Bidirectional annular optical fiber double-optical-comb laser generating device and generating method

Abstract

The invention discloses a bidirectional annular optical fiber double-optical-comb laser generating device and generating method, belongs to the technical field of laser generation, and solves the problem of poor adjustability of repetition frequencies of two pulses when optical fiber double optical combs are realized in the prior art. The device specifically comprises a pump laser, wherein a pump light separation device is arranged at the transmitting end of the pump laser; the light output end of the pump light separation device is connected with two paths of optical fibers, and the two paths of optical fibers are respectively connected with the first wavelength division multiplexer and the second wavelength division multiplexer; the first wavelength division multiplexer and the second wavelength division multiplexer are connected with the clockwise laser mode locking device and the anticlockwise laser mode locking device through two gain optical fibers. In the invention, two nonlinear polarization rotation mode locking devices are respectively arranged on the two laser beam branches, and a section of non-common-path structure is established through the two circulators, so that the repetition frequency difference between two directions can be flexibly adjusted, the simultaneous locking of two repetition frequencies is realized, and the application requirement of higher mutual dryness than that under the condition of free operation can be met.

Description

Technical Field

[0001] The present invention relates to the field of laser generation technology, and in particular to a bidirectional annular optical fiber dual-comb laser generation device and a generation method. Background Art

[0002] Dual optical combs have broad application prospects in the fields of dual optical comb spectroscopy, laser ranging, pump-probe experiments, etc., and are one of the important development directions of precision optical instruments. Mode-locked lasers are currently the most commonly used technical means to realize optical frequency combs. Traditional dual optical comb systems are generally realized by using two independent mode-locked lasers. Under free operation, the mutual coherence of the two independent mode-locked lasers is poor, so it is necessary to lock the frequencies of the two mode-locked lasers with slightly different repetition frequencies. However, the dual optical comb system realized by this method is large, complex and costly, mainly because it requires complex frequency locking related electronic equipment. Therefore, dual optical comb mode-locked lasers in the form of a common cavity are an important development trend that is highly concerned in the field of dual optical comb lasers. The advantage of dual optical comb mode-locked lasers in the form of a common cavity is that the two optical frequency combs can use the characteristics of the common cavity to passively eliminate most of the repetition frequency difference fluctuations caused by changes in the cavity length, so that they still have a high degree of mutual coherence even under free operation, and therefore there is no need for frequency locking electronic devices.

[0003] At present, the common cavity dual-comb mode-locked laser is mainly based on three laser technologies: optical fiber, all-solid-state and semiconductor. Compared with traditional solid-state lasers, fiber lasers have many advantages. First, the geometric shape of the fiber gain medium itself has a large surface area, and the heat generated in the cavity can be easily dissipated into the air or surrounding medium. There is no need to design an additional heat sink, and only a simple cooling device can be used to effectively dissipate heat at a higher output power and obtain a better beam quality. Secondly, due to its longer active cavity length and thinner guide fiber, the electro-optical conversion efficiency of the fiber laser is much higher than that of the traditional solid-state laser, and it does not require too high a pump power to effectively generate lasers. In addition, the limiting effect of the optical fiber waveguide structure on the laser beam also ensures the quality of the output beam, and it is not easy to have the phenomenon of thermally induced mode distortion that often occurs in traditional solid-state lasers. At the same time, the all-fiber structure does not require the use of free-space optical elements, thereby reducing the strict calibration and mechanical stability requirements in traditional lasers, simplifying the laser structure, and helping to achieve the miniaturization of the laser and improve the stability of the laser.

[0004] In the prior art, there are three main methods for realizing single-cavity fiber dual-comb, including wavelength multiplexing, polarization multiplexing, and direction multiplexing. Although single-cavity fiber dual-comb has good co-cavity characteristics, it has three disadvantages: first, there is cross-coupling of the dual-comb, which causes instability factors such as pulse collision and gain competition; second, the adjustability of the repetition frequency difference of the dual-comb is poor, which affects the selection of measurement speed and bandwidth in practical applications; third, it is difficult to lock the repetition frequency at the same time to meet the needs of higher-precision measurements. Therefore, designing a new type of single-cavity fiber dual-comb laser with flexible repetition frequency difference tunability is one of the important development directions in this research field. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a bidirectional annular fiber dual-comb laser generating device and generating method, which solves the problem of poor adjustability of two pulse repetition frequencies when realizing fiber dual-comb in the prior art.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A bidirectional annular fiber dual-comb laser generating device comprises a pump laser, wherein the emitting end of the pump laser is provided with a pump light separation device; the optical output end of the pump light separation device is connected with two optical fibers, and the two optical fibers are respectively connected with a first wavelength division multiplexer and a second wavelength division multiplexer;

