High repetition frequency broadband fast tunable optical parametric oscillator laser system

Abstract

The invention belongs to the technical field of lasers, particularly relates to the technical field of manufacturing of optoelectronic devices, and more particularly relates to a high-repetition-frequency broadband fast tunable optical parametric oscillator laser system. According to the system, high repetition frequency pump light is generated through the femtosecond oscillator, and the output repetition frequency is directly improved. The parametric oscillator adopts synchronous pumping and is matched with the cavity length, and it is ensured that high repetition frequency characteristic output signal light and idler frequency light are maintained in the frequency conversion process. Meanwhile, the beam splitting signal light and the residual pump light generate visible light in the out-of-cavity sum frequency module, and the output wave band is widened. In addition, the control module quickly changes the phase matching condition by adjusting the incident angle of the pump light, so that the wavelength is quickly tuned. Compared with the prior art, the cooperative work enables the system to have high repetition frequency, wide band and fast tuning capability at the same time.

Description

Technical Field

[0001] This application belongs to the field of laser technology, specifically to the field of optoelectronic device manufacturing technology, and more specifically, to a high repetition rate, wide bandwidth, fast tunable optical parametric oscillator laser system. Background Technology

[0002] Tunable light sources in the visible light band, the eye-safe band around 1.5µm, and the mid-infrared band of 3 to 5µm have important applications in military, medical, and communication fields.

[0003] Currently, most parametric oscillators use low-repetition-frequency all-solid-state oscillators as pump sources, making it difficult to increase the repetition frequency to GHz by optimizing the cavity shape. Parametric oscillators rely on temperature tuning, resulting in extremely slow response times and stringent temperature control requirements. Long-term temperature cycling can cause thermal expansion and contraction of the crystal, generating internal stress and potentially leading to polarization period distortion or crystal cracking. Pump light wavelength tuning significantly increases optical losses and degrades system stability. Crystal angle tuning makes the mechanical structure susceptible to vibration, resulting in generally poor stability; tuning accuracy depends on mechanical control and has significant errors. Cavity length tuning easily leads to output power fluctuations, and angle tuning may reduce conversion efficiency.

[0004] While such laser systems can function in laboratory environments when applied to optoelectronic device manufacturing, their inherent limitations in repetition rate, tuning speed, long-term stability, integration, and energy efficiency severely restrict their large-scale and practical application in industrial fields such as high-end optoelectronic device manufacturing, online precision inspection, and semiconductor processes. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this application is to provide a high repetition rate, wide band, fast tunable optical parametric oscillator laser system, which aims to solve the problems of low laser repetition rate, slow wavelength tuning speed and narrow tuning range of the output laser of the existing laser system, making it difficult to apply in high-end manufacturing.

[0006] The first aspect of this application relates to a high repetition rate, wideband, fast tunable optical parametric oscillator laser system, comprising: a femtosecond oscillator module, a control module, a parametric oscillator module, and an external cavity summing module; the output terminal of the control module is electrically connected to the input terminal of the femtosecond oscillator module; the output terminal of the femtosecond oscillator module is optically connected to the input terminal of the parametric oscillator module; the parametric oscillator module is configured with a first output terminal, a second output terminal, a third output terminal, and a fourth output terminal; the third output terminal of the parametric oscillator module is optically connected to the first input terminal of the external cavity summing module; the fourth output terminal of the parametric oscillator module is optically connected to the second input terminal of the external cavity summing module; the femtosecond oscillator module is configured to generate high repetition rate target pump light output to the parametric oscillator module. The parametric oscillator module is configured to convert the target pump light into down-frequency signal light and idler light through synchronous pumping, and split the signal light to generate a first beam and a second beam. The idler light is output through a first output terminal, the first beam is output through a second output terminal, the unconverted target pump light is output to the external summing module through a third output terminal, and the second beam is output to the external summing module through a fourth output terminal. The cavity length of the parametric oscillator module is equal to the cavity length of the femtosecond oscillator module to achieve repetition frequency matching. The external summing module is configured to sum the unconverted target pump light and the second beam to output visible light. The control module is configured to adjust the angle at which the pump light is incident on the parametric oscillator module to achieve rapid tuning of the output wavelength.

[0007] In one embodiment, the femtosecond oscillator module includes: a pump generation unit, a first oscillator unit, and a first emission unit; the output terminal of the pump generation unit is optically connected to the input terminal of the first oscillator unit; the output terminal of the first oscillator unit is optically connected to the first input terminal of the first emission unit; the second input terminal of the first emission unit is electrically connected to a control module; the output terminal of the first emission unit is optically connected to the input terminal of a parametric oscillator module; the pump generation unit is configured to generate initial pump light and output it to the first oscillator unit through collimation and focusing; the first oscillator unit is configured to oscillate the initial pump light to generate a femtosecond laser as the target pump light and output it to the first emission unit; the first emission unit is configured to receive a control signal from the control module to change the angle of the emitted target pump light.

[0008] In one embodiment, the first oscillator unit includes: a first plano-concave mirror, a Yb:CALGO crystal, a second plano-concave partial mirror, a first planar high-reflection mirror, and a first GTI mirror; the first plano-concave mirror, the Yb:CALGO crystal, and the second plano-concave partial mirror are arranged sequentially along the beam propagation direction of the pump generation unit; wherein, the concave surfaces of the first plano-concave mirror and the second plano-concave partial mirror are arranged opposite to each other and face the two ends of the Yb:CALGO crystal respectively; the first planar high-reflection mirror is disposed in the reflection path of the second plano-concave partial mirror for reflecting the laser transmitted from the second plano-concave partial mirror; the first GTI mirror is disposed in the reflection path of the first planar high-reflection mirror for wavelength selection of the laser reflected back by the first planar high-reflection mirror; the laser with wavelength selected by the first GTI mirror returns to the first plano-concave mirror and is finally output from the second plano-concave partial mirror.

[0009] In one embodiment, the first emission unit includes: a Faraday isolator, a half-wave plate, a first plane mirror, a second plane mirror, a motor, and a first plano-convex lens; the Faraday isolator, the half-wave plate, and the first plane mirror are arranged sequentially along the beam propagation direction of the first oscillator unit; the second plane mirror is disposed in the reflection path of the first plane mirror; the first plano-convex lens is disposed in the reflection path of the second plane mirror; the motor is disposed on the back of the first and second plane mirrors and is configured to receive control signals from the control module to change the angles of the first and second plane mirrors.

