pump combiner is connected to the first end of the fixed-length thulium-doped gain fiber, and the first pump combiner is used to receive the 793nm forward pump source and couple the 2μm ultrashort pulse laser and the 793nm forward pump source to the first end of the fixed-length thulium-doped gain fiber;

[0023] A 793nm reverse pump source and a second pump combiner, wherein the second pump combiner is connected to the second end of the fixed-length thulium-doped gain fiber, and the second pump combiner is used to receive the 793nm reverse pump source and couple the 793nm reverse pump source to the second end of the fixed-length thulium-doped gain fiber;

[0024] A filter, the input end of which is connected to the second end of the fixed-length thulium-doped gain fiber, and the filter is used to filter the ultrashort pulse laser with a wide spectrum generated in the thulium-doped gain fiber into a 2.8um mid-infrared laser.

[0025] Furthermore, the system also includes an optical fiber amplifier;

[0026] The optical fiber amplifier is connected to the output end of the filter, and is used to amplify the laser power of the 2.8 μm mid-infrared laser.

[0027] Furthermore, the optical fiber amplifier is LMA Er 3 +: ZBLAN fiber amplifier.

[0028] Furthermore, the 2 μm ultrashort pulse laser is a 2 μm thulium-doped ultrashort pulse laser.

[0029] Compared with the prior art, the method and system for generating mid-infrared laser based on soliton self-frequency shift provided by the present invention, by setting a forward pump source and a reverse pump source at both ends of the gain fiber, and adjusting the ratio between the pump power of the forward pump source in the first end of the gain fiber and the pump power of the reverse pump source in the second end of the gain fiber, when stimulating the gain fiber to output 2.8um mid-infrared laser, generate a variety of soliton self-frequency shift effects to meet the diverse needs of different application scenarios for lasers. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic flow chart of a method for generating mid-infrared laser based on soliton self-frequency shift provided by an embodiment of the present invention;

[0031] Figure 2 A schematic diagram of the structure of a system for generating mid-infrared laser based on soliton self-frequency shift provided by an embodiment of the present invention;

[0032] Figure 3 A nonlinear phase shift variation region diagram of a system for generating mid-infrared laser based on soliton self-frequency shift provided by an embodiment of the present invention.

[0033] Among them, 10 is a 2μm ultrashort pulse laser, 20 is a 793nm forward pump source, 30 is a first pump combiner, 40 is a fixed-length thulium-doped gain fiber, 50 is a second pump combiner, 60 is a 793nm reverse pump source, 70 is a filter, and 80 is a fiber amplifier. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0035] In order to make the description of the disclosed content more detailed and complete, the following is an illustrative description of the implementation mode and specific examples of the present invention; however, this is not the only form of implementing or applying the specific embodiments of the present invention. The implementation mode covers the features of multiple specific embodiments and the method steps and their sequence for constructing and operating these specific embodiments. However, other specific embodiments can also be used to achieve the same or equal functions and step sequences. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0036] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein.

[0037] In the description of the embodiments of the present invention, unless otherwise specified, “ / ” means or, for example, A / B can mean A or B; “and / or” in the text is merely a description of the association relationship of associated objects, indicating that three relationships may exist, for example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, in the description of the embodiments of the present application, “multiple” refers to two or more than two, and other quantifiers are similar. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention, and the embodiments of the present application and the features in the embodiments may be combined with each other without conflict.

[0038] In order to solve the technical problem that only a single soliton self-frequency shift effect can be produced when realizing the wide spectrum tunable output of the existing mid-infrared pulse laser source, the invention provides a method for generating mid-infrared laser based on soliton self-frequency shift, please refer to Figure 1 , Figure 1 A flow chart of a method for generating mid-infrared laser based on soliton self-frequency shift provided in an embodiment of the present invention is provided. The method for generating mid-infrared laser based on soliton self-frequency shift comprises the following steps.