[0008] The first wavelength division multiplexer is connected to the clockwise laser mode locking device through the first gain optical fiber; the optical output end of the clockwise laser mode locking device is connected to the first circulator through the optical fiber; the first circulator is connected to the first wavelength division multiplexer;

[0009] The second wavelength division multiplexer is connected to the counterclockwise laser mode locking device through the second gain optical fiber; the optical output end of the counterclockwise laser mode locking device is connected to the second circulator through the optical fiber; the second circulator is connected to the second wavelength division multiplexer;

[0010] The first circulator and the second circulator are connected via a common path optical fiber.

[0011] In this solution, a pump laser is used to emit a laser beam, and the laser beam is separated into two pump beams by a pump light separation device. The two pump light beams pass through a first wavelength division multiplexer and a second wavelength division multiplexer respectively, so that the two pump light beams have equivalent power and consistent amplitude fluctuations, which is conducive to enhancing the coherence of the two mode-locked pulses; the first wavelength division multiplexer and the second wavelength division multiplexer transmit the 980nm light output by the pump light separation device, and reflect the 1030nm light back into the laser cavity; the two pump light beams transmitted from the first wavelength division multiplexer and the second wavelength division multiplexer pass through the first gain fiber and the second gain fiber, respectively. Two gain optical fibers are converted into stimulated radiation beams of 1030nm; one of the stimulated radiation beams passes through a clockwise laser mode-locking device and a first circulator, and then is transmitted to the second circulator through a common-path optical fiber; the other stimulated radiation beam passes through a counterclockwise laser mode-locking device and a second circulator, and then is transmitted to the first circulator through a common-path optical fiber; the second circulator and the first circulator are placed at both ends of the two mode-locking devices to build a double-branch system, so that the pulse signals generated in the two directions do not interfere with each other in the non-highway part, and the cavity length experienced by the clockwise mode-locked pulse and the counterclockwise mode-locked pulse can be flexibly adjusted.

[0012] Furthermore, the clockwise laser mode locking device includes a first collimator, the light input end of the first collimator is connected to the first gain fiber, the light output end of the first collimator is sequentially provided with a first quarter wave plate, a first half wave plate and a first polarization beam splitter prism; the light output end of the first polarization beam splitter prism is sequentially provided with a second half wave plate, a second quarter wave plate and a second collimator; the light output end of the second collimator is connected to the first circulator through an optical fiber.

[0013] In this scheme, the polarization state is rotated by rotating the first quarter wave plate and the first half wave plate, thereby controlling the peak power of different pulses, forming a saturable absorption effect, and achieving mode locking; compared with most bidirectional mode-locked fiber dual-comb lasers that rely on real mode-locking materials to achieve mode locking, the nonlinear polarization rotation mode-locking mechanism has a faster time response and a wider spectrum width. The second half wave plate is used to adjust the polarization direction of the light beam, and the quarter wave plate converts the elliptically polarized light into linearly polarized light, so that the light beam passes through the first circulator and the second circulator in the form of linearly polarized light.

[0014] Furthermore, a first filter is provided between the first polarization beam splitter prism and the second half wave plate.

[0015] Furthermore, the counterclockwise laser mode locking device includes a third collimator, the light input end of the third collimator is connected to the second gain fiber, the light output end of the third collimator is sequentially provided with a third quarter wave plate, a third half wave plate and a second polarization beam splitter prism; the light output end of the second polarization beam splitter prism is sequentially provided with a fourth half wave plate, a fourth quarter wave plate and a fourth collimator; the light output end of the fourth collimator is connected to the second circulator through an optical fiber.

[0016] Furthermore, a second filter is arranged between the second polarization beam splitter prism and the fourth half wave plate.

[0017] Furthermore, the pump light separation device is a fiber coupler.

