A SESAM-mode-locked high-repetition-rate disk laser

Abstract

This invention discloses a SESAM-mode-locked high-repetition-rate disk laser, belonging to the field of solid-state laser technology. It includes a pump source and a resonant cavity. The resonant cavity comprises a disk-shaped laser crystal, a dispersion compensation unit, a lens, and a semiconductor saturable absorber mirror. The semiconductor saturable absorber mirror is positioned near the focal point of the lens, corresponding to the edge of the stable region of the resonant cavity. This invention solves the problem of low output power caused by the shrinking laser spot size under high repetition frequency conditions by adjusting the mode distribution within the resonant cavity through the lens. Furthermore, by combining a disk-shaped laser crystal and a water-coolable SESAM, and using the disk crystal simultaneously as a gain medium and end-face reflector, it improves both the space utilization within the cavity and the output power, thereby realizing a simple and compact high-power, high-repetition-rate femtosecond disk laser.

Description

Technical Field

[0001] The invention belongs to the technical field of solid lasers, and more specifically, relates to a SESAM mode-locked high repetition frequency disk laser. Background Art

[0002] Since the birth of the world's first laser in the 1960s, laser technology has achieved rapid development. Ultrafast lasers have become an important research direction in the field of laser technology due to their high peak power and narrow pulse width. They have very wide and important applications in basic scientific research, biomedicine, industrial processing, national defense and military fields.

[0003] As an important technical indicator of ultrafast lasers, the pulse repetition frequency has become a key factor limiting its application. When the repetition frequency of laser pulses is low, the corresponding single pulse energy and peak power will be improved. Such laser light sources are mainly used in laser processing and other fields. When the repetition frequency of laser pulses is high, it is mainly used in femtosecond optical frequency combs and ultrafast time-resolved spectroscopy.

[0004] When a femtosecond optical frequency comb is used for optical frequency measurement, the higher the repetition frequency of its seed source, the better. There are two main reasons for this: First, the higher the repetition frequency, the wider the teeth of the optical frequency comb, and the easier it is to determine the location of the light wave. Second, under the condition of a certain average power output by the laser, the higher the repetition frequency, the larger the longitudinal mode spacing, and therefore the higher the average power distributed on each longitudinal mode frequency, and a higher signal-to-noise ratio can be obtained during the beat frequency.

[0005] At present, the lasers that can achieve high repetition rate mainly include fiber lasers, bulk solid lasers and microcavity lasers, and the repetition rates that these lasers can obtain range from 500MHz to hundreds of GHz. However, these high repetition rate lasers have some problems. Without subsequent amplification, the average power of femtosecond pulses that can be achieved is mostly in the mW range. Too low average power will greatly reduce the signal-to-noise ratio, which will also limit the subsequent application of high repetition rate femtosecond laser seed sources.

[0006] Disk-shaped laser crystal is a new type of gain medium. Its geometric shape is a large and thin disk with a very large diameter-to-thickness ratio. The use of impact water cooling to dissipate heat can increase the average power output of the disk laser. The thickness of the disk crystal is very thin, and the nonlinear effect is very weak, so it can support high peak power laser output. In addition, by increasing the pump spot size on the surface of the disk crystal, the pump power can be increased while keeping the power density unchanged, and it has excellent power and energy scalability. Therefore, disk lasers are very suitable for generating high-power, high-energy, and high-peak power laser outputs.