[0010] In one embodiment, the parametric oscillator module includes: a second oscillator unit and a second output unit; the input terminal of the second oscillator unit is optically connected to the output terminal of the femtosecond oscillator module; the first output terminal of the second oscillator unit is optically connected to the first input terminal of the second output unit; the second output terminal of the second oscillator unit is optically connected to the second input terminal of the second output unit; the cavity length of the second oscillator unit is the same as that of the first oscillator unit; the second oscillator unit is configured to convert the target pump light oscillation into a down-frequency signal light and an idler light, and output the idler light and the unconverted target pump light to the second output unit through the first output terminal; output the signal light to the second output unit through the second output terminal; the second output unit is configured to separate the idler light and the target pump light, and output the idler light through the first output terminal and the unconverted target pump light to the external cavity summing module through the third output terminal; it is also configured to split the signal light into a first beam and a second beam, output the first beam through the second output terminal and output the second beam to the external cavity summing module through the fourth output terminal.

[0011] In one embodiment, the second oscillator unit includes: a third plano-concave mirror, an MgO:PPLN crystal, a fourth plano-concave mirror, a second GTI mirror, and an output coupling mirror; the third plano-concave mirror, the MgO:PPLN crystal, and the fourth plano-concave mirror are arranged sequentially along the propagation direction of the pump laser emitted from the femtosecond oscillator module; wherein the concave surfaces of the third and fourth plano-concave mirrors are arranged opposite each other and face the two ends of the MgO:PPLN crystal respectively; the second GTI mirror is disposed in the reflection path of the third plano-concave mirror; and the output coupling mirror is disposed in the reflection path of the fourth plano-concave mirror.

[0012] In one embodiment, the second emitting unit includes a beam splitter and a beam splitter prism; the beam splitter is disposed in the path of the idler light and the unconverted target pump light emitted from the second oscillator unit; the beam splitter prism is disposed in the path of the signal light emitted from the second oscillator unit.

[0013] In one embodiment, the extracavity summing module includes: an incident unit and a summing unit; a first input terminal of the incident unit is optically connected to the third output terminal of the parametric oscillator module; a second input terminal of the incident unit is optically connected to the fourth output terminal of the parametric oscillator module; a first output terminal of the incident unit is optically connected to the first input terminal of the summing unit; a second output terminal of the incident unit is optically connected to the second input terminal of the summing unit; the incident unit is configured to receive unconverted target pump light and a second beam and transmit them to the summing unit; the summing unit is configured to sum the unconverted target pump light and the second beam to output visible light.

[0014] In one embodiment, the incident unit includes: a third plane mirror, a second plano-convex lens, a fourth plane mirror, and a third plano-convex lens; the sum-frequency interaction unit includes: a fifth plane mirror, a ZGP crystal, and a fifth plano-concave mirror; the third plane mirror is disposed in the unconverted pump light output path of the parametric oscillator module; the second plano-convex lens is disposed in the reflection path of the fifth plane mirror; the third plane mirror is disposed in the output path of the second plano-convex lens; the fourth plane mirror is disposed in the second beam output path of the parametric oscillator module; the third plano-convex lens is disposed in the reflection path of the fourth plane mirror; the fifth plano-concave mirror is disposed in the output path of the third plano-convex lens; the concave surface of the fifth plano-concave mirror is disposed opposite to the fifth plane mirror and faces the two ends of the ZGP crystal respectively.

[0015] In one embodiment, the control module is configured to output a control signal to the femtosecond oscillator module based on a non-critical phase matching or critical phase matching mechanism.

[0016] Overall, the technical solutions conceived in this application have the following beneficial effects compared with the prior art: This application utilizes a femtosecond oscillator module to generate high-repetition-rate pump light, directly improving the system's repetition rate reference and overcoming the low repetition rate problem of existing systems. Furthermore, by employing a synchronous pumping method with a parametric oscillator module and ensuring its cavity length is equal to that of the femtosecond oscillator module, repetition rate matching is achieved, thus maintaining high repetition rate characteristics during frequency conversion and ensuring a high repetition rate for the output laser. Simultaneously, an external summing module is used to sum the remaining pump light with the beam-splitting signal light, generating visible light output, expanding the system's output wavelength band, and overcoming the limitation of a narrow tuning range. In addition, the control module rapidly changes the phase matching condition by adjusting the incident angle of the pump light, achieving rapid tuning of the output wavelength and thus improving the tuning speed.

[0017] Compared with existing technologies, this system achieves high repetition frequency, wide-band output and fast wavelength tuning through the synergistic effect of the above-mentioned technologies, meeting the application requirements of high-end manufacturing. Attached Figure Description

[0018] Figure 1 This is one of the structural block diagrams of a high repetition rate, wide bandwidth, fast tunable optical parametric oscillator laser system provided in the embodiments of this application; Figure 2 This is the second structural block diagram of the high repetition rate, wide bandwidth, fast tunable optical parametric oscillator laser system provided in the embodiments of this application; Figure 3 This is a configuration diagram of a specific implementation of the high repetition rate, wide bandwidth, fast tunable optical parametric oscillator laser system provided in this application.

[0019] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 10 is the femtosecond oscillator module; 20 is the parametric oscillator module; 30 is the extracavity sum-frequency module; 40 is the control module; 11 is the pump generation unit; 12 is the first oscillator unit; 13 is the first emission unit; 21 is the second oscillator unit; 22 is the second emission unit; 31 is the incident unit; 32 is the sum-frequency action unit; 111 is the LD pump source; 112 is the collimation and focusing subsystem; 121 is the first plano-concave mirror; 122 is the Yb:CALGO crystal; 123 is the second plano-concave partial mirror; 124 is the first planar high-reflection mirror; 125 is the first GTI mirror; 131 is the Faraday crystal. Isolator; 132 is a half-wave plate; 133 is a first plane mirror; 134 is a second plane mirror; 135 is a first plano-convex lens; 211 is a third plano-concave mirror; 212 is an MgO:PPLN crystal; 213 is a fourth plano-concave mirror; 214 is a second GTI mirror; 215 is an output coupling mirror; 221 is a beam splitter; 222 is a beam splitter prism; 311 is a third plane mirror; 312 is a second plano-convex lens; 313 is a fourth plane mirror; 314 is a third plano-convex lens; 321 is a fifth plane mirror; 322 is a ZGP crystal; 323 is a fifth plano-concave mirror. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0021] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A existing alone, A and B existing simultaneously, and B existing alone. In this application, the symbol " / " indicates that the related objects are in an "or" relationship, for example, A / B means A or B.

[0022] In this application, the terms "first" and "second," etc., are used to distinguish different objects, not to describe a specific order of objects. For example, "first response message" and "second response message," etc., are used to distinguish different response messages, not to describe a specific order of response messages.

