A high-power multi-GHz repetition rate femtosecond optical parametric oscillator

Abstract

The present application relates to the field of ultrafast laser technology, and in particular to a high-power multi-GHz repetition rate femtosecond optical parametric oscillator, comprising: a pump source, a first half-wave plate, a polarization beam splitter, a second half-wave plate, a first reflector, a second reflector, a focusing mirror, a first concave mirror, a nonlinear optical crystal, a second concave mirror, a third reflector, an output coupling mirror and a collimating mirror; the first concave mirror, the second concave mirror, the third reflector and the output coupling mirror constitute a resonant cavity of the femtosecond optical parametric oscillator; when the cavity length of the resonant cavity is set to an integer multiple of the cavity length of the pump source, the femtosecond optical parametric oscillator can simultaneously realize the pulse output of signal light and idler light with a GHz repetition rate; when the cavity length of the resonant cavity is set to increase 1 / K of the cavity length of the pump source on the basis of an integer multiple of the cavity length of the pump source, the repetition rate of the signal light can be increased by K times, thereby realizing the pulse output of multi-GHz signal light.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of ultrafast laser technology, and in particular to a high-power multi-GHz repetition rate femtosecond optical parametric oscillator. Background Art

[0002] Femtosecond lasers with repetition rates up to GHz have important applications in optical frequency combs, biomedical imaging, and laser micro-nano processing. In order to obtain femtosecond lasers with GHz repetition rates, researchers have developed various GHz repetition rate mode-locked lasers, such as mode-locked Ti:sapphire lasers and ytterbium (Yb), erbium (Er), thulium (Tm), and chromium (Cr)-doped mode-locked solid lasers or fiber lasers. However, the output wavelength of the mode-locked laser is limited by the energy level structure of the gain medium. In contrast, optical parametric oscillators synchronously pumped by femtosecond lasers can achieve wavelength output that is difficult to obtain with traditional lasers, and the wavelength can be continuously tuned over a broadband range. At present, femtosecond optical parametric oscillators can generate broadband tuned ultrashort pulses in the ultraviolet to mid-infrared bands, and have become an important tool for ultrafast scientific and industrial applications. Therefore, the development of femtosecond optical parametric oscillators with GHz repetition rates is crucial for practical applications.

[0003] At present, GHz femtosecond optical parametric oscillators generally use conventional MHz repetition rate femtosecond lasers as pump sources. Let the cavity length of the femtosecond optical parametric oscillator be 1 / N or M / N times the cavity length of the pump source (where M and N are mutually prime positive integers), then the repetition frequency of the output signal light is N times the repetition frequency of the pump source.

[0004] However, this approach has the following disadvantages.

[0005] First, since the oscillation pulse can only meet the pump pulse after traveling back and forth N times in the cavity to obtain gain, the round-trip loss is large, and the energy conversion efficiency and output power are low.

[0006] Second, since the oscillation pulse suffers losses each time it travels back and forth within the cavity, the intensity of the signal light pulse sequence gradually decreases within one pumping cycle.

[0007] Third, for a single-resonance optical parametric oscillator, assuming that the signal light oscillates in the cavity, only the repetition frequency of the signal light can reach GHz, while the repetition frequency of the idler light is still consistent with the repetition frequency of the pump source. Therefore, it is impossible to simultaneously obtain signal light and idler light with GHz repetition frequencies.

[0008] In order to solve the above technical problems, a femtosecond laser with a GHz repetition rate can be directly used to pump an optical parametric oscillator. However, the development of GHz femtosecond lasers is still immature, and there are only a few reports on GHz femtosecond Ti:sapphire lasers pumping optical parametric oscillators. Since the output power of femtosecond Ti:sapphire lasers is low, the structure is complex, and the price is expensive, the output power of the optical parametric oscillator pumped by them is low and difficult to apply on a large scale. Summary of the invention

[0009] In order to solve the above technical problems, the embodiments of the present application propose a high-power multi-GHz repetition rate femtosecond optical parametric oscillator, which can simultaneously achieve the output of high-power GHz repetition rate signal light and idler light, and has great application potential in the fields of optical frequency comb, biomedical imaging, and laser micro-nano processing.