[0007] The main ways to generate ultrafast lasers are Kerr lens mode locking and semiconductor saturable absorber mirror (SESAM) mode locking. To achieve Kerr lens mode locking in a disk laser, it is necessary to add an additional Kerr medium to provide the Kerr effect, and the Kerr effect requires a high power density to be generated on the Kerr medium to achieve mode locking, which means that two concave mirrors need to be added to produce a focused spot on the Kerr medium. However, if a higher repetition rate is to be achieved, the cavity length needs to be further shortened, but the short cavity length will inevitably reduce the intracavity mode, making the output power smaller. At the same time, too many optical devices in the cavity are not conducive to increasing the repetition rate of the disk laser. In contrast, SESAM mode locking does not require precise adjustment of the cavity and is easy to start, but there is also a contradiction between high repetition rate and high average power, that is, the resonant cavity length of the high repetition rate is shorter, resulting in a smaller intracavity mode. This will undoubtedly limit the development of high repetition rate and high power disk lasers. Summary of the invention

[0008] In view of the defects and improvement needs of the prior art, the present invention provides a SESAM mode-locked high repetition rate disk laser, the purpose of which is to improve the laser output power of the disk laser at a high repetition rate.

[0009] To achieve the above object, the present invention provides a SESAM mode-locked high repetition rate disk laser, comprising a pump source and a resonant cavity, wherein the resonant cavity comprises: a disk-shaped laser crystal, a dispersion compensation unit, a lens and a semiconductor saturable absorber mirror; the semiconductor saturable absorber mirror is arranged at the near focus of the lens, and the near focus corresponds to the edge position of the stable region of the resonant cavity;

[0010] The pump source is used to output pump laser; the disk-shaped laser crystal is used to receive the pump laser and serve as a gain medium to generate laser, and also serves as the first end mirror of the resonant cavity to reflect the oscillating laser; the lens is used to focus the laser on the semiconductor saturable absorber mirror; the semiconductor saturable absorber mirror is used to start and maintain SESAM mode-locked operation, and also serves as the second end mirror of the resonant cavity to reflect the oscillating laser; the laser oscillates back and forth in the resonant cavity, and the dispersion compensation unit is used to make the total dispersion amount in the cavity negative, and is also used to output high-repetition-rate mode-locked laser pulses.

[0011] Furthermore, the dispersion compensation unit is arranged between the disk-shaped laser crystal and the lens.

[0012] Furthermore, the dispersion compensation unit is a first high-dispersion mirror and a second high-dispersion mirror, the laser is incident on the first high-dispersion mirror, and is reflected by the first high-dispersion mirror to the second high-dispersion mirror.

[0013] Furthermore, the side of the first high-dispersion mirror or the second high-dispersion mirror facing the resonant cavity is coated with a partially transparent film with a transmittance range of 1-20%, and the side facing away from the resonant cavity is coated with an anti-reflection film for the oscillating laser.

[0014] Furthermore, the side of the disk-shaped laser crystal facing the resonant cavity is coated with an anti-reflection film, and the side facing away from the resonant cavity is coated with a high-reflection film; both sides of the lens are coated with anti-reflection films.

[0015] Furthermore, it also includes a pump module arranged in the optical path between the pump source and the disk-shaped laser crystal, which is used to increase the absorption efficiency of the pump laser focused on the disk-shaped laser crystal.

[0016] Furthermore, the pump module includes a parabolic mirror and a series of folding prisms, the disk laser crystal is placed at the focus of the parabolic mirror, and the pump light is focused on the disk laser crystal after multiple reflections of the parabolic mirror and the folding prisms.

[0017] Furthermore, the disk-shaped laser crystal and the semiconductor saturable absorber mirror are fixed on a water-cooled heat sink at a side facing away from the resonant cavity.

[0018] Furthermore, the disk-shaped laser crystal is in the shape of a circular disk or an elliptical disk.

[0019] Furthermore, the material of the disk-shaped laser crystal includes Yb:YAG, Ho:YAG, Tm:YAG, Ho:KYW, Yb:CALGO, Cr:ZnSe, Yb:LuScO3 or Yb:Lu2O3.