[0023] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner. Unless otherwise stated, "multiple" means two or more, for example, multiple processing units means two or more processing units, multiple elements means two or more elements, etc.

[0024] In this application embodiment, the optical lenses involved and their brief functions are described as follows: A plano-concave mirror is a mirror with one side being flat and the other side being concave, used to converge or diverge light beams while changing the direction of the light path; a plano-concave partial mirror is a plano-concave mirror with partial transmittance based on a plano-concave mirror, often used for coupling output or beam splitting within a resonant cavity; a planar high-reflectivity mirror is a planar mirror with high reflectivity, used for almost total internal reflection of light beams to change the light path; a GTI mirror (Gires-Tournois interferometer) is a reflective interferometer used for dispersion compensation or phase modulation; a Faraday isolator is based on the Faraday magneto-optical effect. A unidirectional transmission device is used to isolate back-reflected light and protect the light source; a half-wave plate is an optical waveplate that adjusts the polarization direction by changing the phase difference of polarized light; a plane mirror is used to change the direction of the light path, and its reflectivity can be designed as needed; a plano-convex lens is a lens with one side being flat and the other side being convex, used to converge the light beam; an output coupler is a partially transmissive lens in the resonant cavity used to output laser light, and usually has a specific transmittance; a beam splitter is an optical element that splits incident light into two beams of light, one transmitted and one reflected, according to a certain ratio; a beam splitter prism is a beam splitting device based on a prism structure that can split a beam of light into multiple beams (such as polarization beam splitting or wavelength beam splitting).

[0025] While existing laser systems can function in laboratory environments when applied to optoelectronic device manufacturing, their inherent limitations in repetition rate, tuning speed, long-term stability, integration, and energy efficiency severely restrict their large-scale and practical application in industrial fields such as high-end optoelectronic device manufacturing, online precision inspection, and semiconductor processes.

[0026] Based on this, this application proposes an embodiment of a high repetition rate, wide bandwidth, fast tunable optical parametric oscillator laser system. Please refer to... Figure 1 , Figure 1 This is one of the structural block diagrams of a high repetition rate, wide bandwidth, fast tunable optical parametric oscillator laser system provided in the embodiments of this application.

[0027] In this embodiment, the high repetition rate wideband fast tunable optical parametric oscillator laser system includes: a femtosecond oscillator module 10, a parametric oscillator module 20, an external cavity sum-frequency module 30, and a control module 40.

[0028] It should be noted that the output terminal of the control module 40 is electrically connected to the input terminal of the femtosecond oscillator module 10; the output terminal of the femtosecond oscillator module 10 is optically connected to the input terminal of the parametric oscillator module 20; the parametric oscillator module 20 is configured with a first output terminal, a second output terminal, a third output terminal, and a fourth output terminal; the third output terminal of the parametric oscillator module 20 is optically connected to the first input terminal of the external cavity sum-frequency module 30; and the fourth output terminal of the parametric oscillator module 20 is optically connected to the second input terminal of the external cavity sum-frequency module 30.

[0029] It is understandable that electrical connection refers to transmitting the electrical control signals generated by the control module 40 to the drive mechanism of the femtosecond oscillator module 10 via cables, wires, or printed circuits. These signals can be voltage, current, or digital communication protocol signals, used to adjust the output angle of the femtosecond oscillator module 10. Optical path connection mainly refers to spatial optical path connection, using bulk optical elements such as mirrors, lenses, and prisms to reflect, redirect, collimate, focus, and spatially filter the light beam in free space. A waveguide optical path can also be selected based on actual conditions; no limitation is made here.

[0030] It should be noted that the femtosecond oscillator module 10 is configured to generate high-repetition-rate target pump light output to the parametric oscillator module 20.

[0031] Understandably, high repetition rate refers to a pulse repetition frequency that is typically in the megahertz range or higher. The device that achieves this function can be a ytterbium-doped fiber mode-locked laser or a Ti:sapphire laser based on a semiconductor saturable absorber mirror, and its output light is guided to the parametric oscillator module 20 via an optical path connection.

[0032] Specifically, ytterbium-doped femtosecond lasers possess high power and excellent light source properties, offering significant advantages for applications requiring high average power and narrow pulse output. One approach is to directly pump an optical parametric oscillator (OPO) using a nonlinear crystal as the frequency conversion medium with a high-power ytterbium-doped femtosecond laser to generate femtosecond lasers. This typically employs synchronous pumping, meaning the repetition frequency of the OPO must match the repetition frequency of the pump light. Only in this way will the signal light be amplified each time it passes through the nonlinear crystal. When the gain of the signal light in the OPO cavity exceeds the loss, the energy of the signal light will increase, ultimately resulting in parametric output.

[0033] It should be noted that the parametric oscillator module 20 is configured to convert the target pump light into down-frequency signal light and idler light through synchronous pumping, and split the signal light to generate a first beam and a second beam, so as to output idler light through a first output terminal, output the first beam through a second output terminal, output the unconverted target pump light to the external cavity summing module 30 through a third output terminal, and output the second beam to the external cavity summing module 30 through a fourth output terminal; wherein the cavity length of the parametric oscillator module 20 is equal to the cavity length of the femtosecond oscillator module 10 to achieve repetition frequency matching; the external cavity summing module 30 is configured to sum the unconverted target pump light and the second beam to output visible light.

[0034] Understandably, the synchronous pumping method requires the cavity length of the optical resonant cavity of the parametric oscillator module 20 to be precisely equal to or an integer multiple of the cavity length of the femtosecond oscillator module 10, so as to ensure that the pump light pulse and the signal light pulse circulating in the parametric oscillator resonant cavity are precisely synchronized in time, thereby achieving efficient parametric amplification and oscillation. In this process, the target pump light generates down-frequency signal light and idler light in the nonlinear crystal through the optical parametric down-conversion process. The down-frequency means that the sum of the photon energies of the signal light and the idler light is equal to the photon energy of the pump light, so their frequencies are all lower than the pump light frequency.

[0035] Specifically, periodically polarized lithium niobate (PPLN) crystals have advantages such as large nonlinear coefficients, flexible phase matching methods, and no space walk-off effect. After doping with magnesium oxide (MgO), the damage threshold of magnesium oxide-doped periodically polarized lithium niobate (MgO:PPLN) crystals is further increased, making it one of the most commonly used mid-infrared nonlinear crystals. Therefore, MgO:PPLN crystals are used for nonlinear frequency conversion.

