Multi-wavelength tunable narrow linewidth pulsed laser

Abstract

A kind of multi-wavelength tunable narrow line width pulse laser, including pump laser module, composite cavity optical parametric oscillation module and optical parametric amplification module three parts, to 1 μm laser as foundation, to composite cavity optical parametric oscillator is combined angle tuning optical parametric amplifier as laser technical means, through composite cavity length and parametric oscillation crystal temperature regulation realizes frequency selection and wavelength tuning, through parametric amplification crystal angle tuning realizes the scaling amplification of multiple wavelengths, obtains high energy, narrow line width, 1.5-1.6 μm multi-wavelength tunable pulse laser, with tunable, narrow line width, high energy, simple structure and the like advantages, can be used for a variety of greenhouse gas detection laser radar laser source, promote the development of airborne, spaceborne laser radar multi-substance detection technology.

Description

Technical Field

[0001] This invention relates to the field of pulsed laser technology, and in particular to a multi-wavelength tunable narrow linewidth pulsed laser. Technical Background

[0002] Integral path differential absorption (IPDA) lidar, as an active satellite remote sensing technology, features high spatiotemporal resolution, high detection accuracy, and strong anti-interference capabilities. It can perform global, all-weather, high-precision detection of various greenhouse gases in the atmosphere, such as carbon dioxide, methane, and water vapor, making it the most promising technology for active airborne and spaceborne greenhouse gas detection. Simultaneous detection of multiple greenhouse gases using the same IPD lidar system is a current research hotspot in gas remote sensing technology. Pulsed lasers, as the core component of lidar, must simultaneously meet requirements such as multi-wavelength, tunable, high-energy, narrow-linewidth, and simple structure. Therefore, the invention of a simple, reliable, multi-wavelength tunable narrow-linewidth pulsed laser is of great significance.

[0003] Currently, there are two main technical approaches for multi-wavelength narrow-linewidth pulsed laser sources for spaceborne lidar applications: one is to directly pump the laser gain medium using a laser diode and achieve multi-wavelength pulsed laser output by injecting seed lasers of different wavelengths. However, this approach has a complex structure and low output power, making it unsuitable for spaceborne applications. The other approach is based on a 1μm band pulsed laser pump source, combined with an optical parametric oscillator or optical parametric amplifier with seed lasers of different wavelengths to achieve narrow-pulse-width pulsed laser output at the target wavelength. However, this approach is limited by the tuning properties of the seed source itself, making it difficult to achieve wavelength output covering multiple greenhouse gas absorption lines using a single laser source. Therefore, a seed source is required for each wavelength, resulting in a complex system structure. Therefore, there is an urgent need to develop tunable narrow-linewidth pulsed lasers capable of outputting multiple wavelengths from a single laser system to promote the development of multi-matter detection lidar. Summary of the Invention

[0004] The purpose of this invention is to solve the problems of existing lasers used for greenhouse gas detection in lidar, such as single output wavelength, complex structure, low energy and poor stability. The invention provides a narrow linewidth pulsed laser that can output multiple wavelengths from a single laser, namely a multi-wavelength tunable narrow linewidth pulsed laser, which improves the wavelength tunability and output energy of the narrow linewidth pulsed laser, making it suitable for lidar multi-material detection and other fields.

[0005] Basic principles

[0006] Using a 1μm wavelength laser as the pump source, and combining a composite cavity optical parametric oscillator (OPO) and an angle-tuned optical parametric amplifier (OPA), a waveform converter and delay fiber are used to precisely adjust the pump waveform and the pump delay between the OPO and OPA, achieving high-precision timing matching of the pump. Frequency selection and wavelength tuning are achieved by adjusting the cavity length of the composite cavity and the temperature of the parametric oscillating crystal. Single-frequency tunable OPO laser output can be achieved without seed injection. Rapid switching between multiple wavelengths is achieved by angle tuning of the parametric amplification crystal, realizing calibrated amplification of multiple wavelengths, and obtaining high-energy, narrow-linewidth, 1.5–1.6μm multi-wavelength tunable pulsed laser output.

