Ultra-wideband tunable intermediate infrared laser device and light beam pointing stabilizing method

Abstract

The invention discloses an ultra-wide-band tunable intermediate infrared laser device and a light beam pointing stabilizing method. The device comprises a fundamental frequency pumping source, an ultra-wide tuning annular resonant cavity, a nonlinear frequency conversion crystal, a laser wavelength tuning controller and a light beam pointing stabilizing controller. The fundamental frequency pumping source is used for providing pumping laser for high-peak power pulse emission, the ultra-wide tuning annular resonant cavity adopts a special special-shaped angle design, a high-refractive-index intrinsic substrate is used as an input and output coupling mirror, and the pumping laser enters the high-refractive-index intrinsic substrate at a Bronsted angle and enters the resonant cavity through coupling of the high-refractive-index intrinsic substrate; at least two cavity mirrors in the resonant cavity mirror are gold mirrors highly reflecting near-infrared and middle-infrared bands, the pump light passes through the nonlinear frequency conversion crystal and forms a closed-loop light path in the resonant cavity, efficient optical parametric oscillation is achieved, and middle-infrared laser with an extremely wide wavelength tuning range is generated. And the light beam pointing stabilization controller controls the resonant cavity mirror to compensate light beam pointing deviation, so that continuous wavelength tuning is realized, and the light beam pointing is kept unchanged.

Description

Technical Field

[0001] The present invention relates to the field of laser frequency conversion technology, and in particular to an ultra-wideband tunable mid-infrared laser device and a beam pointing stabilization method. Background Art

[0002] Due to the limitations of the emission spectrum bandwidth of the working medium and the reflection bandwidth of the dielectric film coated on the resonant cavity mirror, existing mid-infrared lasers can only operate in one of the mid-infrared bands such as 3 μm~5 μm, 5 μm~8 μm, 8 μm~10 μm or 9 μm~11 μm. They cannot simultaneously achieve ultra-wideband continuous tuning and high-power operation. In addition, there is a beam pointing deviation problem during the wavelength tuning process of existing mid-infrared lasers, which makes it difficult to meet the actual application needs of mid-infrared lasers. Summary of the invention

[0003] The purpose of the present invention is to overcome at least one of the problems of the existing mid-infrared lasers, such as insufficient continuous wavelength tuning capability, large beam direction changes during the tuning process, and difficulty in high-power operation.

[0004] In order to solve the above technical problems, an embodiment of the present invention provides an ultra-wideband tunable mid-infrared laser device, comprising: A fundamental frequency pump source, used to provide a pump laser for pulse emission; The 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 shaped by the shaping component. The first lens comprises a first mirror surface and a second mirror surface arranged in parallel and a mirror surface arranged in parallel with the first mirror surface. The third mirror is set, or ,in, is the refractive index of the first mirror at the pump laser wavelength, and the angle between the first mirror normal and the incident light of the pump laser is the Bromster angle of the first lens, satisfy: , the first mirror surface and the second mirror surface are mirror surfaces formed by directly polishing the intrinsic substrate, the second mirror surface, the third mirror surface and the fourth mirror surface respectively include the fourth mirror surface, the fifth mirror surface and the sixth mirror surface, the fourth mirror surface is coated with a total reflection gold film, one of the fifth mirror surface and the sixth mirror surface is coated with a total reflection gold film, and the other mirror surface is coated with a total reflection gold film or a film layer that is highly reflective to the pump laser and the signal light and has an increased transmittance to the idler light. The pump laser passes through the first mirror surface and the second mirror surface in sequence, and then passes through the fourth mirror surface, the fifth mirror surface and the sixth mirror surface in sequence to reflect to the second mirror surface to form a ring light path, and the pump laser reflected by the sixth mirror surface is in the incident plane and has an angle of 0.03° with the normal line of the second mirror surface. , the pump laser reflected by the sixth mirror is output from the third mirror after passing through the second 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 of the optical axes of the nonlinear frequency conversion crystal, a normal line of the first light-transmitting end face and an incident pump laser are in the same plane, the nonlinear frequency conversion crystal is located on a ring optical path, is placed between a first lens and a second lens or between a second lens and a third lens, and together with an ultra-wide tuned ring resonator forms an optical parametric oscillator that generates signal light and idler light; A two-color beam splitter is used to separate the pump laser from the laser output from the optical parametric oscillator to form monitoring light; Laser wavelength tuning controller, used 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 and unchanged.