[0036] Understandably, the parametric oscillator module 20 is further equipped with a beam splitter to split the generated signal light into a first beam and a second beam. The beam splitter can be a cubic beam splitter prism with a fixed splitting ratio or a combination of polarization beam splitters with an adjustable splitting ratio. This module outputs idler light through its first output terminal, the first beam through its second output terminal, unconverted target pump light (i.e., residual pump light that has not been converted after passing through the nonlinear crystal) through its third output terminal, and the second beam through its fourth output terminal. The third and fourth output terminals are connected to the first and second input optical paths of the external sum-frequency module 30, respectively.

[0037] Understandably, spectral tuning performance, as one of the important indicators for evaluating optical parametric oscillators, is mainly categorized into pump wavelength tuning, quasi-phase period tuning, crystal temperature tuning, cavity length tuning, and crystal angle tuning. Studies have found that in femtosecond laser-pumped MgO:PPLN crystal parametric oscillators, the optical-to-optical conversion efficiency can reach up to 67.4%. However, a considerable amount of pump light still does not fully participate in the nonlinear frequency conversion and is directly output outside the cavity. If this remaining pump light is used to perform external-cavity frequency summation (SFG) with a portion of the signal light, visible light can be obtained simultaneously.

[0038] Understandably, the frequency summing process, within the frequency summing crystal inside the external frequency summing module 30, nonlinearly sums the unconverted target pump light from the third output end with the second beam from the fourth output end to generate visible light with a frequency equal to the sum of the two frequencies.

[0039] It should be noted that the control module 40 is configured to adjust the angle at which the pump light is incident on the parametric oscillator module 20 in order to achieve rapid tuning of the output wavelength.

[0040] Understandably, this adjustment alters the phase-matching conditions in the nonlinear interaction process, thereby changing the wavelengths of the signal light and idler light generated by the parametric oscillation process. This adjustment can be achieved by rotating the reflector or the nonlinear crystal itself via a precision motor connected to the control module 40. Because it uses mechanical angle scanning rather than temperature control, rapid tuning can be achieved.

[0041] Specifically, control module 40 is configured to output a control signal to femtosecond oscillator module 10 based on a non-critical phase matching or critical phase matching mechanism. When the nonlinear crystal of parametric oscillator module 20 employs critical phase matching, control module 40 is configured to output a control signal that drives optical elements such as mirrors or the crystal itself in the optical path at the output of femtosecond oscillator module 10 or at the input of parametric oscillator module 20 to undergo precise angular rotation. This control signal is typically a voltage pulse sequence that drives a stepper motor or mirror, changing the incident angle of the pump light in the nonlinear crystal, thereby altering the refractive index of the crystal for the interacting light and adjusting the phase matching condition. This method enables rapid and continuous tuning of the output wavelength over a wide range.

[0042] Specifically, when the nonlinear crystal of the parametric oscillator module 20 employs noncritical phase matching, the control module 40 is configured to output a control signal to adjust the temperature of the nonlinear crystal. This signal drives a thermoelectric cooler or heater thermally coupled to the crystal, achieving precise temperature control of the crystal via a high-precision temperature controller. Temperature changes alter the crystal's refractive index, thereby satisfying the phase matching condition at a specific wavelength. This method typically does not change the beam direction, which is beneficial for stable beam coupling and can achieve higher conversion efficiency at specific wavelengths.

[0043] In this embodiment, the use of a femtosecond oscillator module to generate high-repetition-rate pump light directly improves the system's repetition frequency reference, overcoming the problem of low repetition frequency in existing systems. Furthermore, by using a parametric oscillator module with synchronous pumping and ensuring its cavity length is equal to that of the femtosecond oscillator module, repetition frequency matching is achieved, thus maintaining high repetition frequency characteristics during frequency conversion and ensuring a high repetition frequency for the output laser. Simultaneously, an external summing module is used to sum the remaining pump light with the beam-splitting signal light, generating visible light output, expanding the system's output wavelength band, and solving the limitation of narrow tuning range. In addition, the control module adjusts the incident angle of the pump light to quickly change the phase matching condition, achieving rapid tuning of the output wavelength and thus improving the tuning speed.

[0044] Compared with existing technologies, this system achieves high repetition frequency, wide-band output and fast wavelength tuning through the synergistic effect of the above-mentioned technologies, meeting the application requirements of high-end manufacturing.

[0045] Furthermore, this application proposes improved embodiments of the above embodiments. Please refer to... Figure 2 , Figure 2 This is the second structural block diagram of the high repetition rate, wide bandwidth, fast tunable optical parametric oscillator laser system provided in the embodiments of this application.

[0046] In this embodiment, the femtosecond oscillator module 10 includes: a pump generation unit 11, a first oscillator unit 12, and a first emission unit 13.

[0047] It should be noted that the output terminal of the pump generation unit 11 is optically connected to the input terminal of the first oscillator unit 12; the output terminal of the first oscillator unit 12 is optically connected to the first input terminal of the first emission unit 13; the second input terminal of the first emission unit 13 is electrically connected to the control module 40; and the output terminal of the first emission unit 13 is optically connected to the input terminal of the parametric oscillator module 20.

[0048] It should be noted that the pump generation unit 11 is configured to generate initial pump light and output it to the first oscillator unit 12 through collimation and focusing; the first oscillator unit 12 is configured to oscillate the initial pump light to generate femtosecond laser as target pump light and output it to the first emission unit 13; the first emission unit 13 is configured to receive control signals from the control module 40 to change the angle of the emitted target pump light.

[0049] It is understood that the pump generation unit 11 refers to the component that generates and provides an excitation light source. Its implementation device can be a semiconductor laser diode or other device, used to output continuous or pulsed light of a specific wavelength as the initial pump light. The output end of this unit is connected to the input end of the first oscillator unit 12 through an optical path, which means that the initial pump light is guided and injected into the first oscillator unit 12 through an optical transmission medium such as a lens, mirror, or optical fiber.

[0050] It is understandable that the first oscillator unit 12 refers to the core resonant cavity that generates femtosecond pulsed laser. It is configured to receive the initial pump light and, through the synergistic effect of the gain medium, mode-locking device and cavity mirror, convert the energy of the initial pump light into laser with a repetition frequency in the megahertz range and a pulse width in the femtosecond range. This process is called oscillation. A typical oscillator unit can be a ytterbium-doped fiber mode-locked oscillator based on a semiconductor saturable absorber mirror or a Ti:sapphire mode-locked laser. The generated laser is output from the output end of this unit to the first input end of the first output unit 13 as the target pump light. The two are also coupled through the above-mentioned optical path connection.

[0051] Understandably, the first output unit 13 is a component for directional beam output, which has a second input and an output in addition to the first input end; its second input end is electrically connected to the control module 40 through wires or a circuit board to receive control signals from the control module 40; its output end is connected to the input end of the parametric oscillator module 20 through an optical path.