[0010] In order to achieve the above objectives, the embodiments of the present application provide a high-power multi-GHz repetition rate femtosecond optical parametric oscillator, comprising:

[0011] A pump source 1, a first half-wave plate 2, a polarization beam splitter prism 3, a second half-wave plate 4, a first reflector 5, a second reflector 6, a focusing mirror 7, a first concave mirror 8, a nonlinear optical crystal 9, a second concave mirror 10 and a collimating mirror 13 arranged in sequence along the laser output direction of the pump source 1, a third reflector 11 arranged in the reflection direction of the second concave mirror 10, and an output coupling mirror 12 arranged in the reflection direction of the first concave mirror 8;

[0012] A pump source 1, used to generate a femtosecond laser with a GHz repetition rate as a pump laser;

[0013] The first half-wave plate 2 is used to adjust the polarization state of the pump laser output by the pump source 1;

[0014] The polarization beam splitter prism 3 is used to transmit the horizontal polarization component of the pump laser and reflect the vertical polarization component, and adjust the power of the pump laser incident on the nonlinear optical crystal 9 together with the first half-wave plate 2;

[0015] The second half-wave plate 4 is used to adjust the polarization state of the pump laser incident on the nonlinear optical crystal 9;

[0016] The first reflector 5 and the second reflector 6 have high reflectivity to the pump laser and are used to adjust the optical path of the pump laser so that the pump laser is incident on the nonlinear optical crystal 9;

[0017] A focusing mirror 7, used for focusing the pump laser onto a nonlinear optical crystal 9;

[0018] The first concave mirror 8 and the second concave mirror 10 have high transmittance to the pump laser and the idler light and high reflectivity to the signal light, and are used to form a resonant cavity and focus the signal light;

[0019] The nonlinear optical crystal 9 is coated with an anti-reflection film for the pump laser, the signal light and the idler light, and is used to generate the signal light and the idler light;

[0020] The third reflector 11 has a high reflectivity for the signal light and is used to form an end mirror of the resonant cavity;

[0021] The output coupling mirror 12 has partial transmittance to the signal light, and is used to form another end mirror of the resonant cavity and output a part of the signal light;

[0022] The collimator 13 has high transmittance to the idler light and high absorptivity to the pump laser, and is used to separate the idler light from the residual pump laser and collimate the output;

[0023] Among them, the output coupling mirror 12 is fixed on a one-dimensional precision translation stage, which supports precise change of the cavity length of the resonant cavity by adjusting the one-dimensional precision translation stage; when the cavity length of the resonant cavity is set to an integer multiple of the cavity length of the pump source 1, the femtosecond optical parametric oscillator can simultaneously achieve pulse output of high-power femtosecond signal light and idler light with a GHz repetition rate; when the cavity length of the resonant cavity is set to increase 1 / K of the cavity length of the pump source 1 on the basis of an integer multiple of the cavity length of the pump source 1, K is a positive integer, which can increase the repetition frequency of the signal light by K times and achieve multi-GHz pulse output of signal light.

[0024] In some optional embodiments, the pump source 1 is specifically a laser diode pumped GHz repetition rate Kerr lens mode-locked Yb:CYA femtosecond laser, with a central wavelength of 1043nm, an output average power of 10W, a repetition rate of 1.02GHz, and a pulse width of 110fs.

[0025] In some optional embodiments, the focusing lens 7 is specifically a plano-convex lens with a focal length of 125 mm.

[0026] In some optional embodiments, the curvature radius of the first concave mirror 8 and the second concave mirror 10 are both 100 mm, and the transmittance in the wavelength ranges of 1.03 μm to 1.06 μm and 2.6 μm to 4.0 μm is greater than 80%, and the reflectivity in the wavelength range of 1.38 μm to 1.6 μm is greater than 99.5%.

[0027] In some optional embodiments, the nonlinear optical crystal 9 is specifically a periodically poled lithium niobate crystal doped with 5 mol% magnesium oxide, with a length of 3 mm and 5 parallel arranged polarization periods, the 5 polarization periods are 28.5 μm, 29 μm, 29.5 μm, 30 μm and 30.5 μm respectively, and the transmittance in the wavelength range of 1.03 μm to 1.06 μm is greater than 99.5%, the transmittance in the wavelength range of 1.43 μm to 2.13 μm is greater than 99%, and the transmittance in the wavelength range of 2.13 μm to 4.8 μm is greater than 95%.

