Ultra-wideband tunable mid-infrared laser device and beam pointing stabilization method

Abstract

The application discloses a kind of ultra-wide waveband tunable mid-infrared laser device and light beam pointing stability method, the device includes fundamental frequency pump source, ultra-wide tuning ring resonator, nonlinear frequency conversion crystal, laser wavelength tuning controller, light beam pointing stability controller;Fundamental frequency pump source is used to provide the pump laser of high peak power pulse emission, ultra-wide tuning ring resonator adopts special hetero angle design, with high refractive index intrinsic substrate as input and output coupling mirror, pump laser is incident with Bragg angle high refractive index intrinsic substrate and is coupled into resonator by it, at least two cavity mirrors in resonator mirror are gold mirror, which is high reflection for near-infrared and mid-infrared band, pump light is coupled into resonator by nonlinear frequency conversion crystal and forms closed loop optical path in resonator, realizes high-efficiency optical parametric oscillation and generates mid-infrared laser with extremely wide wavelength tuning range, light beam pointing stability controller controls resonator mirror to compensate light beam pointing deviation, realizes wavelength continuous tuning and light beam pointing keeps unchanged.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser frequency conversion, and in particular to an ultra-wide waveband tunable mid-infrared laser device and a beam pointing stabilization method. BACKGROUND

[0002] The existing mid-infrared laser can only work in one of the 3 μm~5 μm, 5 μm~8 μm, 8 μm~10 μm or 9 μm~11 μm mid-infrared wavebands due to the limitations of the emission spectrum bandwidth of the working medium and the medium film reflection bandwidth of the resonant cavity mirror, and cannot simultaneously realize ultra-wide waveband continuous tuning and high-power operation. Moreover, the wavelength tuning process of the existing mid-infrared laser has a problem of beam pointing deviation, which is difficult to meet the actual application requirements of the mid-infrared laser. SUMMARY

[0003] The present application aims to overcome at least one of the problems of insufficient wavelength continuous tuning capability of the existing mid-infrared laser, large beam pointing transformation in the tuning process, and difficulty in high-power operation.

[0004] To solve the above technical problems, the present application provides an ultra-wide waveband tunable mid-infrared laser device, comprising:

[0005] A fundamental frequency pumping source for providing pulse-emitted pumping laser;

[0006] A shaping assembly placed on the output light path of the fundamental frequency pumping source for adjusting the polarization direction, spot size, injection pulse energy and pulse structure of the pumping laser;

[0007] An ultra-wide tuning ring resonant cavity comprising a first mirror, a second mirror, a third mirror and a fourth mirror, placed on the light path of the pumping laser shaped by the shaping assembly, the first mirror comprising a first mirror surface and a second mirror surface arranged in parallel and a third mirror surface arranged at an angle with the first mirror surface, The third mirror surface is arranged at an angle with the first mirror surface, Or Wherein, n1 is the refractive index of the first mirror at the wavelength of the pumping laser, and the angle between the normal line of the first mirror surface and the incident light line of the pumping laser is θB is the Brewster angle of the first mirror, Satisfying: , the first mirror surface and the second mirror surface are mirror surfaces polished directly on intrinsic substrates, the second mirror surface, the third mirror surface and the fourth mirror surface respectively include a fourth mirror surface, a fifth mirror surface and a sixth mirror surface, the fourth mirror surface is coated with a full reflection gold film, one of the fifth mirror surface and the sixth mirror surface is coated with a full reflection gold film, and the other is coated with a full reflection gold film or a film layer with high reflection to pump laser and signal light and high transmission to idler light, the pump laser sequentially passes through the first mirror surface and the second mirror surface, and then sequentially passes through the fourth mirror surface, the fifth mirror surface and the sixth mirror surface to be reflected to the second mirror surface to form a ring light path, the pump laser reflected by the sixth mirror surface is output from the third mirror surface after passing through the second mirror surface; ;

[0008] The nonlinear frequency conversion crystal includes a first light transmission end surface and a second light transmission end surface arranged in parallel, one optical axis of the nonlinear frequency conversion crystal is in the same plane as the normal line of the first light transmission end surface and the incident pump laser, the nonlinear frequency conversion crystal is located on the ring light path and is arranged between the first mirror and the second mirror or between the second mirror and the third mirror, and together with the super-wide tuning ring resonator forms an optical parametric oscillator for generating signal light and idler light;

[0009] The bichromatic spectroscope is used for separating the pump laser and the laser output from the optical parametric oscillator to form monitoring light;

[0010] The laser wavelength tuning controller is used for adjusting the phase matching angle of the nonlinear frequency conversion crystal to realize continuous tuning of the wavelength of the signal light and the idler light.

[0011] The beam pointing stability controller is used for detecting the monitoring light and feeding back and adjusting the angles of the fifth mirror surface and the sixth mirror surface to compensate for the beam pointing deviation of the mid-infrared laser in the tuning process so that the beam pointing of the mid-infrared laser is stable and unchanged.

[0012] Optionally, the distance between the first mirror surface and the second mirror surface is less than 1.5 times the diameter of the pump laser beam. The following conditions are met:

[0013]

[0014] In the formula, D is the diameter of the pump laser beam after being shaped by the shaping assembly, D1 is the Brunost angle of the first mirror. Optionally, when the nonlinear frequency conversion crystal is a type II phase matching crystal, the polarization direction of the signal light is orthogonal to the polarization direction of the pump laser, the second mirror surface partially reflects the signal light and has high transmission to the pump laser and the idler light,

[0015]

[0016] ​​​When the nonlinear frequency conversion crystal is a type I phase matching crystal, the polarization directions of the signal light and the idler light are orthogonal to the polarization direction of the pump laser, the second mirror surface reflects part of the signal light and the idler light and is highly transmissive to the pump laser, and the third mirror surface is coated with an antireflection film for the pump laser, the signal light and the idler light.

[0017] Optionally, the laser wavelength tuning controller comprises a crystal fixing frame, a rotating table and a wavelength-angle correlation controller.

[0018] The crystal fixing frame is configured to fix the nonlinear frequency conversion crystal to the rotating table, and the wavelength-angle correlation controller is configured to control the rotating table to rotate according to a preset wavelength, so as to change the included angle between the normal line of the light transmission end surface and the pump laser beam line incident to the nonlinear frequency conversion crystal. Thus, the phase matching angle inside the crystal is adjusted. to realize the mid-infrared laser output at the target wavelength, and satisfy the following relationship: wherein, is the mid-infrared crystal cut angle.

[0019] Optionally, the light beam pointing stability controller comprises a first adjusting frame, a second adjusting frame, a light beam position monitoring assembly and a feedback controller.