[0020] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

[0021] (1) The present invention sets a semiconductor saturable absorber mirror at the near focus of the lens, adopts lenses of different focal lengths for different repetition frequencies, and adjusts the mode distribution in the resonant cavity through the lens, so that a large-sized laser spot is achieved on the surface of the disk-shaped laser crystal and a small-sized laser spot is achieved on the surface of the SESAM in the cavity; the large laser spot on the surface of the disk-shaped laser crystal can improve the gain utilization of the crystal, thereby improving the output power of the laser; at the same time, the small laser spot on the surface of the SESAM can increase the laser power density on the surface of the SESAM, which is conducive to the formation of mode-locked pulses. Through simulation, the present invention realizes high repetition rate femtosecond laser pulses above 0.5GHz, and the output power of the pulses is relatively high.

[0022] (2) The present invention uses a disk-shaped laser crystal as a gain medium to generate laser light. The pump spot size on its surface is relatively large, and it can support a higher pump power while keeping the power density unchanged, thereby obtaining a high output power. The SESAM mode locking method is adopted, which is easy to start and does not require additional mode locking elements to be added in the cavity, thereby improving space utilization.

[0023] (3) The present invention uses the disk-shaped laser crystal as both a gain medium and an end reflector, which reduces the cavity length, improves the utilization rate of the cavity space, and can maximize the repetition frequency of the disk laser. The entire laser system has a simple and compact structure and is easy to assemble.

[0024] (4) Preferably, two high-dispersion mirrors are arranged between the disc-shaped laser crystal and the lens. The spot size in the cavity at this position is relatively large. Under the condition of a certain power, the laser power density on the surface of the high-dispersion mirror can be reduced, thereby avoiding damage to the high-dispersion mirror due to excessive power in the cavity as much as possible. At the same time, since the high-dispersion mirror is also used as an output mirror, dual-path output of the laser can be achieved. In the field of laser processing, the processing efficiency can be improved and the labor cost can be reduced.

[0025] (5) Preferably, the disk-shaped laser crystal and the semiconductor saturable absorber mirror are fixed on a water-cooled heat sink on one side facing away from the resonant cavity. The heat dissipation efficiency can be improved by cooling by using an impact water cooling method. Under high heat dissipation efficiency, the radial thermal gradient of the disk-shaped laser crystal can be ignored, and a laser with high beam quality can be output. The cooling water takes away the heat from the surface of the SESAM through the heat sink. This method improves the damage threshold of the SESAM and further improves the output power.

[0026] In summary, the laser proposed in the present invention is suitable for fields such as laser high-speed processing, femtosecond optical frequency comb and ultrafast time-resolved spectroscopy. It not only solves the problem of low output power caused by the shrinkage of the intracavity mode under high repetition frequency conditions, but also can fully improve the utilization rate of the intracavity space and maximize the repetition frequency of the disk laser. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic structural diagram of the SESAM mode-locked high repetition rate disk laser provided by the present invention.

[0028] Figure 2 This is the intracavity mode distribution diagram when the repetition frequency is 0.5 GHz in this embodiment.

[0029] Figure 3 : is the intracavity mode distribution diagram when the repetition frequency is 1 GHz in this embodiment.

[0030] In all drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0031] 1- pump source, 2- disk-shaped laser crystal, 3- semiconductor saturable absorber mirror, 4- resonant cavity, 5- lens, 6- first high dispersion mirror, 7- second high dispersion mirror, 8- pump module, 9 and 10 are parabolic mirrors. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0033] In the present invention, the terms "first", "second", etc. in the present invention and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0034] like Figure 1 As shown, the SESAM mode-locked high repetition rate disk laser provided by the present invention mainly includes: a pump source 1, a pump module 8, a disk-shaped laser crystal 2, a dispersion compensation unit, a lens 5 and a semiconductor saturable absorber mirror 3; wherein the disk-shaped laser crystal 2, the dispersion compensation unit, the lens 5 and the semiconductor saturable absorber mirror 3 constitute a resonant cavity 4 for providing a reciprocating oscillating laser; the semiconductor saturable absorber mirror 3 is arranged at the near focus of the lens, and the near focus corresponds to the edge position of the stable zone of the resonant cavity.