[0028] In some optional embodiments, the transmittance of the output coupling mirror 12 in the wavelength range of 1.4 μm to 1.8 μm is 1.5%.

[0029] In some optional embodiments, the collimator 13 is specifically a plano-convex lens with a focal length of 100 mm, a base material of which is silicon, and a transmittance within a wavelength range of 2 μm to 5 μm is greater than 90%.

[0030] In some optional embodiments, by changing the polarization period of the nonlinear optical crystal 9, the quasi-phase matching condition can be changed, thereby changing the wavelengths of the output signal light and idler light.

[0031] The present application proposes a high-power multi-GHz repetition rate femtosecond optical parametric oscillator, which uses a GHz femtosecond mode-locked laser as a pump source, and the resonant cavity of the femtosecond optical parametric oscillator is composed of a first concave mirror, a second concave mirror, a third reflector and an output coupling mirror. Since the output coupling mirror is fixed on a one-dimensional precision translation stage, the cavity length of the resonant cavity can be precisely changed by adjusting the one-dimensional precision translation stage. When the cavity length of the resonant cavity of the femtosecond optical parametric oscillator is set to an integer multiple of the cavity length of the pump source, the femtosecond optical parametric oscillator can simultaneously achieve pulse output of high-power femtosecond signal light and idler light with a GHz repetition rate. When the cavity length of the resonant cavity of the femtosecond optical parametric oscillator is set to increase the cavity length of the pump source by 1 / K on the basis of the integer multiple of the cavity length of the pump source, the repetition frequency of the signal light can be increased by K times, thereby achieving pulse output of multi-GHz signal light. Such a femtosecond optical parametric oscillator has great application potential in the fields of optical frequency combs, biomedical imaging, and laser micro-nano processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the related technologies, the drawings required for use in the embodiments of the present application or the related technical descriptions will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 It is a schematic structural diagram of a high-power multi-GHz repetition rate femtosecond optical parametric oscillator provided in one embodiment of the present application;

[0034] Figure 2 It is a schematic diagram of the variation of the output power of the signal light and the idler light with the pump power provided in one embodiment of the present application;

[0035] Figure 3 It is a schematic diagram of the spectrum change of the signal light when the crystal polarization period is changed and the cavity length is fine-tuned when the pump power is 8 W, provided in one embodiment of the present application;

[0036] Figure 4 It is a schematic diagram of the spectrum change of idler light when the crystal polarization period is changed and the cavity length is fine-tuned when the pump power is 8 W, provided in one embodiment of the present application;

[0037] Figure 5 is a schematic diagram of an autocorrelation curve when the signal light pulse width is the shortest when the pump power is 8 W, provided in one embodiment of the present application;

[0038] Figure 6 is a schematic diagram of an autocorrelation curve when the idler light pulse width is the shortest when the pump power is 8 W, provided in one embodiment of the present application;

[0039] Figure 7 Provided in one embodiment of the present application, is a schematic diagram of the radio frequency (RF) spectrum of the signal light obtained by changing the cavity length of the femtosecond optical parametric oscillator when the pump power is 8 W. DETAILED DESCRIPTION

[0040] To make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the embodiments of the present application will be described in detail below in conjunction with the accompanying drawings. In the various embodiments of the present application, in order to enable the reader to better understand the present application, many technical details are proposed. However, even without these technical details and various changes and modifications based on the following embodiments, the technical scheme claimed in the present application can also be implemented. The division of the following embodiments is only for the convenience of description, and the specific implementation of the present application should not constitute any limitation, and the various embodiments can be combined with each other and quoted on the premise of no contradiction.

[0041] An embodiment of the present application proposes a high-power multi-GHz repetition rate femtosecond optical parametric oscillator. The implementation details of the high-power multi-GHz repetition rate femtosecond optical parametric oscillator proposed in this embodiment are described in detail below. The following content is only the implementation details provided for the convenience of understanding and is not necessary for the implementation of this solution.