[0039] S10, obtain a 2 μm ultrashort pulse laser pump source, a forward pump source, and a reverse pump source. Specifically, in the embodiment of the present invention, first, obtain a 2 μm ultrashort pulse laser pump source as an excitation source. It should be noted that the ultrashort pulse laser has an extremely short pulse width, usually in picoseconds (10 -12 seconds) or femtoseconds (10 -15 Seconds), its high energy is concentrated and released in a short time, which can induce specific nonlinear optical effects in the gain fiber, laying the foundation for the subsequent generation of soliton self-frequency shift. Secondly, obtain the forward pump source and reverse pump source to assist the ultrashort pulse laser pump source. The forward pump source inputs energy from one end of the gain fiber, and the reverse pump source inputs energy from the other end of the gain fiber. By providing energy to the gain fiber from two directions at the same time, the light field distribution and energy transmission in the gain fiber can be better controlled.

[0040] S20, the obtained 2μm ultrashort pulse laser pump source and the forward pump source are coupled to the first end of the gain fiber through the first pump combiner, and the obtained reverse pump source is coupled to the second end of the gain fiber through the second pump combiner. Specifically, in the embodiment of the present invention, the gain fiber is doped with a gain medium such as rare earth elements. When the forward pump source and the reverse pump source are coupled to the gain fiber respectively, the gain medium in the gain fiber absorbs energy to form a population inversion distribution, thereby achieving light amplification. At the same time, under the action of the ultrashort pulse laser pump source, nonlinear optical effects such as soliton self-frequency shift will also occur in the gain fiber.

[0041] S30, adjusting the ratio between the pump power of the forward pump source in the first end of the gain fiber and the pump power of the reverse pump source in the second end of the gain fiber, and exciting the 2μm ultrashort pulse laser pump source in the gain fiber to produce soliton self-frequency shift, so as to obtain a wide-spectrum ultrashort pulse laser. Specifically, in the embodiment of the present invention, in the gain fiber, when the 2μm ultrashort pulse laser pump source acts together with the forward pump source and the reverse pump source, the soliton self-frequency shift phenomenon will occur due to the nonlinear characteristics of the optical fiber and the dispersion effect.

[0042] It should be noted that when ultrashort pulse lasers are transmitted in optical fibers, their own nonlinear interactions and the dispersion of the optical fibers are balanced to form a stable pulse structure, namely optical solitons. During the transmission process, the frequency of the optical solitons will shift, causing the central wavelength of the pulse to change, thereby generating ultrashort pulse lasers with a wide spectrum. This wide spectrum laser contains multiple wavelength components, which provides the basis for the subsequent acquisition of 2.8μm mid-infrared lasers.

[0043] S40, inputting the generated wide spectrum ultrashort pulse laser into the filter for wavelength filtering to obtain 2.8μm mid-infrared laser. Specifically, in the embodiment of the present invention, the generated wide spectrum ultrashort pulse laser contains multiple wavelength components, and the filter can filter the wide spectrum laser, allowing only the pulse laser with a wavelength of 2.8μm to pass, while filtering out the pulse lasers of other wavelengths, and finally obtaining 2.8μm mid-infrared laser.

[0044] As a further preferred embodiment, the ratio between the pump power of the forward pump source in the first end of the gain fiber and the pump power of the reverse pump source in the second end of the gain fiber is adjusted to excite the 2 μm ultrashort pulse laser pump source in the gain fiber to generate soliton self-frequency shift, thereby obtaining ultrashort pulse laser with a wide spectrum, including:

[0045] S31: The peak power of the 2 μm ultrashort pulse laser in the gain fiber is set to a fixed value to obtain a fixed nonlinear phase shift or a fixed soliton self-frequency shift state in the gain fiber. Specifically, in the embodiment of the present invention, when the peak power of the 2 μm ultrashort pulse laser in the gain fiber is fixed, a fixed nonlinear phase shift or a fixed soliton self-frequency shift state will be obtained in the gain fiber, and the energy distribution and transmission conditions in the gain fiber can be changed by adjusting the pump power ratio of the pump sources at both ends of the gain fiber.