[0007] The technical solution of the present invention is as follows:

[0008] A multi-wavelength tunable narrow-linewidth pulsed laser is characterized by comprising three parts: a pump laser module, a composite cavity optical parametric oscillator module, and an optical parametric amplification module. The pump laser module generates a first pump laser and a second pump laser with a linewidth of 1 μm. The composite cavity optical parametric oscillator module receives the first pump laser and generates a single-frequency signal light with a linewidth of 1.5–1.6 μm. The optical parametric amplification module receives the second pump laser and the single-frequency signal light to generate a high-energy pulsed laser. The high-energy pulsed laser is a 1.5–1.6 μm narrow-linewidth tunable pulsed laser. The specific structure is as follows:

[0009] The pump laser module includes a 1μm single-frequency continuous seed laser for generating single-frequency continuous seed laser. The single-frequency continuous seed laser, after its output waveform is adjusted by a waveform converter, is split into a first split laser and a second split laser by an optical fiber beam splitter. The first split laser is transmitted via a first delay fiber to a first solid-state pre-amplification module for amplification, and then its polarization state is adjusted by a first half-wave plate before being output, forming the first pump laser. The second split laser, after being transmitted via a second delay fiber, is sequentially amplified by a second solid-state pre-amplification module and a solid-state main amplification module, and its polarization state is adjusted by a second half-wave plate before being output, forming the second pump laser.

[0010] The composite cavity optical parametric oscillator module is used to receive the first pump laser and generate a 1.5–1.6 μm single-frequency signal light. The first pump laser is split into a first reflection pump laser and a first transmission pump laser by a first polarization beam splitter. The first reflection pump laser is polarized by a third half-wave plate and then pumps the first composite cavity optical parametric oscillator to generate a first signal light and a first idler light. The first composite cavity optical parametric oscillator includes a first parametric cavity mirror, a first parametric crystal, and a second parametric cavity mirror. The first signal light is reflected by a first reflector to a first dichroic mirror and transmitted through the first dichroic mirror. The first idler light oscillates between the first parametric cavity mirror and the second parametric cavity mirror. The pump laser, after being reflected by the second mirror, pumps the second composite cavity optical parametric oscillator (CPOS) and generates a second signal light and a second idler light. The second composite cavity CPOS includes a third parametric cavity mirror, a second parametric crystal, and a fourth parametric cavity mirror. The second signal light is reflected by the first dichroic mirror and output. The second idler light oscillates between the third and fourth parametric cavity mirrors. The center wavelength of the first signal light can be tuned by adjusting the cavity length of the first composite cavity CPOS and the temperature of the first parametric crystal. The center wavelength of the second signal light can also be tuned by adjusting the temperature of the second composite cavity CPOS and the second parametric crystal. Both the first and second signal lights are single-frequency tunable pulsed lasers.

[0011] The optical parametric amplification module is used to receive the second pump laser, the first signal light, and the second signal light, and generate a high-energy, narrow-linewidth pulsed laser. The second pump laser is split into a second reflection pump laser and a second transmission pump laser by a second polarization beam splitter. The second reflection pump laser is transmitted to a second dichroic mirror after its polarization state is adjusted by a fourth half-wave plate. The second dichroic mirror transmits the second reflection pump laser and reflects the first and second signal lights to a first parametric amplification crystal. The first parametric amplification crystal amplifies the first signal light or the second signal light by angle adjustment and outputs a third signal light and a third idler light. The remaining second reflection pump laser and the third... The idler light is transmitted and output through the third dichroic mirror. The third signal light is reflected by the third dichroic mirror and then by the fourth dichroic mirror to the second parametric amplification crystal. The second transmission pump laser is reflected by the third mirror and transmitted through the fourth dichroic mirror to the second parametric amplification crystal. The second parametric amplification crystal amplifies the third signal light by adjusting the angle and outputs the fourth signal light and the fourth idler light. The remaining second transmission pump laser and the fourth idler light are transmitted and output through the fifth dichroic mirror. The fourth signal light is reflected and output by the fifth dichroic mirror. The third signal light and the fourth signal light have the same wavelength. The fourth signal light is a 1.5-1.6μm high-energy tunable narrow-linewidth pulsed laser.

[0012] The first composite cavity optical parametric oscillator comprises a first parametric cavity mirror and a second parametric cavity mirror forming a first idler cavity. A film layer is deposited on the end face of the first parametric crystal near the first parametric cavity mirror, forming a first signal cavity with the second parametric cavity mirror. The lengths of the first idler cavity and the first signal cavity are adjustable. The length of the first idler cavity is L1, and the frequency of the first idler light is ω1. The length of the first signal cavity is L2, and the frequency of the first signal light is ω2. Let the moving distance of the first parametric cavity mirror be ΔL1, and the moving distance of the second parametric cavity mirror be ΔL2. To achieve single-frequency pulse laser output through frequency selection by adjusting the cavity length, the following tuning relationship must be satisfied:

