Bi2Te3 / Sb2Te3-based saturable absorber and all-solid-state passive Q-switched mode-locked pulse laser

Abstract

The invention discloses a saturable absorber based on Bi2Te3 / Sb2Te3 and an all-solid-state passive Q-switched mode-locked pulse laser based on Bi2Te3 / Sb2Te3. The structure of the saturable absorber based on Bi2Te3 / Sb2Te3 comprises a substrate and a saturable absorption layer arranged on the surface of the substrate, wherein the saturable absorption layer comprises a polymer matrix and a Bi2Te3 / Sb2Te3 transverse heterojunction material. According to the invention, the thermal stability and the mechanical strength of Bi2Te3 / Sb2Te3 can be effectively improved. In an all-solid-state laser, a saturable absorber based on a Bi2Te3 / Sb2Te3 transverse heterojunction material is used as a Q-switched mode-locked starting element, stable passive Q-switched mode-locked laser operation with the wavelength of 1064 nm is achieved, and obtained pulse laser output has high peak power, narrow pulse width, excellent light beam quality and high stability.

Description

Technical Field

[0001] The present invention relates to the technical field of laser devices, and in particular to a saturable absorber based on Bi2Te3 / Sb2Te3 and an all-solid-state passively Q-switched mode-locked pulse laser. Background Art

[0002] In recent years, pulsed lasers have been widely used in scientific research, industrial processing, medical treatment and other fields. In particular, the performance of pulsed lasers is particularly important in high-demand applications such as high-precision processing and medical imaging. In order to achieve high peak power, narrow pulse width and high stability of laser output, saturable absorber (SA) as a key component of Q-switched mode-locked lasers has received widespread attention.

[0003] Traditionally, saturable absorbers based on a single material, such as the single topological insulator Bi2Te3, have achieved pulsed laser output to a certain extent, but they have some significant disadvantages. For example, the saturation absorption efficiency of a single material is low, the thermal stability and mechanical strength are insufficient, and it is easy to deform or damage during high-power laser operation, thus limiting its wide application in high-performance pulsed lasers. In addition, the Q-switching and mode-locking performance of a single material is limited and cannot meet the stringent requirements of certain high-precision applications for laser performance.

[0004] In order to overcome these shortcomings, researchers began to explore the application of composite materials and heterojunction materials. Heterojunction materials can improve the stability and strength of materials while optimizing nonlinear optical properties by combining the advantages of different materials. For example, Bi2Te3 / Sb2Te3 heterojunction material has become an ideal saturable absorber due to its excellent nonlinear optical properties and high saturation absorption efficiency. However, relying solely on Bi2Te3 / Sb2Te3 heterojunction materials still faces problems such as large material scattering losses and particle agglomeration, resulting in insufficient optical performance. At the same time, the stability and mechanical strength of the individual Bi2Te3 / Sb2Te3 heterojunction materials also need to be improved. Summary of the invention

[0005] The purpose of the present invention is to overcome the above technical deficiencies, propose a saturable absorber based on Bi2Te3 / Sb2Te3 and an all-solid-state passively Q-switched mode-locked pulsed laser, and solve the problems in the prior art based on Bi2Te3. e3 There are still technical issues to be improved in the performance of the saturable absorber of / Sb2Te3 heterojunction materials.

[0006] In the first aspect, the present invention provides a saturable absorber based on Bi2Te3 / Sb2Te3, whose structure includes: a substrate and a saturable absorption layer arranged on the surface of the substrate; wherein the saturable absorption layer includes: a polymer matrix and a Bi2Te3 / Sb2Te3 lateral heterojunction material, and the Bi2Te3 / Sb2Te3 lateral heterojunction material is doped in the polymer matrix; the Bi2Te3 / Sb2Te3 lateral heterojunction material has a lateral heterostructure with Bi2Te3 in the middle and Sb2Te3 around.

[0007] In a second aspect, the present invention provides a method for preparing a saturable absorber based on Bi2Te3 / Sb2Te3, comprising the following steps: Dispersing Bi2Te3 / Sb2Te3 lateral heterojunction material and polymer in an organic solvent to obtain a film-forming solution; The film-forming liquid is coated on the surface of the substrate, and after drying, a saturable absorber of Bi2Te3 / Sb2Te3 is obtained.

[0008] In a third aspect, the present invention provides an all-solid-state passively Q-switched mode-locked pulse laser, comprising a pump source, an optical fiber, a coupling system, an input mirror, a laser gain medium, a first reflector, a second reflector, a saturable absorber, and an output mirror connected in sequence; wherein the input mirror, the first reflector, the second reflector, and the output mirror together constitute a resonant cavity; the saturable absorber is a saturable absorber based on Bi2Te3 / Sb2Te3 provided in one aspect of the present invention.