[0046] S32: Adjust the ratio between the pump power of the forward pump source in the first end of the gain fiber and the pump power of the reverse pump source in the second end of the gain fiber, and excite the high-frequency component of the 2μm ultrashort pulse laser in the gain fiber to pump toward the low-frequency component, so as to generate ultrashort pulse lasers with different powers and wide spectra. Specifically, in the embodiment of the present invention, when the pump power of the forward pump source in the first end of the gain fiber and the pump power of the reverse pump source in the second end of the gain fiber are adjusted to reach a specific ratio, the high-frequency component of the 2μm ultrashort pulse laser in the gain fiber will be excited to pump toward the low-frequency component, and the spectrum of the ultrashort pulse laser will be broadened, thereby generating ultrashort pulse lasers with wide spectra. At the same time, because the ratio of the pump power of the forward pump source in the first end of the gain fiber and the pump power of the reverse pump source in the second end of the gain fiber is different, the energy distribution input into the gain fiber is also different, which results in different powers of the generated wide-spectrum ultrashort pulse lasers in the process of high-frequency to low-frequency pumping, and the maximum power output at the 2.8μm band can be achieved under a specific pump power ratio.

[0047] As a further preferred embodiment, the method further comprises: adjusting the ratio between the pump power of the forward pump source in the first end of the gain fiber and the pump power of the reverse pump source in the second end of the gain fiber to excite the 2 μm ultrashort pulse laser pump source in the gain fiber to generate soliton self-frequency shift, thereby obtaining ultrashort pulse laser with a wide spectrum;

[0048] Step S33: The peak power of the ultrashort pulse laser with a wide spectrum in the gain fiber is set to a fixed value, and the ratio between the pump power of the forward pump source in the first end of the gain fiber and the pump power of the reverse pump source in the second end of the gain fiber is adjusted. Specifically, in the embodiment of the present invention, after the peak power of the ultrashort pulse laser with a wide spectrum is set, the light field intensity, energy density, etc. at different positions inside the gain fiber can be changed by changing the ratio between the pump power of the forward pump source in the first end of the gain fiber and the pump power of the reverse pump source in the second end of the gain fiber.

[0049] Step S34: The high-frequency component of the 2μm ultrashort pulse laser in the gain fiber is excited to be pumped toward the low-frequency component to obtain different nonlinear phase shifts or different soliton self-frequency shift states in the gain fiber. Specifically, in the embodiment of the present invention, different pump power ratios will change the light intensity distribution, thereby resulting in different nonlinear phase shift amounts. In addition, different pump power ratios will affect the transmission conditions of the optical soliton in the gain fiber, thereby resulting in different soliton self-frequency shift states, such as the self-frequency shift rate, the final frequency reached, etc. These different states are very important for generating ultrashort pulse lasers with specific spectral and frequency characteristics, and can meet the diverse needs of different application scenarios for lasers.

[0050] As a further preferred embodiment, after the generated wide spectrum ultrashort pulse laser is input into a filter for wavelength filtering processing to obtain a 2.8μm mid-infrared laser, the method further includes: inputting the 2.8μm mid-infrared laser into an optical fiber amplifier for laser power amplification processing to obtain a 2.8μm mid-infrared laser after laser power amplification. Specifically, in an embodiment of the present invention, after obtaining the 2.8μm mid-infrared laser, the 2.8μm mid-infrared laser can be input into an optical fiber amplifier for laser power amplification processing, the 2.8μm mid-infrared laser is power amplified, and finally the 2.8μm mid-infrared laser after laser power amplification is output.

[0051] As a further preferred embodiment, the forward pump source is a 793nm forward pump source, and the reverse pump source is a 793nm reverse pump source. Specifically, in the embodiment of the present invention, the forward pump source and the reverse pump source use the same wavelength, and are simultaneously pumped at both ends of the gain fiber, which can form a more uniform energy distribution inside the fiber. And both the forward pump source and the reverse pump source use a 793nm wavelength, which has a good match with the absorption peak of the doped ions in the gain fiber.