[0020] The first adjusting frame is configured to fix the third mirror and adjust the angle of the fifth mirror.

[0021] The second adjusting frame is configured to fix the fourth mirror and adjust the angle of the sixth mirror.

[0022] The light beam position monitoring assembly comprises a first pinhole diaphragm, a second pinhole diaphragm and a laser detector arranged in sequence, the centers of the first pinhole diaphragm, the second pinhole diaphragm and the laser detector are placed on the light path of initial monitoring light, the initial monitoring light is monitoring light reflected by the dichroic mirror when the pump laser is vertically incident to the nonlinear frequency conversion crystal, the light beam position monitoring assembly is configured to acquire the light beam information of the monitoring light and send it to the feedback controller, the light beam information comprises the power and / or the spot position recorded by the laser detector, and the feedback controller is configured to compare the light beam information recorded by the light beam position monitoring assembly with initial light beam information, and feed back to control the first adjusting frame and the second adjusting frame so that the light beam information recorded by the light beam position monitoring assembly is consistent with the initial light beam information, so as to realize the stability of the light beam pointing during the tuning process of the mid-infrared laser, and the initial light beam information comprises the power and / or the spot position of the initial monitoring light.

[0023] Optionally, when the pulse width of the pump laser is ≥300 ps, the super-wide tuning ring resonator works in a short cavity optical parametric oscillation mode, and the cavity length is satisfies: wherein is the speed of light;

[0024] When the pulse width of the pump laser satisfies 300 ps, the super-wideband tunable ring cavity works in the synchronous pump optical parametric oscillation mode, and the cavity length of the super-wideband tunable ring cavity satisfies and the pulse repetition frequency of the pump laser satisfies satisfies: wherein is a positive integer less than 100, is the speed of light.

[0025] Optionally, the first mirror substrate material is zinc selenide, and the absorption coefficient of the zinc selenide to the 0.8-14-micron-band laser satisfies satisfies: and the refractive index of the zinc selenide to the 0.8-14-micron-band laser is between 2.35 and 2.55.

[0026] Optionally, the shaping assembly comprises a half-wave plate, a polarization beam splitter, a shaping lens combination, and a chopping modulator arranged in the light path of the pump laser output by the fundamental frequency pump source, the half-wave plate is used to adjust the polarization direction of the pump laser, the polarization beam splitter is used to separate the pump laser with orthogonal polarization, the polarization beam splitter and the half-wave plate are used in combination to adjust the energy of the pump laser injected into the super-wideband tunable ring cavity, and the shaping lens combination at least comprises a convex lens used to adjust the spot appearance and the beam diameter width of the pump laser. The chopping modulator comprises at least one of an acousto-optic chopping modulator, an electro-optic chopping modulator, and a mechanical chopper, and is used to perform chopping operation on the optical pulse of the pump laser in the time domain to obtain the pump laser with a required pulse repetition frequency and pulse train structure.

[0027] Optionally, the pump laser is one or more lasers with a wavelength in the range of 0.8-3 microns, the peak power of the pump laser is greater than 1 kW, the pulse width of the pump laser satisfies , and the pulse energy of the pump laser satisfies . .

[0028] The application further provides a method for stabilizing the pointing direction of a super-wideband tunable mid-infrared laser beam, which is used for the super-wideband tunable mid-infrared laser device in any of the above embodiments, and the method comprises the following steps:

[0029] adjusting the angle of the nonlinear frequency conversion crystal by the laser wavelength tuning controller so that the pump laser is incident on the light-transmitting end surface of the nonlinear frequency conversion crystal vertically, to realize the output of the mid-infrared laser along a preset direction;

[0030] The light beam pointing stability controller acquires initial light beam information of the monitoring light, and the initial light beam information includes light beam information of the monitoring light when the pump laser is incident on the light-transmitting end surface of the nonlinear frequency conversion crystal;

[0031] The laser wavelength tuning controller adjusts the angle of the nonlinear frequency conversion crystal to obtain a middle infrared laser output at any target wavelength in a tunable range;

[0032] The light beam pointing stability controller acquires light beam information of the monitoring light, and the light beam information includes at least one of power, energy, and spot position information of the monitoring light;

[0033] The light beam pointing stability controller compares the monitored light beam information with the initial light beam information to obtain a light beam pointing change value of the middle infrared laser at the target wavelength, and adjusts the angles of the fifth mirror and the sixth mirror according to the light beam pointing change value, so that the monitored light beam information is consistent with the initial light beam information, to achieve that the light beam pointing of the middle infrared laser at the target wavelength is consistent with the preset direction.

[0034] The application provides an ultra-wide-band tunable middle infrared laser device and a light beam pointing stability method. The ultra-wide-band tunable ring resonator cavity adopts a special special-shaped angle design, uses a high refractive intrinsic substrate as an input and output coupling mirror, and the pump laser is incident on the high refractive intrinsic substrate at a Brewster angle and coupled into the resonator cavity. At least two cavity mirrors in the resonator cavity are gold mirrors with high reflectivity for near-infrared and middle infrared bands. The pump light passes through the nonlinear frequency conversion crystal and forms a closed loop optical path in the resonator cavity, realizes high-efficiency optical parametric oscillation, and generates middle infrared laser. Since the first mirror surface and the second mirror surface of the first mirror do not need to be coated for specific wavelength lasers, and the first mirror has polarization selectivity for the reflectivity of the ultra-wide-band middle infrared laser, the first mirror serves as an input and output coupling mirror for horizontally polarized pump laser and middle infrared laser, and also serves as a partial reflector for vertically polarized middle infrared laser, which can provide the required resonant light reflectivity for the optical parametric oscillator in the ultra-wide middle infrared band. Therefore, at least two cavity mirrors of the remaining cavity mirrors of the ultra-wide-band tunable ring resonator cavity can adopt a full reflection gold mirror design, and the full reflection gold mirror has a reflectivity of more than 90% for the entire near-infrared and middle infrared bands. In summary, the ultra-wide-band tunable ring resonator cavity has a resonant capability in the ultra-wide middle infrared band. Meanwhile, the first mirror does not need to be coated with an antireflection medium film for specific wavelength pump lasers, which reduces the pump laser loss and widens the wavelength selection range of the pump laser. Through the pump light ring cavity closed loop optical path design, the return light interference of the pump laser is avoided, and the high-power operation capability is ensured. Finally, by monitoring the separated pump laser, the beam pointing deviation of the pump laser during the tuning process is fed back, the resonator mirror can be controlled to move to compensate for the beam pointing deviation of the middle infrared laser caused by the rotation of the middle infrared crystal, and the beam pointing stability is unchanged during the wavelength tuning process of the middle infrared laser output. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction is given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0036] Figure 1 A schematic structural diagram of an ultra-wideband tunable mid-infrared laser device provided by an embodiment of the present invention;

