A visible near-infrared laser light source

Abstract

A visible near-infrared laser light source comprises: a pump laser generating module, which is suitable for generating pump laser; a seed laser generating module, which is suitable for generating seed laser, wherein the seed laser is in the visible near-infrared laser band; a cavity mirror module, which comprises: a resonant cavity, which is suitable for receiving the pump laser and the seed laser; a nonlinear optical crystal, which is located in the resonant cavity and is suitable for causing the pump laser to undergo nonlinear conversion to generate coherently superimposed signal light, wherein the seed laser is suitable for guiding the nonlinear conversion process so that the wavelength of the obtained signal light is the same as that of the seed laser; the signal light oscillates in the resonant cavity and is output, thereby obtaining the visible near-infrared laser; and a control module, which is suitable for controlling the wavelength of the seed laser generated by the seed laser generating module.

Description

Technical Field

[0001] The invention relates to the field of optical instruments, and in particular to a visible near-infrared laser light source. Background Art

[0002] Optical parametric oscillation (OPO) technology, as a method of generating lasers in the visible and near-infrared bands, has the advantages of wide wavelength tuning range, high energy conversion efficiency, the ability to simultaneously generate two entangled coherent light beams, and an all-solid-state structure. In optical parametric oscillation technology, by injecting seed light into the resonant cavity, the oscillation threshold of the resonant cavity can be significantly reduced, thereby improving the efficiency and stability of the laser output. However, due to the conditions for the generation of standing waves, only lasers with specific frequencies can exist stably in the resonant cavity. The specific frequencies that exist stably in the cavity of the resonant cavity are called the longitudinal modes of the cavity. There is a fixed frequency interval c / 2L between the longitudinal modes, where c is the speed of light and L is the cavity length of the resonant cavity. In practical applications, laser light sources need to be able to achieve wavelength tuning, but the existence of the longitudinal modes of the resonant cavity will cause the wavelength to be interrupted during the tuning process, that is, it is impossible to continuously cover all desired wavelength ranges. In order to overcome this limitation, in theory, it is necessary to adjust the cavity length of the resonant cavity in real time to match the required wavelength, but this method is not only technically complex and costly, but also difficult to achieve long-term stable operation. Summary of the invention

[0003] In view of this, in order to at least partially solve at least one of the above-mentioned technical problems, the present invention provides a visible near-infrared laser light source.

[0004] According to an embodiment of the present invention, the visible near-infrared laser light source comprises:

[0005] A pump laser generating module, adapted to generate a pump laser;

[0006] A seed laser generation module is suitable for generating seed lasers, and the seed lasers are in the visible near-infrared laser band;

[0007] Laparoscopic module, including:

[0008] A resonant cavity, suitable for receiving pump laser and seed laser;

[0009] A nonlinear optical crystal, located in the resonant cavity, is suitable for causing the pump laser to undergo nonlinear conversion and generate coherently superimposed signal light;

[0010] The seed laser is suitable for guiding nonlinear conversion so that the wavelength of the signal light is the same as that of the seed laser, and the signal light oscillates in the resonant cavity and is output to obtain visible near-infrared laser.

[0011] A control module, adapted to control the wavelength of the seed laser generated by the seed laser generating module;

[0012] In which, a longitudinal mode is formed in the resonant cavity during the oscillation of the signal light in the resonant cavity; the pump laser and / or the seed laser can excite the resonant cavity to generate high-order transverse modes in the resonant cavity, and the high-order transverse modes can reduce the frequency interval between the longitudinal modes to avoid mode hopping when the wavelength of the seed laser changes.

[0013] According to an embodiment of the present invention, the pump laser and / or the seed laser can excite the resonant cavity, and the generation of a high-order transverse mode in the resonant cavity includes at least one of the following situations:

[0014] The spot size of the pump laser can excite the resonant cavity and generate high-order transverse modes in the resonant cavity;

[0015] The incident angle of the pump laser can excite the resonant cavity and generate high-order transverse modes in the resonant cavity;

[0016] The incident angle of the seed laser can excite the resonant cavity and generate high-order transverse modes in the resonant cavity;

[0017] The incident angle of the pump laser is the angle between the pump laser and the optical axis of the resonant cavity, and the incident angle of the seed laser is the angle between the seed laser and the optical axis of the resonant cavity.

[0018] According to an embodiment of the present invention, the pump laser generating module comprises:

[0019] A first laser, adapted to generate a first laser;

[0020] A first polarization unit is used to convert the first laser into a pump laser, where the pump laser is a polarized laser, and the polarization direction of the pump laser is configured to meet a phase matching condition of a nonlinear effect;

[0021] A spot adjustment unit, suitable for adjusting the spot size of the pump laser;

[0022] The first angle adjustment unit is suitable for adjusting the incident angle of the pump laser.