[0052] As a further preferred embodiment, the gain fiber is a thulium-doped gain fiber of fixed length. Specifically, in the embodiment of the present invention, the thulium-doped gain fiber has a gain effect on light of a specific wavelength, and the fixed-length thulium-doped gain fiber makes the gain effect of the gain fiber on the 2μm ultrashort pulse laser pump source stable, ensuring that under the same pumping conditions, the gain amount obtained by the 2μm ultrashort pulse laser in the gain fiber is consistent, thereby stably outputting lasers with specific power and spectral characteristics, which is conducive to obtaining stable 2.8μm mid-infrared lasers.

[0053] On the other hand, the present invention also provides a system for generating mid-infrared laser based on soliton self-frequency shift, please refer to Figure 2 , Figure 2A schematic diagram of the structure of a system for generating mid-infrared laser based on soliton self-frequency shift provided by an embodiment of the present invention, the system comprises a 2 μm ultrashort pulse laser 10 and a fixed-length thulium-doped gain fiber 40, the fixed-length thulium-doped gain fiber 40 is used to excite a 2 μm ultrashort pulse laser pump source to generate soliton self-frequency shift, thereby obtaining a wide-spectrum ultrashort pulse laser; a 793 nm forward pump source 20 and a first pump combiner 30, the first pump combiner 30 is connected to a first end of the fixed-length thulium-doped gain fiber 40, the first pump combiner 30 is used to receive the 793 nm forward pump source 20, and couple the 2 μm ultrashort pulse laser 10 and the 793 nm forward pump source 20. Combined to the first end of the fixed-length thulium-doped gain fiber 40; a 793nm reverse pump source 60 and a second pump combiner 50, the second pump combiner 50 is connected to the second end of the fixed-length thulium-doped gain fiber 40, the second pump combiner 50 is used to receive the 793nm reverse pump source 60, and couple the 793nm reverse pump source 60 to the second end of the fixed-length thulium-doped gain fiber 40; a filter 70, the input end of the filter 70 is connected to the second end of the fixed-length thulium-doped gain fiber 40, the filter 70 is used to filter the wide-spectrum ultrashort pulse laser generated in the thulium-doped gain fiber 40 into a 2.8um mid-infrared laser. Specifically, in the embodiment of the present invention, a thulium-doped gain fiber 40 of a fixed length can be provided, and by adjusting the 793nm forward pump source 20 and the 793nm reverse pump source 60, usually in the case, in order to control the appropriate nonlinear phase shift, the pump power of the reverse pump source 60 during the adjustment process is greater than the pump power of the forward pump source 20, and the ratio between the pump power of the forward pump source in the first end of the gain fiber and the pump power of the reverse pump source in the second end of the gain fiber can be adjusted to output 2.8um mid-infrared lasers with different powers. When the pump power of the forward pump source reaches a specific ratio to the pump power of the reverse pump source in the second end of the gain optical fiber, the maximum intensity output of the mid-infrared laser at a wavelength of 2.8 μm will be achieved, and the obtained 2.8 μm mid-infrared laser will not have soliton splitting and multiple peaks. At the same time, the present invention can also obtain different nonlinear phase shift and soliton self-frequency shift effects by fixing the laser output power of 2.8 um and allocating the ratio between the pump power of the forward pump source in the first end of the gain optical fiber and the pump power of the reverse pump source in the second end of the gain optical fiber.

[0054] When implementing specific controls, please refer to Figure 3 , Figure 3A nonlinear phase shift change region diagram of a system for generating mid-infrared laser based on soliton self-frequency shift provided by an embodiment of the present invention. The present invention can adjust the B integral output by the system for generating mid-infrared laser based on soliton self-frequency shift, adjust the 2μm ultrashort pulse laser pump source to generate soliton self-frequency shift, and obtain a result of ultrashort pulse laser with a wide spectrum. The B integral of the system for generating mid-infrared laser based on soliton self-frequency shift is set between B1 and B2, wherein B1 is the B integral in the system for generating mid-infrared laser based on soliton self-frequency shift when reverse pumping is used alone, and B2 is the B integral in the system for generating mid-infrared laser based on soliton self-frequency shift when forward pumping is used alone.