[0005] Optionally, the distance between the first mirror surface and the second mirror surface satisfy: In the formula, is the pump laser beam diameter after shaping by the shaping component ( ), is the Bromster angle of the first lens.

[0006] 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 partially reflects the signal light and is highly transparent to the pump laser and the 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 anti-reflection coating for pump laser, signal light and idler light.

[0007] Optionally, the laser wavelength tuning controller includes a crystal holder, a rotating table, 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 mid-infrared crystal.

[0008] Optionally, 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 angle of the sixth mirror surface; The beam position monitoring component includes a first pinhole aperture, a second pinhole aperture and a laser detector which are 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 the beam information of the monitoring light and send it to the feedback controller. The beam information includes the power and / or the 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 realize that the beam pointing of the mid-infrared laser is stable and unchanged during the tuning process. The initial beam information includes the power and / or the spot position of the initial monitoring light.

[0009] Optionally, 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 At 300 ps, ​​the ultra-wide tuned ring resonator operates in the synchronous pump light parametric oscillation mode, and its cavity length The pulse repetition rate of the pump laser satisfy: ,in is a positive integer less than 100, The speed of light.

[0010] Optionally, 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 for lasers in the 0.8~14 micron band is between 2.35 and 2.55.

[0011] Optionally, 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, which is used to adjust the spot morphology and beam diameter width of the pump laser, and the chopper modulator includes at least one of an acousto-optic modulation chopper, an electro-optic modulation chopper and a mechanical chopper, which is used to perform a chopping operation on the optical pulse of the pump laser in the time domain to obtain a pump laser with a desired pulse repetition frequency and a pulse train structure.

[0012] Optionally, the pump laser has a wavelength between 0.8 and 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 .

[0013] 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 an ultra-wideband tunable mid-infrared laser beam comprises: The angle of the nonlinear frequency conversion crystal is adjusted by a laser wavelength tuning controller so that the pump laser is incident perpendicularly to the light-passing end face of the nonlinear frequency conversion crystal, so as to realize the output of the mid-infrared laser in a preset direction; The beam pointing stabilization controller obtains initial beam information of the monitoring light, and the initial beam information includes beam information of the monitoring light when the pump laser is incident on the light-passing end face of the vertical 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 obtains 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 the beam pointing change value of the mid-infrared laser of the target wavelength, 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 the beam pointing of the mid-infrared laser of the target wavelength is consistent with the preset direction.

[0014] The invention provides an ultra-wide band tunable mid-infrared laser device and a beam pointing stabilization method. The ultra-wide tuned ring resonator adopts a special special-shaped angle design, and uses a high-refractive index intrinsic substrate as an input and output coupling mirror. The pump laser is incident on the high-refractive index intrinsic substrate at a Bronwitz angle and coupled into the resonator through the substrate. At least two cavity mirrors in the resonator are gold mirrors with high reflection in both near-infrared and mid-infrared bands. The pump light passes through a nonlinear frequency conversion crystal and forms a closed-loop optical path in the resonator to achieve efficient optical parametric oscillation and generate mid-infrared laser. Since the first mirror surface and the second mirror surface of the first mirror do not need to be coated for lasers of a specific wavelength, and the first mirror surface set at the Bronwitz angle has polarization selectivity for the reflectivity of the ultra-wide band mid-infrared laser, the first mirror serves as both an input and output coupling mirror of the horizontally polarized pump laser and the mid-infrared laser, and as a partial reflector of the vertically polarized mid-infrared laser, and can provide resonant light with required reflectivity for the optical parametric oscillator in the ultra-wide mid-infrared band. Therefore, at least two of the remaining cavity 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 lens 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 stable beam pointing during the tuning of the mid-infrared laser output wavelength. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces 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 creative work.