[0052] The specific functional configuration is as follows: the pump generation unit 11 is configured to generate initial pump light and collimate and focus the beam through an optical system including a collimating lens and a focusing lens, that is, firstly, the diverging beam is collimated into a parallel beam and then focused into the gain medium of the first oscillator unit 12 to achieve efficient pumping. The first oscillator unit 12 is configured to use the pump light to generate and output a femtosecond laser in its optical resonant cavity through stimulated emission and mode-locking mechanism. This femtosecond laser is defined as the target pump light used to pump subsequent parametric processes. The first emission unit 13 is configured to receive the target pump light and simultaneously receive control signals from the control module 40. The unit contains a beam angle adjustment device that can be driven by an electrical signal, such as a reflector or acousto-optic deflector mounted on a precision electrically controlled rotary table. The unit is configured to drive the aforementioned angle adjustment device according to the received control signal, thereby changing the angle of the emitted target pump light, that is, changing the propagation direction of the beam that ultimately hits the input end of the parametric oscillator module 2).

[0053] In one specific implementation, please refer to Figure 3 , Figure 3 This is a configuration diagram of a specific implementation of the high repetition rate, wide bandwidth, fast tunable optical parametric oscillator laser system provided in this application.

[0054] It should be noted that the pump generation unit 11 includes: an LD pump source 111 and a collimation and focusing subsystem 112. The first oscillator unit 12 includes: a first plano-concave mirror 121, a ytterbium-doped calcium gadolinium aluminum oxide (Yb:CALGO) crystal 122, a second plano-concave partial mirror 123, a first planar high-reflection mirror 124, and a first GTI mirror 125.

[0055] It should be noted that the first plano-concave reflector 121, the Yb:CALGO crystal 122, and the second plano-concave partial reflector 123 are arranged sequentially along the beam propagation direction of the pump generation unit 11; wherein, the concave surfaces of the first plano-concave reflector 121 and the second plano-concave partial reflector 123 are arranged opposite to each other and face the two ends of the Yb:CALGO crystal 122 respectively; the first planar high-reflection mirror 124 is disposed in the reflection path of the second plano-concave partial reflector 123 and is used to reflect the laser transmitted from the second plano-concave partial reflector 123; the first GTI mirror 125 is disposed in the reflection path of the first planar high-reflection mirror 124 and is used to perform wavelength selection on the laser reflected back by the first planar high-reflection mirror 124; the laser with wavelength selected by the first GTI mirror 125 returns to the first plano-concave reflector 121 and is finally output from the second plano-concave partial reflector 123.

[0056] It should be noted that the descriptions such as "reflection path" primarily express the relative positional relationship of the lenses, meaning that the specific distances and angles between them can be adjusted according to the actual design. For example... Figure 3 The content shown below will not be repeated.

[0057] It should be noted that the second plano-concave part of the reflector has a special coating and also serves as the output coupling mirror of the femtosecond oscillator.

[0058] Understandably, the LD pump source 111 provides the energy required for population inversion in the Yb:CALGO crystal 122; the collimation and focusing subsystem 112 shapes and collimates the initial pump light and focuses it onto the Yb:CALGO crystal 122; the first plano-concave mirror 121 and the second plano-concave partial mirror 123 are used to change the cavity mode distribution so that the intracavity oscillating laser is focused onto the Yb:CALGO crystal 122. The first plano-concave mirror 121 is coated with an optical film that is highly transparent to the pump light and highly reflective at the 1050nm wavelength, and the second plano-concave pump mirror is coated with an optical film that has a reflectivity of 95% at 1050nm, so that the femtosecond laser can be reflected from the second plano-concave partial mirror. The other side of the mirror 123 outputs a first planar high-reflection mirror 124 used to fold the optical path. The first GTI mirror 125 provides negative dispersion within the cavity to compensate for positive dispersion caused by the cavity mirror crystal, lens, air, and Kerr effect. Meanwhile, the ring oscillator has two oscillation modes: clockwise and counterclockwise. By changing the distance between the Yb:CALGO crystal 122 and the second plano-concave part of the mirror 123, the oscillator can maintain clockwise oscillation. The mode-locking method adopts Kerr lens mode-locking. The cavity length is 200mm, and finally a femtosecond laser with an output wavelength of 1050nm and a repetition frequency of 1.5GHz is obtained, which is used as the target pump light to realize the pump source of the parametric oscillator.

[0059] It should be noted that the first emission unit 13 includes: a Faraday isolator 131, a half-wave plate 132, a first plane mirror 133, a second plane mirror 134, a motor, and a first plano-convex lens 135; the Faraday isolator 131, the half-wave plate 132, and the first plane mirror 133 are arranged sequentially along the beam propagation direction of the first oscillator unit 12; the second plane mirror 134 is disposed in the reflection path of the first plane mirror 133; the first plano-convex lens 135 is disposed in the reflection path of the second plane mirror 134; the motor is disposed on the back of the first plane mirror 133 and the second plane mirror 134, and is configured to receive control signals from the control module 40 to change the angles of the first plane mirror 133 and the second plane mirror 134.

[0060] Understandably, the Faraday isolator 131 ensures unidirectional laser passage, the half-wave plate 132 adjusts the polarization direction of the pump light, and the control module 40 drives the motor to rotate the first plane mirror 133 and the second plane mirror 134, thereby controlling the incident angle of the pump light of the parametric oscillator. The first plano-convex lens 135 focuses the pump light onto the subsequent parametric oscillator module 20.

[0061] In this embodiment, Figure 2 The parametric oscillator module 20 includes: a second oscillator unit 21 and a second output unit 22.

[0062] It should be noted that the input terminal of the second oscillator unit 21 is optically connected to the output terminal of the femtosecond oscillator module 10; the first output terminal of the second oscillator unit 21 is optically connected to the first input terminal of the second emission unit 22; and the second output terminal of the second oscillator unit 21 is optically connected to the second input terminal of the second emission unit 22.

[0063] It should be noted that the second oscillator unit 21 has the same cavity length as the first oscillator unit 12. The second oscillator unit 21 is configured to convert the target pump light oscillation into a down-frequency signal light and an idler light, and output the idler light and the unconverted target pump light to the second output unit 22 through the first output terminal; and output the signal light to the second output unit 22 through the second output terminal. The second output unit 22 is configured to separate the idler light and the target pump light, and output the idler light through the first output terminal and the unconverted target pump light through the third output terminal to the external cavity summing module 30; it is also configured to split the signal light into a first beam and a second beam, output the first beam through the second output terminal and the second beam through the fourth output terminal to the external cavity summing module 30.