[0037] Figure 2 A schematic diagram of the structure of a first lens and its transmission light path provided by an embodiment of the present invention;

[0038] Figure 3 A schematic diagram of the structure of another first lens and its transmission light path provided by an embodiment of the present invention;

[0039] Figure 4 A schematic structural diagram of an ultra-wide tuned ring resonator provided by an embodiment of the present invention;

[0040] Figure 5 A schematic diagram of the internal transmission optical path of a nonlinear frequency conversion crystal provided by an embodiment of the present invention;

[0041] Figure 6 A schematic structural diagram of another ultra-wideband tunable mid-infrared laser device provided by an embodiment of the present invention;

[0042] Figure 7 A schematic diagram of the structure of another ultra-wideband tunable mid-infrared laser device provided by an embodiment of the present invention

[0043] Figure 8 A schematic structural diagram of a laser wavelength tuning controller provided by an embodiment of the present invention;

[0044] Figure 9 A schematic structural diagram of a light beam pointing stabilization controller provided by an embodiment of the present invention;

[0045] Figure 10 A structural diagram of a shaping component provided by an embodiment of the present invention;

[0046] Figure 11 This is a wavelength tuning curve of the optical parametric oscillator under the control of the laser wavelength tuning controller of Example 1 of the present invention. DETAILED DESCRIPTION

[0047] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0048] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the application. However, it will be apparent to one of ordinary skill in the art that the application can be practiced without some of these specific details. In other instances, well-known methods have not been described in detail in order to avoid unnecessarily obscuring the present application.

[0049] It should be noted that the embodiments and features in the present application can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and embodiments.

[0050] Reference Figure 1 As shown in the figure, the ultra-wideband tunable mid-infrared laser device of the present application comprises a fundamental pump source 1, a shaping assembly 2, an ultra-wide tuning ring resonator 3, a nonlinear frequency conversion crystal 4, a laser wavelength tuning controller 5, a double-color beamsplitter 6, and a beam pointing stability controller 7.

[0051] The fundamental pump source 1 is used to provide pulse-emitted pump laser. In order to ensure efficient conversion of the pump laser into mid-infrared laser, the fundamental pump source needs to provide high-peak-power pulse pump laser with a peak power density of up to MW / cm 2 .

[0052] The shaping assembly 2 is placed on the output light path of the fundamental pump source 1 and is used to adjust the polarization direction, spot size, injection pulse energy and pulse structure of the pump laser. The polarization direction of the pump laser needs to be adjusted according to the structure of the ultra-wide tuning ring resonator 3 and the main plane where the optical axis of the nonlinear frequency conversion crystal 4 is located, so as to ensure efficient conversion of the pump laser into mid-infrared laser. The selection of the spot size needs to be determined according to the damage threshold of the nonlinear frequency conversion crystal 4 and the peak power density corresponding to the optimal conversion efficiency. In the case of not damaging the nonlinear frequency conversion crystal 4, the spot size is adjusted to the spot size corresponding to the optimal conversion efficiency as much as possible. The adjustment of the injection pulse energy and the pulse structure is to control the pulse energy and the pulse structure of the output mid-infrared laser. The pulse structure mainly includes pulse duration, pulse time interval and macro-micro pulse duty cycle, etc.

[0053] The super-wide tuning ring resonator 3 comprises a first mirror 31, a second mirror 32, a third mirror 33 and a fourth mirror 34, which are arranged in the light path of the shaped pump laser from the shaping assembly 2. The first mirror 31 comprises a first mirror surface 311 and a second mirror surface 312 arranged in parallel, and a third mirror surface 313 arranged at an angle with the first mirror surface. The third mirror surface 313 is arranged at an angle with the first mirror surface. Or wherein, n1 is the refractive index of the first mirror at the pump laser wavelength, Figure 2 and Figure 3 the structure of the first mirror 31 and the schematic diagram of the transmission light path thereof when and The pump laser enters the super-wide tuning ring resonator 3 through the first mirror surface 311 and the second mirror surface 312, and exits from the third mirror surface 313. The normal line of the first mirror surface 311 and the incident light ray of the pump laser form an incident plane, which is parallel to the polarization direction of the pump laser, as shown in FIG. 1, the angle between the normal line of the first mirror surface 311 and the incident light ray of the pump laser is Figure 4 The angle between the normal line of the first mirror surface 311 and the incident light ray of the pump laser is n1 is the Brewster angle of the first mirror 31, satisfying: The second mirror 32, the third mirror 33 and the fourth mirror 34 each comprise a fourth mirror surface 321, a fifth mirror surface 331 and a sixth mirror surface 341. The pump laser sequentially passes through the first mirror surface 311 and the second mirror surface 312, and then sequentially passes through the fourth mirror surface 321, the fifth mirror surface 331 and the sixth mirror surface 341 to form a ring light path, and the pump laser reflected by the sixth mirror surface 341 is in the incident plane and forms an angle of with the normal line of the second mirror surface 312. After the pump laser reflected by the sixth mirror surface 341 passes through the second mirror surface 312, it exits from the third mirror surface 313. Since the super-wide tuning ring resonator 3 is composed of four mirrors, the placement positions of the second mirror 32, the third mirror 33 and the fourth mirror 34 and the incident angle of the pump laser are not limited, and can be adjusted according to the actual light path requirements, as long as the ring light path is closed.

[0054] The nonlinear frequency conversion crystal 4 is a block crystal with type I or type II phase matching cutting. For convenience of use, the nonlinear frequency conversion crystal 4 is usually a cuboid block crystal, and the length direction is the light transmission direction. As shown in FIG. 2, Figure 5As shown, the nonlinear frequency conversion crystal 4 includes a first light transmission end face 41 and a second light transmission end face 42 arranged in parallel. In order to meet the phase matching condition and facilitate rotation of the crystal angle to tune the mid-infrared laser wavelength, the optical axis 43 of the nonlinear frequency conversion crystal 4 is in the same plane as the normal line of the first light transmission end face 41 and the incident pump laser. The nonlinear frequency conversion crystal 4 is located on the ring-shaped optical path and is arranged between the first mirror 31 and the second mirror 32 or between the second mirror 32 and the third mirror 33. In order to shorten the length of the ring cavity and reduce the reflection loss of the pump light, the nonlinear frequency conversion crystal 4 is preferably arranged between the second mirror 32 and the third mirror 33. The nonlinear frequency conversion crystal 4 and the super-wide tuning ring resonator cavity 3 together constitute an optical parametric oscillator for generating signal light and idler light. The first light transmission end face 41 and the second light transmission end face 42 are coated with a wide-spectrum antireflection film for pump light, signal light and idler light. In order to prevent interference of the reverse reflection of the pump light, the transmittance of the pump light should be as high as possible during coating, and the transmittance of the pump light is usually greater than 98%. The wide-spectrum antireflection film should cover the output wavelength range of the signal light and the idler light, and the transmittance of the wide-spectrum antireflection film in the 2 μm ~ 12 μm mid-infrared waveband is usually greater than 80%.