[0023] According to an embodiment of the present invention, the seed laser generating module includes:

[0024] A second laser, adapted to generate a second laser;

[0025] A beam shaping unit, adapted to shape the beam of the second laser;

[0026] A second polarization unit is used to convert the shaped second laser into a seed laser, where the seed laser is a polarized laser, and the polarization direction of the seed laser is configured to meet a phase matching condition for guiding nonlinear conversion;

[0027] The second angle adjustment unit is suitable for adjusting the incident angle of the seed laser.

[0028] According to an embodiment of the present invention, the second laser is a semiconductor laser, and the wavelength range of the second laser output by the second laser is 1000 nm to 1500 nm.

[0029] According to an embodiment of the present invention, the seed laser generating module further includes:

[0030] The isolation unit is arranged between the beam shaping unit and the second polarization unit, and is suitable for ensuring that the shaped second laser is unidirectionally transmitted to the second polarization unit to protect the second laser.

[0031] According to an embodiment of the present invention, the resonant cavity comprises:

[0032] A first cavity mirror, a second cavity mirror and a third cavity mirror that are non-collinear; wherein the three cavity mirrors are configured to enable the signal light to be reflected back and forth by the three cavity mirrors along a preset direction, so that the signal light oscillates in the resonant cavity along the preset direction; and the nonlinear optical crystal is located between the first cavity mirror and the second cavity mirror;

[0033] A first dichroic mirror is located between the first cavity mirror and the nonlinear optical crystal. The first dichroic mirror is used to receive the pump laser and reflect the pump laser so that the pump laser is incident on the nonlinear optical crystal. The signal light obtained after the pump laser is incident on the nonlinear optical crystal is reflected by the second cavity mirror and oscillates in the resonant cavity along a preset direction.

[0034] The seed laser is incident on the resonant cavity through the first cavity mirror, and enters the nonlinear optical crystal after passing through the first dichroic mirror to guide the nonlinear conversion process.

[0035] According to an embodiment of the present invention, the first cavity mirror and the second cavity mirror are both long-wave dichroic mirrors, the starting wavelength of the long-wave dichroic mirror is 1000 nm, and the third cavity mirror is an output coupling mirror. It can be seen that the near-infrared laser is output from the output coupling mirror.

[0036] According to an embodiment of the present invention, the resonant cavity further comprises:

[0037] The intracavity plano-convex lens is arranged between any two cavity mirrors and is suitable for converging the seed laser to ensure that the signal light oscillates in the resonant cavity.

[0038] According to an embodiment of the present invention, the control module is also adapted to adjust the direction of the optical axis of the nonlinear optical crystal, and the control module comprises:

[0039] The sampling unit is suitable for sampling the visible near-infrared laser output by the resonant cavity to obtain the wavelength of the visible near-infrared laser output by the resonant cavity.

[0040] The adjustment unit is used to adjust the optical axis direction of the nonlinear optical crystal according to the sampling result, so that the nonlinear optical crystal meets the phase matching condition of nonlinear optical conversion.

[0041] According to an embodiment of the present invention, a pump laser and / or a seed laser is used to excite a high-order transverse mode. Since the high-order transverse mode can shorten the longitudinal mode frequency interval to be smaller than the laser line width of the visible near-infrared laser output by the resonant cavity, the seed laser can be injected into the optical resonant cavity for a long time and efficiently when the wavelength of the seed laser changes continuously, thereby reducing the oscillation threshold of the optical parameter and making the wavelength tuning range of the visible near-infrared laser light source large. In addition, shortening the longitudinal mode frequency interval can also ensure that when the wavelength of the seed laser changes continuously, the wavelength of the visible near-infrared laser can be tuned over a large range without mode hopping. Therefore, the resonant cavity can output the same visible near-infrared laser as the real-time wavelength of the changing seed laser. The visible near-infrared laser light source provided according to the embodiment of the present invention can achieve a large-scale tuning of the wavelength of the visible near-infrared laser without changing the cavity length of the resonant cavity. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0043] Figure 1 A structural block diagram of a visible near-infrared laser light source provided according to an embodiment of the present invention is shown;

[0044] Figure 2 The optical path diagram of the visible near-infrared laser light source provided according to an embodiment of the present invention is shown.