[0064] It is understood that the second oscillator unit 21 refers to an optical parametric oscillator resonant cavity, whose input end is connected to the output end optical path of the femtosecond oscillator module 10 through a spatial optical path composed of a mirror and a lens, so as to receive the target pump light from the latter. This unit has the same cavity length as the first oscillator unit 12 in the femtosecond oscillator module 10. Here, "same cavity length" means that the optical lengths of the two optical resonant cavities are precisely matched to be equal or integer multiples of each other. Its physical significance is to achieve synchronous pumping, that is, to ensure that the pump light pulse and the signal light pulse established in the parametric oscillator resonant cavity are precisely overlapped in time, thereby achieving cumulative optical parametric amplification.

[0065] It is understandable that converting the target pump light oscillation into down-frequency signal light and idler light specifically refers to the fact that the unit contains a nonlinear crystal and a cavity mirror, forming an optical resonant cavity. The target pump light undergoes an optical parametric down-conversion process in the nonlinear crystal within this cavity. The oscillation in this process refers to the signal light (or idler light) being amplified multiple times within the resonant cavity to form laser oscillation. The unit outputs a combination of idler light and residual pump light that has not been consumed by the nonlinear process (i.e., the unconverted target pump light) to the first input of the second output unit 22 through its first output terminal, and outputs signal light to the second input of the second output unit 22 through its second output terminal.

[0066] Understandably, the second output unit 22 is a beam processing component configured to perform two main functions. First, it separates the idler light and the target pump light, achieved, for example, by using a dichroic mirror that is highly transparent to the idler light but highly reflective of the pump light wavelength, thus spatially separating the two. After separation, the idler light is output through the unit's first output terminal, while the unconverted target pump light is output to the external cavity summing module 30 through the third output terminal. Second, it splits the signal light into a first beam and a second beam, achieved by a beam splitter, such as a cubic beam-splitting prism with a specific splitting ratio for the signal light wavelength. The resulting first beam is output through the unit's second output terminal, while the second beam is output to the external cavity summing module 30 through the fourth output terminal.

[0067] Specifically, Figure 3 The second oscillator unit 21 includes: a third plano-concave mirror 211, an MgO:PPLN crystal 212, a fourth plano-concave mirror 213, a second GTI mirror 214, and an output coupling mirror 215; the third plano-concave mirror 211, the MgO:PPLN crystal 212, and the fourth plano-concave mirror 213 are arranged sequentially along the propagation direction of the pump laser emitted from the femtosecond oscillator module 10; wherein, the concave surfaces of the third plano-concave mirror 211 and the fourth plano-concave mirror 213 are arranged opposite each other and face the two ends of the MgO:PPLN crystal 212 respectively; the second GTI mirror 214 is disposed in the reflection path of the third plano-concave mirror 211; and the output coupling mirror 215 is disposed in the reflection path of the fourth plano-concave mirror 213.

[0068] Understandably, the first plano-convex lens 135 focuses the pump light onto the MgO:PPLN crystal 212, ensuring good mode matching between the target pump light and the oscillating light. Through a nonlinear frequency conversion effect, the target pump light is converted into two lower-frequency signal lights and idler lights. The signal light is laser a in the 1.3µm to 1.7µm band, and the idler light is laser b in the 3µm to 5µm band. The third plano-concave mirror 211 and the fourth plano-concave mirror 213 accumulate the signal light. Multiple pulse passes through the crystal cause pulse broadening and efficiency reduction; therefore, a second GTI mirror 214 is needed to compensate for the positive dispersion generated within the cavity. The signal light is output from the output coupling mirror 215, which has a transmittance of 15%. The idler light and pump light will pass through the third plano-concave mirror 211 and exit the cavity.

[0069] Specifically, Figure 3 The second emitting unit 22 includes a beam splitter 221 and a beam splitter prism 222. The beam splitter 221 is disposed in the path of the idler light and the unconverted target pump light emitted from the second oscillator unit 21. The beam splitter prism 222 is disposed in the path of the signal light emitted from the second oscillator unit 21.

[0070] Understandably, the beam splitter is coated with an optical film that provides high reflection in the 1050nm band and high transmission in the 3 to 5µm band, thus separating the unconverted residual pump light from the idler light. The signal light is then split into two beams by the beam splitter prism, namely the first beam and the second beam.

[0071] In this embodiment, Figure 2 The external frequency module 30 includes an incident unit 31 and a frequency-enhancing unit 32.

[0072] It should be noted that the first input terminal of the incident unit 31 is optically connected to the third output terminal of the parametric oscillator module 20; the second input terminal of the incident unit 31 is optically connected to the fourth output terminal of the parametric oscillator module 20; the first output terminal of the incident unit 31 is optically connected to the first input terminal of the sum-frequency action unit 32; and the second output terminal of the incident unit 31 is optically connected to the second input terminal of the sum-frequency action unit 32.

[0073] It should be noted that the incident unit 31 is configured to receive the unconverted target pump light and the second beam and transmit them to the sum-frequency action unit 32; the sum-frequency action unit 32 is configured to perform a sum-frequency operation on the unconverted target pump light and the second beam to output visible light.

[0074] Understandably, the incident unit 31 is a beam receiving and coupling component. Its first input terminal receives the unconverted target pump light from the third output terminal of the parametric oscillator module 20 via an optical path connection, and its second input terminal receives the second beam from the fourth output terminal of the parametric oscillator module 20 via an optical path connection. This unit is configured to receive the two beams and guide and transmit them to the sum-frequency interaction unit 32. Specifically, this transmission function is achieved through an optical system including mirrors, lenses, and possibly beam combiners. The key is to spatially collimate the two beams and point them towards the input terminal of the sum-frequency interaction unit 32, preparing for subsequent nonlinear interactions.

[0075] Understandably, the sum-frequency interaction unit 32 is an enhancement device for performing a sum-frequency process, configured to receive two beams of light from the incident unit 31 and perform a sum-frequency interaction on them. Sum-frequency interaction is a second-order nonlinear optical process in which two beams of light with different frequencies interact in a nonlinear medium to produce a new photon beam with a frequency equal to the sum of their frequencies. In this configuration, the process occurs within a sum-frequency crystal inside the sum-frequency interaction unit 32. This unit is further configured to output visible light as the generated sum-frequency light, where visible light refers to light whose wavelength falls within the human visual response range, typically 380 nm to 780 nm. For example, by summing a near-infrared pump beam with an infrared signal beam, i.e., a second beam, green light with a wavelength of 633.8 nm to 686.7 nm can be produced.