[0013] The second composite cavity optical parametric oscillator includes a second idler cavity formed by the third and fourth parametric cavity mirrors. A film layer is deposited on the end face of the second parametric crystal near the third parametric cavity mirror, forming a second signal cavity with the fourth parametric cavity mirror. The cavity lengths of the second idler cavity and the second signal cavity are adjustable. The cavity length of the second idler cavity is L3, and the frequency of the second idler light is ω3. The cavity length of the second signal cavity is L4, and the frequency of the second signal light is ω4. Assuming the moving distance of the third parametric cavity mirror is ΔL3 and the moving distance of the fourth parametric cavity mirror is ΔL4, to achieve single-frequency pulse laser output through frequency selection by adjusting the cavity length, the following tuning relationship must be satisfied:

[0014] The first composite cavity optical parametric oscillator includes a first parametric cavity mirror coated with a 0° 1μm antireflection film and a 3.3μm high reflectivity film; a second parametric cavity mirror coated with a 0° 1μm high reflectivity film, a 3.3μm high reflectivity film, and a 1.5μm dielectric film with 30% to 60% transmittance; a first parametric crystal with a 0° 1μm antireflection film, a 3.3μm antireflection film, and a 1.5μm high reflectivity film on its end face near the first parametric cavity mirror; and a first parametric crystal with a 0° 1μm, 3.3μm, and 1.5μm antireflection film on its end face near the second parametric cavity mirror.

[0015] The second composite cavity optical parametric oscillator includes a third parametric cavity mirror coated with a 0° 1μm antireflection film and a 3μm high reflectivity film; a second parametric cavity mirror coated with a 0° 1μm high reflectivity film, a 3μm high reflectivity film, and a 1.6μm dielectric film with 30% to 60% transmittance; a second parametric crystal with a 0° 1μm antireflection film, a 3μm antireflection film, and a 1.6μm high reflectivity film on its end face near the third parametric cavity mirror; and a second parametric crystal with a 0° 1μm, 3μm, and 1.6μm antireflection film on its end face near the fourth parametric cavity mirror.

[0016] The surface of the first reflector is coated with a 1.5-1.6 μm high-reflectivity film at a 45° angle; the surfaces of the second and third reflectors are coated with a 1 μm high-reflectivity film at a 45° angle.

[0017] The first dichroic mirror is coated with a 1.5μm antireflective film and a 1.6μm high-reflective film at a 45° angle; the second dichroic mirror is coated with a 1μm antireflective film and a 1.5-1.6μm high-reflective film at a 45° angle; the third dichroic mirror is coated with a 1μm and a 3.0-3.3μm antireflective film at a 45° angle, and a 1.5-1.6μm high-reflective film at a 1.6μm angle; the fourth dichroic mirror is coated with a 1μm antireflective film at a 45° angle, and a 1.5-1.6μm high-reflective film at a 1.6μm angle; and the fifth dichroic mirror is coated with a 1μm and a 3.0-3.3μm antireflective film at a 45° angle, and a 1.5-1.6μm high-reflective film at a 1.6μm angle.

[0018] The first parametric crystal and the second parametric crystal are periodically polarized lithium niobate (PPLN) crystals; the first parametric amplification crystal and the second parametric amplification crystal are potassium titanate oxyphosphate (KTA) crystals or potassium titanate oxyphosphate (KTP) crystals, and the two end faces of the crystals are coated with 0° antireflection films of 1μm, 1.5-1.6μm and 3.0-3.3μm.

[0019] The first, second, third, and fourth half-wave plates are all 1μm half-wave plates, and their surfaces are all coated with a 0° 1μm antireflection film.

[0020] The first and second solid-state pre-amplification modules include a pre-amplification crystal and a pump source, wherein the pre-amplification crystal is an Nd:YVO4 crystal or an Nd:YAG crystal; the solid-state main amplification module includes a main amplification crystal and a pump source, wherein the main amplification crystal is an Nd:YAG crystal.

[0021] The technical effects of this invention are as follows:

[0022] Compared with existing technologies, the multi-wavelength tunable narrow-linewidth pulsed laser of this invention uses a 1μm wavelength laser as the pump source and employs a waveform converter and delay fiber to precisely adjust the pump waveform and the pump delay between the OPO and OPA, achieving high-precision timing matching and high-efficiency laser output. It adopts a composite cavity OPO design, achieving frequency selection and wavelength tuning by adjusting the cavity length and temperature of the parametric oscillating crystal, enabling single-frequency tunable OPO laser output without seed injection. Furthermore, it employs an angle-tunable OPA design, achieving rapid switching between multiple wavelengths through angle tuning of the parametric amplification crystal, enabling calibrated amplification of multiple wavelengths, and obtaining high-energy, narrow-linewidth, 1.5–1.6μm multi-wavelength tunable pulsed laser output.