[0045] Description of reference numerals:

[0046] 100 - pump laser generating module; 110 - first laser; 120 - first polarization unit;

[0047] 121 - a first half-wave plate; 122 - a first polarization beam splitter cube; 123 - a first light collector;

[0048] 124-a second half-wave plate; 130-a light spot adjustment unit; 131-an extracavity plano-convex lens;

[0049] 132-plano-concave lens; 140-first angle adjustment unit; 200-seed laser generating module;

[0050] 210 - second laser; 220 - beam shaping unit; 230 - second polarization unit;

[0051] 231 - third half-wave plate; 232 - second polarization beam splitter cube; 233 - second light collector; 234 - fourth half-wave plate; 240 - second angle adjustment unit; 250 - isolation unit;

[0052] 300-cavity mirror module; 310-resonant cavity; 311-first cavity mirror; 312-second cavity mirror;

[0053] 313 - third cavity mirror; 320 - nonlinear optical crystal; 314 - first dichroic mirror;

[0054] 315 - second dichroic mirror; 316 - third light collector; 317 - intracavity plano-convex lens;

[0055] 318 - fourth light collector; 400 - control module; 410 - sampling unit; 411 - sampling mirror; 412 - lens; 413 - wavelength meter; 420 - adjustment unit. DETAILED DESCRIPTION

[0056] Below, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of embodiments of the present invention. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of concepts of the present invention.

[0057] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The term "comprising" used herein indicates the existence of features, steps, operations, but does not exclude the existence or addition of one or more other features.

[0058] In the case of using expressions such as "at least one of A, B, and C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.). In the case of using expressions such as "at least one of A, B, or C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally understood by those skilled in the art (for example, "a system having at least one of A, B, or C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0059] Figure 1A structural block diagram of a visible near-infrared laser light source provided according to an embodiment of the present invention is shown;

[0060] Figure 2 The optical path diagram of the visible near-infrared laser light source provided according to an embodiment of the present invention is shown.

[0061] like Figure 1-Figure 2 As shown, the visible near-infrared laser light source includes: a pump laser generating module 100, a seed laser generating module 200, a cavity mirror module 300, and a control module 400. The pump laser generating module 100 is suitable for generating a pump laser. The seed laser generating module 200 is suitable for generating a seed laser, and the seed laser is in the visible near-infrared laser band. The cavity mirror module 300 includes a resonant cavity 310 and a nonlinear optical crystal 320. The resonant cavity 310 is suitable for receiving the pump laser and the seed laser. The nonlinear optical crystal 320 is located in the resonant cavity 310, and the nonlinear optical crystal 320 has a nonlinear optical effect. Under the action of the nonlinear optical crystal 320, the pump laser undergoes nonlinear conversion to generate a coherently superimposed signal light. Among them, the seed laser is suitable for guiding the process of the nonlinear conversion so that the wavelength of the obtained signal light is the same as the wavelength of the seed laser. Among them, the signal light oscillates in the resonant cavity 310 and outputs a visible near-infrared laser. The control module 400 is suitable for controlling the wavelength of the seed laser generated by the seed laser generating module.

[0062] In which, during the oscillation of the signal light in the resonant cavity 310, a longitudinal mode is formed in the resonant cavity 310; the pump laser generating module 100 and the seed laser generating module 200 are constructed so that the pump laser and / or the seed laser can excite the resonant cavity 310, and generate high-order transverse modes in the resonant cavity 310. The high-order transverse modes can reduce the frequency interval between the longitudinal modes in the resonant cavity to avoid the phenomenon of mode modulation when the wavelength of the seed laser changes, that is, to ensure that the resonant cavity 310 can output a visible near-infrared laser with the same wavelength as the seed laser after the wavelength is changed.

[0063] According to the embodiment of the present invention, a nonlinear conversion effect occurs after the pump laser is incident on the nonlinear optical crystal 320, and in addition to the coherent signal light, the coherent idler light can also be obtained. The frequency of the pump laser is equal to the sum of the frequency of the signal light and the frequency of the idler light.

[0064] According to the embodiment of the present invention, the signal light oscillates in the resonant cavity 310 and the power is amplified.