[0076] Understandably, to achieve efficient sum-frequency conversion, the sum-frequency action unit 32 can be designed to place the sum-frequency crystal within an optical resonant cavity that resonates with the generated visible light wavelength to enhance power, or simply place the crystal at the intersection of two precisely focused incident beams. Alternative implementations include: the incident unit 31 can use an optical fiber combiner to combine the two input beams before output; the sum-frequency action unit 32 can use a quasi-phase-matched crystal to improve conversion efficiency and tuning convenience; or, the sum-frequency action unit 32 can also forgo a resonant cavity and instead employ a single-pass structure, precisely adjusting the crystal's angle or temperature to meet the phase-matching condition.

[0077] Specifically, Figure 3 The incident unit 31 includes: a third plane mirror 311, a second plano-convex lens 312, a fourth plane mirror 313, and a third plano-convex lens 314; the sum-frequency interaction unit 32 includes: a fifth plane mirror 321, a zinc germanium phosphorus (ZGP) crystal 322, and a fifth plano-concave mirror 323.

[0078] It should be noted that the third plane mirror 311 is disposed in the unconverted pump light emission path of the parametric oscillator module 20; the second plano-convex lens 312 is disposed in the reflection path of the fifth plane mirror 321; the fifth plane mirror 321 is disposed in the emission path of the second plano-convex lens 312; the fourth plane mirror 313 is disposed in the second beam emission path of the parametric oscillator module 20; the third plano-convex lens 314 is disposed in the reflection path of the fourth plane mirror 313; the fifth plano-concave mirror 323 is disposed in the emission path of the third plano-convex lens 314; the concave surface of the fifth plano-concave mirror 323 is disposed opposite to the fifth plane mirror 321 and faces the two ends of the ZGP crystal 322 respectively.

[0079] Understandably, the fourth plane mirror 313 is used to fold the optical path of the second beam so that it is focused on the ZGP crystal 322 by the third plano-convex lens 314, and the third plane mirror 311 is used to fold the optical path of the unconverted pump light so that it is focused on the ZGP crystal 322 by the second plano-convex lens 312. The fifth plane mirror 321 and the fifth plano-concave mirror 323 together achieve efficient extracavity frequency conversion, thereby obtaining visible light c from 633.8 nm to 686.7 nm.

[0080] The specific implementation method is as follows: First, a high-power femtosecond oscillator is run, and its output light is used as the pump light of the parametric oscillator. The synchronous pumping method is adopted, and the cavity length of the parametric oscillator and the ring oscillator are controlled to be equal, so that the repetition frequency of the parametric oscillator is consistent with that of the femtosecond oscillator. Combined with the external cavity sum-frequency technology, three high repetition rate femtosecond lasers are output simultaneously. By changing the incident angle of the pump light of the parametric oscillator, the output wavelength is rapidly tuned.

[0081] In this embodiment, a high-repetition-rate ring femtosecond oscillator is used as the OPO pump source, employing synchronous pumping to achieve a multi-band laser repetition frequency of GHz. A parametric oscillator combined with extracavity sum-frequency technology is used to simultaneously output three femtosecond laser beams, ensuring that the output wavelengths cover the visible, near-infrared, and mid-infrared bands. A control module drives an angle deflection device to adjust the angle of the parametric oscillator pump light incident on the OPO crystal in real time. Based on non-critical phase matching (NCPM) or critical phase matching (CPM) mechanisms, continuous tuning of the output wavelength within the hundreds of nanometers range is achieved.

[0082] It should be understood that expressions such as “comprising” and “may include” used in this application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In this application, terms such as “comprising” and / or “having” are to be interpreted as indicating a particular characteristic, number, operation, constituent element, component, or combination thereof, but not to exclude the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0083] Furthermore, in this application, the expression "and / or" includes any and all combinations of the associated listed words. For example, the expression "A and / or B" may include A, may include B, or may include both A and B.

[0084] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the term "connection" should be interpreted broadly. For example, "connection" can be a detachable connection or a non-detachable connection; it can be a direct connection or an indirect connection through an intermediate medium. "Fixed connection" refers to a connection where the relative positional relationship remains unchanged after connection. "Rotary connection" refers to a connection where the components can rotate relative to each other after connection. "Sliding connection" refers to a connection where the components can slide relative to each other after connection. The directional terms mentioned in the embodiments of this application, such as "top," "bottom," "inner," "outer," "left," and "right," are only for reference to the directions in the accompanying drawings. Therefore, the directional terms used are for better and clearer explanation and understanding of the embodiments of this application, and are not intended to indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0085] Furthermore, the mathematical concepts mentioned in the embodiments of this application, such as symmetry, equality, parallelism, and perpendicularity, are limitations specific to the current technological level, rather than absolute and strict mathematical definitions. Slight deviations are permissible; approximations of symmetry, equality, parallelism, and perpendicularity are all acceptable. For example, "A and B are parallel" means that A and B are parallel or approximately parallel, and the angle between A and B can be between 0 and 10 degrees. "A and B are perpendicular" means that A and B are perpendicular or approximately perpendicular, and the angle between A and B can be between 80 and 100 degrees.

[0086] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A high repetition rate, wide bandwidth, fast tunable optical parametric oscillator laser system, characterized in that, include: Femtosecond oscillator module, parametric oscillator module, external cavity frequency summation module, and control module; The output terminal of the control module is electrically connected to the input terminal of the femtosecond oscillator module; the output terminal of the femtosecond oscillator module is optically connected to the input terminal of the parametric oscillator module; the parametric oscillator module is configured with a first output terminal, a second output terminal, a third output terminal, and a fourth output terminal; the third output terminal of the parametric oscillator module is optically connected to the first input terminal of the external cavity sum-frequency module; the fourth output terminal of the parametric oscillator module is optically connected to the second input terminal of the external cavity sum-frequency module. The femtosecond oscillator module is configured to generate high-repetition-rate target pump light output to the parametric oscillator module; The parametric oscillator module is configured to convert the target pump light into down-frequency signal light and idler light via synchronous pumping, and split the signal light to generate a first beam and a second beam. The idler light is output through a first output terminal, the first beam through a second output terminal, and the unconverted target pump light is output to the external cavity summing module through a third output terminal. The second beam is output to the external cavity summing module through a fourth output terminal. The cavity length of the parametric oscillator module is equal to the cavity length of the femtosecond oscillator module to achieve repetition frequency matching. The extracavity sum-frequency module is configured to sum-frequency the unconverted target pump light with the second beam to output visible light; The control module is configured to adjust the angle at which the pump light is incident on the parametric oscillator module in order to achieve rapid tuning of the output wavelength.

