A mid-infrared laser generation system based on dispersion-managed soliton pulse

Abstract

A kind of mid-infrared laser generation system based on dispersion control soliton group pulse, can obtain high-power, high-efficiency, high-occupancy mid-infrared laser output, has the advantages of all-fiber, compact structure, high power occupancy in mid-infrared rear spectrum. The pulsed fiber laser generates nanosecond pulsed laser at 1.5 microns wavelength; the fiber pulse stretcher is a single-mode quartz optical fiber, which splits the nanosecond pulse into multiple ultrafast soliton pulses through nonlinear effect, and performs spectral energy conversion from 1.5 microns to 2.4 microns; the fiber laser amplifier further improves the output power of the stretched pulse laser and expands the spectrum to 2.7 microns wavelength, while improving the pulse energy after 2.3 microns wavelength; the fiber mode field adapter efficiently couples the pulse generated in the fiber laser amplifier into the nonlinear fiber; the nonlinear fiber expands the laser to the mid-infrared 3-5 microns wavelength, and obtains high-power, high-efficiency, high-occupancy mid-infrared laser output.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of mid-infrared laser, and particularly relates to a mid-infrared laser generation system based on dispersion regulation soliton group pulses. BACKGROUND

[0002] The mid-infrared 3-5 micron band covers a high-transmittance atmospheric window, covers a variety of molecular characteristic absorption spectra, and is also a common response spectrum of various detectors in photoelectric countermeasures, so the mid-infrared band laser has very wide applications in the fields of basic scientific research, biological medicine, molecular spectroscopy and photoelectric countermeasures. Supercontinuum is a phenomenon that the pulse spectrum is greatly broadened by the combined action of self-phase modulation, modulation instability, cross-phase modulation, four-wave mixing, stimulated Raman scattering and soliton splitting and group velocity dispersion when a strong laser pulse is transmitted in a nonlinear optical medium. The supercontinuum light source based on an optical fiber has the characteristics of high efficiency, high beam quality, compact structure, high reliability and high stability. Especially after the emergence of high-nonlinear mid-infrared soft glass optical fibers (such as fluorozirconate optical fiber, fluorine indium optical fiber, tellurite optical fiber and sulfur optical fiber), the supercontinuum light source based on mid-infrared optical fiber has become the main direction of broadband light source research. However, due to the different doping materials of the soft glass optical fiber, the material loss of different soft glass optical fibers in different mid-infrared wavelength regions rises sharply, resulting in a narrow spectral range of the obtained mid-infrared supercontinuum light source and a low long-wave spectral component. Moreover, the traditional scheme of directly generating mid-infrared laser based on rare earth ion doped gain has the problems of low conversion efficiency, low output power, poor environmental adaptability and complex structure, and therefore, it is of great significance to further study the efficient generation of mid-infrared band laser. SUMMARY

[0003] To overcome the defects of the prior art, the technical problem to be solved by the present application is to provide a mid-infrared laser generation system based on dispersion regulation soliton group pulses, which can obtain high-power, high-efficiency and high-occupancy mid-infrared laser output, and has the advantages of all-fiber, compact structure and high power occupancy in the mid-infrared rear spectral band.

[0004] The technical scheme of the present application is that the mid-infrared laser generation system based on dispersion regulation soliton group pulses comprises a pulse fiber laser (1), a fiber pulse stretcher (2), a fiber laser amplifier (3), a fiber mode field adapter (4) and a nonlinear optical fiber (5) connected in sequence, each part is cooled by water or a semiconductor cooler, and the connection is achieved by fiber fusion splicing.

[0005] The pulse fiber laser generates nanosecond pulse laser in the 1.5 micron band.