[0023] This invention aims to solve key technical problems such as tunable output of high-energy, narrow-linewidth laser wavelength under a simple structure, effectively promoting the research and development of long-distance, high-precision detection technology for various substances, and is applicable to various fields such as spaceborne and airborne lidar for greenhouse gas detection. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the multi-wavelength tunable narrow linewidth pulsed laser structure of the present invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the present invention clearer, the technology of the present invention will be further described below in conjunction with the embodiments and accompanying drawings, but this should not be construed as limiting the scope of protection of the present invention.

[0026] Example

[0027] Figure 1 This is a schematic diagram of the structure of the multi-wavelength tunable narrow linewidth pulsed laser of the present invention, as shown below. Figure 1As shown, the embodiment of the multi-wavelength tunable narrow-linewidth pulsed laser of the present invention comprises three parts: a pump laser module 1, a composite cavity optical parametric oscillation module 2, and an optical parametric amplification module 3. The pump laser module 1 generates a first pump laser and a second pump laser with a linewidth of 1.06 μm. The composite cavity optical parametric oscillation module 2 receives the first pump laser and generates a single-frequency signal light with a linewidth of 1.57–1.65 μm in the μJ range. The optical parametric amplification module 3 receives the second pump laser and the single-frequency signal light and generates a high-energy pulsed laser. The high-energy pulsed laser is a narrow-linewidth tunable pulsed laser with a linewidth of 1.57–1.65 μm.

[0028] In this embodiment, to obtain high-energy target multi-wavelength tunable narrow-linewidth pulsed laser output, the pump laser module 1 includes a 1.06μm single-frequency continuous seed laser 1-1 for generating μJ-level single-frequency continuous seed laser. After the single-frequency continuous seed laser's output waveform is adjusted by a waveform converter 1-2, it is split into a first split laser and a second split laser by an optical fiber beam splitter 1-3. The first split laser is transmitted through a first delay fiber 1-4 to a first solid-state pre-amplification module 1-5 for amplification, and then its polarization state is adjusted by a first half-wave plate 1-6 before being output to form the first pump laser. The second split laser is transmitted through a second delay fiber 1-7 and then amplified sequentially by a second solid-state pre-amplification module 1-8 and a solid-state main amplification module 1-9, and its polarization state is adjusted by a second half-wave plate 1-10 before being output to form the second pump laser.

[0029] The composite cavity optical parametric oscillator module 2 is used to receive the first pump laser and generate a 1.57–1.65 μm signal light. The first pump laser is split into a first reflection pump laser and a first transmission pump laser by a first polarization beam splitter 2-1. The first reflection pump laser is adjusted in polarization state by a third half-wave plate 2-2 and then pumps the first composite cavity optical parametric oscillator 2-3 to generate a first signal light with a wavelength of 1.572 μm and a first idler light with a wavelength of 3.292 μm. The first composite cavity optical parametric oscillator 2-3 includes a first parametric cavity mirror 231, a first parametric crystal 232, and a second parametric cavity mirror 233. The first signal light is reflected by a first reflecting mirror 2-4 to a first dichroic mirror 2-7 and then transmitted and output by the first dichroic mirror 2-7. The first idler light oscillates between the first parametric cavity mirror 231 and the second parametric cavity mirror 233. The first signal laser, after being reflected by the second mirror 2-5, pumps the second composite cavity optical parametric oscillator 2-6 to generate a second signal light with a wavelength of 1.645 μm and a second idler light with a wavelength of 3.012 μm. The second composite cavity optical parametric oscillator 2-6 includes a third parametric cavity mirror 261, a second parametric crystal 262, and a fourth parametric cavity mirror 263. The second signal light is reflected by the first dichroic mirror 2-7 and output. The second idler light oscillates between the third parametric cavity mirror 261 and the fourth parametric cavity mirror 263. The center wavelength of the first signal light can be tuned by adjusting the cavity length of the first composite cavity optical parametric oscillator 2-3 and the temperature of the first parametric crystal 232. The center wavelength of the second signal light can be tuned by adjusting the temperature of the second composite cavity optical parametric oscillator 2-6 and the second parametric crystal 262. The first signal light and the second signal light are single-frequency tunable pulsed lasers.