[0035] A pump source 1 is used to output pump laser; a pump module 8 is used to improve the absorption efficiency of the disk-shaped laser crystal 2 to the pump laser; the disk-shaped laser crystal 2 is used as a gain medium to generate laser, and the disk-shaped laser crystal 2 also serves as the first end mirror of the resonant cavity to reflect the oscillated laser; a lens 5 is used to adjust the mode distribution in the cavity; a semiconductor saturable absorption mirror 3 is used to start and maintain the SESAM mode-locked operation, and also serves as the second end mirror of the resonant cavity to reflect the oscillated laser; the laser oscillates back and forth in the resonant cavity, and a dispersion compensation unit is used to compensate for the dispersion amount in the cavity so that the total dispersion amount in the cavity is a negative value, and is also used to output high-repetition-rate and high-power stable mode-locked laser pulses.

[0036] Specifically, the pump source includes but is not limited to semiconductor lasers, fiber lasers, and solid-state lasers with an output wavelength in the range of 300 nm to 5 μm.

[0037] Specifically, the pump module 8 includes a parabolic mirror and a series of reentrant prisms, which are placed in the optical path between the pump source and the disk-shaped laser crystal according to a set rule. The pump light passes through the pump module and travels back and forth on the disk-shaped laser crystal for many times, so that it is fully absorbed by the disk-shaped laser crystal. The disk laser crystal 2 is placed at the focus of the parabolic mirror, and the input pump light is focused on the disk crystal after multiple reflections of the parabolic mirror and the reentrant prism. This example adopts a 48-pass pumping structure, that is, the pump laser passes through the disk crystal 48 times, which greatly improves the absorption efficiency of the disk crystal for the pump light.

[0038] Specifically, the disk-shaped laser crystal is used as a gain medium and an end reflector at the same time, which reduces the cavity length and improves the space utilization rate in the cavity. The disk-shaped laser crystal proposed in the present invention requires both pump light excitation to generate laser light and serves as the first end mirror of the resonant cavity to reflect the oscillating laser light. Therefore, different dielectric films are plated on both sides of the disk-shaped laser crystal. The side facing the resonant cavity is plated with an anti-reflection film for the pump light and the oscillating laser light, and the side facing away from the resonant cavity is plated with a high-reflection film for the pump light and the oscillating laser light. The surface plated with the high-reflection film is fixed on a water-cooled heat sink.

[0039] Preferably, the disc-shaped laser crystal is in the shape of a disc or an elliptical disc, with a thickness of 10 μm to 1 mm and a diameter of 3 mm to 30 mm. In this embodiment, the disc-shaped laser crystal has a thickness of 220 μm and a shape of a disc or an elliptical disc with a diameter of 10 mm. This large and thin disc shape can make the pump spot as large as possible on the crystal surface by adjusting the pump optical path. Under the same pump power, the pump power density borne by the crystal is greatly reduced, so it can support higher power pumping, and thus can generate higher output power. At the same time, the disc-shaped laser crystal has a large diameter-to-thickness ratio, and the heat dissipation efficiency can be effectively improved, so the radial thermal gradient of the crystal can be almost negligible, which makes the laser output by the disc laser have a good beam quality. In addition, the disc crystal is thin, the nonlinear effect is very weak, and it can also support high peak power laser output. Therefore, the disc-shaped laser crystal used in the present invention as a gain medium can produce high-power, high beam quality, and high peak power laser output. The materials of the disk-shaped laser crystal include but are not limited to Yb:YAG, Ho:YAG, Tm:YAG, Ho:KYW, Yb:CALGO, Cr:ZnSe, Yb:LuScO3, Yb:Lu2O3 and the like which are suitable for processing into a disk-shaped laser crystal.

[0040] Specifically, the lens is coated with an antireflection film on both sides, and the focal length is between 4mm and 100mm. The focal length of the lens is selected according to the requirements of different cavity lengths corresponding to different repetition frequencies. Preferably, when the repetition frequency is set to 0.5GHz, the focal length of the lens is 75mm; when the repetition frequency is set to 1GHz, the focal length of the lens is 30mm.