[0016] Figure 1A schematic structural diagram of an ultra-wideband tunable mid-infrared laser device provided by an embodiment of the present invention; Figure 2 A schematic diagram of the structure of a first lens and the optical path of its transmission provided by an embodiment of the present invention; 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; Figure 4 A schematic diagram of the structure of an ultra-wide tuned ring resonator provided by an embodiment of the present invention; Figure 5 A schematic diagram of an internal transmission optical path of a nonlinear frequency conversion crystal provided by an embodiment of the present invention; Figure 6 A schematic structural diagram of another ultra-wideband tunable mid-infrared laser device provided by an embodiment of the present invention; Figure 7 A schematic diagram of the structure of another ultra-wideband tunable mid-infrared laser device provided in an embodiment of the present invention Figure 8 A schematic diagram of the structure of a laser wavelength tuning controller provided by an embodiment of the present invention; Fig. 9 A schematic diagram of the structure of a light beam pointing stabilization controller provided by an embodiment of the present invention; Fig.10 A structural schematic diagram of a shaping component provided by an embodiment of the present invention; Fig.11 This is a wavelength tuning curve of an optical parametric oscillator under the control of the laser wavelength tuning controller of Example 1 of the present invention. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] In the following detailed description, many specific details are provided in order to provide a comprehensive understanding of the present invention. However, it is obvious to those skilled in the art that the present invention can be implemented without some of these specific details. The following description of the embodiments is only intended to provide a better understanding of the present invention by illustrating examples of the present invention.

[0019] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0020] Reference Figure 1 As shown, the ultra-wideband tunable mid-infrared laser device of the present invention comprises: a fundamental frequency pump source 1, a shaping component 2, an ultra-wide tuned ring resonator 3, a nonlinear frequency conversion crystal 4, a laser wavelength tuning controller 5, a dichroic beam splitter 6, and a beam pointing stabilization controller 7; The fundamental frequency pump source 1 is used to provide pulsed pump laser. In order to ensure that the pump laser is efficiently converted into mid-infrared laser, the fundamental frequency pump source needs to provide a peak power density of up to MW / cm 2 High peak power pulse pump laser.

[0021] The shaping component 2 is placed on the output optical path of the fundamental frequency pump source 1, and is used to adjust the polarization direction, spot size, injected 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 tuned ring resonator 3 and the main plane where the optical axis of the nonlinear frequency conversion crystal 4 is located, so as to ensure that the pump laser can be efficiently converted into a 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. Without 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 injected pulse energy and the pulse structure is to control the pulse energy and pulse structure of the output mid-infrared laser. The pulse structure mainly includes pulse duration, pulse time interval, and macro-micro pulse duty cycle.

[0022] The ultra-wide tuned ring resonator 3 includes a first lens 31, a second lens 32, a third lens 33, and a fourth lens 34, which are placed on the optical path of the pump laser after being shaped by the shaping component 2. The first lens 31 includes a first mirror surface 311 and a second mirror surface 312 arranged in parallel, and a first mirror surface 311 and a second mirror surface 312 arranged in parallel with the first mirror surface 311. The third mirror 313 is provided, or ,in, is the refractive index of the first lens at the pump laser wavelength, Figure 2 and Figure 3 They are and The structure of the first mirror 31 and its transmission optical path diagram are shown in FIG. 1 . The pump laser enters the ultra-wide tuned ring resonator 3 through the first mirror 311 and the second mirror 312, and is emitted from the third mirror 313. The normal of the first mirror 311 and the incident light of the pump laser form an incident plane, and the incident plane is parallel to the polarization direction of the pump laser. Figure 4 As shown, the angle between the normal line of the first mirror 311 and the incident light of the pump laser is is the Bromster angle of the first lens 31, satisfy: The second lens 32, the third lens 33, and the fourth lens 34 respectively include a fourth mirror 321, a fifth mirror 331, and a sixth mirror 341. The pump laser sequentially passes through the first mirror 311 and the second mirror 312, and then sequentially passes through the fourth mirror 321, the fifth mirror 331, and the sixth mirror 341 to reflect to the second mirror 312 to form a ring light path. The pump laser reflected by the sixth mirror 341 is within the incident plane and has an angle with the normal of the second mirror 312 of , the pump laser reflected by the sixth mirror 341 passes through the second mirror 312 and then exits from the third mirror 313. Since the ultra-wide tuned 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 optical path requirements, as long as the annular optical path is closed.