[0018] In a second aspect, the present invention provides a bidirectional annular fiber dual-comb laser generating method based on the bidirectional annular fiber dual-comb laser generating device provided in the first aspect, comprising the following steps:

[0019] S1: The pump laser emits a pump laser beam;

[0020] S2: The pump laser beam is divided into two pump beams of equal power by the pump light separation device, and the two pump light beams are respectively input into the first wavelength division multiplexer and the second wavelength division multiplexer through two optical fibers;

[0021] S3: The two pump lights transmitted through the first wavelength division multiplexer and the second wavelength division multiplexer are respectively transmitted to the first gain fiber and the second gain fiber, and converted into a stimulated radiation beam of 1030 nm;

[0022] S4: The stimulated radiation beam output by the first gain fiber passes through the clockwise laser mode-locking device, the first circulator and the second circulator in sequence, and returns to the first wavelength division multiplexer to construct a clockwise resonant cavity, thereby forming a continuous light output in the clockwise direction;

[0023] The stimulated radiation beam output by the second gain fiber passes through the counterclockwise laser mode-locking device, the second circulator and the first circulator in sequence, and returns to the second wavelength division multiplexer to construct a counterclockwise resonant cavity, thereby forming a continuous light output in the counterclockwise direction;

[0024] S5: The clockwise continuous light passes through the clockwise laser mode-locking device, and the first quarter-wave plate and the first half-wave plate are rotated to control the peak power of different pulses. The saturable absorption effect is formed through the first polarization beam splitter prism to achieve clockwise mode-locked pulse output;

[0025] The counterclockwise continuous light passes through the counterclockwise laser mode-locking device, and the third quarter-wave plate and the third half-wave plate are rotated to control the peak powers of different pulses. The saturable absorption effect is formed through the second polarization beam splitter prism to achieve counterclockwise mode-locked pulse output.

[0026] The beneficial effects of the present invention are:

[0027] In the bidirectional annular fiber dual-comb laser generating device provided by the present invention, the pump laser beam output by the pump laser is divided into two beams by a pump light separation device to form two laser beam branches, and two gain optical fibers are respectively used in the non-common path section of each laser beam branch to eliminate the gain competition between the two laser beams, which is simple to operate and compact in structure. Two nonlinear polarization rotation mode-locking devices are respectively used on the laser beam branches of two different circulation directions, and a non-common path structure of laser beams in different directions is established by the first circulator and the second circulator, so that the repetition frequency difference between the two directions can be flexibly adjusted; by rotating the first quarter wave plate and the first half wave plate to control different pulse peak powers, a saturable absorption effect is formed to achieve mode locking; compared with the bidirectional mode-locked fiber dual-comb laser that relies on real mode-locking materials, the time response of nonlinear polarization rotation is faster and the spectral width is wider. By adjusting the wave plates of the clockwise laser mode-locking device and the counterclockwise laser mode-locking device, the simultaneous locking of the two repetition frequencies can be achieved, which can adapt to the application requirements of higher mutual coherence than the free operation.

[0028] The bidirectional annular optical fiber dual-comb laser generating device of the present invention breaks through the limitation of the pulse energy of traditional lasers and generates a single pulse energy greater than 10 nJ. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic structural diagram of a bidirectional annular fiber dual-comb laser generating device of the present invention.

[0030] Reference numerals:

[0031] 1. Pump laser; 2. Pump light separation device; 3. First wavelength division multiplexer; 4. Second wavelength division multiplexer; 5. First gain fiber; 6. Second gain fiber; 7. Clockwise laser mode locking device; 71. First collimator; 72. First quarter wave plate; 73. First half wave plate; 74. First polarization beam splitter; 75. Second half wave plate; 76. Second quarter wave plate; 77. Second collimator; 8. Counterclockwise laser mode locking device; 81. Third collimator; 82. Third quarter wave plate 83, third half-wave plate; 84, second polarization beam splitter; 85, fourth half-wave plate; 86, fourth quarter-wave plate; 87, fourth collimator; 9, first filter; 10, second filter; 11, first circulator; 111, first port; 112, second port; 113, third port; 12, second circulator; 121, first interface; 122, second interface; 123, third interface; 13, clockwise mode-locked pulse; 14, counterclockwise mode-locked pulse; DETAILED DESCRIPTION

[0032] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments. The specific implementation of the present invention is described below to facilitate the understanding of the present invention by those skilled in the art, but it should be clear that the present invention is not limited to the scope of the specific implementation. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention defined and determined by the attached claims, these changes are obvious, and all inventions and creations using the concept of the present invention are protected.