[0006] The fiber pulse stretcher is a single-mode quartz optical fiber arranged between a pulse fiber laser and a fiber laser amplifier, which splits nanosecond pulses into a plurality of superfast soliton pulses through a nonlinear effect, and performs spectral energy conversion of nanosecond pulse laser at 1.5 microns to 2.4 microns; the fiber laser amplifier further improves the output power of the pulse laser after the stretching and expands the spectrum to the 2.7 micron band, while improving the pulse energy after the 2.3 micron band;

[0007] The fiber mode field adapter efficiently couples the pulse generated in the fiber laser amplifier into the nonlinear optical fiber;

[0008] The nonlinear optical fiber expands the laser to the mid-infrared 3-5 micron band to obtain high-power, high-efficiency, and high-occupancy mid-infrared laser output.

[0009] In the engineering application aspect, the present application realizes the full-fiber structure of the system through the fiber fusion method, and each part adopts water cooling or semiconductor refrigerator device, so that the mid-infrared wide-spectrum fiber laser system has the advantages of compact structure, high integration, good stability, high conversion efficiency, is not sensitive to vibration and other interference factors in the working environment, greatly improves the stability and reliability of the laser operation, and is suitable for industrial production. In the technical advantage aspect, the dispersion control mechanism of the high peak power soliton group pulse is used to improve the pulse energy of the spectrum after the spectrum, which effectively improves the power ratio of the mid-infrared spectrum after the spectrum; finally, the high-power wide-spectrum laser output with enhanced mid-infrared after-spectrum is obtained, which is beneficial to the application in the fields of gas detection, biological medicine and military. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 It is a structure schematic diagram of the mid-infrared laser generation system based on dispersion control soliton group pulse according to the present application. DETAILED DESCRIPTION

[0011] In order for those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should belong to the scope of protection of the present application.

[0012] It should be noted that the term "comprising" and any variations thereof in the specification, claims and accompanying drawings of this invention are intended to cover non-exclusive inclusion. For example, a process, method, apparatus, product or device that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products or devices.

[0013] like Figure 1 As shown, this mid-infrared laser generation system based on dispersion-controlled soliton group pulses includes a pulsed fiber laser 1, a fiber pulse stretcher 2, a fiber laser amplifier 3, a fiber mode field adapter 4, and a nonlinear fiber 5 connected in sequence. Each part is cooled by water or a thermoelectric cooler (TEC, Thermo Electric Cooler) and connected by fiber fusion splicing.

[0014] The pulsed fiber laser generates nanosecond pulsed lasers in the 1.5-micrometer band;

[0015] The fiber pulse stretcher is a single-mode silica fiber located between the pulsed fiber laser and the fiber laser amplifier. It splits the nanosecond pulse into multiple ultrafast soliton pulses through nonlinear effects and performs spectral energy conversion of the nanosecond pulsed laser from 1.5 micrometers to 2.4 micrometers. The fiber laser amplifier further increases the output power of the stretched pulsed laser and extends the spectrum to the 2.7 micrometer band, while also increasing the pulse energy after the 2.3 micrometer band.

[0016] The fiber mode field adapter efficiently couples the pulses generated in the fiber laser amplifier into the nonlinear fiber.

[0017] The nonlinear optical fiber extends the laser to the mid-infrared 3-5 micrometer band, achieving high-power, high-efficiency, and high-proportion mid-infrared laser output.

[0018] In terms of engineering applications, this invention achieves an all-fiber structure through fiber fusion splicing, with each component employing water-cooling or semiconductor cooler devices. This results in a mid-infrared broadband fiber laser system that is compact, highly integrated, stable, and has high conversion efficiency. It is also insensitive to interference factors such as vibration in the working environment, significantly improving the stability and reliability of laser operation, making it suitable for industrial mass production. Regarding technical advantages, the invention utilizes a dispersion control mechanism based on high peak power soliton group pulses to enhance the pulse energy in the back spectral band, effectively increasing the power proportion of the mid-infrared back spectral band. Ultimately, this yields a high-power broadband laser output with enhanced mid-infrared back spectral band, beneficial for applications in gas detection, biomedicine, and military fields.