[0023] The nonlinear frequency conversion crystal 4 is a block crystal cut by type I or type II phase matching. For ease of use, the nonlinear frequency conversion crystal 4 is usually a rectangular block crystal, and the length direction is the light transmission direction. Figure 5 As shown, the nonlinear frequency conversion crystal 4 includes a first light-transmitting end face 41 and a second light-transmitting end face 42 arranged in parallel. In order to meet the phase matching condition and to facilitate the rotation of the crystal angle to tune the wavelength of the mid-infrared laser, the optical axis 43 of the nonlinear frequency conversion crystal 4 and the normal of the first light-transmitting end face 41 and the incident pump laser are in the same plane. The nonlinear frequency conversion crystal 4 is located on the annular optical path and is placed between the first lens 31 and the second lens 32 or between the second lens 32 and the third lens 33. In order to shorten the length of the annular cavity and reduce the reflection loss of the pump light, the nonlinear frequency conversion crystal 4 is preferably placed between the second lens 32 and the third lens 33. The nonlinear frequency conversion crystal 4 and the ultra-wide tuned ring resonator 3 together constitute an optical parametric oscillator that generates signal light and idler light. The first light-transmitting end face 41 and the second light-transmitting end face 42 are plated with a wide-spectrum anti-reflection film for the pump laser, signal light and idler light. In order to prevent the interference of pump laser back reflection, the pump laser transmittance should be increased as much as possible during coating. The pump laser transmittance is usually greater than 98%. The transmittance range of the broadband anti-reflection film should cover the output wavelength range of the signal light and the idler light. Usually, the transmittance of the broadband anti-reflection film in the mid-infrared band of 2μm ~12μm is greater than 80%.

[0024] The two-color beam splitter 6 is used to separate the pump laser from the laser output from the optical parametric oscillator to form monitoring light. Usually, the two-color beam splitter is coated with a narrowband high-reflection film for the pump laser and a broadband anti-reflection film for the signal light and the idler light. The reflectivity of the pump laser is as high as more than 99%, and the transmittance of the signal light and the idler light is greater than 80%. The monitoring light is the remaining pump laser after the optical parametric oscillator is consumed. By monitoring it, the operation of the optical parametric oscillator can be observed. For example, by monitoring the power of the monitoring light, it can be determined whether there is any device damage in the optical parametric oscillator and the operating stability of the optical parametric oscillator can be evaluated. If the beam and spot position of the monitoring light are monitored, the refraction offset of the beam caused by the mid-infrared crystal can be evaluated.

[0025] The refractive index of the substrate material of the first lens 31 in the mid-infrared band of 2μm ~12μm is greater than 2, and the absorption coefficient of the pump laser and the mid-infrared laser in the band of 2~12 microns 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 formed by polishing the substrate material directly. 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 and 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 to ensure that the second mirror surface 312 The parametric light of vertical polarization (polarization direction is perpendicular to the incident plane) with an angle of incidence has a larger reflectivity. The larger the refractive index of the substrate material, the greater the reflectivity of the second mirror 312 to the vertically polarized parametric light, and the lower the light emission threshold of the optical parametric oscillator. The absorption coefficient of the substrate material is required to be less than This is to reduce the absorption loss of pump laser, signal light and idler light. The fourth mirror 321 is plated with a total reflection gold film, one of the fifth mirror 331 and the sixth mirror 341 is plated with a total reflection gold film, and the other mirror is plated with a total reflection gold film or a film layer that reflects the pump laser and signal light and increases the transmittance of the idler light. In order to improve the anti-laser damage threshold of the total reflection gold film, the total reflection gold film is usually plated on a pure copper substrate. The pure copper substrate has a very good heat dissipation capacity, which reduces the heat deposition of the total reflection gold film.

