2m-band GHz solid mode locking device based on electric regulation and control

Abstract

The invention discloses a 2m-band GHz solid mode-locking device based on electric regulation and control, which belongs to the technical field of ultrafast laser technology and semiconductor device, and comprises a high-brightness fiber laser pumping source, a light focusing and coupling system for focusing and collimating the pumping source, a first input mirror for transmitting and reflecting a focused laser beam, and a second input mirror for transmitting and reflecting the focused laser beam. The first input mirror and the second input mirror are used for focusing laser beams, the gain medium is used for generating and amplifying laser, the second input mirror and the third input mirror are used for reflecting the focused laser beams, and the two-dimensional Bi2O2Se electro-optical modulator is used for modulating the laser beams. According to the invention, a two-dimensional Bi2O2Se electro-optical modulator with low saturation flux, fast saturation recovery time and moderate modulation depth is developed to overcome the technical barrier of solid GHz femtosecond mode locking.

Description

Technical Field

[0001] The invention belongs to the field of ultrafast laser technology and semiconductor device technology, and in particular relates to a 2µm band GHz solid mode-locked device based on electrical regulation. Background Art

[0002] 2 µm band gigahertz (GHz) high repetition rate ultrafast laser has important application prospects in large-capacity free-space optical communications, optical frequency combs, ultra-high precision molecular spectroscopy and precision polymer processing. For example, as one of the important atmospheric transmission windows, this band has strong penetration of fog, smoke and dust, and GHz high repetition rate ultrafast laser can significantly improve the transmission capacity of optical signal processing systems, which has a great driving effect on the development of large-capacity free-space optical communication technology in the "last mile" of broadband networks.

[0003] There are three main ways to generate 2 µm-band GHz ultrashort pulses: The first is to convert the mature 1 µm band GHz ultrashort pulses to the 2 µm band through nonlinear frequency conversion technologies such as optical parametric oscillation (OPO). However, the characteristics of ultrafast laser emission, such as wide spectrum, short pulse duration, and high peak power, bring extremely high challenges to the strict phase matching and precise synchronization of pump light, signal light, and idler light in the process of ultrafast laser pumping OPO, and it is very easy to cause optical damage to nonlinear crystal materials, resulting in complex system structure, low reliability and life.

[0004] The second is based on Tm 3+ 、Ho 3+ Doped fiber mode-locking technology. Compared with OPO technology, this technology can realize the direct output of 2 µm band GHz ultrashort pulses from the oscillator, with simple system design and high conversion efficiency. However, rare earth ion doped 2 µm band GHz ultrafast fiber lasers still face the following challenges: (1) NPR mode locking is highly dependent on the nonlinear effect of the fiber and the polarization state of the light. Changes in the external environment temperature can cause the mode-locked laser to lose lock; (2) High-order harmonics of harmonic mode locking can easily cause pulse timing jitter and amplitude fluctuation, affecting the stability of the laser and the beam quality; (3) It is difficult to directly obtain high-output power fundamental frequency light femtosecond pulses. The short gain fiber required for GHz repetition rate depends on a high doping concentration, but the current high-doped fiber technology is not mature, which can easily lead to insufficient fiber uniformity. In addition, the strong nonlinear effect of the fiber itself, limited energy storage, and low damage threshold make it particularly difficult to obtain high-power 2 µm band GHz mode-locked femtosecond pulses directly from the fiber oscillator.

[0005] The third is based on Tm 3+ 、Ho 3+High-power solid-state mode-locked laser technology with doped crystals. Compared with 2 µm band optical fiber materials, the growth and preparation technology of laser crystals in this band in China has reached the international leading level. These laser crystals have the characteristics of high damage threshold, low nonlinear effect, low cost and high doping, which provides a strong guarantee for the realization of 2 µm band GHz high-power mode-locked femtosecond laser. At present, Tm 3+ 、Ho 3+ Important research progress has been made in solid-state mode-locked lasers with doped crystals. However, to date, there has been no report on 2 µm-band GHz solid-state femtosecond lasers with saturable absorber mode-locking. The reason for this is that, in addition to the immaturity of the 2 µm-band short-cavity mode-locking technology, there is a lack of 2 µm-band GHz solid-state mode-locked components with low saturation flux, fast saturation recovery time, and moderate modulation depth.