[0033] Example 1

[0034] like Figure 1 As shown, this embodiment provides a bidirectional annular fiber dual-comb laser generating device, in which two nonlinear polarization rotation mode locking devices are respectively used on the laser beam branches in two different directions, so that the repetition frequency difference between the two directions can be flexibly adjusted to achieve simultaneous locking of two repetition frequencies, which is suitable for application requirements with higher mutual coherence; it specifically includes:

[0035] Pump laser 1, pump light separation device 2, first wavelength division multiplexer 3, second wavelength division multiplexer 4, first gain fiber 5, second gain fiber 6, clockwise laser mode locking device 7, counterclockwise laser mode locking device 8, first circulator 11 and second circulator 12;

[0036] Among them, the pump laser 1 is used to emit a laser beam, and a pump light separation device 2 is provided at the emission end of the pump laser 1. The laser beam passes through the pump light separation device 2 to separate into two beams of pump light; the optical output end of the pump light separation device 2 is connected with two optical fibers, and the two optical fibers are respectively connected to the first wavelength division multiplexer 3 and the second wavelength division multiplexer 4; the two beams of pump light pass through the first wavelength division multiplexer 3 and the second wavelength division multiplexer 4 respectively, and the first wavelength division multiplexer 3 and the second wavelength division multiplexer 4 transmit the 980nm light output by the pump light separation device 2, and reflect the 1030nm light back into the laser cavity.

[0037] The first wavelength division multiplexer 3 is connected to the clockwise laser mode-locking device 7 through the first gain fiber 5, and the first gain fiber 5 is used to convert the pump light transmitted from the first wavelength division multiplexer 3 into a stimulated radiation beam of 1030nm; the light output end of the clockwise laser mode-locking device 7 is connected to the first circulator 11 through the optical fiber; the first circulator 11 is connected to the first wavelength division multiplexer 3. The second wavelength division multiplexer 4 is connected to the counterclockwise laser mode-locking device 8 through the second gain fiber 6, and the second gain fiber 6 is used to convert the pump light transmitted from the second wavelength division multiplexer 4 into a stimulated radiation beam of 1030nm; the light output end of the counterclockwise laser mode-locking device 8 is connected to the second circulator 12 through the optical fiber; the second circulator 12 is connected to the second wavelength division multiplexer 4.

[0038] The first circulator 11 and the second circulator 12 are connected through a common optical fiber. The stimulated radiation beam output by the first gain optical fiber 5 passes through the clockwise laser mode-locking device 7, then enters the first port 111 of the first circulator 11 through the optical fiber, and is output to the common optical fiber from the next port of the first port 111, that is, the second port 112; then it is transmitted to the first interface 121 of the second circulator 12 through the common optical fiber, and is output to the first wavelength division multiplexer 3 from the second interface 122 of the second circulator 12. The stimulated radiation beam output by the second gain optical fiber 6 passes through the counterclockwise laser mode-locking device 8, then enters the third interface 123 of the second circulator 12 through the optical fiber, and is output to the common optical fiber from the next interface of the third interface 123, that is, the first interface 121; then it is transmitted to the second port 112 of the first circulator 11 through the common optical fiber, and is output to the second wavelength division multiplexer 4 from the third interface 123 of the first circulator 11.

[0039] The clockwise laser mode locking device 7 comprises a first collimator 71, a first quarter wave plate 72, a first half wave plate 73, a first polarization beam splitter prism 74, a second half wave plate 75, a second quarter wave plate 76 and a second collimator 77; the light input end of the first collimator 71 is connected to the first gain fiber 5, and the light output end of the first collimator 71 is sequentially provided with the first quarter wave plate 72, the first half wave plate 73 and the first polarization beam splitter prism 74, the first quarter wave plate 72, the first half wave plate 73 and the first polarization beam splitter prism 74 are placed in parallel, and the mirror surface is perpendicular to the incident light; the light output end of the first polarization beam splitter prism 74 is sequentially provided with the second half wave plate 75, the second quarter wave plate 76 and the second collimator 77; the light output end of the second collimator 77 is connected to the first circulator 11 through an optical fiber. By rotating the first quarter wave plate 72 and the first half wave plate 73, the polarization state is rotated, thereby controlling the peak powers of different pulses, forming a saturable absorption effect, and achieving mode locking; compared with most bidirectionally mode-locked fiber dual-comb lasers that rely on real mode-locking materials to achieve mode locking, the nonlinear polarization rotation mode-locking mechanism has a faster time response and a wider spectral width.