[0019] Preferably, the pulse fiber laser comprises: a 1550nm distributed feedback semiconductor laser 1-1, a wavelength division multiplexer 1-2, a 976nm single-mode semiconductor laser 1-3, a single-mode erbium-doped fiber 1-4, and a fiber isolator 1-5, which are connected in sequence by single-mode fibers to form a linear cavity structure; and the above devices are connected by fiber fusion.

[0020] Preferably, the 976nm single-mode semiconductor laser provides pump light, the pump light is input through the wavelength division multiplexer and pumps the single-mode erbium-doped fiber, wherein the 1550nm distributed feedback semiconductor laser serves as a seed source, generates a 1.5-micron nanosecond pulse seed laser through modulation by a control circuit, and performs preliminary power amplification in the single-mode erbium-doped fiber, and then transmits the generated 1.5-micron nanosecond pulse laser to the fiber pulse stretcher through the fiber isolator.

[0021] Preferably, the fiber laser amplifier comprises: a fiber combiner 4-1, a 793nm semiconductor laser 4-2, a large-mode-area double-clad thulium-doped fiber 4-3, and a fiber isolator 4-4, the 793nm semiconductor laser provides pump light for the large-mode-area double-clad thulium-doped fiber through the fiber combiner, and the fiber isolator isolates feedback light formed by a subsequent optical path; and the above devices are connected by fiber fusion.

[0022] Preferably, the fiber mode field adapter connects the large-mode-area fiber and the single-mode fiber to match the nonlinear fiber; and the above devices are connected by fiber fusion.

[0023] Preferably, the nonlinear fiber uses a dispersion regulation mechanism to expand the spectrum generated by the fiber laser amplifier to a 5-micron waveband, to realize high-power, high-efficiency, and high-occupancy mid-infrared laser output, the nonlinear fiber is a longitudinally-dispersed germanate fiber, a fluoride fiber, a tellurite fiber, or a chalcogenide fiber, the longitudinal dispersion design of the nonlinear fiber comprises three parts: a dispersion flat region for a soliton self-frequency shift process, a dispersion transition region for accumulating the number of soliton group pulses, and a dispersion steep increase region for enhancing the intensity of the soliton group pulses; the nonlinear fiber and the fiber mode field adapter are connected by fiber fusion, and the fiber output end of the nonlinear fiber is subjected to 15° angle cutting processing to prevent Fresnel reflection.

[0024] Preferably, the 1550nm distributed feedback semiconductor laser of the pulse fiber laser is controlled by a driving circuit and a computer according to the actual situation and the pulse characteristics and pump power of the seed laser.

[0025] The application will be described in more detail below.

[0026] Figure 1A structure schematic diagram of a high-efficiency mid-infrared laser generation system based on dispersion-controlled soliton group pulses provided by the application is provided. The high-efficiency mid-infrared laser generation system based on dispersion-controlled soliton group pulses comprises, in sequence, a pulse fiber laser 1, a fiber pulse stretcher 2, a fiber laser amplifier 3, a fiber mode field adapter 4, and a nonlinear fiber 5.

[0027] The pulse fiber laser generates nanosecond pulse laser at a wavelength of 1.5 microns.

[0028] The fiber pulse stretcher performs spectral energy conversion of the nanosecond pulse laser from 1.5 microns to 2.4 microns.

[0029] The fiber laser amplifier further improves the output power of the pulse laser after the pulse laser is stretched and expands the spectrum to a wavelength of 2.7 microns, while improving the pulse energy at a wavelength of 2.3 microns.

[0030] The fiber mode field adapter efficiently couples the pulse generated by the fiber laser amplifier into the nonlinear fiber.

[0031] The nonlinear fiber expands the laser to a mid-infrared wavelength of 3-5 microns to obtain high-power, high-efficiency, and high-occupancy mid-infrared laser output.