[0055] The dichroic mirror 6 is used to separate the pump light from the output laser in the optical parametric oscillator to form monitoring light. The dichroic mirror is usually coated with a narrow-band high-reflection film for pump light and a wide-band antireflection film for signal light and idler light. The reflectivity of the dichroic mirror for pump light is as high as 99% or more, and the transmittance of the dichroic mirror for signal light and idler light is greater than 80%. The monitoring light is the residual pump light after passing through the optical parametric oscillator. By monitoring the monitoring light, the operation of the optical parametric oscillator can be observed. For example, power monitoring of the monitoring light can determine whether the optical parametric oscillator is damaged and evaluate the operation stability of the optical parametric oscillator. If the beam and spot position of the monitoring light are monitored, the beam refraction offset caused by the mid-infrared crystal can be evaluated.

[0056] The refractive index of the substrate material of the first mirror 31 in the 2 μm ~ 12 μm mid-infrared waveband is greater than 2, and the absorption coefficient of the substrate material for pump light and 2 ~ 12 μm mid-infrared laser is less than Common substrate materials include ZnSe, ZnS, GaAs, Ge, etc. The first mirror surface 311 and the second mirror surface 312 are mirror surfaces polished directly from the substrate material. Since no coating treatment is performed, the reflectivity and transmittance of the first mirror surface 311 and the second mirror surface 312 are determined by the refractive index, absorption coefficient of the substrate material, and the incident angle and polarization direction of the incident laser. The refractive index of the substrate material is required to be greater than 2 in order to ensure that the second mirror surface 312 has a high reflectivity for pump light and 2 ~ 12 μm mid-infrared laser. The parametric light of vertical polarization (polarization direction perpendicular to the incident plane) at the angle of incidence has a greater reflectivity. The greater the refractive index of the substrate material, the greater the reflectivity of the second mirror 312 to the parametric light of vertical polarization, and the lower the light output threshold of the optical parametric oscillator. The absorption coefficient of the substrate material is required to be less than 10"4cm"1 In order to reduce the absorption loss of the pump laser, the signal light and the idler light, the fourth mirror 321 is coated with a full reflection gold film, one of the fifth mirror 331 and the sixth mirror 341 is coated with a full reflection gold film, and the other is coated with a full reflection gold film or a film layer that reflects the pump laser and the signal light and transmits the idler light. In order to improve the laser damage threshold of the full reflection gold film, the full reflection gold film is usually coated on a pure copper substrate, which has very good heat dissipation capacity and reduces the heat deposition of the full reflection gold film.

[0057] When the fourth mirror 321, the fifth mirror 331 and the sixth mirror 341 are all coated with a full reflection gold film, the pump laser, the signal light and the idler light are output from the third mirror 313 after passing through the first mirror 31, and part of the signal light and the idler light is reflected by the second mirror 312 and continues to oscillate in the ring cavity. Specifically, when the fourth mirror 321, the fifth mirror 331 and the sixth mirror 341 are all coated with a full reflection gold film, when the nonlinear frequency conversion crystal 4 is a type I phase matching crystal, the pump laser is horizontally polarized light (polarization direction parallel to the incident plane), and the signal light and the idler light are vertically polarized light. At this time, the second mirror 312 is highly transmissive to the pump laser, partially reflective and partially transmissive to the signal light and the idler light, the optical parametric oscillator is a double resonant optical parametric oscillator, and has a lower light output threshold; when the nonlinear frequency conversion crystal 4 is a type II phase matching crystal, the pump laser and the idler light are horizontally polarized light, and the signal light is vertically polarized light. At this time, the second mirror 312 is highly transmissive to the pump laser and the idler light, and partially reflective and partially transmissive to the idler light, the optical parametric oscillator is a single resonant optical parametric oscillator, and has a higher light output threshold, but it is easier to achieve higher output power and conversion efficiency.

[0058] Under the condition that the fourth mirror 321 and the sixth mirror 341 are coated with a full reflection gold film, in order to improve the output power and conversion efficiency of the optical parametric oscillator when a type I crystal is selected, the fifth mirror 331 is coated with a dielectric film that reflects the pump laser and the signal light and transmits the idler light. At this time, the idler light is first output from the third mirror 33, only part of the signal light is reflected by the second mirror 312 and continues to oscillate in the ring cavity, the optical parametric oscillator is still a single resonant optical parametric oscillator, and has a higher output power and conversion efficiency.

[0059] In general, the super-wide tuning annular resonator 3 provided by the present application has two reasons for the super-wide band resonant capability. One is that the substrate materials such as ZnSe, ZnS, GaAs and Ge have a transmittance in the 2-12 μm or even wider waveband and a refractive index greater than 2, and the first mirror with the Brewster angle has polarization selectivity for the reflectivity of the extremely wide mid-infrared waveband laser. The first mirror 311 and the second mirror 312 have high transmittance for horizontally polarized laser of all wavelengths and similar reflectivity and transmittance for vertically polarized laser of all wavelengths, and have stable coupling output rate in the super-wide waveband range. The other is that the full reflection gold film has high reflectivity for wavelengths above 0.8 μm and is not sensitive to the angle of incident laser, and the fourth mirror 321, the fifth mirror 331 or the sixth mirror 341 coated with the full reflection gold film has the reflection capability for the 0.8-12 μm or even wider waveband laser. Therefore, the wavelength tuning range of the mid-infrared laser output by the optical parametric oscillator mainly depends on the transmittance range and phase matching interval of the nonlinear frequency conversion crystal 4. If the nonlinear frequency conversion crystal 4 is an excellent crystal such as phosphorus germanium zinc (ZGP) or barium gallium selenide (BGSe) which has a transmittance range and phase matching interval covering 2-12 μm, the wavelength tuning range of the mid-infrared laser output by the optical parametric oscillator can also cover the 2-12 μm mid-infrared waveband.

[0060] The laser wavelength tuning controller 5 is used to adjust the phase matching angle of the nonlinear frequency conversion crystal 4 to realize continuous super-wide tuning of the wavelengths of the signal light and the idler light.