[0006] Summarizing the current research status, there are still many problems to be solved. The lack of 2 µm band GHz solid-state mode-locked elements with low saturation flux, fast saturation recovery time, and moderate modulation depth is the main reason why it is difficult to achieve 2 µm band solid-state GHz femtosecond lasers. Summary of the invention

[0007] In view of the above technical barriers, the present invention proposes a 2 µm band GHz solid mode-locked device based on electrical control to solve the problems existing in the above-mentioned prior art.

[0008] To achieve the above object, the present invention provides a 2 µm band GHz solid mode-locked device based on electrical control, comprising the following structure: A fiber laser pump source for emitting a laser beam; A mode-locked resonant cavity, comprising an input mirror group and a two-dimensional electro-optical modulation device, wherein the mode-locked resonant cavity is used to reflect and modulate the laser beam; An output mirror is used to reflect the laser back into the resonant cavity for gain amplification and output a modulated laser beam; Wherein, the two-dimensional electro-optical modulation device is composed of two-dimensional Bi2O2Se, a graphene electrode, a boron nitride insulating layer and a gold electrode; The two-dimensional electro-optical modulation device is used to control the Fermi level of two-dimensional Bi2O2Se by applying an external electric field, thereby realizing the control of the saturation absorption characteristics of two-dimensional Bi2O2Se.

[0009] Optionally, the input mirror group includes a first input mirror, a second input mirror and a third input mirror; Among them, the laser beam can be input into the two-dimensional electro-optical modulation device along the first input mirror, the second input mirror and the third input mirror in sequence, and the laser beam reflected by the two-dimensional electro-optical modulation device can be input into the output mirror along the third input mirror, the second input mirror and the first input mirror in sequence to output the laser beam.

[0010] Optionally, the first input mirror and the second input mirror are both concave mirrors with a curvature radius of 50 mm and are negative dispersion mirrors, and the third input mirror is a concave mirror with a curvature radius of 100 mm.

[0011] Optionally, it also includes a plane mirror, which is used to vertically deflect the laser beam emitted by the fiber laser pump source, and the plane mirror is placed at an angle of 45 degrees relative to the direction of the laser beam.

[0012] Optionally, it also includes an optical focusing coupling system, which is used to focus and collimate the laser beam emitted by the fiber laser pump source, and the focusing ratio of the optical focusing coupling system is 5:1.

[0013] Optionally, the fiber laser pump source uses a fiber laser with a wavelength of 1700 nm.

[0014] Optionally, a laser gain medium is also included, and the laser gain medium is used to generate and amplify laser.

[0015] Optionally, the laser gain medium is Tm, Ho: CaLYLO or Tm, Ho: CALGO crystal; wherein Tm 3+ The ion doping concentration is 5at.%, Ho 3+ The ion doping concentration is 0.5at.%.

[0016] Optionally, after passing through the first input mirror, the light is focused to the center of the laser gain medium, and then reflected to the third input mirror and the two-dimensional electro-optical modulation device in sequence through the second input mirror, and then reflected to the third input mirror, the second input mirror and the first input mirror in sequence through the two-dimensional electro-optical modulation device, and finally the laser beam is output through the output mirror.

[0017] The present invention also provides a method for preparing a two-dimensional Bi2O2Se electro-optical modulation device, which is used to prepare a two-dimensional electro-optical modulation device in a 2 µm band GHz solid mode-locked device based on electrical control, and the process includes: Transfer the prepared two-dimensional Bi2O2Se to the surface of the high-reflection end mirror; Design electrode structure, determine channel length, and etch source, drain, and gate based on electron beam lithography technology; After etching, 5 nm thick chromium and 50 nm thick gold were evaporated in a vacuum environment to form highly conductive electrodes; Boron nitride thin film was prepared by mechanical exfoliation and transferred to the surface of the electrode layer as an insulating layer; Graphene was transferred to the top gate position using ice-assisted transfer technology to serve as the top gate electrode.

[0018] Compared with the prior art, the present invention has the following advantages and technical effects: The present invention provides a 2 µm band GHz solid mode-locked device based on electric field control of two-dimensional Bi2O2Se saturation absorption. Two-dimensional Bi2O2Se is an excellent broadband saturable absorption material with a large nonlinear absorption coefficient, excellent air stability, ultrafast saturation recovery time and good Fermi level tunability. The saturation absorption parameters of two-dimensional Bi2O2Se can be precisely controlled by an external electric field to achieve high-performance 2 µm band GHz solid mode-locked laser output.