[0026] When the fourth mirror 321, the fifth mirror 331, and the sixth mirror 341 are all coated with a total reflection gold film, the pump laser, signal light, and idler light are output from the third mirror 313 after passing through the first mirror 31, and a part of the signal light and idler light are reflected by the second mirror 312 and continue to oscillate in the ring cavity. Specifically, under the condition that the fourth mirror 321, the fifth mirror 331, and the sixth mirror 341 are all coated with a total reflection gold film, when the nonlinear frequency conversion crystal 4 is a type I phase-matched crystal, the pump laser is horizontally polarized light (the polarization direction is parallel to the incident plane), and the signal light and the idler light are vertically polarized light. At this time, the second mirror 312 has high transmittance to the pump laser, partially reflects the signal light and the idler light and partially transmits it, and the optical parametric oscillator is a dual-resonance optical parametric oscillator with a lower light emission threshold; when the nonlinear frequency conversion crystal 4 is a type II phase-matched 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 has high transmittance to the pump laser and the idler light, partially reflects the idler light and partially transmits it, and the optical parametric oscillator is a single-resonance optical parametric oscillator with a higher light emission threshold, but it is easier to achieve higher output power and conversion efficiency.

[0027] Under the condition that the fourth mirror 321 and the sixth mirror 341 are coated with a total 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 is highly reflective to the pump laser and signal light and has enhanced transmittance to the idle light. At this time, the idle light is first output from the third mirror 33, and only a part of the signal light continues to oscillate in the ring cavity after being reflected by the second mirror 312. The optical parametric oscillator is still a single-resonance optical parametric oscillator with higher output power and conversion efficiency.

[0028] In general, there are two reasons why the ultra-wide tuned ring resonator 3 provided by the present invention has the resonance capability of an ultra-wide band. First, since substrate materials such as ZnSe, ZnS, GaAs, and Ge are transparent in a band of 2μm to 12μm or even wider and their refractive indices are all greater than 2, and the reflectivity of the first lens set at the Bromster angle to the laser in an extremely wide mid-infrared band has polarization selectivity, the first mirror 311 and the second mirror 312 are highly transparent to all wavelengths of horizontally polarized lasers, and have similar reflectivity and transmittance to all wavelengths of vertically polarized lasers, and have a stable coupling output rate within the ultra-wide band; second, the total reflection gold film has the characteristics of high reflection to wavelengths above 0.8 microns and insensitivity to the angle of the incident laser, so the fourth mirror 321, the fifth mirror 331 or the sixth mirror 341 coated with the total reflection gold film has the reflection capability to the laser in a band of 0.8 to 12 microns or even wider. 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 zinc germanium phosphide (ZGP) and barium gallium selenide (BGSe) whose transmittance range and phase matching interval can cover 2~12 microns, then the wavelength tuning range of the mid-infrared laser output by the optical parametric oscillator can also cover the mid-infrared band of 2μm~12μm.

[0029] The laser wavelength tuning controller 5 is used to adjust the phase matching angle of the nonlinear frequency conversion crystal 4 to achieve continuous ultra-wide tuning of the wavelengths of the signal light and the idler light.

[0030] The beam pointing stabilization controller 7 is used to detect the monitoring light and feedback-adjust the fifth mirror 331 and the sixth mirror angle 341 to compensate for the beam pointing deviation of the mid-infrared laser during the tuning process to stabilize the beam pointing.