[0061] The beam pointing stability controller 7 is used to detect the monitoring light and feedback adjust the angles of the fifth mirror 331 and the sixth mirror 341 to compensate for the beam pointing deviation of the mid-infrared laser in the tuning process so that the beam pointing is stable and unchanged.

[0062] The present invention provides an ultra-wideband tunable mid-infrared laser device. The ultra-wideband tunable ring resonator adopts a special special-shaped angle design and uses a high-refractive-index intrinsic substrate as the input and output coupling mirrors. The pump laser is incident on the high-refractive-index intrinsic substrate at the Brounst angle and coupled into the resonator through it. At least two of the resonator mirrors are gold mirrors with high reflectivity in both the near-infrared and mid-infrared bands. The pump light passes through a nonlinear frequency-converting crystal and forms a closed-loop optical path within the resonator, achieving efficient optical parametric oscillation and generating mid-infrared laser light. Because the first and second mirror surfaces of the first mirror do not need to be coated for lasers of specific wavelengths, and the first mirror set at the Brounst angle has polarization selectivity for the reflectivity of ultra-wideband mid-infrared laser light, the first mirror serves as both the input and output coupling mirrors for horizontally polarized pump laser and mid-infrared laser light, and as a partial reflector for vertically polarized mid-infrared laser light, it can provide resonant light with the required reflectivity for the optical parametric oscillator within the ultra-wide mid-infrared band. Therefore, at least two of the remaining mirrors of the ultra-wide tuned ring resonator can be designed with a total reflection gold mirror, and the reflectivity of the total reflection gold mirror to the laser in the entire near-infrared and mid-infrared bands is above 90%. In summary, the ultra-wide tuned ring resonator of the present invention has the resonance capability of an ultra-wide mid-infrared band. At the same time, the first mirror does not need to be plated with an anti-reflection dielectric film for a specific wavelength pump laser, which reduces the loss of the pump laser while broadening the wavelength selection range of the pump laser. The closed-loop optical path design of the pump light ring cavity avoids the interference of the return light of the pump laser, ensuring high-power operation capability. Finally, by monitoring the separated pump laser and feeding back the beam pointing offset of the pump laser during the tuning process, the movement of the resonant cavity mirror can be controlled to compensate for the beam pointing offset of the mid-infrared laser caused by the rotation of the mid-infrared crystal, thereby achieving a stable beam pointing during the tuning of the mid-infrared laser output wavelength.

[0063] In some embodiments, as Figure 2 and Figure 3 As shown, the incident laser is represented by a solid line. After passing through the first mirror 311 and the second mirror 312, it enters the annular cavity and is emitted from the third mirror 313 after transmitting one circle in the cavity. The emitted laser is represented by a dotted line. The emitted laser light intersects the incident laser light at a point on the second mirror 312. Since the actual laser beam has a certain beam diameter, when the first lens 31 is too thin, the projection spot area of ​​the incident laser on the first mirror 311 and the projection spot area of ​​the emitted laser on the third mirror 313 overlap, and the transmittance and spot shape of the incident laser and the emitted laser will be affected. In order to avoid affecting the transmittance and spot shape of the incident laser and the emitted laser, when designing the first lens 31, the distance between the first mirror 311 and the second mirror 312 is 1 / 4 of the diameter of the incident laser. Should meet the following requirements:

[0064]

[0065] Where, is the pump laser beam diameter after shaping by the shaping component ( ), is the Bromster angle of the first lens.

[0066] In some embodiments, the nonlinear frequency conversion crystal 3 is a type II phase matching crystal, and the angle between the first mirror 311 and the third mirror 313 is ,like Figure 6 As shown in the figure, the polarization direction of the signal light is orthogonal to that of the pump laser. The pump laser and idler light are horizontally polarized, while the signal light is vertically polarized. The second mirror 312 partially reflects the signal light but is highly transparent to the pump laser and idler light. The first mirror 311 is parallel to the third mirror 313. The polarization directions of the pump light and idler light are both parallel to the incident plane and can be emitted from the third mirror 313 with almost no loss. The optical parametric oscillator is a single-resonance optical parametric oscillator for signal light, and the idler light has high conversion efficiency and output power.

[0067] In some embodiments, the nonlinear frequency conversion crystal 4 is a type I phase matching crystal, and the first lens is cut with an anisotropic angle so that the angle between the first mirror surface 311 and the third mirror surface 313 is The third mirror 313 is coated with an anti-reflection film for pump laser, signal light and idler light. Figure 7 At this time, the polarization directions of the signal light and the idler light are orthogonal to the polarization direction of the pump laser. The second mirror 312 reflects a portion of the signal light and the idler light and has high transmittance to the pump laser. The polarization directions of the signal light and the idler light are perpendicular to the incident plane. After passing through the second mirror 312, part of the signal light and the idler light is reflected and oscillates in the ring cavity, and the transmitted part is output from the third mirror 313. In order to avoid the reflection loss of the output signal light and the idler light by the third mirror 313, the first mirror 31 needs to be cut so that the angle between the first mirror 311 and the third mirror 313 is This cutting angle can reduce the difficulty of coating the third mirror 313 with an anti-reflection film for pump laser, signal light and idler light.

[0068] In some embodiments, as Figure 8 As shown, the laser wavelength tuning controller 5 includes a crystal fixing frame 51, a rotating stage 52, and a wavelength and angle correlation controller 53. The crystal fixing frame 51 is used to fix the nonlinear frequency conversion crystal 4 to the rotating stage 52. The wavelength and angle correlation controller 53 is used to control the rotation of the rotating stage 52 according to the preset wavelength. The rotating stage 52 is used to change the angle between the normal line of the light-passing end face and the pump laser beam line incident on the nonlinear frequency conversion crystal 4. , thereby adjusting the phase matching angle inside the crystal To achieve mid-infrared laser output of target wavelength, and Satisfaction relationship: ,in, is the cutting angle of the mid-infrared crystal.