[0019] The present invention selects Tm, Ho: CaLYLO or Tm, Ho: CALGO crystal as the laser gain medium, which has a larger emission cross section and a wider emission spectrum. At the same time, a high-brightness fiber laser with a wavelength of 1700 nm is used as a pump source, which can improve the quantum efficiency and compress the mode area in the locked cavity.

[0020] The present invention optimizes the mode radius of the laser gain medium and the saturable absorber through the ABCD matrix, selects the classic X-type cavity as the mode-locked resonant cavity, and selects small-curvature concave mirrors for the first input mirror and the second input mirror and uses them as negative dispersion mirrors, which can reduce the oscillation laser mode in the gain medium and shorten the cavity length.

[0021] The device prepared by the present invention has the advantages of low saturation flux, fast saturation recovery time and moderate modulation depth, and effectively breaks through the existing technical barriers. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings: Figure 1 A schematic diagram of a solid mode-locking device based on Bi2O2Se saturation absorption according to an embodiment of the present invention; Figure numerals: 1. Fiber laser pump source; 2. Plane mirror; 3. Light focusing coupling system; 4. First input mirror; 5. Laser gain medium; 6. Second input mirror; 7. Third input mirror; 8. Two-dimensional electro-optical modulation device; 9. Output mirror. DETAILED DESCRIPTION

[0023] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0024] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0025] By regulating the Fermi level of two-dimensional materials through an external electric field, not only can the insertion loss of the device be effectively reduced, but also the dynamic process of photogenerated carriers and nonlinear absorption characteristics can be flexibly controlled, thereby achieving precise control of saturable absorption parameters (saturation recovery time, saturation flux, modulation depth). It is reported that two-dimensional Bi2O2Se is an excellent broadband saturable absorption material with a large nonlinear absorption coefficient, ultrafast saturation recovery time, good Fermi level tunability and air stability. Therefore, the use of an external electric field can accurately and dynamically control the saturable absorption parameters of two-dimensional Bi2O2Se, and its parameters are highly controllable, thus meeting the requirements of high-power 2 µm band solid GHz mode-locked femtosecond lasers for key modulation parameters of saturable absorption devices.

[0026] Based on the above technical conception, the present invention proposes a 2 µm band GHz solid mode-locked device based on electric field regulation of two-dimensional Bi2O2Se saturated absorption, develops a mode-locked element with flexibly adjustable modulation parameters, studies the formation mechanism of 2 µm band GHz mode-locked femtosecond pulses, overcomes key technologies such as solid mode-locked laser short cavity design, and realizes efficient and stable operation of 2 µm band GHz solid femtosecond laser.

[0027] like Figure 1 As shown, in this embodiment, a solid mode-locked device based on electric field regulation of two-dimensional Bi2O2Se saturation absorption is provided, including: A fiber laser pump source 1, used for emitting a laser beam; A mode-locked resonant cavity, comprising an input mirror assembly and a two-dimensional electro-optical modulation device 8, wherein the mode-locked resonant cavity is used to reflect and modulate the laser beam; The output mirror 9 is used to reflect the laser back into the resonant cavity for gain amplification and gradually output the modulated laser beam; Wherein, the two-dimensional electro-optical modulation device 8 is composed of two-dimensional Bi2O2Se, a graphene electrode, a boron nitride insulating layer and a gold electrode; The two-dimensional electro-optical modulation device 8 is used to adjust the Fermi level by applying an external electric field, thereby achieving precise control of the saturation absorption characteristics of the two-dimensional Bi2O2Se.

[0028] Specifically, it includes a high-brightness fiber laser pump source 1 for emitting a laser beam, a plane mirror 2 capable of vertically deflecting the laser, an optical focusing coupling system 3 for focusing and collimating the laser, a first input mirror 4 for transmitting and reflecting the focused laser beam, a gain medium 5 for generating and amplifying the laser beam, a second input mirror 6 and a third input mirror 7 for reflecting the focused laser beam, and a two-dimensional electro-optical modulation device 8 for modulating the reflected laser beam. The laser resonant cavity of the high-brightness fiber laser pump source 1 adopts an X-type resonant cavity, the laser gain medium 5 is Tm, Ho:CaLYLO or Tm, Ho:CALGO crystal, the two-dimensional electro-optical modulation device 8 is Bi2O2Se material, and the plane mirror is placed at an angle of 45 degrees.

[0029] The laser further comprises an output mirror 9, which is used to output the target laser beam.