[0032] The pulse fiber laser comprises a 1550nm distributed feedback semiconductor laser 1-1, a wavelength division multiplexer 1-2, a 976nm single-mode semiconductor laser 1-3, a single-mode erbium-doped fiber 1-4, and a fiber isolator 1-5, which are connected in sequence by a single-mode fiber to form a linear cavity structure. The above devices are connected by fiber fusion. The 976nm single-mode semiconductor laser provides pump light, the pump light is input through the wavelength division multiplexer and pumps the single-mode erbium-doped fiber, wherein the 1550nm distributed feedback semiconductor laser serves as a seed source, generates a 1.5-micron nanosecond pulse seed laser through modulation by a control circuit, performs preliminary power amplification in the single-mode erbium-doped fiber, and then transmits the generated 1.5-micron nanosecond pulse laser to the fiber pulse stretcher through the fiber isolator.

[0033] It can be seen that the connection relationship and working principle of each optical device of the pulse fiber laser 1 are as follows: the 1550nm distributed feedback semiconductor laser 1-1, the wavelength division multiplexer 1-2, the 976nm single-mode semiconductor laser 1-3 connected with the wavelength division multiplexer 1-2 through an optical fiber, the single-mode erbium-doped fiber 1-4 and the optical fiber isolator 1-5 are sequentially arranged along the optical path. In the linear cavity, the 976nm single-mode semiconductor laser 1-3 is coupled into the cavity through the wavelength division multiplexer 1-2 by the fiber core pumping mode to pump the single-mode erbium-doped fiber 1-4, the 1550nm distributed feedback semiconductor laser 1-1 acts as a seed light source, a 1.5 micron nanosecond pulse seed laser is generated through modulation by a control circuit, and the optical fiber isolator 1-5 acts as a pulse fiber laser output. The packaging mode adopts a full-fiber packaging mode, and the experiment is feasible in the experiment.

[0034] It should be noted that the 1550nm distributed feedback semiconductor laser of the pulse fiber laser can be controlled by a driving circuit and a computer, and can be adjusted according to the pulse characteristics of the seed laser, the pumping power and the like.

[0035] The fiber pulse stretcher 2 is arranged between the pulse fiber laser 1 and the fiber laser amplifier 3, and the fiber pulse stretcher 2 can split the nanosecond pulse into a plurality of superfast soliton pulses and cause frequency conversion and pulse spectrum width expansion to long waves in the 1.5-2.4 micron wave band through nonlinear effect, so as to provide abundant soliton group pulses for the next-stage fiber laser amplifier, and further improve the pulse power and the spectrum width.

[0036] The fiber laser amplifier comprises a fiber combiner 4-1, a 793nm semiconductor laser 4-2, a large-mode-area double-cladding thulium-doped fiber 4-3 and an optical fiber isolator 4-4. The 793nm semiconductor laser provides pumping light for the large-mode-area double-cladding thulium-doped fiber through the fiber combiner, and the optical fiber isolator isolates the feedback light formed by the subsequent optical path.

[0037] Therefore, the working principle of the pump light source of the high-efficiency mid-infrared laser generation system based on dispersion control soliton group pulses according to the application is as follows: the pulse fiber laser 1 is used to generate stable nanosecond pulse laser, the fiber pulse stretcher 2 splits the nanosecond pulse into a plurality of superfast soliton pulses through nonlinear effect, causes frequency conversion to long waves, and outputs the split superfast soliton pulse laser to the fiber laser amplifier 3, the fiber laser amplifier 3 is used to amplify the laser after pulse spectrum expansion, and improve the laser pulse energy after 2.3 microns, and the long-wave spectrum edge covering 2.7 micron wave band high-power laser is output after the fiber laser amplifier 3, which is used as the pump light source of the nonlinear optical fiber 5.

[0038] The fiber mode field adapter 4 efficiently couples the pulses generated in the fiber laser amplifier into the nonlinear fiber.