[0065] According to an embodiment of the present invention, the transverse mode refers to the distribution mode of the light field in the resonant cavity 310 in the direction perpendicular to the optical axis. The fundamental transverse mode is the simplest and most basic transverse mode, which usually refers to a mode in which the distribution of the light spot on the cross section is uniform or nearly uniform. The longitudinal mode refers to the distribution mode of the light field in the resonant cavity 310 in the direction of the optical axis, which determines the number of round trips and the resonant frequency of the light beam in the resonant cavity 310. When the resonant cavity 310 is not excited to produce a high-order transverse mode, only the fundamental transverse mode exists in the resonant cavity 310. And when only the fundamental transverse mode exists in the resonant cavity 310, the size of the specific frequency interval between adjacent longitudinal modes in the resonant cavity 310 is c / 2L, where c is the speed of light and L is the cavity length of the resonant cavity 310. When the resonant cavity 310 is excited by the pump laser and / or the seed laser to produce a high-order transverse mode, the high-order transverse mode shortens the interval between the longitudinal modes by changing the reflection of the light beam in the resonant cavity. When the resonant cavity is excited to produce a high-order transverse mode, the frequency interval between adjacent longitudinal modes is less than c / 2L.

[0066] According to an embodiment of the present invention, a pump laser and / or a seed laser are used to excite a high-order transverse mode. Since the high-order transverse mode can shorten the longitudinal mode frequency interval to be smaller than the laser line width of the visible near-infrared laser output by the resonant cavity 310 (i.e., the line width of the visible near-infrared laser light source), the seed laser can be injected into the optical resonant cavity for a long time and efficiently when the wavelength of the seed laser changes continuously, thereby reducing the oscillation threshold of the optical parameter and making the wavelength tuning range of the visible near-infrared laser light source large. In addition, shortening the longitudinal mode frequency interval to be smaller than the laser line width of the visible near-infrared laser output by the resonant cavity 310 can also ensure that when the wavelength of the seed laser changes continuously, the wavelength of the visible near-infrared laser can be tuned over a large range without mode hopping. Therefore, the resonant cavity 310 can output a visible near-infrared laser with the same real-time wavelength as the changing seed laser.

[0067] The visible near-infrared laser light source provided according to the embodiment of the present invention can achieve wide-range tuning of the visible near-infrared laser wavelength without changing the cavity length of the resonant cavity.

[0068] According to an embodiment of the present invention, the pump laser and / or the seed laser can excite the resonant cavity 310, and the generation of high-order transverse modes in the resonant cavity 310 includes at least one of the following situations: the spot size of the pump laser can excite the resonant cavity 310, and generate high-order transverse modes in the resonant cavity 310; the incident angle of the pump laser can excite the resonant cavity 310, and generate high-order transverse modes in the resonant cavity 310; and the incident angle of the seed laser can excite the resonant cavity 310, and generate high-order transverse modes in the resonant cavity. The incident angle of the pump laser is the angle between the pump laser and the optical axis of the resonant cavity, and the incident angle of the seed laser is the angle between the seed laser and the optical axis of the resonant cavity. When the spot size of the pump laser is used to excite the high-order transverse mode, the spot size of the pump laser needs to be larger, for example, it can be 5mm. When the incident angle of the pump laser is used to excite the high-order transverse mode, the incident angle needs to be 0°~180°, that is, the beam of the pump laser is not parallel to the optical axis of the resonant cavity. When the incident angle of the seed laser is used to excite high-order transverse modes, the incident angle needs to be 0°~180°, that is, the beam of the seed laser is not parallel to the optical axis of the resonant cavity.

[0069] According to an embodiment of the present invention, the pump laser generating module 100 includes: a first laser 110 , a first polarization unit 120 , a first light spot adjustment unit 130 , and a first angle adjustment unit 140 .

[0070] The first laser 110 is suitable for generating a first laser. The first laser 110 may be, for example, a Nd:YAG laser, and the wavelength of the first laser may be, for example, 532 nm.

[0071] The first polarization unit 120 is suitable for converting the first laser into a pump laser, which is a polarized laser, and the polarization direction of the pump laser is configured to meet the phase matching condition of the nonlinear effect. The first polarization unit 120 includes a first half-wave plate 121, a first polarization beam splitter cube 122, a first light collector 123 and a second half-wave plate 124. The first half-wave plate 121 is used to change the polarization state of the first laser. The first polarization beam splitter cube 122 is suitable for splitting the first laser after the polarization state is changed into a first sub-laser and a second sub-laser, the first sub-laser and the second sub-laser are both polarized lasers and the polarization directions of the first sub-laser and the second sub-laser are perpendicular. The first light collector 123 is suitable for collecting the first sub-laser or the second sub-laser. For example, the polarization direction of the first sub-laser is a vertical direction, the polarization direction of the second sub-laser is a horizontal direction, and the first light collector 123 is suitable for collecting the first sub-laser. The first half-wave plate 121 and the first polarization beam splitter cube 122 are used in combination to achieve the purpose of continuously changing the energy of the second sub-laser. According to an embodiment of the present invention, under the premise of ensuring that the power density of the pump laser is not greater than the damage threshold of the nonlinear optical crystal and each optical element and that the high-order transverse mode effectively excites the longitudinal mode, the power density (energy density) of the pump laser is increased, thereby improving the efficiency of nonlinear conversion. The second half-wave plate 124 is used to change the polarization direction of the second sub-laser to obtain the pump laser. Under the action of the second half-wave plate 124, the polarization direction of the pump laser is configured to meet the phase matching condition of the nonlinear conversion.