[0030] As an optional implementation, the input mirror group includes a first input mirror 4, a second input mirror 6 and a third input mirror 7; Among them, the laser beam can be input to the two-dimensional electro-optical modulation device 8 along the first input mirror 4, the second input mirror 6 and the third input mirror 7 in sequence, and the laser beam reflected by the two-dimensional electro-optical modulation device 8 can be input to the output mirror 9 along the third input mirror 7, the second input mirror 6 and the first input mirror 4 in sequence to output the laser beam.

[0031] As an optional implementation, the first input mirror 4 and the second input mirror 6 are both concave mirrors with a curvature radius of 50 mm and negative dispersion mirrors, and the third input mirror 7 is a concave mirror with a curvature radius of 100 mm.

[0032] Specifically, the first input mirror 4 and the second input mirror 6 are both concave mirrors with a curvature radius of 50 mm, and the coating parameters are: AR@1700 nm and 1900-2200 nm@HR. The third input mirror 7 is a concave mirror with a curvature radius of 100 mm, and the coating parameters are: AR@1700 nm and 1900-2200 nm@HR. The output mirror 9 has a transmittance of 0.5% for 1900-2200 nm laser.

[0033] As an optional implementation, it further includes a plane mirror 2, which is used to vertically deflect the laser beam emitted by the fiber laser pump source 1, and the plane mirror 2 is placed at an angle of 45 degrees relative to the direction of the laser beam.

[0034] As an optional implementation, it further includes an optical focusing coupling system 3, which is used to focus and collimate the laser beam emitted by the fiber laser pump source 1, and the focusing ratio of the optical focusing coupling system 3 is 5:1.

[0035] As an optional implementation, the fiber laser pump source 1 adopts a 1700 nm fiber laser.

[0036] Specifically, the central wavelength of the fiber laser pump source 1 is 1700 nm, and the focusing ratio of the optical focusing coupling system 3 is 5: 1. Considering the absorption loss of water vapor at 1900 nm and the thermal effect of the gain medium, this embodiment selects a laser gain medium 5 with an emission wavelength greater than 2000 nm, a large emission cross section, and a wide emission spectrum, and uses a high-brightness fiber laser with a wavelength of 1700 nm as a pump source to improve quantum efficiency and compress the mode area in the locked cavity.

[0037] As an optional implementation, it further comprises a laser gain medium 5, wherein the laser gain medium 5 is used to amplify the emitted laser light beam.

[0038] As an optional embodiment, the laser gain medium 5 is Tm, Ho: CaLYLO or Tm, Ho: CALGO crystal; wherein Tm 3+ The ion doping concentration is 5at.%, Ho 3+ The ion doping concentration is 0.5at.%.

[0039] As an optional embodiment, the light is focused to the center of the laser gain medium 5 after passing through the first input mirror 4, and then reflected to the third input mirror 7 and the two-dimensional electro-optical modulation device 8 in sequence through the second input mirror 6, and then reflected to the third input mirror 7, the second input mirror 6 and the first input mirror 4 in sequence through the two-dimensional electro-optical modulation device 8, and finally the laser beam is output through the output mirror 9.

[0040] Specifically, the laser emitted by the fiber laser pump source 1 is vertically reflected by the 45-degree plane mirror 2, focused and collimated by the optical focusing coupling system 3, and concentrated to the center of the laser gain medium 5 after passing through the first input mirror 4, and then reflected to the third input mirror 7 and the two-dimensional electro-optical modulation device 8 in sequence through the second input mirror 6, and then reflected to the third input mirror 7, the second input mirror 6 and the first input mirror 4 in sequence through the two-dimensional electro-optical modulation device 8, and finally the laser beam is output through the output mirror 9.

[0041] The present invention also provides a method for preparing a two-dimensional Bi2O2Se electro-optical modulation device, which is used to prepare a two-dimensional electro-optical modulation device in a 2 µm band GHz solid mode-locked device based on electrical control, and the process includes: Transfer the prepared two-dimensional Bi2O2Se to the surface of the high-reflection end mirror; Design electrode structure, determine channel length, and etch source, drain, and gate based on electron beam lithography technology; After etching, 5 nm thick chromium and 50 nm thick gold were evaporated in a vacuum environment to form highly conductive electrodes; Boron nitride thin film was prepared by mechanical exfoliation and transferred to the surface of the electrode layer as an insulating layer; Graphene was transferred to the top gate position using ice-assisted transfer technology to serve as the top gate electrode.

[0042] As an additional implementation manner, the two-dimensional electro-optical modulation device 8 is a two-dimensional Bi2O2Se electro-optical modulation device.