[0039] The nonlinear fiber 5 has a designed dispersion curve, characterized by its relatively flat shape in the near-zero dispersion region, an increasing absolute dispersion value with increasing wavelength, a sharply increasing slope in the 4-micrometer region, and a wide infrared transmission window. The nonlinear fiber 6 is a germanate fiber, fluoride fiber, or tellurate fiber. Under the influence of nonlinear effects such as self-phase modulation, modulation instability, and soliton self-frequency shift, the nonlinear fiber 5 extends the spectrum generated by the fiber laser amplifier 3 to the 5-micrometer band, achieving high-power, high-efficiency, and high-proportion mid-infrared laser output. The nonlinear fiber 5 and the fiber mode field adapter 4 are connected by fiber fusion splicing. The output end of the nonlinear fiber 5 is cut at a 15° angle to prevent Fresnel reflection.

[0040] Therefore, the working principle of the spectral broadening portion of the high-efficiency mid-infrared laser generation system based on dispersion-controlled soliton group pulses, according to the present invention, is as follows:

[0041] The dispersion regulation is reflected in two places: one is that a 1.5-micron pulse fiber laser is used instead of a conventional 2-micron thulium-doped fiber laser, and when the split soliton group pulse is used as the seed laser of the fiber laser amplifier, the spectrum of the output supercontinuum spectrum laser is more flat. The main reason is that the soliton group pulse actually contains a large number of soliton pulses with high peak power at different wavelengths, which can obtain different gains when evolving in the fiber laser amplifier, and different degrees of nonlinear evolution occur, which has an average effect on the supercontinuum spectrum, which is beneficial to the energy of the pulse at 2.3 microns in the fiber laser amplifier, so that the pump laser can first obtain a pulse with a high energy ratio at the long wave, which is beneficial to the spectrum expansion and the power ratio improvement of the later spectrum; the other is the nonlinear fiber part, which can obtain high-power, high-efficiency and high-occupancy mid-infrared laser output due to the dispersion control mechanism of the high-peak-power soliton group pulse. The dispersion curve of the nonlinear fiber can be divided into three stages. First, in the dispersion platform area, the pulse output by the fiber laser amplifier propagates to the near-zero dispersion area of the nonlinear fiber, the dispersion curve is relatively flat, and the spectral broadening is mainly dominated by soliton splitting and Raman soliton self-frequency shift. In the dispersion transition area, as the absolute value of the fiber dispersion gradually increases, the peak power of the soliton pulse with longer wavelength decreases due to dispersion, and the frequency shift speed slows down, so that the soliton pulse gradually accumulates at the long wave. In the steep increase area of the dispersion curve, the slope of the dispersion curve increases sharply in the 5-micron region, further weakening the red shift of the soliton pulse, causing the spectral broadening of the pulse to stop at around 5 microns, forming a long-wave boundary. At the same time, the short-wave pulse component continues to red shift, while the long-wave part stops, realizing the energy transfer from the short-wave to the long-wave region, thereby enhancing the mid-infrared waveband laser, and finally obtaining high-power, high-efficiency and high-occupancy mid-infrared laser in the 3-5-micron waveband.

[0042] In summary, the present application uses dispersion regulation technology to produce high-peak-power soliton group pulses as pump light through soliton pulse splitting, and the different degrees of nonlinear effects in different regions of the mid-infrared nonlinear fiber dispersion curve to improve the energy of the long-wave soliton pulse, shift the short-wave soliton pulse, and stop the long-wave part, so that high-power, high-efficiency and high-occupancy mid-infrared laser in the 3-5-micron waveband can be obtained. The present application uses a full-fiber structure, so that the laser has the advantages of compact structure, high integration, good stability and high conversion efficiency.

[0043] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Any simple modification, equivalent change and modification made according to the technical essence of the present application to the above embodiment still belongs to the protection scope of the technical solution of the present application.