[0072] The spot adjustment unit 130 includes an extracavity plano-convex lens 131 and a plano-concave lens 132. The extracavity plano-convex lens 131 and the plano-concave lens 132 are used together to form a Galilean telescope assembly, which is used to change the spot size of the pump laser. After the pump laser passes through the Galilean telescope assembly, the spot size is reduced from 10 mm to 5 mm. The plane portion of the extracavity plano-convex lens 131 is adjacent to the plane portion of the plano-concave lens 132, and the plane portion of the extracavity plano-convex lens 131 is arranged in parallel with the plane portion of the plano-concave lens 132, and the distance between the extracavity plano-convex lens 131 and the plano-concave lens 132 is the sum of the focal lengths of the extracavity plano-convex lens 131 and the plano-concave lens 132.

[0073] The first angle adjustment unit 140 is suitable for adjusting the incident angle of the pump laser. The first angle adjustment unit 140 may be, for example, a first reflector, and the incident angle of the pump laser may be changed by rotating the first reflector.

[0074] According to an embodiment of the present invention, the seed laser generating module 200 includes: a second laser 210 , a beam shaping unit 220 , a second polarization unit 230 , and a second angle adjustment unit 240 .

[0075] The second laser 210 is suitable for generating a second laser. The wavelength range of the second laser output by the second laser 210 is 1000 nm to 1500 nm. The second laser 210 can be a semiconductor laser, and the wavelength of the second laser can be tuned within 1000 nm to 1500 nm by changing the semiconductor chip and the grating angle in the semiconductor laser.

[0076] The beam shaping unit 220 is suitable for shaping the beam of the second laser. The beam shaping unit 220 can be, for example, a deformable prism pair, the deformable prism has a beam expansion ratio of 1:5, and the light spot of the second laser output by the second laser 210 (a long rice grain-shaped light spot of 1.2 mm×6.2 mm) is shaped by the deformable prism into a circular light spot of about 6 mm to match the pump laser.

[0077] The second polarization unit 230 is suitable for converting the second laser after shaping into a seed laser. The polarization direction of the seed laser is configured to meet the phase matching condition for guiding nonlinear conversion. The second polarization unit 230 includes a third half-wave plate 231, a second polarization beam splitter cube 232, a second light collector 233, and a fourth half-wave plate 234. The third half-wave plate 231 is suitable for changing the polarization state of the second laser after shaping. The second polarization beam splitter cube 232 is used to divide the second laser after the polarization state of the third half-wave plate 231 is changed into a third sub-laser and a fourth sub-laser. The third sub-laser and the fourth sub-laser are both polarized lasers, and the polarization directions of the two are perpendicular. The second light collector 233 is suitable for collecting the third sub-laser or the fourth sub-laser. For example, the polarization direction of the third sub-laser is horizontal, the polarization direction of the fourth sub-laser is vertical, and the second light collector 233 is suitable for collecting the third sub-laser. The third half-wave plate 231 and the second polarization beam splitter cube 232 are used in combination to achieve the purpose of continuously changing the energy of the fourth sub-laser. The fourth half-wave plate 234 is used to change the polarization direction of the fourth sub-laser to obtain a seed laser.

[0078] The second angle adjustment unit 240 is suitable for adjusting the incident angle of the seed laser. The second angle adjustment unit 240 can be, for example, a short-wave dichroic mirror, the short-wave dichroic mirror having a cutoff wavelength of 1000 nm. The short-wave dichroic mirror divides the incident light beam into transmitted light and reflected light according to the wavelength, has high transmittance for a band less than the cutoff wavelength, and has high reflectivity for a band greater than the cutoff wavelength. Since the wavelength of the seed laser is 1000 nm to 1500 nm, the short-wave dichroic mirror can reflect the seed laser and reflect the seed laser to the resonant cavity 310. Rotating the short-wave dichroic mirror can make the seed laser incident on the resonant cavity 310 at different incident angles. Since the short-wave dichroic mirror has a high transmittance for a band less than the cutoff wavelength, the short-wave dichroic mirror can prevent the pump laser (generated by the signal light and the idler light) with a wavelength different from the seed laser and the signal light generated subsequently from being incident on the semiconductor laser, causing damage to the semiconductor chip.