[0055] It should be noted that the B integral is a quantity used to describe the degree of accumulation of nonlinear phase shift of laser pulses during propagation. The larger the B integral, the greater the accumulation of nonlinear phase shift, the soliton self-frequency shift generated by the 2μm ultrashort pulse laser pump source, and the wider spectrum of the ultrashort pulse laser. By precisely controlling the ratio between the pump power of the forward pump source in the first end of the gain fiber and the pump power of the reverse pump source in the second end of the gain fiber, the nonlinear phase shift of the system that generates mid-infrared laser based on soliton self-frequency shift is obtained to be between the nonlinear phase shifts generated by the forward pump and the reverse pump.

[0056] As a further preferred embodiment, the system further includes an optical fiber amplifier 80; the optical fiber amplifier 80 is connected to the output end of the filter 70, and the optical fiber amplifier 80 is used to amplify the laser power of the 2.8μm mid-infrared laser. Specifically, in the embodiment of the present invention, the optical fiber amplifier is internally doped with rare earth elements, and these rare earth element ions will achieve a population inversion distribution of energy levels under the action of pump light. When the 2.8μm mid-infrared laser passes through the doped optical fiber, the rare earth ions at high energy levels will be stimulated to radiate, generating photons with the same frequency, phase and polarization direction as the incident laser, thereby achieving amplification of the 2.8μm mid-infrared laser.

[0057] As a further preferred embodiment, the optical fiber amplifier 80 is a LMA Er 3 +: ZBLAN fiber amplifier. Specifically, in the embodiment of the present invention, LMA Er 3 +: ZBLAN fiber amplifiers have a larger mode field area and can accommodate higher optical power density when amplifying 2.8μm mid-infrared lasers, effectively reducing the impact of nonlinear effects, thereby achieving higher fiber gain and laser power amplification multiples.

[0058] As a further preferred embodiment, the 2 μm ultrashort pulse laser is a 2 μm thulium-doped ultrashort pulse laser. Specifically, in the embodiment of the present invention, the 2 μm thulium-doped ultrashort pulse laser can generate ultrashort pulses with high energy density and high peak power in the 2 μm band.

[0059] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0060] The above embodiments only express the preferred implementation modes of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for generating mid-infrared laser based on soliton self-frequency shift, characterized in that: include: Obtain 2μm ultrashort pulse laser pump source, forward pump source and reverse pump source; The obtained 2 μm ultrashort pulse laser pump source and the forward pump source are coupled to the first end of the gain fiber through a first pump combiner, and the obtained reverse pump source is coupled to the second end of the gain fiber through a second pump combiner; Adjusting the ratio between the pump power of the forward pump source in the first end of the gain fiber and the pump power of the reverse pump source in the second end of the gain fiber, and exciting the 2 μm ultrashort pulse laser pump source in the gain fiber to generate soliton self-frequency shift, thereby obtaining ultrashort pulse laser with a wide spectrum; The generated wide-spectrum ultrashort pulse laser is input into a filter for wavelength filtering to obtain a 2.8μm mid-infrared laser.

2. The method for generating mid-infrared laser based on soliton self-frequency shift according to claim 1, characterized in that: The method comprises adjusting the ratio between the pump power of the forward pump source in the first end of the gain optical fiber and the pump power of the reverse pump source in the second end of the gain optical fiber, exciting the 2 μm ultrashort pulse laser pump source in the gain optical fiber to generate soliton self-frequency shift, and obtaining ultrashort pulse laser with a wide spectrum, including: The peak power of the 2 μm ultrashort pulse laser in the gain fiber is set to a fixed value to obtain a fixed nonlinear phase shift or a fixed soliton self-frequency shift state in the gain fiber; The ratio between the pump power of the forward pump source in the first end of the gain fiber and the pump power of the reverse pump source in the second end of the gain fiber is adjusted, and the high-frequency component of the 2μm ultrashort pulse laser in the gain fiber is excited to be pumped toward the low-frequency component to generate ultrashort pulse lasers with a wide spectrum of different powers.