[0031] The ultra-wide band tunable mid-infrared laser device provided by the present invention adopts a special special-shaped angle design for the ultra-wide tuned ring resonant cavity, uses a high refractive index intrinsic substrate as an input and output coupling mirror, the pump laser is incident on the high refractive index intrinsic substrate at a Bronwitz angle and coupled into the resonant cavity through the substrate, at least two cavity mirrors in the resonant cavity mirrors are gold mirrors with high reflection in both near-infrared and mid-infrared bands, the pump light passes through a nonlinear frequency conversion crystal and forms a closed-loop optical path in the resonant cavity, realizes efficient optical parametric oscillation and generates mid-infrared laser, since the first mirror surface and the second mirror surface of the first mirror do not need to be coated for lasers of a specific wavelength, and the first mirror surface set at the Bronwitz angle has polarization selectivity for the reflectivity of the ultra-wide band mid-infrared laser, therefore, the first mirror surface serves as both the input and output coupling mirrors of the horizontally polarized pump laser and the mid-infrared laser, and as a partial reflector of the vertically polarized mid-infrared laser, and can provide resonant light with required reflectivity for the optical parametric oscillator in the ultra-wide mid-infrared band. Therefore, at least two of the remaining cavity 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 lens 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 stable beam pointing during the tuning of the mid-infrared laser output wavelength.

[0032] In some embodiments, 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 overlaps with the projection spot area of ​​the emitted laser on the third mirror 313, and the transmittance and spot morphology of the incident laser and the emitted laser are affected. In order to avoid affecting the transmittance and spot morphology 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 set to 1 / 4 of the diameter of the incident laser. Should meet: In the formula, is the pump laser beam diameter after shaping by the shaping component ( ), is the Bromster angle of the first lens.

[0033] 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 At this time, the polarization direction of the signal light is orthogonal to the polarization direction of the pump laser, the pump laser and the idler light are horizontally polarized light, the signal light is vertically polarized light, the second mirror 312 partially reflects the signal light and is highly transparent to the pump laser and the idler light, the first mirror 311 is parallel to the third mirror 313, the polarization directions of the pump light and the 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 signal light single-resonance optical parametric oscillator, and the idler light has a high conversion efficiency and output power.

[0034] 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 surface 313 is coated with an anti-reflection film for pump laser, signal light and idler light, such as 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 part 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 them 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.

[0035] In some embodiments, Figure 8 As shown, the laser wavelength tuning controller 5 includes a crystal fixing frame 51, a rotating platform 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 platform 52. The wavelength and angle correlation controller 53 is used to control the rotation of the rotating platform 52 according to a preset wavelength. The rotating platform 52 is used to change the angle between the normal line of the light-transmitting 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 mid-infrared crystal.

[0036] In some embodiments, Fig. 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 which are 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 beam splitter 6 when 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.

[0037] 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 oscillator 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 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 The pulse repetition rate of the pump laser satisfy: ,in is a positive integer less than 100, The speed of light.

[0038] 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 for lasers in the 0.8–14 μm band is between 2.35 and 2.55.

[0039] In some embodiments, Fig.10 As shown, the shaping component 2 includes a half wave plate 21, a polarization beam splitter 22, a shaping lens combination 23 and a chopper modulator 24 placed on the output optical path of the baseband pump source 1. The half wave plate 21 is used to adjust the polarization direction of the pump laser, 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 combination 23 includes at least one convex lens, which is used to adjust the spot morphology and beam diameter width of the pump laser, and the chopper modulator 24 includes at least one of an acousto-optic modulation chopper, an electro-optic modulation chopper and a mechanical chopper, which is used to chop the optical pulse of the pump laser in the time domain to obtain a pump laser with a desired pulse repetition frequency and a pulse train structure.

[0040] In some embodiments, the pump laser emitted by the fundamental frequency pump source 1 has a wavelength between 0.8 μm and 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 .