[0069] In some embodiments, as Figure 9 As shown, the beam pointing stabilization controller 7 includes a first adjustment frame 71, a second adjustment frame 72, a beam position monitoring component 73 and a feedback controller 74. The first adjustment frame 71 fixes the third lens 33 for adjusting the angle of the fifth mirror 331. The second adjustment frame 72 fixes the fourth lens 34 for adjusting the angle of the sixth mirror 341. The beam position monitoring component 73 includes a first pinhole aperture 731, a second pinhole aperture 732 and a laser detector 733 arranged in sequence. The laser detector 733 includes at least one of a power detector, an energy detector and a spot detector. The centers of the first pinhole aperture 731, the second pinhole aperture 732 and the laser detector 733 are placed on the optical path of the initial monitoring light. The initial monitoring light corresponds to the vertical direction of the pump laser. The monitoring light is reflected by the dichroic spectrometer 6 when it is incident on the nonlinear frequency conversion crystal 4. The beam position monitoring component 73 is used to obtain the beam information of the monitoring light and send it to the feedback controller 74. The beam information includes at least one of the power, energy, and spot position information recorded by the laser detector 733. The feedback controller 74 is used to receive the beam information recorded by the beam position monitoring component 73 and compare it with the initial beam information. According to the comparison result, the first adjustment frame 71 and the second adjustment frame 72 are feedback-controlled so that the beam information recorded by the beam position monitoring component 73 is consistent with the initial beam information, so as to achieve stable beam pointing during the tuning process of the mid-infrared laser. The initial beam information includes at least one of the power, energy, and spot position information of the initial monitoring light. In some specific embodiments, the beam position monitoring component 73 includes a translation slide 734 and a CCD camera 735 placed on the translation slide. The center of the CCD camera 735 is placed on the optical path of the initial monitoring light. The beam position monitoring component 73 is used to obtain the beam information of the monitoring light and send it to the feedback controller 74. The beam information includes the spot position information recorded by the CCD camera 735. The feedback controller 74 is used to receive the beam information recorded by the beam position monitoring component 73 and compare it with the initial beam information. According to the comparison result, the first adjustment frame 71 and the second adjustment frame 72 are feedback-controlled so that the beam information recorded by the beam position monitoring component 73 is consistent with the initial beam information, so as to achieve stable beam pointing during the tuning process of the mid-infrared laser. The initial beam information includes the spot position information of the initial monitoring light.

[0070] In some embodiments, the cavity length of the ultra-wide tuned ring resonator 3 is The pulse width of the pump laser should be and the pulse repetition frequency of the pump laser When the pulse width of the pump laser is When the optical parametric oscillator works in the short cavity optical parametric oscillation mode, the ultra-wide tuned ring resonator 3 should adopt a short cavity design with a cavity length of and satisfy: ,in is the speed of light; when the pulse width of the pump laser is When the optical parametric oscillator works in the synchronous pump optical parametric oscillator mode, the ultra-wide tuned ring resonator 3 should adopt a long cavity design with a cavity length of and the pulse repetition frequency of the pump laser satisfy: ,in is a positive integer less than 100, The speed of light.

[0071] In some embodiments, the substrate material of the first lens 31 is zinc selenide, and the absorption coefficient of the laser in the 0.8-14 micron band is satisfy: The refractive index of the laser in the 0.8–14 μm band is between 2.35 and 2.55.

[0072] In some embodiments, as Figure 10 As shown, the shaping component 2 includes a half-wave plate 21, a polarization beam splitter 22, a shaping lens assembly 23, and a chopper modulator 24 placed on the output optical path of the fundamental frequency pump source 1. The half-wave plate 21 is used to adjust the polarization direction of the pump laser, and the polarization beam splitter 22 is used to separate the orthogonally polarized pump lasers. The polarization beam splitter 22 and the half-wave plate 21 are used in combination to adjust the power of the pump laser injected into the ultra-wide tuned ring resonator 3. The shaping lens assembly 23 includes at least one convex lens for adjusting the spot shape and beam diameter width of the pump laser. The chopper modulator 24 includes at least one of an acousto-optic modulation chopper, an electro-optic modulation chopper, and a mechanical chopper, and is used to chop the optical pulses of the pump laser in the time domain to obtain a pump laser with a desired pulse repetition frequency and pulse train structure.

[0073] In some embodiments, the pump laser emitted by the fundamental frequency pump source 1 has a wavelength of 0.8 μm to 3 One or more laser beams within the range, the peak power of the pump laser is greater than 1 kW, and the pulse width of the pump laser satisfies , the pulse energy of the pump laser satisfy .

[0074] The present invention also provides a method for stabilizing the pointing of an ultra-wideband tunable mid-infrared laser beam, which is used in the ultra-wideband tunable mid-infrared laser device of any of the above embodiments. The method for stabilizing the pointing of the beam comprises:

[0075] The laser wavelength tuning controller 5 adjusts the angle of the nonlinear frequency conversion crystal 4 so that the pump laser is incident on the light transmission end surface of the nonlinear frequency conversion crystal 4 vertically to achieve the output of the mid-infrared laser along the preset direction;

[0076] The light beam pointing stability controller 7 obtains initial light beam information of the monitoring light, and the initial light beam information includes light beam information of the monitoring light when the pump laser is incident on the light transmission end surface of the nonlinear frequency conversion crystal 4 vertically;

[0077] The laser wavelength tuning controller 5 adjusts the angle of the nonlinear frequency conversion crystal 4 to obtain the mid-infrared laser of any target wavelength in the tunable range;

[0078] The light beam pointing stability controller 7 obtains light beam information of the monitoring light, and the light beam information includes at least one of power, energy, and spot position information of the monitoring light;

[0079] The light beam pointing stability controller 7 compares the monitored light beam information with the initial light beam information to obtain a light beam pointing change value of the target wavelength mid-infrared laser, and adjusts the angles of the fifth mirror 331 and the sixth mirror 341 according to the light beam pointing change value so that the monitored light beam information is consistent with the initial light beam information, to achieve the consistency of the light beam pointing of the target wavelength mid-infrared laser with the preset direction.

[0080] The ultra-wide waveband tunable mid-infrared laser device provided by the application will be described below through specific embodiments.

[0081] Embodiment 1

[0082] The specific device of this embodiment is shown in Figure 1 The fundamental pump source 1 is a Ho:YAG nanosecond laser with active Q switching, the output wavelength is 2.09 µm, the pulse width is 40 ns, the repetition frequency is 1 kHz, the power is 20 W, the output spot diameter is 1 mm, the divergence angle is 3 mrad, and the output peak power is higher than 500 kW, which provides the pump laser with high peak power pulse emission for the generation of the mid-infrared laser.

[0083] The shaping assembly 2 includes a half-wave plate 21, a polarization beam splitter 22, and a shaping lens combination 23 arranged in the light path of the pump laser output by the fundamental pump source 1 in sequence, the half-wave plate 21 and the polarization beam splitter 22 are combined to adjust the polarization direction and injection power of the pump laser, the shaping lens combination 23 includes a plano-concave lens with a focal length of -75 mm and a plano-convex lens with a focal length of 100 mm, and the two lenses are placed with a spacing of 75 mm to adjust the beam diameter width of the pump laser to 2.5 mm. When the output power of the fundamental pump source 1 is 20 W, the peak power density of the pump laser is 10.2 MW / cm 2The high peak power density of the pump laser ensures the conversion efficiency of the subsequent mid-infrared laser.