3. The method for generating mid-infrared laser based on soliton self-frequency shift according to claim 1, characterized in that: The method further comprises: adjusting the ratio between the pump power of the forward pump source in the first end of the gain optical fiber and the pump power of the reverse pump source in the second end of the gain optical fiber to excite the 2 μm ultrashort pulse laser pump source in the gain optical fiber to generate soliton self-frequency shift, thereby obtaining ultrashort pulse laser with a wide spectrum; The peak power of the ultrashort pulse laser with a wide spectrum in the gain fiber is set to a fixed value, and the ratio between the pump power of the forward pump source in the first end of the gain fiber and the pump power of the reverse pump source in the second end of the gain fiber is adjusted; The high-frequency component of the 2μm ultrashort pulse laser in the exciting gain fiber is pumped toward the low-frequency component to obtain different nonlinear phase shifts or different soliton self-frequency shift states in the gain fiber.

4. The method for generating mid-infrared laser based on soliton self-frequency shift according to claim 1, characterized in that: After the generated wide spectrum ultrashort pulse laser is input into the filter for wavelength filtering to obtain 2.8 μm mid-infrared laser, the method further comprises: The 2.8 μm mid-infrared laser is input into an optical fiber amplifier to amplify the laser power, thereby obtaining a 2.8 μm mid-infrared laser after laser power amplification.

5. The method for generating mid-infrared laser based on soliton self-frequency shift according to claim 1, characterized in that: The forward pump source is a 793nm forward pump source, and the reverse pump source is a 793nm reverse pump source.

6. The method for generating mid-infrared laser based on soliton self-frequency shift according to claim 1, characterized in that: The gain optical fiber is a thulium-doped gain optical fiber with a fixed length.

7. A system for generating mid-infrared laser based on soliton self-frequency shift, characterized in that: include: 2 μm ultrashort pulse laser and fixed-length thulium-doped gain fiber, wherein the fixed-length thulium-doped gain fiber is used to excite the 2 μm ultrashort pulse laser pump source to generate soliton self-frequency shift, thereby obtaining ultrashort pulse laser with a wide spectrum; A 793nm forward pump source and a first pump combiner, wherein the first pump combiner is connected to the first end of the fixed-length thulium-doped gain fiber, and the first pump combiner is used to receive the 793nm forward pump source and couple the 2μm ultrashort pulse laser and the 793nm forward pump source to the first end of the fixed-length thulium-doped gain fiber; A 793nm reverse pump source and a second pump combiner, wherein the second pump combiner is connected to the second end of the fixed-length thulium-doped gain fiber, and the second pump combiner is used to receive the 793nm reverse pump source and couple the 793nm reverse pump source to the second end of the fixed-length thulium-doped gain fiber; A filter, the input end of which is connected to the second end of the fixed-length thulium-doped gain fiber, and the filter is used to filter the ultrashort pulse laser with a wide spectrum generated in the thulium-doped gain fiber into a 2.8um mid-infrared laser.

8. The system for generating mid-infrared laser based on soliton self-frequency shift according to claim 7, characterized in that: The system also includes a fiber amplifier; The optical fiber amplifier is connected to the output end of the filter, and is used to amplify the laser power of the 2.8 μm mid-infrared laser.

9. The system for generating mid-infrared laser based on soliton self-frequency shift according to claim 8, characterized in that: The optical fiber amplifier is LMA Er 3 +: ZBLAN fiber amplifier.

10. The system for generating mid-infrared laser based on soliton self-frequency shift according to claim 7, characterized in that: The 2 μm ultrashort pulse laser is a 2 μm thulium-doped ultrashort pulse laser.

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