[0079] According to an embodiment of the present invention, the seed laser generating module 200 further includes an isolation unit 250, which is disposed between the beam shaping unit 220 and the second polarization unit 230, and is adapted to ensure that the second laser after shaping is unidirectionally transmitted to the second polarization unit 230, so as to protect the second laser 210. The isolation unit 250 may be, for example, an optical isolator. The optical isolator, the second polarization beam splitting cube 232, and the short-wave pass dichroic mirror may jointly ensure that the light in the optical path is prevented from entering the second laser 210.

[0080] According to an embodiment of the present invention, the resonant cavity 310 includes: a non-collinear first cavity mirror 311, a second cavity mirror 312, and a third cavity mirror 313. The three cavity mirrors are configured to enable the signal light to be reflected back and forth by the three cavity mirrors along a preset direction, so that the signal light oscillates in the resonant cavity along a preset direction. The preset direction may be, for example, a clockwise direction.

[0081] According to an embodiment of the present invention, the nonlinear optical crystal 320 is located between the first cavity mirror 311 and the second cavity mirror 312. The nonlinear optical crystal 320 may be, for example, a KTiOPO4 crystal (KTP crystal), the KTP crystal having a length of 20 mm and a cross section of 14×9 mm. 2 The light-transmitting surfaces are all coated with broadband anti-reflection coatings, and the principal axis plane is the XZ plane, where the X direction is the direction of the minimum refractive index of the KTP crystal, the Z direction is the direction of the optical axis, the XZ plane is the plane where the X and Z directions are located, the cutting angles are θ=70 degrees and φ=0 degrees, and type II phase matching is adopted.

[0082] According to an embodiment of the present invention, the first cavity mirror 311 may be, for example, a first long-wave dichroic mirror, and the second cavity mirror 312 may be, for example, a second long-wave dichroic mirror. The first long-wave dichroic mirror has high reflectivity in a band shorter than the starting wavelength, and has high transmittance in a band longer than the starting wavelength. The starting wavelength of the first long-wave dichroic mirror is 1000 nm, so the first long-wave dichroic mirror has a higher transmittance to the seed laser and a higher reflectivity to the signal light. The second long-wave dichroic mirror has high transmittance in a band longer than the starting wavelength, and has high reflectivity in a band shorter than the starting wavelength. The starting wavelength of the second long-wave dichroic mirror is 1000 nm, so the second long-wave dichroic mirror has a higher reflectivity to the signal light. The third cavity mirror 313 is an output coupling mirror, which can reflect part of the signal light (reflectivity is about 30%), and the reflected part of the signal light oscillates in the resonant cavity, and the output coupling mirror can also output the remaining other part of the signal light, that is, the visible near-infrared laser.

[0083] According to an embodiment of the present invention, the resonant cavity 310 further includes a first dichroic mirror 314, which is located between the first cavity mirror 311 and the nonlinear optical crystal 320. The first dichroic mirror 314 is used to receive the pump laser and reflect the pump laser so that the pump laser is incident on the nonlinear optical crystal 320. After the pump laser is incident on the nonlinear optical crystal, the signal light obtained is reflected by the second cavity mirror 312 and oscillates in the resonant cavity 310 along a preset direction.

[0084] According to an embodiment of the present invention, the seed laser is incident on the resonant cavity 310 through the first cavity mirror 311, and enters the nonlinear optical crystal 320 after passing through the first dichroic mirror 314 to guide the nonlinear conversion process. The first dichroic mirror 314 has a high reflectivity for the pump laser and a high transmittance for the idler light, the signal light and the seed laser.

[0085] According to an embodiment of the present invention, the resonant cavity further includes a second dichroic mirror 315 , a third light collector 316 , an intra-cavity plano-convex lens 317 and a fourth light collector 318 .

[0086] After the pump laser enters the nonlinear optical crystal 320, a part of the pump laser is converted into signal light and idler light, and the other part of the remaining pump laser is emitted from the nonlinear optical crystal 320. The second dichroic mirror 315 has a high reflectivity for the pump laser and a high transmittance for the seed laser, signal light and idler light. The second dichroic mirror 315 is used to reflect the other part of the remaining pump laser. The third light collector 316 is used to collect the other part of the remaining pump laser reflected by the second dichroic mirror 315. The intracavity plano-convex lens 317 is set between any two cavity mirrors to replace the concave mirror in the general optical resonant cavity, converge (converge) the seed laser, and make the signal light oscillate stably in the resonant cavity. According to the relationship that the pump laser, signal light and idler light satisfy the energy conservation, the wavelength of the idler light can be inferred by obtaining the wavelength of the signal light. Then, by selecting the second cavity mirror 312, the idler light can be transmitted from the second cavity mirror 312, and the fourth light collector 318 is used to collect the idler light output by the second cavity mirror 312.