[0042] The specific structure of a high-power multi-GHz repetition rate femtosecond optical parametric oscillator proposed in this embodiment can be as follows: Figure 1 As shown, it includes: a pump source 1, a first half-wave plate 2, a polarization beam splitter prism 3, a second half-wave plate 4, a first reflector 5, a second reflector 6, a focusing mirror 7, a first concave mirror 8, a nonlinear optical crystal 9, a second concave mirror 10 and a collimating mirror 13 arranged in sequence along the laser output direction of the pump source 1, a third reflector 11 arranged in the reflection direction of the second concave mirror 10, and an output coupling mirror 12 arranged in the reflection direction of the first concave mirror 8.

[0043] The following is a detailed introduction to the materials, parameters and uses of each component in the femtosecond optical parametric oscillator.

[0044] The pump source 1 is used to generate a femtosecond laser with a GHz repetition rate as a pump laser. Specifically, the pump source 1 can be a laser diode-pumped GHz repetition rate Kerr lens mode-locked ytterbium-doped calcium yttrium aluminate (Yb:CYA) femtosecond laser with a central wavelength of 1043 nm, an average output power of 10 W, a repetition rate of 1.02 GHz, and a pulse width of 110 fs.

[0045] The first half-wave plate 2 is used to adjust the polarization state of the pump laser output by the pump source 1 .

[0046] The polarization beam splitter prism 3 is used to transmit the horizontal polarization component of the pump laser and reflect the vertical polarization component, and adjust the power of the pump laser incident on the nonlinear optical crystal 9 together with the first half-wave plate 2 .

[0047] The second half-wave plate 4 is used to adjust the polarization state of the pump laser incident on the nonlinear optical crystal 9 .

[0048] The first reflecting mirror 5 and the second reflecting mirror 6 have high reflectivity to the pump laser, and are used to adjust the optical path of the pump laser so that the pump laser is incident on the nonlinear optical crystal 9 .

[0049] The focusing mirror 7 is used to focus the pump laser onto the nonlinear optical crystal 9. The focusing mirror 7 can specifically be a plano-convex lens with a focal length of 125 mm.

[0050] The first concave mirror 8 and the second concave mirror 10 have high transmittance to the pump laser and the idler light, and high reflectance to the signal light, and are used to form a resonant cavity and focus the signal light. The first concave mirror 8 and the second concave mirror 10 both have a radius of curvature of 100 mm, and a transmittance greater than 80% in the wavelength range of 1.03 μm to 1.06 μm and 2.6 μm to 4.0 μm, and a reflectance greater than 99.5% in the wavelength range of 1.38 μm to 1.6 μm.

[0051] The nonlinear optical crystal 9 is coated with an anti-reflection film for the pump laser, signal light and idler light, and is used to generate the signal light and the idler light. The nonlinear optical crystal 9 can be specifically selected from a periodically poled lithium niobate (MgO:PPLN) crystal doped with 5 mol% magnesium oxide, with a length of 3 mm, 5 parallel polarization periods, and the 5 polarization periods are 28.5 μm, 29 μm, 29.5 μm, 30 μm and 30.5 μm, respectively, and the transmittance in the wavelength range of 1.03 μm to 1.06 μm is greater than 99.5%, the transmittance in the wavelength range of 1.43 μm to 2.13 μm is greater than 99%, and the transmittance in the wavelength range of 2.13 μm to 4.8 μm is greater than 95%.

[0052] The third reflector 11 has a high reflectivity for the signal light and is used to form an end mirror of the resonant cavity. The reflectivity of the third reflector 11 in the wavelength range of 1.38 μm to 1.6 μm is greater than 99.5%.

[0053] The output coupling mirror 12 has partial transmittance to the signal light, and is used to form another end mirror of the resonant cavity and output a part of the signal light. The transmittance of the output coupling mirror 12 in the wavelength range of 1.4 μm to 1.8 μm is 1.5%.

[0054] The collimator 13 has high transmittance to idle light and high absorptivity to pump laser, and is used to separate the idle light from the residual pump laser and collimate the output. The collimator 13 can be a plano-convex lens with a focal length of 100 mm, whose base material is silicon and has a transmittance greater than 90% in the wavelength range of 2 μm to 5 μm.