[0043] During the experiment, the prepared two-dimensional Bi2O2Se was first transferred to the high-reflection end mirror, and then the appropriate electrode structure and channel length were designed. Then, the source, drain and gate were etched using electron beam exposure technology, 5 nm of chromium and 50 nm of gold were evaporated in a vacuum environment, and boron nitride was prepared as the insulating layer material by mechanical stripping and transferred to the device through a transfer table. In addition, in order to reduce the loss of incident light by the gold electrode, CVD-grown graphene was selected as the top gate electrode, and transferred through an ice-assisted scheme to prepare a two-dimensional electro-optical modulation device 8.

[0044] In this embodiment, the saturable absorption parameters of the two-dimensional Bi2O2Se are precisely and dynamically controlled by means of an external electric field, and the position and angle of the two-dimensional electro-optical modulation device 8 and the output mirror 9 are adjusted, so as to achieve a mode-locked laser output with a repetition frequency ≥1 GHz, an average power ≥300 mW and a pulse width ≤50 fs.

[0045] In this embodiment, the prepared two-dimensional Bi2O2Se is first transferred to the high-reflection end mirror. This step uses a precision transfer table to peel the Bi2O2Se from the original substrate and ensure that it is intactly attached to the surface of the high-reflection end mirror to ensure its good optical properties. In this process, Bi2O2Se, as a saturated absorption material, can provide excellent nonlinear absorption performance in subsequent electro-optical modulation.

[0046] Next, design a suitable electrode structure, including the source, drain and gate, and determine the channel length. The design of these electrode structures will affect the electrical performance of the device. In particular, the adjustment of the channel length can control the migration speed of electrons, thereby optimizing the response time and regulation ability of the device. After the design is completed, the source, drain and gate are precisely etched using electron beam lithography technology to form the required electrode structure. Electron beam lithography can control the generation of patterns at the nanoscale to ensure the accuracy of electrodes and channels.

[0047] Subsequently, an evaporation process is carried out in a vacuum environment, first evaporating 5 nm thick chromium as an adhesion layer, and then evaporating 50 nm thick gold to form a highly conductive electrode structure. The role of chromium is to ensure good adhesion between the metal layer and the substrate, while gold has excellent conductivity.

[0048] In order to achieve good light transmittance and ensure the gate voltage regulation effect, this embodiment uses boron nitride with a large dielectric constant as the insulating layer material. Boron nitride is prepared by mechanical stripping and accurately transferred to the device using a transfer table. The large dielectric constant of boron nitride can broaden the tuning range of the two-dimensional Bi2O2Se Fermi level, and good light transmittance helps to reduce the loss of the electro-optical modulation device.

[0049] In the next step, in order to reduce the loss of incident light by the gold electrode, this embodiment uses graphene as the top gate electrode. Graphene not only has excellent conductivity, but also has extremely high light transmittance, which can reduce light absorption loss and improve the photoelectric conversion efficiency of the device. Through ice-assisted transfer technology, graphene is accurately transferred to the specified position of the device, ensuring its good match with other structures.

[0050] Through the above steps, a two-dimensional electro-optical modulator was successfully prepared. In this example, by developing a two-dimensional Bi2O2Se electro-optical modulator with low saturation flux, fast recovery time and moderate modulation depth, high-performance 2 µm-band GHz solid-state mode-locked laser operation was finally achieved. This laser is suitable for high-speed optical communications, ultrafast lasers and other application scenarios.

[0051] According to the above specific implementations, the technical effects of the present invention can be summarized as follows: High-efficiency optical modulation performance: By using the two-dimensional material Bi2O2Se as a saturated absorber, it has excellent nonlinear absorption characteristics. By regulating its Fermi level with an external electric field, the parameters of saturated absorption can be flexibly adjusted to achieve efficient modulation of the saturated absorption characteristics of two-dimensional Bi2O2Se, and finally achieve 2 µm band GHz solid-state mode-locked laser operation. This laser meets the needs of high-speed optical communications and precision laser processing.

[0052] Low loss, high light transmittance: In order to reduce the loss of incident light by the electrode and the insulating layer, the present invention uses transparent and highly conductive graphene as the top gate electrode, and uses boron nitride with a large dielectric constant as the insulating layer. Compared with the traditional metal electrode and insulating layer SiO2, the use of graphene and boron nitride greatly reduces the light absorption loss, thereby improving the overall photoelectric conversion efficiency. This allows the device to maintain low energy loss when working with high-power lasers.