[0087] According to an embodiment of the present invention, the control module 400 is also suitable for adjusting the direction of the optical axis of the nonlinear optical crystal, and the control module 400 includes: a sampling unit 410 and an adjustment unit 420. The sampling unit 410 is suitable for sampling the visible near-infrared laser output by the resonant cavity 310 to obtain the wavelength of the visible near-infrared laser output by the resonant cavity 310, and to achieve real-time monitoring of the wavelength of the visible near-infrared laser output by the resonant cavity 310. The adjustment unit 420 is suitable for adjusting the direction of the optical axis of the nonlinear optical crystal according to the sampling result, so that the nonlinear optical crystal meets the phase matching condition of the nonlinear optical conversion.

[0088] The sampling unit 410 includes a sampling mirror 411, a lens 412, and a wavelength meter 413. The adjustment unit 420 may include, for example, a computer. Based on the polarization direction of the visible near-infrared laser, the uncoated surface of the sampling mirror 411 samples 1-10% from the visible near-infrared laser using the Fresnel reflection principle. Different proportions of light are reflected according to different polarization directions of the light. When the visible near-infrared laser is horizontally polarized light and is incident on the sampling mirror 411 at an angle of 45°, the sampling mirror 411 will produce about 1% reflection to it. When the visible near-infrared laser is vertically polarized light and is incident on the sampling mirror 411 at an angle of 45°, the sampling mirror 411 will produce about 10% reflection to it. Due to the reflection of the sampling mirror 411, the energy of the visible near-infrared laser will be reduced after passing through the sampling mirror. The lens 403 is used to focus the visible near-infrared laser sample obtained by the sampling mirror 411, and the focused visible near-infrared light sample is introduced into the wavelength meter 413. The wavelength meter 413 is used to measure the wavelength of the visible near-infrared laser sample.

[0089] The adjustment unit 420 is used to display the wavelength measured by the wavelength meter in real time. The nonlinear optical crystal 320 is located on a precision electric rotation stage 330. The adjustment unit 420 controls the precision electric rotation stage 330 (positioning accuracy is better than 0.1 mrad) according to the measured real-time wavelength data, thereby driving the rotation of the nonlinear optical crystal 320 in the direction of the optical axis to obtain the phase matching condition at the desired wavelength (measured wavelength).

[0090] In the resonant cavity provided by the embodiment of the present invention, the photons of the signal light travel back and forth between the three cavity mirrors along the axis of the resonant cavity 310. The design of three cavity mirrors enables the photons of the signal light to pass through the nonlinear optical crystal multiple times, thereby increasing the effective optical path and thus improving the efficiency of light energy conversion.

[0091] According to an embodiment of the present invention, a convex lens is inserted between the three cavity mirrors to replace the concave mirror, so as to obtain a three-cavity mirror stable cavity, so that the light remains in the cavity of the resonant cavity 310 after multiple oscillations, which helps to obtain a stable resonant cavity 310, that is, the photons remain in the cavity after multiple reflections in the resonant cavity 310, thereby realizing the stable output of visible near-infrared laser.

[0092] According to the visible near-infrared laser light source provided by the embodiment of the present invention, a pump laser with a wavelength of 532nm and a single pulse energy of 160mJ and a seed laser with a power greater than 50mW and a spot diameter of 5mm are used to pump the KTP crystal, and the laser with a wavelength covering the visible light to near-infrared range is successfully output. Without actively locking the cavity length of the resonant cavity, the output line width can be stably less than 0.006cm -1 Near-infrared laser with single pulse energy greater than 10mJ.

[0093] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A visible near-infrared laser light source, characterized in that: include: A pump laser generating module, adapted to generate a pump laser; A seed laser generating module, adapted to generate a seed laser, wherein the seed laser is in the visible near-infrared laser band; Laparoscopic module, including: A resonant cavity, adapted to receive the pump laser and the seed laser; A nonlinear optical crystal, located in the resonant cavity, is suitable for causing the pump laser to undergo nonlinear conversion to generate coherently superimposed signal light; The seed laser is suitable for guiding the nonlinear conversion so that the wavelength of the signal light is the same as the wavelength of the seed laser, and the signal light oscillates and outputs in the resonant cavity to obtain visible near-infrared laser; A control module, adapted to control the wavelength of the seed laser generated by the seed laser generating module; In which, during the oscillation of the signal light in the resonant cavity, a longitudinal mode is formed in the resonant cavity; the pump laser and / or the seed laser can excite the resonant cavity to generate high-order transverse modes in the resonant cavity, and the high-order transverse modes can reduce the frequency interval between the longitudinal modes to avoid mode hopping when the wavelength of the seed laser changes.