2. The high repetition rate, wide bandwidth, fast tunable optical parametric oscillator laser system as described in claim 1, characterized in that, The femtosecond oscillator module includes: a pump generation unit, a first oscillator unit, and a first emission unit; The output terminal of the pump generation unit is optically connected to the input terminal of the first oscillator unit; the output terminal of the first oscillator unit is optically connected to the first input terminal of the first emission unit. The second input terminal of the first emission unit is electrically connected to the control module; the output terminal of the first emission unit is optically connected to the input terminal of the parametric oscillator module. The pump generation unit is configured to generate initial pump light and output it to the first oscillator unit via collimation and focusing. The first oscillator unit is configured to oscillate the initial pump light to generate a femtosecond laser as the target pump light and output it to the first emission unit; The first emission unit is configured to receive control signals from the control module to change the angle of the emitted target pump light.

3. The high repetition rate, wideband, fast tunable optical parametric oscillator laser system as described in claim 2, characterized in that, The first oscillator unit includes: a first plano-concave mirror, a Yb:CALGO crystal, a second plano-concave partial mirror, a first planar high-reflection mirror, and a first GTI mirror; The first plano-concave reflector, the Yb:CALGO crystal, and the second plano-concave partial reflector are arranged sequentially along the beam propagation direction of the pump generation unit; The concave surfaces of the first plano-concave reflector and the second plano-concave partial reflector are arranged opposite each other and face the two ends of the Yb:CALGO crystal, respectively. The first planar high-reflection mirror is disposed in the reflection path of the second plano-concave partial reflector and is used to reflect the laser transmitted from the second plano-concave partial reflector. The first GTI mirror is disposed in the reflection path of the first planar high-reflection mirror and is used to perform wavelength selection on the laser reflected back by the first planar high-reflection mirror. The laser with wavelength selected by the first GTI mirror returns to the first plano-concave reflector and is finally output from the second plano-concave partial reflector.

4. The high repetition rate, wide-band, fast tunable optical parametric oscillator laser system as described in claim 2, characterized in that, The first emission unit includes: a Faraday isolator, a half-wave plate, a first plane mirror, a second plane mirror, a motor, and a first plano-convex lens; The Faraday isolator, the half-wave plate, and the first plane mirror are arranged sequentially along the beam propagation direction of the first oscillator unit; the second plane mirror is disposed in the reflection path of the first plane mirror; and the first plano-convex lens is disposed in the reflection path of the second plane mirror. The motor is located on the back of the first and second planar reflectors and is configured to receive control signals from the control module to change the angles of the first and second planar reflectors.

5. The high repetition rate, wide-band, fast tunable optical parametric oscillator laser system as described in claim 1, characterized in that, The parametric oscillator module includes: a second oscillator unit and a second output unit; The input terminal of the second oscillator unit is optically connected to the output terminal of the femtosecond oscillator module; the first output terminal of the second oscillator unit is optically connected to the first input terminal of the second emission unit; and the second output terminal of the second oscillator unit is optically connected to the second input terminal of the second emission unit. The second oscillator unit has the same cavity length as the first oscillator unit. The second oscillator unit is configured to convert the target pump light oscillation into down-frequency signal light and idler light, and output the idler light and unconverted target pump light to the second emission unit through the first output terminal; and output the signal light to the second emission unit through the second output terminal. The second output unit is configured to separate the idler light and the target pump light, output the idler light through the first output terminal, and output the unconverted target pump light to the external cavity summing module through the third output terminal; it is also configured to split the signal light into a first beam and a second beam, output the first beam through the second output terminal, and output the second beam to the external cavity summing module through the fourth output terminal.

6. The high repetition rate, wideband, fast tunable optical parametric oscillator laser system as described in claim 5, characterized in that, The second oscillator unit includes: a third plano-concave mirror, an MgO:PPLN crystal, a fourth plano-concave mirror, a second GTI mirror, and an output coupling mirror; The third plano-concave mirror, the MgO:PPLN crystal, and the fourth plano-concave mirror are arranged sequentially along the propagation direction of the pump laser emitted from the femtosecond oscillator module; wherein the concave surfaces of the third plano-concave mirror and the fourth plano-concave mirror are arranged opposite each other and face the two ends of the MgO:PPLN crystal, respectively. The second GTI mirror is positioned in the reflection path of the third plano-concave mirror; the output coupling mirror is positioned in the reflection path of the fourth plano-concave mirror.

7. The high repetition rate, wide-band, fast tunable optical parametric oscillator laser system as described in claim 5, characterized in that, The second output unit includes: a beam splitter and a beam splitting prism; The beam splitter is positioned in the path of the idler light and the unconverted target pump light emitted from the second oscillator unit; the beam splitter prism is positioned in the path of the signal light emitted from the second oscillator unit.

8. The high repetition rate, wideband, fast tunable optical parametric oscillator laser system as described in claim 1, characterized in that, The extracavity sum-frequency module includes: an incident unit and a sum-frequency action unit; The first input terminal of the incident unit is optically connected to the third output terminal of the parametric oscillator module; the second input terminal of the incident unit is optically connected to the fourth output terminal of the parametric oscillator module; the first output terminal of the incident unit is optically connected to the first input terminal of the sum-frequency action unit; and the second output terminal of the incident unit is optically connected to the second input terminal of the sum-frequency action unit. The incident unit is configured to receive the unconverted target pump light and the second beam and transmit them to the sum-frequency action unit; the sum-frequency action unit is configured to perform a sum-frequency operation on the unconverted target pump light and the second beam to output visible light.

9. The high repetition rate, wideband, fast tunable optical parametric oscillator laser system as described in claim 8, characterized in that, The incident unit includes: a third plane mirror, a second plano-convex lens, a fourth plane mirror, and a third plano-convex lens; the sum-frequency interaction unit includes: a fifth plane mirror, a ZGP crystal, and a fifth plano-concave mirror; The third planar reflector is disposed in the unconverted pump light emission path of the parametric oscillator module; the second plano-convex lens is disposed in the reflection path of the fifth planar reflector; the fifth planar reflector is disposed in the emission path of the second plano-convex lens; The fourth planar reflector is disposed in the second beam emission path of the parametric oscillator module; the third plano-convex lens is disposed in the reflection path of the fourth planar reflector; the fifth plano-concave reflector is disposed in the emission path of the third plano-convex lens; the concave surface of the fifth plano-concave reflector is disposed opposite to the fifth planar reflector and faces the two ends of the ZGP crystal respectively.

10. The high repetition rate, wideband, fast tunable optical parametric oscillator laser system as described in claim 1, characterized in that, The control module is configured to output a control signal to the femtosecond oscillator module based on a non-critical phase matching or critical phase matching mechanism.

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