[0030] The optical parametric amplification module 3 is used to receive the second pump laser, the first signal light, and the second signal light, and generate a high-energy, narrow-linewidth pulsed laser. The second pump laser is split into a second reflection pump laser and a second transmission pump laser by a second polarization beam splitter 3-1. The second reflection pump laser is transmitted to a second dichroic mirror 3-3 after its polarization state is adjusted by a fourth half-wave plate 3-2. The second dichroic mirror 3-3 transmits the second reflection pump laser and reflects the first and second signal lights to a first parametric amplification crystal 3-4. The first parametric amplification crystal 3-4 amplifies the first signal light or the second signal light by angle adjustment and outputs a third signal light and a third idler light. The remaining second reflection pump laser and the third idler light are then transmitted through a third... The third signal light is transmitted and output through the dichroic mirror 3-5. The third signal light is reflected by the third dichroic mirror 3-5 and then by the fourth dichroic mirror 3-7 to the second parametric amplification crystal 3-8. The second transmission pump laser is reflected by the third mirror 3-6 and transmitted through the fourth dichroic mirror 3-7 to the second parametric amplification crystal 3-8. The second parametric amplification crystal 3-8 amplifies the third signal light by adjusting the angle and outputs the fourth signal light and the fourth idler light. The remaining second transmission pump laser and the fourth idler light are transmitted and output through the fifth dichroic mirror 3-9. The fourth signal light is reflected and output by the fifth dichroic mirror 3-9. The third signal light and the fourth signal light have the same wavelength. The fourth signal light is a 1.57-1.65μm high-energy tunable narrow-linewidth pulsed laser.

[0031] In this embodiment, the first composite cavity optical parametric oscillator 2-3 includes a first parametric cavity mirror 231 and a second parametric cavity mirror 233 forming a first idler cavity. A film layer is deposited on the end face of the first parametric crystal 232 near the first parametric cavity mirror 231, forming a first signal cavity with the second parametric cavity mirror 233. The cavity lengths of the first idler cavity and the first signal cavity are adjustable. The cavity length of the first idler cavity is L1, and the frequency of the first idler light is ω1. The cavity length of the first signal cavity is L2, and the frequency of the first signal light is ω2. Let the moving distance of the first parametric cavity mirror 231 be ΔL1, and the moving distance of the second parametric cavity mirror 233 be ΔL2. To achieve single-frequency pulse laser output by adjusting the cavity length for frequency selection, the following tuning relationship must be satisfied:

[0032] The second composite cavity optical parametric oscillator 2-6 includes a second idler cavity composed of a third parametric cavity mirror 261 and a fourth parametric cavity mirror 263. A film layer is deposited on the end face of the second parametric crystal 262 near the third parametric cavity mirror 261, forming a second signal cavity with the fourth parametric cavity mirror 263. The cavity lengths of the second idler cavity and the second signal cavity are adjustable. The cavity length of the second idler cavity is L3, and the frequency of the second idler light is ω3. The cavity length of the second signal cavity is L4, and the frequency of the second signal light is ω4. Assuming the moving distance of the third parametric cavity mirror 261 is ΔL3 and the moving distance of the fourth parametric cavity mirror 263 is ΔL4, to achieve single-frequency pulse laser output through frequency selection by adjusting the cavity length, the following tuning relationship must be satisfied:

[0033]

[0034] In this embodiment, the first composite cavity parametric oscillator 2-3 includes a first parametric cavity mirror 231 coated with a 0° 1.06μm antireflection film and a 3.29μm high reflectivity film; a second parametric cavity mirror 233 coated with a 0° 1.06μm high reflectivity film, a 3.29μm high reflectivity film, and a 1.57μm 30% transmittance dielectric film; a first parametric crystal 232 with a 0° 1.06μm antireflection film, a 3.29μm antireflection film, and a 1.57μm high reflectivity film near the end face of the first parametric cavity mirror 231; and a first parametric crystal 232 with a 0° 1.06μm, 3.29μm, and 1.57μm antireflection film near the end face of the second parametric cavity mirror 233.

[0035] The second composite cavity parametric oscillator 2-6 includes the third parametric cavity mirror 261 coated with a 0° 1.06μm antireflection film and a 3.01μm high reflectivity film; the second parametric cavity mirror 263 coated with a 0° 1.06μm high reflectivity film, a 3.01μm high reflectivity film, and a 1.65μm 30 transmittance dielectric film; the second parametric crystal 262 is coated with a 0° 1.06μm antireflection film, a 3.01μm antireflection film, and a 1.65μm high reflectivity film on its end face near the third parametric cavity mirror 261; and the second parametric crystal 262 is coated with a 0° 1.06μm, 3.01μm, and 1.65μm antireflection film on its end face near the fourth parametric cavity mirror 263.