[0041] The water-cooled SESAM, i.e., the semiconductor saturable absorber mirror, generates a mode-locked pulse sequence through its saturable absorption effect and is used as the second end mirror of the resonant cavity for reflecting laser light. It is arranged at the near focus of the lens 5, which is the first edge position of the first stable region of the resonant cavity. For different repetition frequencies, through the intracavity mode analysis, lenses with different focal lengths are used to increase the laser spot size on the surface of the disk-shaped laser crystal to increase the output power of the resonant cavity. At the same time, the SESAM is arranged at the near focus of the lens 5, and the spot size focused on the SESAM can also be reduced to increase the laser power density on the surface of the SESAM to cause the saturable absorption effect to achieve mode locking.

[0042] The water-cooled SESAM is coated with a saturable absorption film for oscillating laser and a multilayer dielectric film with high reflection to oscillating laser in sequence from the side facing the resonant cavity. The absorption of SESAM is 0.1% to 2%, preferably 0.7% to 1.5%; the reflectivity is >99%, and the multilayer dielectric film with high reflection to oscillating laser is grown on the substrate. The modulation depth of SESAM is >0.4%, preferably 0.6% to 1.2%; the unsaturated loss of SESAM is <1%, preferably 0.4% to 0.5%; the saturated flux of SESAM is 20μJ / cm 2 ~150μJ / cm 2 , preferably, the saturation flux is 100 μJ / cm 2 The side of the SESAM facing away from the resonant cavity is fixed on a water-cooled heat sink.

[0043] Specifically, the dispersion compensation unit is used to compensate for the dispersion introduced by the optical elements in the cavity, such as the disk-shaped laser crystal, lens, SESAM, etc., so that the total dispersion in the cavity is negative. The dispersion compensation unit is arranged in the resonant cavity, and the specific position is not limited. Preferably, the dispersion compensation unit is arranged between the disk-shaped laser crystal 2 and the lens 5, because the spot size in the cavity is larger at this position, and the laser power density on the surface of the high dispersion mirror can be reduced under the condition of a certain power, so as to avoid the damage of the dispersion compensation unit due to excessive power in the cavity as much as possible, and at the same time, the dual-path output of the laser can be realized.

[0044] Specifically, the dispersion compensation unit is a first high dispersion mirror 6 and a second high dispersion mirror 7. The laser output by the disc-shaped laser crystal 2 is incident on the first high dispersion mirror 6, reflected by the first high dispersion mirror 6 to the second high dispersion mirror 7, and then incident on the SESAM after being focused by the lens 5. The first high dispersion mirror 6 and the second high dispersion mirror 7 can compensate for the dispersion of the air and components in the cavity. Among them, the first high dispersion mirror 6 and the second high dispersion mirror 7 can both be used as plane output mirrors. In this embodiment, the first high dispersion mirror 6 is used as a plane output mirror, and the side of the first high dispersion mirror 6 facing the resonant cavity is coated with a partially transparent film for the oscillating laser, and the transmittance range is 1 to 20%, and the side facing away from the resonant cavity is coated with an anti-reflection film for the oscillating laser, and the transmittance is greater than 99%.