[0055] It should be noted that the resonant cavity of the femtosecond optical parametric oscillator is actually composed of four parts: the first concave mirror 8, the second concave mirror 10, the third reflector 11 and the output coupling mirror 12. The first concave mirror 8, the second concave mirror 10 and the third reflector 11 cannot be changed, but the output coupling mirror 12 is fixed on a one-dimensional precision translation stage, so the cavity length of the resonant cavity can be precisely changed by adjusting the one-dimensional precision translation stage.

[0056] When the cavity length of the resonant cavity is set to an integer multiple of the cavity length of the pump source 1, the femtosecond optical parametric oscillator can simultaneously achieve pulse output of high-power femtosecond signal light and idler light with a GHz repetition rate. When the cavity length of the resonant cavity is set to increase 1 / K of the cavity length of the pump source 1 on the basis of an integer multiple of the cavity length of the pump source 1 (K is a positive integer), the repetition frequency of the signal light can be increased by K times, thereby achieving pulse output of multi-GHz signal light.

[0057] The advantages of the high-power multi-GHz repetition rate femtosecond optical parametric oscillator proposed in this embodiment are described below in conjunction with experiments.

[0058] First, the cavity length of the resonant cavity composed of the first concave mirror 8, the second concave mirror 10, the third reflector 11 and the output coupling mirror 12 is set to 588 mm, which is 4 times the cavity length of the pump source 1. The polarization period of the MgO:PPLN crystal is selected to be 30 μm. At this time, the output power of the femtosecond optical parametric oscillator changes with the pump power as shown in Figure 2 As shown. Figure 2 It can be seen that when the pump power is 8.4 W, the output powers of the signal light and the idler light are 1.58 W and 1 W, respectively, corresponding to slope efficiencies of 23.7% and 15.5%, respectively.

[0059] Changing the polarization period of the MgO:PPLN crystal can change the quasi-phase matching condition, thereby changing the wavelength of the output signal light and idler light. When the pump power is 8W, the polarization period of the crystal is selected to be 28.5μm, 29μm, 29.5μm, 30μm and 30.5μm, respectively, and the signal light spectrum obtained is as follows Figure 3 The obtained idler spectrum is shown as the solid line from (a) to (e) in Figure 4 In addition, fine-tuning the cavity length of the optical parametric oscillator can also finely change the wavelength of the signal light and the idler light. When the polarization period of the crystal is selected to be 30.5μm, fine-tuning the cavity length can further broaden the wavelength tuning range of the signal light and the idler light, and the obtained signal light spectrum is shown in Figure 3 As shown by the dashed line in part (f), the idler spectrum is Figure 4 As shown by the dotted line in part (f), it can be seen that by changing the crystal polarization period and fine-tuning the cavity length, the output wavelengths of the signal light and the idler light can be continuously tuned in the range of 1.41μm to 1.64μm and 2.8μm to 4.0μm, respectively.

[0060] When the polarization period of the MgO:PPLN crystal is selected to be 30.5μm, the pulse width of the signal light and the idler light reaches the minimum. The autocorrelation curve of the signal light can be found in Figure 5 , the autocorrelation curve of idler light can be found in Figure 6 . Using sech 2 By fitting the autocorrelation curve with the function, it can be seen that the shortest pulse widths of the signal light and the idler light are 139fs and 103fs, respectively.

[0061] When the cavity length of the femtosecond optical parametric oscillator is set to 4 times the cavity length of the pump source, the RF spectrum of the signal light is as follows: Figure 7 As shown in part (a) of Figure 7From part (a), we can see that the fundamental frequency of the signal light is 1.02 GHz, the signal-to-noise ratio is 64 dB, and no obvious side peaks of the fundamental frequency or harmonics are observed, indicating that the signal light operates stably at a repetition frequency of 1.02 GHz. In addition, since each pump pulse generates a signal light pulse and an idler light pulse in the MgO:PPLN crystal, the repetition frequency of the idler light pulse is equal to the repetition rate of the pump pulse, which is also 1.02 GHz.