[0036] The surface of the first reflector 2-4 is coated with a 1.57-1.65μm high-reflectivity film at a 45° angle; the surfaces of the second reflector 2-5 and the third reflector 3-6 are coated with a 1.06μm high-reflectivity film at a 45° angle.

[0037] The first dichroic mirror 2-7 has a 45° antireflective coating of 1.57μm and a 1.65μm high reflective coating on its surface; the second dichroic mirror 3-3 has a 45° antireflective coating of 1.06μm and a 1.57-1.65μm high reflective coating on its surface; the third dichroic mirror 3-5 has a 45° antireflective coating of 1.06μm and 3.01-3.29μm and a 1.54-1.65μm high reflective coating on its surface; the fourth dichroic mirror 3-7 has a 45° antireflective coating of 1.06μm and a 1.57-1.65μm high reflective coating on its surface; and the fifth dichroic mirror 3-9 has a 45° antireflective coating of 1.06μm and 3.01-3.29μm and a 1.57-1.65μm high reflective coating on its surface.

[0038] In this embodiment, the first parametric crystal 232 and the second parametric crystal 262 are periodically polarized lithium niobate (PPLN) crystals with a length of 10 mm; the first parametric amplification crystal 3-4 and the second parametric amplification crystal 3-8 are type II matched potassium titanyl arsenate (KTA) crystals with a cutting angle θ = 41.8°. The crystal measures 8×8×20mm and has antireflective coatings of 1.06μm, 1.57~1.65μm, and 3.01~3.29μm at 0° on its two end faces.

[0039] In this embodiment, the first half-wave plate 1-6, the second half-wave plate 1-9, the third half-wave plate 2-2 and the fourth half-wave plate 3-2 are all 1.06μm half-wave plates, and their surfaces are all coated with a 0° 1.06μm antireflection film.

[0040] In this embodiment, the first solid-state pre-amplification module 1-5 and the second solid-state pre-amplification module 1-8 include a pre-amplification crystal and a pump source, wherein the pre-amplification crystal is an Nd:YVO4 crystal; the solid-state main amplification module 1-8 includes a main amplification crystal and a pump source, wherein the main amplification crystal is an Nd:YAG crystal.

[0041] Experiments show that this invention uses a 1.06μm wavelength laser as the pump source and employs a waveform converter and delay fiber to precisely adjust the pump delay between the OPO and OPA, achieving high-precision timing matching and high-efficiency laser output. The composite cavity OPO design, through frequency selection and wavelength tuning by adjusting the cavity length and temperature of the parametric oscillating crystal, enables single-frequency tunable OPO laser output without seed injection. The angle-tunable OPA design, through angle tuning of the parametric amplification crystal, allows for rapid switching between multiple wavelengths, achieving calibration amplification of multiple wavelengths. This results in high-energy, narrow-linewidth, 1.5–1.6μm multi-wavelength tunable pulsed laser output, possessing advantages such as high beam quality and simple structure. This invention is of great significance for the development of airborne and spaceborne integral path differential absorption lidar for the simultaneous and independent detection of multiple greenhouse gases.

[0042] The embodiments are merely illustrative of the technical features of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this invention should be included within the scope of protection of this invention. Therefore, the scope of protection of this invention should be determined by the scope of the claims.