[0040] A first filter 9 is further disposed between the first polarization beam splitter prism 74 and the second half wave plate 75 ; the first filter 9 is used to select light of a specific wavelength band to make the mode locking more stable.

[0041] The counterclockwise laser mode locking device 8 includes a third collimator 81, a third quarter wave plate 82, a third half wave plate 83, a second polarization beam splitter prism 84, a fourth half wave plate 85, a fourth quarter wave plate 86 and a fourth collimator 87; the light input end of the third collimator 81 is connected to the second gain fiber 6, and the light output end of the third collimator 81 is sequentially provided with the third quarter wave plate 82, the third half wave plate 83 and the second polarization beam splitter prism 84; the light output end of the second polarization beam splitter prism 84 is sequentially provided with the fourth half wave plate 85, the fourth quarter wave plate 86 and the fourth collimator 87; the light output end of the fourth collimator 87 is connected to the second circulator 12 through an optical fiber.

[0042] The second filter 10 is disposed between the second polarization splitter prism 84 and the fourth half wave plate 85 .

[0043] The pump light separation device 2 uses a fiber coupler.

[0044] In this embodiment, the devices are connected via single-mode optical fibers and gain optical fibers, and the specific connection method is to use an optical fiber fusion splicer.

[0045] Example 2

[0046] like Figure 1 As shown, this embodiment provides a bidirectional annular fiber dual-comb laser generating method based on the bidirectional annular fiber dual-comb laser generating device provided in Example 1, including the following steps:

[0047] S1: Pump laser 1 emits a pump laser beam;

[0048] S2: The pump laser beam is divided into two pump lights of equal power by the pump light separation device 2, and the two pump lights are respectively input into the first wavelength division multiplexer 3 and the second wavelength division multiplexer 4 through two optical fibers;

[0049] S3: The two pump lights transmitted through the first wavelength division multiplexer 3 and the second wavelength division multiplexer 4 are respectively transmitted to the first gain fiber 5 and the second gain fiber 6, and converted into stimulated radiation beams of 1030 nm;

[0050] S4: The stimulated radiation beam output by the first gain fiber 5 passes through the clockwise laser mode-locking device 7, the first circulator 11 and the second circulator 12 in sequence, and returns to the first wavelength division multiplexer 3 to construct a clockwise resonant cavity, forming a continuous light output in the clockwise direction;

[0051] The stimulated radiation beam output by the second gain fiber 6 passes through the counterclockwise laser mode-locking device 8, the second circulator 12 and the first circulator 11 in sequence, and returns to the second wavelength division multiplexer 4 to construct a counterclockwise resonant cavity, forming a continuous light output in the counterclockwise direction;

[0052] S5: The clockwise continuous light passes through the clockwise laser mode-locking device 7, and the first quarter-wave plate 72 and the first half-wave plate 73 are rotated to control the peak power of different pulses, and a saturable absorption effect is formed through the first polarization beam splitter prism 74, so as to realize the output of the clockwise mode-locked pulse 13;

[0053] The counterclockwise continuous light passes through the counterclockwise laser mode-locking device 8, and the third quarter-wave plate 82 and the third half-wave plate 83 are rotated to control different pulse peak powers, and a saturable absorption effect is formed through the second polarization beam splitter prism 84, so as to realize the output of the counterclockwise mode-locked pulse 14;

[0054] The output clockwise mode-locked pulse 13 and counterclockwise mode-locked pulse 14 can be detected by an oscilloscope.

[0055] Those skilled in the art will appreciate that the embodiments herein are intended to help readers understand the principles of the present invention, and should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific variations and combinations that do not deviate from the essence of the present invention based on the technical revelations disclosed by the present invention, and these variations and combinations are still within the protection scope of the invention.