[0084] The super-wide tuning annular resonant cavity 3 comprises a first mirror 31, a second mirror 32, a third mirror 33 and a fourth mirror 34, which are arranged on the pump laser path after the shaping of the shaping assembly 2. The base material of the first mirror 31 is zinc selenide (ZnSe), the absorption coefficient of the 0.8-14 micrometer wave band laser is , the refractive index of the 0.8-14 micrometer wave band laser is between 2.35 and 2.55, the refractive index at the pump laser wavelength is , the included angle between the first mirror surface 311 and the third mirror surface 312 is 17.6°, the third mirror surface 313 is coated with a 2-12 micrometer wide spectrum antireflection film, the pump laser is horizontally polarized light, the Brunost angle of the first mirror 31 is 72.3°, and the pump laser is incident to the first mirror surface 311 at an angle of 72.3°. At this time, the transmittance of the first mirror surface 311, the second mirror surface 312 and the third mirror surface 313 to the pump laser is higher than 98%. The base materials of the second mirror 32, the third mirror 33 and the fourth mirror 34 are pure copper, and the fourth mirror surface 321, the fifth mirror surface 331 and the sixth mirror surface 341 are all coated with a full reflection gold film, and the reflectivity of the 0.8-12 micrometer wave band laser is higher than 95%. The pump laser transmits through the first mirror surface and the second mirror surface in sequence, and then is reflected by the fourth, fifth and sixth mirror surfaces to the second mirror surface to form an annular light path. The incident angle of the pump laser reflected by the sixth mirror surface to the second mirror surface is 72.3°. The super-wide tuning annular resonant cavity adopts a short cavity design, and the cavity length is 165 mm.

[0085] The nonlinear frequency conversion crystal 4 used in the embodiment is a phosphorus germanium zinc (ZGP) crystal with a type I phase matching cut. The appearance is a cuboid, the crystal size is 5 mm*8 mm*25 mm, the cut angle is 52.2°, and the light transmission direction length is 25 mm. The nonlinear frequency conversion crystal 4 comprises a first light transmission end surface 41 and a second light transmission end surface 42 arranged in parallel. The light transmission end surface size is 5 mm*7 mm. The optical axis of the nonlinear frequency conversion crystal 4 is in the same plane as the normal line of the first light transmission end surface 41 and the incident pump laser. The ZGP crystal is located on the annular light path and is placed between the second mirror 32 and the third mirror 33. The first light transmission end surface 41 and the second light transmission end surface 42 are coated with a 2-12 micrometer wide spectrum antireflection film, and the average transmittance in the 2-12 micrometer wave band is higher than 90%. The transmittance at the pump laser wavelength is greater than 98%.

[0086] In the embodiment, the pump laser is horizontally polarized light, the nonlinear frequency conversion crystal 4 is a ZGP crystal, type I phase matching is adopted, the generated signal light and idler light are vertically polarized light, the second mirror surface 312 is highly transmissive to the pump laser and partially reflective and partially transmissive to the signal light and idler light, the pump laser, the signal light and the idler light are output from the third mirror surface 313 after passing through the first mirror 31, a part of the signal light and the idler light is reflected by the second mirror surface 312 and continues to oscillate in the ring cavity, the optical parametric oscillator is a double-resonance optical parametric oscillator, and the optical parametric oscillator has a low light output threshold. When the pump laser is incident on the first light-transmitting end surface 41 perpendicularly, the output signal light has a wavelength of 3.1 microns, and the output idler light has a wavelength of 6.4 microns.

[0087] The laser wavelength tuning controller is used to adjust the phase matching angle of the ZGP crystal to realize continuous tuning of the wavelengths of the signal light and the idler light. Figure 11 The wavelength tuning curve of the optical parametric oscillator controlled by the laser wavelength tuning controller in the embodiment is shown in the following table when the crystal is rotated. The phase matching angle is changed in the range of 49.72°-49.82°. When the phase matching angle is changed in the range of 49.72°-49.82°, the tuning range of the output signal light and idler light covers the mid-infrared waveband of 2.6-10.6 microns.

[0088] The above merely illustrates the specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of various equivalent modifications or replacements within the technical range disclosed by the present application, and these modifications or replacements should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. An ultra-wideband tunable mid-infrared laser device, characterized in that: include: A fundamental frequency pump source, used to provide a pump laser for pulse emission; A shaping component is placed on the output optical path of the fundamental frequency pump source and is used to adjust the polarization direction, spot size, injected pulse energy, and pulse structure of the pump laser; The ultra-wide tuned ring resonator comprises a first lens, a second lens, a third lens and a fourth lens, which are placed on the optical path of the pump laser after being shaped by the shaping component. The first lens comprises a first mirror and a second mirror arranged in parallel, and a mirror arranged parallel to the first mirror. The third mirror is set, or ,in, is the refractive index of the first lens at the wavelength of the pump laser, and the angle between the normal line of the first mirror surface and the incident light of the pump laser is is the Bromster angle of the first lens, satisfy: The first mirror and the second mirror are mirrors formed by directly polishing the intrinsic substrate. The second mirror, the third mirror, and the fourth mirror respectively include a fourth mirror, a fifth mirror, and a sixth mirror. The fourth mirror is coated with a total reflection gold film. One of the fifth and sixth mirrors is coated with a total reflection gold film, and the other mirror is coated with a total reflection gold film or a film layer that is highly reflective of the pump laser and signal light and increases the transmittance of idler light. The pump laser passes through the first and second mirrors in sequence, and then passes through the fourth, fifth, and sixth mirrors in sequence to reflect to the second mirror to form a ring light path. The pump laser reflected by the sixth mirror is in the incident plane and has an angle of 0.03° with the normal of the second mirror. , the pump laser reflected by the sixth mirror is transmitted through the second mirror and then output from the third mirror; a nonlinear frequency conversion crystal, comprising a first light-transmitting end face and a second light-transmitting end face arranged in parallel, wherein one optical axis of the nonlinear frequency conversion crystal, a normal to the first light-transmitting end face, and an incident pump laser are coplanar; the nonlinear frequency conversion crystal is located on the annular optical path, placed between the first lens and the second lens or between the second lens and the third lens, and together with the ultra-wide tuned ring resonator constitutes an optical parametric oscillator that generates signal light and idler light; a dichroic beam splitter, used for separating the pump laser from the laser output from the optical parametric oscillator to form monitoring light; A laser wavelength tuning controller, configured to adjust the phase matching angle of the nonlinear frequency conversion crystal to achieve continuous wavelength tuning of the signal light and the idler light; The beam pointing stabilization controller is used to detect the monitoring light and feedback-adjust the angles of the fifth mirror and the sixth mirror to compensate for the beam pointing deviation of the mid-infrared laser during the tuning process so that the beam pointing is stable.