2. The visible near-infrared laser light source according to claim 1, characterized in that: The pump laser and / or the seed laser can excite the resonant cavity, and generating a high-order transverse mode in the resonant cavity includes at least one of the following situations: The spot size of the pump laser can excite the resonant cavity and generate a high-order transverse mode in the resonant cavity; The incident angle of the pump laser can excite the resonant cavity and generate a high-order transverse mode in the resonant cavity; The incident angle of the seed laser can excite the resonant cavity and generate a high-order transverse mode in the resonant cavity; The incident angle of the pump laser is the angle between the pump laser and the optical axis of the resonant cavity, and the incident angle of the seed laser is the angle between the seed laser and the optical axis of the resonant cavity.

3. The visible near-infrared laser light source according to claim 2, characterized in that: The pump laser generating module comprises: A first laser, adapted to generate a first laser; A first polarization unit, adapted to convert the first laser into the pump laser, wherein the pump laser is a polarized laser, and the polarization direction of the pump laser is configured to satisfy a phase matching condition of the nonlinear conversion; A spot adjustment unit, adapted to adjust the spot size of the pump laser; The first angle adjustment unit is adapted to adjust the incident angle of the pump laser.

4. The visible near-infrared laser light source according to claim 2, characterized in that: The seed laser generating module comprises: A second laser, adapted to generate a second laser; A beam shaping unit, adapted to shape the beam of the second laser; A second polarization unit is used to convert the shaped second laser into a seed laser, wherein the seed laser is a polarized laser, and the polarization direction of the seed laser is configured to satisfy a phase matching condition for guiding the nonlinear conversion; The second angle adjustment unit is adapted to adjust the incident angle of the seed laser.

5. The visible near-infrared laser light source according to claim 4, characterized in that: The second laser is a semiconductor laser, and the wavelength range of the second laser output by the second laser is 1000 nm to 1500 nm.

6. The visible near-infrared laser light source according to claim 4, characterized in that: The seed laser generating module also includes: The isolation unit is arranged between the beam shaping unit and the second polarization unit, and is suitable for ensuring that the shaped second laser is unidirectionally transmitted to the second polarization unit to protect the second laser.

7. The visible near-infrared laser light source according to claim 1, characterized in that: The resonant cavity comprises: A first cavity mirror, a second cavity mirror and a third cavity mirror that are non-collinear; wherein the three cavity mirrors are configured to enable the signal light to be reflected back and forth by the three cavity mirrors along a preset direction, so that the signal light oscillates in the resonant cavity along the preset direction; the nonlinear optical crystal is located between the first cavity mirror and the second cavity mirror; a first dichroic mirror, located between the first cavity mirror and the nonlinear optical crystal, the first dichroic mirror being used to receive the pump laser and reflect the pump laser so that the pump laser is incident on the nonlinear optical crystal; after the pump laser is incident on the nonlinear optical crystal, the signal light obtained is reflected by the second cavity mirror and oscillates in the resonant cavity along the preset direction; The seed laser is incident on the resonant cavity through the first cavity mirror, and enters the nonlinear optical crystal after passing through the first dichroic mirror to guide the nonlinear conversion process.

8. The visible near-infrared laser light source according to claim 7, characterized in that: The first cavity mirror and the second cavity mirror are both long-wave dichroic mirrors, the starting wavelength of the long-wave dichroic mirror is 1000 nm, the third cavity mirror is an output coupling mirror, and the visible near-infrared laser is output from the output coupling mirror.

9. The visible near-infrared laser light source according to claim 7, characterized in that: The resonant cavity further comprises: The intracavity plano-convex lens is arranged between any two cavity mirrors and is suitable for converging the seed laser to ensure that the signal light oscillates in the resonant cavity.

10. The visible near-infrared laser light source according to claim 1, characterized in that: The control module is also adapted to adjust the direction of the optical axis of the nonlinear optical crystal, and the control module comprises: A sampling unit, adapted to sample the visible near-infrared laser output by the resonant cavity to obtain the wavelength of the visible near-infrared laser output by the resonant cavity; The adjustment unit is adapted to adjust the optical axis direction of the nonlinear optical crystal according to the sampling result, so that the nonlinear optical crystal satisfies the phase matching condition of the nonlinear conversion.

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