[0053] Flexible and adjustable saturation absorption parameters: By using an external electric field to control the two-dimensional Bi2O2Se, the saturation absorption parameters of the two-dimensional Bi2O2Se can be flexibly adjusted to adapt to different laser resonant cavity types. The flexible output parameters of the laser have strong adjustability.

[0054] In summary, the present invention significantly improves the optical control performance and stability of the mode-locked modulator, and by optimizing the device structure and materials, successfully breaks through the technical barrier of 2 µm band GHz solid mode locking, making it suitable for application scenarios such as large-capacity free-space optical communications and precision laser processing.

[0055] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A 2 µm band GHz solid mode-locked device based on electrical control, characterized in that: include: A fiber laser pump source (1) for emitting a laser beam; A mode-locked resonant cavity, comprising an input mirror group and a two-dimensional electro-optical modulation device (8), wherein the mode-locked resonant cavity is used to reflect and modulate the laser beam; An output mirror (9) is used to reflect the laser light back into the resonant cavity for gain amplification and partially output a modulated laser light beam; Wherein, the two-dimensional electro-optical modulation device (8) is composed of two-dimensional Bi2O2Se, a graphene electrode, a boron nitride insulating layer and a gold electrode; The two-dimensional electro-optical modulation device (8) is used to control the Fermi level of two-dimensional Bi2O2Se by applying an external electric field, thereby realizing the control of the saturation absorption characteristics of the two-dimensional Bi2O2Se.

2. The device according to claim 1, characterized in that The input mirror group comprises a first input mirror (4), a second input mirror (6) and a third input mirror (7); The laser beam can be sequentially input to the two-dimensional electro-optical modulation device (8) along the first input mirror (4), the second input mirror (6) and the third input mirror (7), and the laser beam reflected by the two-dimensional electro-optical modulation device (8) can be sequentially input to the output mirror (9) along the third input mirror (7), the second input mirror (6) and the first input mirror (4) to output the laser beam.

3. The device according to claim 2, characterized in that The first input mirror (4) and the second input mirror (6) are both concave mirrors with a curvature radius of 50 mm and are negative dispersion mirrors, and the third input mirror (7) is a concave mirror with a curvature radius of 100 mm.

4. The device according to claim 1, characterized in that It also comprises a plane mirror (2), which is used to vertically deflect the laser beam emitted by the fiber laser pump source (1), and the plane mirror (2) is placed at an angle of 45 degrees relative to the direction of the laser beam.

5. The device according to claim 1, characterized in that It also comprises an optical focusing coupling system (3), wherein the optical focusing coupling system (3) is used to focus and collimate the laser beam emitted by the optical fiber laser pump source (1), and the focusing ratio of the optical focusing coupling system (3) is 5:

1.

6. The device according to claim 1, characterized in that The fiber laser pump source (1) adopts a fiber laser with a wavelength of 1700 nm.

7. The device according to claim 2, characterized in that It also includes a laser gain medium (5), wherein the laser gain medium (5) is used to generate and amplify a laser beam.

8. The device according to claim 7, characterized in that The laser gain medium (5) is Tm, Ho: CaLYLO or Tm, Ho: CALGO crystal; wherein Tm 3+ The ion doping concentration is 5at.%, Ho 3+ The ion doping concentration is 0.5at.%.

9. The device according to claim 7, characterized in that After passing through the first input mirror (4), the light is focused to the center of the laser gain medium (5), and then is reflected in sequence to the third input mirror (7) and the two-dimensional electro-optical modulation device (8) through the second input mirror (6), and then is reflected in sequence to the third input mirror (7), the second input mirror (6) and the first input mirror (4) through the two-dimensional electro-optical modulation device (8), and finally the laser beam is output through the output mirror (9).

10. A method for preparing a two-dimensional Bi2O2Se electro-optical modulation device, characterized in that: A process for preparing a two-dimensional electro-optical modulation device in a 2 µm band GHz solid mode-locked device based on electrical control as described in any one of claims 1 to 9, comprising: Transfer the prepared two-dimensional Bi2O2Se to the surface of the high-reflection end mirror; Design electrode structure, determine channel length, and etch source, drain, and gate based on electron beam lithography technology; After etching, 5 nm thick chromium and 50 nm thick gold were evaporated in a vacuum environment to form highly conductive electrodes; Boron nitride thin film was prepared by mechanical exfoliation and transferred to the surface of the electrode layer as an insulating layer; Graphene was transferred to the top gate position using ice-assisted transfer technology to serve as the top gate electrode.

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