[0062] In order to obtain a higher repetition rate of signal light pulses, the cavity length of the femtosecond optical parametric oscillator is increased by 1 / 2, 1 / 3 and 1 / 4 of the cavity length of the pump source, respectively, on the basis that the cavity length of the femtosecond optical parametric oscillator is 4 times the cavity length of the pump source, that is, the cavity length is increased by 73.5mm, 49mm and 36.75mm on the basis of 588mm, respectively. The RF spectrum of the obtained signal light is shown in Figure 7 (b) to (d) in the figure. In these RF spectra, the main frequency peak and its harmonics, as well as the lower comb spectrum with an interval equal to the repetition frequency of the pump source, can be clearly seen. When the cavity length of the femtosecond optical parametric oscillator increases by 1 / 2, 1 / 3 and 1 / 4 of the cavity length of the pump source, the repetition rate of the signal light increases to 2, 3 and 4 times that of the pump source, which is 2.04 GHz, 3.06 GHz and 4.08 GHz, respectively. In addition, since the idler light pulse only passes through the MgO:PPLN crystal once, the repetition frequency of the idler light pulse is always consistent with the repetition rate of the pump source, which is 1.02 GHz. In addition, when the pump power is 8 W, as the repetition frequency of the signal light increases, the output power of the signal light and the idler light gradually decreases. For the 4.08 GHz signal light, its output power is still as high as 1 W, which shows that the repetition frequency of the signal light still has the potential to be further improved.

[0063] A high-power multi-GHz repetition rate femtosecond optical parametric oscillator proposed in this embodiment uses a GHz femtosecond mode-locked laser as a pump source, and the resonant cavity of the femtosecond optical parametric oscillator is composed of a first concave mirror, a second concave mirror, a third reflector and an output coupling mirror. Since the output coupling mirror is fixed on a one-dimensional precision translation stage, the cavity length of the resonant cavity can be precisely changed by adjusting the one-dimensional precision translation stage. When the cavity length of the resonant cavity of the femtosecond optical parametric oscillator is set to an integer multiple of the cavity length of the pump source, the femtosecond optical parametric oscillator can simultaneously achieve pulse output of high-power femtosecond signal light and idler light with a GHz repetition rate. When the cavity length of the resonant cavity of the femtosecond optical parametric oscillator is set to increase the cavity length of the pump source by 1 / K on the basis of an integer multiple of the cavity length of the pump source, the repetition frequency of the signal light can be increased by K times, thereby achieving pulse output of multi-GHz signal light. Such a femtosecond optical parametric oscillator has great application potential in the fields of optical frequency combs, biomedical imaging, and laser micro-nano processing.

[0064] The above is a detailed introduction to a high-power multi-GHz repetition rate femtosecond optical parametric oscillator provided by the present application. Although the present application has been described to a certain extent, it is obvious that appropriate changes can be made to various conditions without departing from the spirit and scope of the present application, for example, using other Yb-doped gain media, other GHz-level all-solid-state femtosecond mode-locked lasers with other repetition rates as pump sources, using other nonlinear optical crystals, adjusting the cavity length of the femtosecond optical parametric oscillator to other multiples of the cavity length of the pump source, etc. It can be understood that the present application is not limited to the above embodiments, and any changes should be included in the protection scope of the present application without departing from the spirit and scope of the technical solution of the present application.