Claims

1. A mid-infrared laser generation system based on dispersion-managed soliton group pulses, characterized by: It comprises a pulse fiber laser (1), a fiber pulse stretcher (2), a fiber laser amplifier (3), a fiber mode adapter (4), and a nonlinear fiber (5) connected in sequence, each part is connected by water cooling or semiconductor cooler, and is connected by fiber fusion; The pulse fiber laser generates nanosecond pulse laser of 1.5 micron band; The fiber pulse stretcher is a single-mode quartz optical fiber arranged between the pulse fiber laser and the fiber laser amplifier, which splits the nanosecond pulse into multiple superfast soliton pulses through nonlinear effect, and performs spectral energy conversion of the nanosecond pulse laser from 1.5 micron to 2.4 micron; The fiber laser amplifier further improves the output power of the pulse laser after the pulse is stretched and expands the spectrum to 2.7 micron band, while improving the pulse energy after 2.3 micron band; The fiber mode adapter efficiently couples the pulse generated in the fiber laser amplifier into the nonlinear fiber; The nonlinear fiber expands the laser to mid-infrared 3-5 micron band, and obtains high-power, high-efficiency, and high-occupancy mid-infrared laser output; The pulse fiber laser comprises a 1550nm distributed feedback semiconductor laser (1-1), a wavelength division multiplexer (1-2), a 976nm single-mode semiconductor laser (1-3), a single-mode erbium-doped optical fiber (1-4), and a first fiber isolator (1-5), which are connected in sequence by single-mode optical fibers to form a linear cavity structure; each device of the pulse fiber laser is connected by fiber fusion; The 976nm single-mode semiconductor laser provides pump light, which is input through the wavelength division multiplexer and pumps the single-mode erbium-doped optical fiber, wherein the 1550nm distributed feedback semiconductor laser acts as a seed source, generates 1.5 micron nanosecond pulse seed laser through modulation by a control circuit, preliminarily amplifies the power in the single-mode erbium-doped optical fiber, and then transmits the generated 1.5 micron nanosecond pulse laser to the fiber pulse stretcher through the first fiber isolator; The fiber laser amplifier comprises a fiber combiner (4-1), a 793nm semiconductor laser (4-2), a large-mode-area double-clad thulium-doped optical fiber (4-3), and a second fiber isolator (4-4), the 793nm semiconductor laser provides pump light for the large-mode-area double-clad thulium-doped optical fiber through the fiber combiner, and the second fiber isolator isolates the feedback light formed by the subsequent optical path; each device of the fiber laser amplifier is connected by fiber fusion; The fiber mode adapter connects the large-mode-area double-clad thulium-doped optical fiber and the single-mode optical fiber to match the nonlinear fiber; the fiber mode adapter connects the large-mode-area double-clad thulium-doped optical fiber and the single-mode optical fiber by fiber fusion. The nonlinear optical fiber utilizes a dispersion regulation mechanism to expand the spectrum generated by the fiber laser amplifier to the 5-micron wave band, realizes high-power, high-efficiency and high-occupancy mid-infrared laser output, and the nonlinear optical fiber is a longitudinally dispersed germanate optical fiber, a fluoride optical fiber, a tellurite optical fiber or a chalcogenide optical fiber, the longitudinal dispersion design of the nonlinear optical fiber includes three parts: a dispersion flat area for a soliton self-frequency shift process; a dispersion transition area for accumulating the number of soliton group pulses; and a dispersion steep increase area for enhancing the intensity of the soliton group pulses; the nonlinear optical fiber and the optical fiber mode field adapter are connected in a fiber fusion manner, and the optical fiber output end of the nonlinear optical fiber is subjected to 15-degree angle cutting treatment to prevent Fresnel reflection.

2. The mid-infrared laser generation system based on dispersion managed soliton pulses of claim 1, wherein: The 1550nm distributed feedback semiconductor laser of the pulse fiber laser is controlled by a driving circuit and a computer, and is adjusted according to the pulse characteristics of the seed laser and the pumping power.

Images