Claims

1. A multi-wavelength tunable narrow linewidth pulsed laser, characterized in that, The system comprises three parts: a pump laser module (1), a composite cavity optical parametric oscillation module (2), and an optical parametric amplification module (3). The pump laser module (1) generates a first pump laser and a second pump laser with a diameter of 1 μm. The composite cavity optical parametric oscillation module (2) receives the first pump laser and generates a single-frequency signal light with a diameter of 1.5~1.6 μm. The optical parametric amplification module (3) receives the second pump laser and the single-frequency signal light to generate a high-energy pulsed laser. The high-energy pulsed laser is a 1.5~1.6 μm narrow-linewidth tunable pulsed laser. The specific structure is as follows: The pump laser module (1) includes a 1 μm single-frequency continuous seed laser (1-1) for generating a single-frequency continuous seed laser. After the output waveform of the single-frequency continuous seed laser is adjusted by a waveform converter (1-2), it is split into a first split laser and a second split laser by an optical fiber beam splitter (1-3). The first split laser is transmitted to a first solid-state pre-amplification module (1-5) via a first delay fiber (1-4) and amplified. Then, the polarization state is adjusted by a first half-wave plate (1-6) and output to form a first pump laser. The second split laser is transmitted via a second delay fiber (1-7) and then amplified by a second solid-state pre-amplification module (1-8) and a solid-state main amplification module (1-9). After the polarization state is adjusted by a second half-wave plate (1-10), it is output to form a second pump laser. The composite cavity optical parametric oscillator module (2) is used to receive the first pump laser and generate a 1.5~1.6 μm single-frequency signal light. The first pump laser is split into a first reflection pump laser and a first transmission pump laser by a first polarization beam splitter (2-1). The first reflection pump laser is adjusted in polarization state by a third half-wave plate (2-2) and then pumps the first composite cavity optical parametric oscillator (2-3) to generate a first signal light and a first idler light. The first composite cavity optical parametric oscillator (2-3) includes a first parametric cavity mirror (231), a first parametric crystal (232), and a second parametric cavity mirror (233). The first signal light is reflected by a first reflector (2-4) to a first dichroic mirror (2-7) and then transmitted through the first dichroic mirror (2-7). The first idler light oscillates between the first parametric cavity mirror (231) and the second parametric cavity mirror (233). The first transmission pump laser is reflected by a second reflector (2-5) and then pumps the first composite cavity optical parametric oscillator (2-3). A dual-cavity optical parametric oscillator (2-6) generates a second signal light and a second idler light. The second dual-cavity optical parametric oscillator (2-6) includes a third parametric cavity mirror (261), a second parametric crystal (262), and a fourth parametric cavity mirror (263). The second signal light is reflected and output through the first dichroic mirror (2-7). The second idler light oscillates between the third parametric cavity mirror (261) and the fourth parametric cavity mirror (263). The center wavelength of the first signal light can be tuned by adjusting the cavity length of the first dual-cavity optical parametric oscillator (2-3) and the temperature of the first parametric crystal (232). The center wavelength of the second signal light can be tuned by adjusting the temperature of the second dual-cavity optical parametric oscillator (2-6) and the second parametric crystal (262). The first signal light and the second signal light are single-frequency tunable pulsed lasers. The optical parametric amplification module (3) is used to receive the second pump laser, the first signal light, and the second signal light, and generate a high-energy, narrow-linewidth pulsed laser. The second pump laser is split into a second reflection pump laser and a second transmission pump laser by a second polarization beam splitter (3-1). The second reflection pump laser is transmitted to a second dichroic mirror (3-3) after its polarization state is adjusted by a fourth half-wave plate (3-2). The second dichroic mirror (3-3) transmits the second reflection pump laser and reflects the first and second signal lights to a first parametric amplification crystal (3-4). The first parametric amplification crystal (3-4) amplifies the first signal light or the second signal light by adjusting the angle and outputs a third signal light and a third idler light. The remaining second reflection pump laser and the third... The idler light is transmitted and output through the third dichroic mirror (3-5). The third signal light is reflected by the third dichroic mirror (3-5) and then by the fourth dichroic mirror (3-7) to the second parametric amplification crystal (3-8). The second transmission pump laser is reflected by the third mirror (3-6) and then transmitted through the fourth dichroic mirror (3-7) to the second parametric amplification crystal (3-8). The second parametric amplification crystal (3-8) amplifies the third signal light by angle adjustment and outputs the fourth signal light and the fourth idler light. The remaining second transmission pump laser and the fourth idler light are transmitted and output through the fifth dichroic mirror (3-9). The fourth signal light is reflected and output by the fifth dichroic mirror (3-9). The third signal light and the fourth signal light have the same wavelength. The fourth signal light is a 1.5~1.6 μm high-energy tunable narrow-linewidth pulsed laser.

2. The multi-wavelength tunable narrow linewidth pulsed laser according to claim 1, characterized in that, The first composite cavity optical parametric oscillator (2-3) comprises a first parametric cavity formed by the first parametric cavity mirror (231) and the second parametric cavity mirror (233). A first parametric crystal (232) deposits a film on its end face near the first parametric cavity mirror (231) and together with the second parametric cavity mirror (233), forms a first signal cavity. The lengths of the first idler cavity and the first signal cavity are adjustable. The length of the first idler cavity is... The first idler frequency is The length of the first signal cavity is The frequency of the first signal light is Let the moving distance of the first parametric endoscope (231) be... The second parametric endoscope (233) moves a distance of 100 km. To achieve single-frequency pulse laser output through cavity length adjustment, the following tuning relationship must be satisfied: ; The second composite cavity optical parametric oscillator (2-6) comprises a second idler cavity formed by the third parametric cavity mirror (261) and the fourth parametric cavity mirror (263). A film is deposited on the end face of the second parametric crystal (262) near the third parametric cavity mirror (261), forming a second signal cavity with the fourth parametric cavity mirror (263). The lengths of the second idler cavity and the second signal cavity are adjustable. The length of the second idler cavity is... The second idler frequency is The length of the second signal cavity is The frequency of the second signal light is Let the moving distance of the third parameter laparoscope (261) be... The fourth parametric endoscope (263) moves a distance of 100 km. To achieve single-frequency pulse laser output through cavity length adjustment, the following tuning relationship must be satisfied: .