[0045] Specifically, in this embodiment, a semiconductor laser with fiber-coupled output is selected as the pump source, and the pump laser wavelength is 940nm. It is focused on a disk-shaped laser crystal through a pump module. The disk crystal is a disk-shaped Yb:YAG (doping concentration is 7%) laser crystal with a diameter of 10mm and a thickness of 220μm. The disk crystal is coated with different dielectric films on both sides. The side facing the resonant cavity is coated with an anti-reflection film for the oscillating laser and the pump laser, and the side facing away from the resonant cavity is coated with a high-reflection film for the oscillating laser and the pump laser. The side of the disk crystal facing away from the resonant cavity is fixed on a heat sink, and the heat is taken away by water cooling. The pump spot size on the surface of the disk-shaped laser crystal is about 3mm. The 1030nm laser generated by the Yb:YAG gain medium is incident on the first high-dispersion mirror, and part of the laser is reflected by the first high-dispersion mirror to the second high-dispersion mirror, and the other part of the laser passes through the first high-dispersion mirror and outputs to form a first stable high-power and high-repetition-rate femtosecond laser pulse. The laser reflected by the first high-dispersion mirror to the second high-dispersion mirror is reflected by the second high-dispersion mirror and reaches the lens, and is focused by the lens onto the SESAM (or the second end mirror). The SESAM returns the laser along the original path, passes through the lens, and is reflected by the second high-dispersion mirror to the first high-dispersion mirror again. Part of the laser is reflected by the first high-dispersion mirror to the disc-shaped laser crystal and oscillates back and forth in the resonant cavity again, and the other part of the laser is output through the first high-dispersion mirror to form a second stable high-power and high-repetition-rate femtosecond laser pulse. The output directions of the two lasers are at an angle.

[0046] The SESAM mode-locked femtosecond disk laser proposed in the present invention aims to achieve high repetition frequency and high power femtosecond laser pulses with a repetition frequency greater than 0.5 GHz. Since different repetition frequencies correspond to different cavity lengths, the selection of specific optical element parameters is slightly different. Here, only the cavity structures with repetition frequencies of 0.5 GHz and 1 GHz are introduced in detail. According to the same method, high power femtosecond laser pulses with higher repetition frequency can be achieved by selecting lenses with different focal lengths and combining intracavity mode and stable zone analysis.

[0047] according to Figure 1 It can be seen that due to the multi-pass pumping structure of the disk laser crystal, a parabolic mirror needs to be installed in front of the disk laser crystal to focus the pump light onto the disk. The middle of the two parabolic mirrors 9 and 10 is the laser light hole, and there is a distance of about 70 mm between the disk laser crystal and the light hole. This distance is inside the disk module and it is difficult to use this distance to place optical components. Therefore, this is a factor that cannot be ignored in the subsequent cavity design process.

[0048] According to the above example, the two end mirrors of the resonant cavity are disk laser crystal and SESAM. Figure 2 As shown in the figure, when the repetition frequency is 0.5 GHz, the total length of the resonant cavity does not exceed 300 mm, when the focal length of the lens is 75 mm, and the distance between the lens and the SESAM is 75.2 mm, the spot size on the disk-shaped laser crystal is 1.6 mm, and the laser spot size on the SESAM surface is 60 μm. Figure 3 As shown, when the repetition frequency is 1 GHz, the total length of the resonant cavity does not exceed 150 mm. Preferably, when the focal length of the lens is 30 mm and the distance between the lens and the SESAM is 30.2 mm, the spot size on the disc-shaped laser crystal is 0.86 mm, and the laser spot size on the SESAM surface is 40 μm. That is, the mode distribution in the resonant cavity is adjusted by the lens, so that the surface of the disc-shaped laser crystal has a large-sized laser spot and the surface of the SESAM has a small-sized laser spot in the cavity, which increases the mode volume in the cavity and thus improves the output power of the laser. And the SESAM is arranged at the near focus of the lens, which can ensure that the resonant cavity is in the stable zone. In addition, the use of the lens can shorten the cavity length of the resonant cavity compared with the prior art, which is conducive to achieving a high repetition rate. Both sides of the lens surface are coated with an anti-reflection film (T>99.9%) for the oscillating laser. The first high-dispersion mirror is a plane output mirror, and the side facing the resonant cavity is coated with a partially transparent film for the oscillating laser. The present invention adopts a plane output mirror with an output coupling rate of 1% to 20%, and the side facing away from the resonant cavity is coated with an anti-reflection film (T>99.9%) for the oscillating laser. The output mirror is located at the position of the return mirror in the cavity and can output two lasers at the same time.