Claims

1. A bidirectional ring fiber dual-comb laser generator, characterized in that: It comprises a pump laser (1), wherein the emission end of the pump laser (1) is provided with a pump light separation device (2); the optical output end of the pump light separation device (2) is connected to two optical fibers, and the two optical fibers are respectively connected to a first wavelength division multiplexer (3) and a second wavelength division multiplexer (4); The first wavelength division multiplexer (3) is connected to a clockwise laser mode locking device (7) via a first gain optical fiber (5); the optical output end of the clockwise laser mode locking device (7) is connected to a first circulator (11) via an optical fiber; and the first circulator (11) is connected to the first wavelength division multiplexer (3); The second wavelength division multiplexer (4) is connected to a counterclockwise laser mode locking device (8) via a second gain optical fiber (6); the optical output end of the counterclockwise laser mode locking device (8) is connected to a second circulator (12) via an optical fiber; and the second circulator (12) is connected to the second wavelength division multiplexer (4); The first circulator (11) and the second circulator (12) are connected via a common path optical fiber.

2. The bidirectional ring fiber dual-comb laser generator according to claim 1, characterized in that: The clockwise laser mode locking device (7) comprises a first collimator (71); the light input end of the first collimator (71) is connected to the first gain optical fiber (5); the light output end of the first collimator (71) is provided with a first quarter wave plate (72), a first half wave plate (73) and a first polarization beam splitter prism (74) in sequence; the light output end of the first polarization beam splitter prism (74) is provided with a second half wave plate (75), a second quarter wave plate (76) and a second collimator (77) in sequence; and the light output end of the second collimator (77) is connected to the first circulator (11) via an optical fiber.

3. The bidirectional ring fiber dual-comb laser generator according to claim 2, characterized in that: A first filter (9) is also provided between the first polarization beam splitter prism (74) and the second half-wave plate (75).

4. The bidirectional annular fiber dual-comb laser generator according to claim 1, characterized in that: The counterclockwise laser mode locking device (8) comprises a third collimator (81); the light input end of the third collimator (81) is connected to the second gain optical fiber (6); the light output end of the third collimator (81) is provided with a third quarter wave plate (82), a third half wave plate (83) and a second polarization beam splitter prism (84) in sequence; the light output end of the second polarization beam splitter prism (84) is provided with a fourth half wave plate (85), a fourth quarter wave plate (86) and a fourth collimator (87) in sequence; and the light output end of the fourth collimator (87) is connected to the second circulator (12) via an optical fiber.

5. The bidirectional ring fiber dual-comb laser generator according to claim 4, characterized in that: A second filter (10) is arranged between the second polarization beam splitter (84) and the fourth half-wave plate (85).

6. The bidirectional ring fiber dual-comb laser generator according to claim 1, characterized in that: The pump light separation device (2) is a fiber optic coupler.

7. A method for generating a laser according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1: Pump laser (1) emits a pump laser beam; S2: The pump laser beam is divided into two beams of pump light of equal power by the pump light separation device (2), and the two beams of pump light are respectively input into the first wavelength division multiplexer (3) and the second wavelength division multiplexer (4) through two optical fibers; S3: The two pump lights transmitted through the first wavelength division multiplexer (3) and the second wavelength division multiplexer (4) are respectively transmitted to the first gain fiber (5) and the second gain fiber (6) to be converted into stimulated radiation beams of 1030 nm; S4: The stimulated radiation beam output by the first gain optical fiber (5) passes through the clockwise laser mode-locking device (7), the first circulator (11) and the second circulator (12) in sequence, and returns to the first wavelength division multiplexer (3), constructing a clockwise resonant cavity, thereby forming a continuous light output in the clockwise direction; The stimulated radiation beam output by the second gain optical fiber (6) passes through the counterclockwise laser mode locking device (8), the second circulator (12) and the first circulator (11) in sequence, and returns to the second wavelength division multiplexer (4), constructing a counterclockwise resonant cavity, thereby forming a continuous light output in the counterclockwise direction; S5: The continuous light in the clockwise direction passes through the clockwise laser mode-locking device (7), the first quarter-wave plate (72) and the first half-wave plate (73) are rotated to control the peak power of different pulses, and a saturable absorption effect is formed through the first polarization beam splitter prism (74), so as to realize the output of the clockwise mode-locked pulse (13); Continuous light in the counterclockwise direction passes through a counterclockwise laser mode-locking device (8), and the third quarter-wave plate (82) and the third half-wave plate (83) are rotated to control different pulse peak powers, and a saturable absorption effect is formed through a second polarization beam splitter prism (84), thereby realizing the output of a counterclockwise mode-locked pulse (14).

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