2. The ultra-wideband tunable mid-infrared laser device according to claim 1, characterized in that: The distance between the first mirror surface and the second mirror surface satisfy: Where, is the pump laser beam diameter after shaping by the shaping component ( ), is the Bromster angle of the first lens.

3. The ultra-wideband tunable mid-infrared laser device according to claim 1, characterized in that: When the nonlinear frequency conversion crystal is a type II phase matching crystal, the polarization direction of the signal light is orthogonal to the polarization direction of the pump laser, the second mirror partially reflects the signal light and has high transmittance to the pump laser and idler light, ; When the nonlinear frequency conversion crystal is a type I phase-matched crystal, the polarization directions of the signal light and the idler light are orthogonal to the polarization direction of the pump laser, the second mirror reflects a portion of the signal light and the idler light and has high transmittance to the pump laser, The third mirror is coated with an anti-reflection film for the pump laser, signal light and idler light.

4. The ultra-wideband tunable mid-infrared laser device according to claim 1, characterized in that: The laser wavelength tuning controller includes a crystal fixing frame, a rotating stage, and a wavelength and angle correlation controller; The crystal holder is used to fix the nonlinear frequency conversion crystal to the rotating stage. The wavelength and angle association controller is used to control the rotation of the rotating stage according to the preset wavelength. The rotating stage is used to change the angle between the normal line of the light-passing end face and the pump laser beam incident on the nonlinear frequency conversion crystal. , thereby adjusting the phase matching angle inside the crystal To achieve mid-infrared laser output of target wavelength, and Satisfaction relationship: ,in, is the cutting angle of the mid-infrared crystal.

5. The ultra-wideband tunable mid-infrared laser device according to claim 1, characterized in that: The beam pointing stabilization controller includes a first adjustment frame, a second adjustment frame, a beam position monitoring component and a feedback controller; The first adjustment frame is used to fix the third lens and adjust the angle of the fifth mirror surface; The second adjustment frame is used to fix the fourth lens and adjust the sixth mirror angle; The beam position monitoring component includes a first pinhole aperture, a second pinhole aperture and a laser detector arranged in sequence. The centers of the first pinhole aperture, the second pinhole aperture and the laser detector are placed on the optical path of the initial monitoring light. The initial monitoring light is the monitoring light reflected by the dichroic beam splitter when the pump laser is vertically incident on the nonlinear frequency conversion crystal. The beam position monitoring component is used to obtain beam information of the monitoring light and send it to the feedback controller. The beam information includes the power and / or spot position recorded by the laser detector. The feedback controller is used to receive the beam information recorded by the beam position monitoring component and compare it with the initial beam information. According to the comparison result, the first adjustment frame and the second adjustment frame are feedback-controlled so that the beam information recorded by the beam position monitoring component is consistent with the initial beam information, so as to achieve stable beam pointing of the mid-infrared laser during the tuning process. The initial beam information includes the power and / or spot position of the initial monitoring light.

6. The ultra-wideband tunable mid-infrared laser device according to claim 1, characterized in that: When the pulse width of the pump laser ≥300 ps, ​​the ultra-wide tuned ring resonator operates in the short cavity optical parametric oscillation mode, and its cavity length and satisfy: ,in is the speed of light; When the pulse width of the pump laser 300 ps, ​​the ultra-wide tuned ring resonator operates in the synchronous pump light parametric oscillation mode, and its cavity length is The pulse repetition frequency of the pump laser satisfy: ,in is a positive integer less than 100, The speed of light.

7. The ultra-wideband tunable mid-infrared laser device according to claim 1, characterized in that: The first lens substrate material is zinc selenide, and the absorption coefficient of the laser in the 0.8~14 micron band is satisfy: The refractive index of laser light in the 0.8~14 micron band is between 2.35 and 2.

55.

8. The ultra-wideband tunable mid-infrared laser device according to claim 1, characterized in that: The shaping component includes a half-wave plate, a polarization beam splitter, a shaping lens combination, and a chopper modulator placed on the optical path of the pump laser output by the fundamental frequency pump source. The half-wave plate is used to adjust the polarization direction of the pump laser. The polarization beam splitter is used to separate the orthogonally polarized pump lasers. The polarization beam splitter and the half-wave plate are used in combination to adjust the energy of the pump laser injected into the ultra-wide tuned ring resonator. The shaping lens combination includes at least one convex lens for adjusting the spot shape and beam diameter width of the pump laser. The chopper modulator includes at least one of an acousto-optic modulation chopper, an electro-optic modulation chopper, and a mechanical chopper for performing a chopping operation on the optical pulses of the pump laser in the time domain to obtain a pump laser with a desired pulse repetition frequency and pulse train structure.

9. The ultra-wideband tunable mid-infrared laser device according to claim 1, characterized in that: The pump laser has a wavelength of 0.8~3 One or more laser beams within the range, the peak power of the pump laser is greater than 1 kW, and the pulse width of the pump laser satisfies , the pulse energy of the pump laser satisfy .

10. A method for stabilizing the pointing direction of an ultra-wideband tunable mid-infrared laser beam, characterized in that: For the ultra-wideband tunable mid-infrared laser device according to any one of claims 1 to 9, the beam pointing stabilization method comprises: Adjusting the angle of the nonlinear frequency conversion crystal by a laser wavelength tuning controller makes the pump laser incident perpendicular to the light-passing end face of the nonlinear frequency conversion crystal, so as to achieve mid-infrared laser output along a preset direction; The beam pointing stabilization controller acquires initial beam information of the monitoring light, wherein the initial beam information includes beam information of the monitoring light when the pump laser is incident perpendicularly to the light-passing end face of the nonlinear frequency conversion crystal; The laser wavelength tuning controller adjusts the angle of the nonlinear frequency conversion crystal to obtain mid-infrared laser output of any target wavelength within the tunable range; The beam pointing stabilization controller acquires beam information of the monitoring light, where the beam information includes at least one of power, energy, and spot position information of the monitoring light; The beam pointing stabilization controller compares the monitored beam information with the initial beam information to obtain a beam pointing change value of the target wavelength mid-infrared laser, and adjusts the angles of the fifth mirror and the sixth mirror according to the beam pointing change value, so that the monitored beam information is consistent with the initial beam information, so as to achieve that the beam pointing of the target wavelength mid-infrared laser is consistent with a preset direction.

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