[0049] The laser using the above method can obtain stable high-repetition-rate and high-power femtosecond laser pulses above 0.5GHz. The high-repetition-rate and high-power femtosecond disk laser proposed in the present invention has a simple, compact and easy-to-start structure, is suitable for repeated assembly and production, can be mass-produced, and the output laser pulses have the advantages of high power and high beam quality. It can be widely used in scientific research, laser processing, femtosecond optical frequency combs and other fields, and has good commercial value and application prospects.

[0050] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A SESAM mode-locked high repetition rate disk laser, comprising a pump source (1) and a resonant cavity (4), characterized in that: The resonant cavity (4) comprises: a disk-shaped laser crystal (2), a dispersion compensation unit, a lens (5) and a semiconductor saturable absorption mirror (3); the semiconductor saturable absorption mirror (3) is arranged at the near focus of the lens (5), and the near focus corresponds to the edge position of the stable zone of the resonant cavity (4); The pump source (1) is used to output pump laser; the disk-shaped laser crystal (2) is used to receive the pump laser and serve as a gain medium to generate laser, and also serves as a first end mirror of the resonant cavity (4) to reflect the oscillated laser; the lens (5) is used to focus the laser on the semiconductor saturable absorber mirror (3); the semiconductor saturable absorber mirror (3) is used to start and maintain SESAM mode-locking operation, and also serves as a second end mirror of the resonant cavity (4) to reflect the oscillated laser; the laser oscillates back and forth in the resonant cavity, and the dispersion compensation unit is used to make the total dispersion amount in the cavity negative, and is also used to output high-repetition-rate mode-locked laser pulses.

2. The laser according to claim 1, characterized in that The dispersion compensation unit is arranged between the disk-shaped laser crystal (2) and the lens (5).

3. The laser according to claim 1 or 2, characterized in that: The dispersion compensation unit comprises a first high-dispersion mirror (6) and a second high-dispersion mirror (7); the laser is incident on the first high-dispersion mirror (6) and is reflected by the first high-dispersion mirror (6) to the second high-dispersion mirror (7).

4. The laser according to claim 3, characterized in that The first high-dispersion mirror (6) or the second high-dispersion mirror (7) is coated with a partially transparent film on the side facing the resonant cavity, with a transmittance range of 1 to 20%, and is coated with an anti-reflection film for oscillating laser on the side facing away from the resonant cavity.

5. The laser according to claim 4, characterized in that The side of the disk-shaped laser crystal facing the resonant cavity is coated with an anti-reflection film, and the side facing away from the resonant cavity is coated with a high-reflection film; both sides of the lens are coated with anti-reflection films.

6. The laser according to claim 5, characterized in that It also comprises a pump module (8) arranged in the optical path between the pump source (1) and the disk-shaped laser crystal (2), and used for increasing the absorption efficiency of the pump laser focused on the disk-shaped laser crystal (2).

7. The laser according to claim 6, characterized in that The pump module (8) comprises a parabolic mirror and a series of folding prisms, the disk laser crystal (2) is placed at the focus of the parabolic mirror, and the pump light is focused onto the disk laser crystal (2) after multiple reflections from the parabolic mirror and the folding prisms.

8. The laser according to claim 7, characterized in that The side of the disk-shaped laser crystal and the semiconductor saturable absorption mirror facing away from the resonant cavity is fixed on a water-cooled heat sink.

9. The laser according to claim 8, characterized in that The disk-shaped laser crystal is in the shape of a circular disk or an elliptical disk.

10. The laser according to any one of claims 4 to 9, characterized in that: The material of the disk-shaped laser crystal includes Yb:YAG, Ho:YAG, Tm:YAG, Ho:KYW, Yb:CALGO, Cr:ZnSe, Yb:LuScO3 or Yb:Lu2O3.

Images