[0041] 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 an ultra-wideband tunable mid-infrared laser beam comprises: The laser wavelength tuning controller 5 is used to adjust the angle of the nonlinear frequency conversion crystal 4 so that the pump laser is incident perpendicularly to the light-passing end face of the nonlinear frequency conversion crystal 4, so as to realize the output of the mid-infrared laser in a preset direction; The beam pointing stabilization controller 7 obtains the initial beam information of the monitoring light, and the initial beam information includes the beam information of the monitoring light when the pump laser is incident on the light-transmitting end face of the vertical nonlinear frequency conversion crystal 4; The laser wavelength tuning controller 5 adjusts the nonlinear frequency conversion crystal angle 4 to obtain mid-infrared laser output of any target wavelength within the tunable range; The beam pointing stabilization controller 7 obtains the beam information of the monitoring light, where the beam information includes at least one of the power, energy, and spot position information of the monitoring light; The beam pointing stabilization controller 7 compares the monitored beam information with the initial beam information to obtain the beam pointing change value of the mid-infrared laser of the target wavelength, and adjusts the angles of the fifth mirror 331 and the sixth mirror 341 according to the beam pointing change value, so that the monitored beam information is consistent with the initial beam information, so as to achieve the beam pointing of the mid-infrared laser of the target wavelength is consistent with the preset direction.

[0042] The ultra-wide-band tunable mid-infrared laser device provided by the present invention is described below through specific embodiments.

[0043] Example 1 The specific device of this embodiment is shown in Figure 1 The fundamental frequency pump source 1 is an actively Q-switched Ho:YAG nanosecond laser with an output wavelength of 2.09 µm, a pulse width of 40 ns, a repetition rate of 1 kHz, a power of 20 W, an output spot diameter of 1 mm, a divergence angle of 3 mrad, and an output peak power of more than 500 kW, providing a high-peak-power pulsed pump laser for the generation of mid-infrared lasers.

[0044] The shaping component 2 includes a half wave plate 21, a polarization beam splitter 22, and a shaping lens assembly 23, which are sequentially placed on the optical path of the pump laser output by the fundamental frequency pump source 1. The half wave plate 21 and the polarization beam splitter 22 are used to adjust the polarization direction and injection power of the pump laser. The shaping lens assembly 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. The two lenses are placed 75 mm apart to adjust the beam diameter width of the pump laser to 2.5 mm. When the output power of the fundamental frequency pump source 1 is 20 W, the peak power density of the pump laser is 10.2 MW / cm 2 The high peak power density of the pump laser ensures the conversion efficiency of the subsequent mid-infrared laser.

[0045] The ultra-wide tuned ring resonator 3 includes a first lens 31, a second lens 32, a third lens 33, and a fourth lens 34, which are placed on the pump laser path after the shaping component 2. The substrate material of the first lens 31 is zinc selenide (ZnSe), and the absorption coefficient of the laser in the 0.8~14 micron band is The refractive index of the laser in the 0.8~14 μm band is between 2.35 and 2.55, and the refractive index at the pump laser wavelength is , the angle between the first mirror surface 311 and the third mirror surface 312 is 17.6°, the third mirror 313 is coated with a 2-12 μm wide-spectrum anti-reflection film, the pump laser is horizontally polarized light, and the Bromster angle of the first mirror 31 is The angle of the pump laser incident on the first mirror 311 is 72.3°. At this time, the transmittance of the pump laser to the first mirror 311, the second mirror 312, and the third mirror 313 is higher than 98%. The base material of the second mirror 32, the third mirror 33, and the fourth mirror 34 is pure copper. The fourth mirror 321, the fifth mirror 331, and the sixth mirror 341 are all coated with a total reflection gold film, and the reflectivity of the laser in the 0.8-12 micron band is higher than 95%. The pump laser passes through the first mirror and the second mirror 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 incident angle of the pump laser reflected by the sixth mirror to the second mirror is 72.3°. The ultra-wide tuned ring resonator adopts a short cavity design with a cavity length of 165 mm.

[0046] The nonlinear frequency conversion crystal 4 used in this embodiment is a zinc germanium phosphate (ZGP) crystal cut using type I phase matching, with a rectangular appearance and a crystal size of 5 mm*8 mm*25 mm. The cutting angle is The angle of the optical path is 52.2°, the length in the light-transmitting direction is 25 mm, and it includes a first light-transmitting end face 41 and a second light-transmitting end face 42 arranged in parallel. The size of the light-transmitting end face is 5 mm*7 mm. The optical axis of the nonlinear frequency conversion crystal 4 and the normal of the first light-transmitting end face 41 and the incident pump laser are in the same plane. The ZGP crystal is located on the annular optical path and is placed between the second lens 32 and the third lens 33. The first light-transmitting end face 41 and the second light-transmitting end face 42 are coated with a 2-12 micron wide-spectrum anti-reflection film, and the average transmittance in the range of 2-12 microns is higher than 90%, and the transmittance at the pump laser wavelength is greater than 98%.