Claims

1. A high-power multi-GHz repetition rate femtosecond optical parametric oscillator, characterized in that: include: A pump source (1), a first half-wave plate (2), a polarization beam splitter (3), a second half-wave plate (4), a first reflector (5), a second reflector (6), a focusing mirror (7), a first concave mirror (8), a nonlinear optical crystal (9), a second concave mirror (10) and a collimating mirror (13) arranged in sequence along the laser output direction of the pump source (1), a third reflector (11) arranged in the reflection direction of the second concave mirror (10), and an output coupling mirror (12) arranged in the reflection direction of the first concave mirror (8); A pump source (1) for generating a femtosecond laser with a GHz repetition rate as a pump laser; A first half-wave plate (2) used to adjust the polarization state of the pump laser output by the pump source (1); A polarization beam splitter prism (3) for transmitting the horizontal polarization component of the pump laser and reflecting the vertical polarization component, and adjusting the power of the pump laser incident on the nonlinear optical crystal (9) together with the first half-wave plate (2); A second half-wave plate (4) for adjusting the polarization state of the pump laser incident on the nonlinear optical crystal (9); The first reflector (5) and the second reflector (6) have high reflectivity for the pump laser and are used to adjust the optical path of the pump laser so that the pump laser is incident on the nonlinear optical crystal (9); A focusing mirror (7) for focusing the pump laser onto the nonlinear optical crystal (9); The first concave mirror (8) and the second concave mirror (10) have high transmittance for pump laser and idler light and high reflectivity for signal light, and are used to form a resonant cavity and focus the signal light; The nonlinear optical crystal (9) is coated with an anti-reflection film for the pump laser, the signal light and the idler light, and is used to generate the signal light and the idler light; The third reflector (11) has a high reflectivity for the signal light and is used to form an end mirror of the resonant cavity; The output coupling mirror (12) has a partial transmittance to the signal light and is used to form another end mirror of the resonant cavity and output a part of the signal light; The collimator (13) has a high transmittance for idler light and a high absorptivity for pump laser, and is used to separate the idler light from the residual pump laser and collimate the output; The output coupling mirror (12) is fixed on a one-dimensional precision translation stage, and supports precise change of the cavity length of the resonant cavity by adjusting the one-dimensional precision translation stage; when the cavity length of the resonant cavity is set to an integer multiple of the cavity length of the pump source (1), the femtosecond optical parametric oscillator can simultaneously achieve pulse output of high-power femtosecond signal light and idler light with a GHz repetition rate; when the cavity length of the resonant cavity is set to increase the cavity length of the pump source (1) by 1 / K based on the integer multiple of the cavity length of the pump source (1), K is a positive integer, the repetition frequency of the signal light can be increased by K times, thereby achieving pulse output of multi-GHz signal light.

2. A high-power multi-GHz repetition rate femtosecond optical parametric oscillator according to claim 1, characterized in that: The pump source (1) is specifically a laser diode-pumped GHz repetition rate Kerr lens mode-locked Yb:CYA femtosecond laser with a central wavelength of 1043 nm, an output average power of 10 W, a repetition rate of 1.02 GHz, and a pulse width of 110 fs.

3. The high-power multi-GHz repetition rate femtosecond optical parametric oscillator according to claim 1, characterized in that: The focusing lens (7) is specifically a plano-convex lens with a focal length of 125 mm.

4. The high-power multi-GHz repetition rate femtosecond optical parametric oscillator according to claim 1, characterized in that: The first concave mirror (8) and the second concave mirror (10) both have a radius of curvature of 100 mm, and have a transmittance greater than 80% in the wavelength ranges of 1.03 μm to 1.06 μm and 2.6 μm to 4.0 μm, and a reflectance greater than 99.5% in the wavelength range of 1.38 μm to 1.6 μm.

5. The high-power multi-GHz repetition rate femtosecond optical parametric oscillator according to claim 1, characterized in that: The nonlinear optical crystal (9) is specifically a periodically poled lithium niobate crystal doped with 5 mol % magnesium oxide, having a length of 3 mm and 5 parallel polarization periods, the 5 polarization periods being 28.5 μm, 29 μm, 29.5 μm, 30 μm and 30.5 μm, respectively, and having a transmittance greater than 99.5% in the wavelength range of 1.03 μm to 1.06 μm, a transmittance greater than 99% in the wavelength range of 1.43 μm to 2.13 μm, and a transmittance greater than 95% in the wavelength range of 2.13 μm to 4.8 μm.

6. The high-power multi-GHz repetition rate femtosecond optical parametric oscillator according to claim 1, characterized in that: The reflectivity of the third reflector (11) in the wavelength range of 1.38 μm to 1.6 μm is greater than 99.5%.

7. The high-power multi-GHz repetition rate femtosecond optical parametric oscillator according to claim 1, characterized in that: The output coupling mirror (12) has a transmittance of 1.5% in the wavelength range of 1.4 μm to 1.8 μm.

8. The high-power multi-GHz repetition rate femtosecond optical parametric oscillator according to claim 1, characterized in that: The collimator (13) is specifically a plano-convex lens with a focal length of 100 mm, a base material of which is silicon, and a transmittance within a wavelength range of 2 μm to 5 μm of which is greater than 90%.

9. The high-power multi-GHz repetition rate femtosecond optical parametric oscillator according to claim 5, characterized in that: By changing the polarization period of the nonlinear optical crystal (9), the quasi-phase matching condition can be changed, thereby changing the wavelengths of the output signal light and idler light.

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