3. The multi-wavelength tunable narrow linewidth pulsed laser according to claim 1, characterized in that, The first composite cavity parametric oscillator (2-3) includes a first parametric cavity mirror (231) coated with a 0° 1 μm antireflection film and a 3.3 μm high reflectivity film; a second parametric cavity mirror (233) coated with a 0° 1 μm high reflectivity film, a 3.3 μm high reflectivity film and a 1.5 μm 30%~60% transmittance dielectric film; a first parametric crystal (232) with a 0° 1 μm antireflection film, a 3.3 μm antireflection film and a 1.5 μm high reflectivity film near the end face of the first parametric cavity mirror (231); and a first parametric crystal (232) with a 0° 1 μm, 3.3 μm and 1.5 μm antireflection film near the end face of the second parametric cavity mirror (233). The second composite cavity optical parametric oscillator (2-6) includes the third parametric cavity mirror (261) coated with a 0° 1 μm antireflection film and a 3 μm high reflectivity film, the fourth parametric cavity mirror (263) coated with a 0° 1 μm high reflectivity film, a 3 μm high reflectivity film and a 1.6 μm 30%~60% transmittance dielectric film, the second parametric crystal (262) near the end face of the third parametric cavity mirror (261) coated with a 0° 1 μm antireflection film, a 3 μm antireflection film and a 1.6 μm high reflectivity film, and the second parametric crystal (262) near the end face of the fourth parametric cavity mirror (263) coated with a 0° 1 μm, 3 μm and 1.6 μm antireflection film; The surface of the first reflector (2-4) is coated with a 1.5~1.6 μm high-reflectivity film at a 45° angle; the surfaces of the second reflector (2-5) and the third reflector (3-6) are coated with a 1 μm high-reflectivity film at a 45° angle. The surface of the first dichroic mirror (2-7) is coated with a 1.5 μm antireflective coating and a 1.6 μm high-reflective coating at a 45° angle; the surface of the second dichroic mirror (3-3) is coated with a 1 μm antireflective coating at a 45° angle and a 1.5~1.6 μm high-reflective coating; the surface of the third dichroic mirror (3-5) is coated with a 1 μm and a 3.0~3.3 μm antireflective coating at a 45° angle and a 1.5~1.6 μm high-reflective coating; the surface of the fourth dichroic mirror (3-7) is coated with a 1 μm antireflective coating at a 45° angle and a 1.5~1.6 μm high-reflective coating; and the surface of the fifth dichroic mirror (3-9) is coated with a 1 μm and a 3.0~3.3 μm antireflective coating at a 45° angle and a 1.5~1.6 μm high-reflective coating.

4. The multi-wavelength tunable narrow linewidth pulsed laser according to claim 1, characterized in that, The first parametric crystal (232) and the second parametric crystal (262) are periodically polarized lithium niobate (PPLN) crystals; the first parametric amplification crystal (3-4) and the second parametric amplification crystal (3-8) are potassium titanate oxy arsenate (KTA) crystals or potassium titanate oxy phosphate (KTP) crystals, and the two end faces of the crystals are coated with 0° 1 μm, 1.5~1.6 μm and 3.0~3.3 μm antireflection films.

5. The multi-wavelength tunable narrow linewidth pulsed laser according to claim 1, characterized in that, The first half-wave plate (1-6), the second half-wave plate (1-10), the third half-wave plate (2-2), and the fourth half-wave plate (3-2) are all 1 μm half-wave plates, and their surfaces are all coated with a 0° 1 μm antireflection film.

6. The multi-wavelength tunable narrow linewidth pulsed laser according to any one of claims 1 to 5, characterized in that, The first solid-state pre-amplification module (1-5) and the second solid-state pre-amplification module (1-8) include a pre-amplification crystal and a pump source, wherein the pre-amplification crystal is an Nd:YVO4 crystal or an Nd:YAG crystal; the solid-state main amplification module (1-9) includes a main amplification crystal and a pump source, wherein the main amplification crystal is an Nd:YAG crystal.

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