[0047] In this embodiment, the pump laser is horizontally polarized light, the nonlinear frequency conversion crystal 4 is a ZGP crystal, and type I phase matching is adopted. The generated signal light and idler light are vertically polarized light. The second mirror 312 is highly transparent to the pump laser, and partially reflects and partially transmits the signal light and idler light. The pump laser, signal light and idler light are output from the third mirror 313 after passing through the first mirror 31. A part of the signal light and idler light is reflected by the second mirror 312 and continues to oscillate in the ring cavity. The optical parametric oscillator is a dual-resonance optical parametric oscillator with a lower light output threshold. When the pump laser is incident perpendicular to the first light-transmitting end face 41, the output signal light wavelength is 3.1 microns, and the output idler light wavelength is 6.4 microns.

[0048] The laser wavelength tuning controller is used to adjust the phase matching angle of the ZGP crystal to achieve continuous wavelength tuning of the signal light and the idler light, such as Fig.11 is the wavelength tuning curve of the optical parametric oscillator under the control of the laser wavelength tuning controller in this embodiment. Phase matching angle When the angle varies from 49.72° to 49.82°, the tuning range of the output signal light and idler light covers the mid-infrared band of 2.6-10.6 microns.

[0049] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on 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 shaped by the shaping component, wherein the first lens comprises a first mirror and a second mirror arranged in parallel and a mirror arranged in parallel with 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 first mirror normal and the incident light of the pump laser is the Bromster angle of the first lens, satisfy: , the first mirror surface and the second mirror surface are mirror surfaces formed by direct polishing of the intrinsic substrate, the second mirror surface, the third mirror surface and the fourth mirror surface respectively include the fourth mirror surface, the fifth mirror surface and the sixth mirror surface, the fourth mirror surface is coated with a total reflection gold film, one of the fifth mirror surface and the sixth mirror surface is coated with a total reflection gold film, and the other mirror surface is coated with a total reflection gold film or a film layer that is highly reflective to the pump laser and the signal light and has an increased transmittance to the 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 reflect to the second mirror surface to form a ring light path, the pump laser reflected by the sixth mirror surface is within the incident surface and has an angle of 2.5 with the normal line of the second mirror surface. , 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 of the optical axes of the nonlinear frequency conversion crystal, a normal line of the first light-transmitting end face and an incident pump laser are in the same plane, the nonlinear frequency conversion crystal is located on the annular optical path, and is 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, forms an optical parametric oscillator that generates signal light and idler light; A two-color 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, used for adjusting 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 and unchanged.

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: In the formula, 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-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 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 table, and a wavelength and angle correlation controller; The crystal fixing frame 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, and the rotating stage is used to change the angle between the normal line of the light-transmitting 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 mid-infrared crystal.

5. The ultra-wideband tunable mid-infrared laser device according to claim 1, characterized in that: The beam pointing stability controller comprises 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 fifth mirror angle; 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 which are 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 the beam information of the monitoring light and send it to the feedback controller. The beam information includes the power and / or the 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 the 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 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 for lasers 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 baseband 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 morphology 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, and is used to perform a chopping operation on the optical pulse of the pump laser in the time domain to obtain a pump laser with a desired pulse repetition frequency and a 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 𝜏 of the pump laser satisfies , the pulse energy of the pump laser satisfy .

10. A method for stabilizing the pointing 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: The angle of the nonlinear frequency conversion crystal is adjusted by a laser wavelength tuning controller so that the pump laser is incident perpendicularly to the light-passing end face of the nonlinear frequency conversion crystal, so as to realize the output of the mid-infrared laser in 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, wherein 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 the beam pointing change value of the mid-infrared laser at the target wavelength, 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 mid-infrared laser at the target wavelength is consistent with a preset direction.

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