[0009] Compared with the prior art, the beneficial effects of the present invention include: The present invention uses Bi2Te3 / Sb2Te3 lateral heterojunction material as the core material of the saturable absorber and dopes it into a polymer matrix. The combination of the two can effectively improve the thermal stability and mechanical strength of Bi2Te3 / Sb2Te3. In the all-solid-state laser, a saturable absorber based on Bi2Te3 / Sb2Te3 lateral heterojunction material is used as a Q-switched mode-locked starting element to achieve stable passive Q-switched mode-locked laser operation with a wavelength of 1064 nm. The obtained pulsed laser output has high peak power and narrow pulse width, excellent beam quality and high stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 AFM images of the saturable absorber based on Bi2Te3 / Sb2Te3 of the present invention; (a) is comparative example 1, and (b) is example 1; Figure 2 is the near-infrared nonlinear transmittance curve of Sb2Te3 used in the present invention; Figure 3 is the near-infrared nonlinear transmittance curve of Bi2Te3 used in the present invention; Figure 4 is the near-infrared nonlinear transmittance curve of Bi2Te3 / Sb2Te3 used in the present invention; Figure 5 Schematic diagram of the structure of the all-solid-state passively Q-switched mode-locked pulse laser in Example 2 of the present invention; wherein 1 is a pump source, 2 is an optical fiber, 3 is a coupling system, 4 is an input mirror, 5 is a laser gain medium, 6 is a first reflector, 7 is a second reflector, 8 is a saturable absorber, 9 is an output mirror, 10 is a power meter, 11 is a photodiode, and 12 is an oscilloscope; Figure 6 This is a spectrum diagram of the all-solid-state passively Q-switched mode-locked pulse laser in Example 2 of the present invention; Figure 7 is a graph showing the relationship between the average output power and the pulse energy of the Q-switched envelope of the all-solid-state passively Q-switched mode-locked pulse laser and the pump power in Example 2 of the present invention; Figure 8 This is a pulse sequence diagram of the all-solid-state passively Q-switched mode-locked pulse laser in Example 2 of the present invention, with a scanning time of 10 μs; Fig. 9 : is a pulse sequence diagram of the all-solid-state passively Q-switched mode-locked pulse laser in Example 2 of the present invention, with a scanning time of 500 ns; Fig.10 This is a pulse sequence diagram of the all-solid-state passively Q-switched mode-locked pulse laser in Example 2 of the present invention, with a scanning time of 20ns; Fig.11 This is a laser beam quality diagram of the all-solid-state passively Q-switched mode-locked pulse laser in Example 2 of the present invention; Fig.12 2D and 3D intensity diagrams of the laser beam of the all-solid-state passively Q-switched mode-locked pulse laser in Example 2 of the present invention. DETAILED DESCRIPTION

[0011] In order to make the purpose, technical solution 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.

[0012] In the first aspect, the present invention provides a saturable absorber based on Bi2Te3 / Sb2Te3, whose structure includes: a substrate and a saturable absorption layer arranged on the surface of the substrate; wherein the saturable absorption layer includes: a polymer matrix and a Bi2Te3 / Sb2Te3 lateral heterojunction material, and the Bi2Te3 / Sb2Te3 lateral heterojunction material is doped in the polymer matrix; the Bi2Te3 / Sb2Te3 lateral heterojunction material has a lateral heterostructure with Bi2Te3 in the middle and Sb2Te3 around.

[0013] The present invention uses Bi2Te3 / Sb2Te3 lateral heterojunction material as the core material of the saturable absorber and dopes it into a polymer matrix, which not only maintains the excellent optical properties of Bi2Te3 / Sb2Te3 lateral heterojunction material (including pulsed laser output with high peak power and narrow pulse width), but also significantly improves the stability and durability of the material, better meeting the needs of high-performance pulsed laser applications. This innovation solves the limitations of saturable absorbers based on traditional single materials and broadens their application prospects in high-performance pulsed lasers.

[0014] In this embodiment, the material of the polymer matrix is ​​polymethyl methacrylate (PMMA).

[0015] Specifically, the molecular weight of polymethyl methacrylate is 10,000-50,000, and further 30,000.

[0016] The present invention does not limit the preparation method of Bi2Te3 / Sb2Te3 lateral heterojunction material, and those skilled in the art can make a choice according to actual conditions. In some specific embodiments of the present invention, the Bi2Te3 / Sb2Te3 lateral heterojunction material is formed by epitaxially growing Sb2Te3 lateral to form a Bi2Te3 / Sb2Te3 lateral heterostructure by a two-step solvothermal method using Bi2Te3 as a template. The specific steps are as follows: Dissolve the Bi source, the first Te source, the first reducing agent, and the first surfactant in the first solvent, and then perform a first solvothermal reaction to obtain a Bi2Te3 suspension; wherein the molar ratio of Bi to Te in the Bi source and the first Te source is 1:(1.4-1.6), further 1:1.5; the molar ratio of the Bi source to the reducing agent is 1:(8-12), further 1:10; the molar ratio of the Bi source to the first surfactant is 1:(0.01-0.015); the dosage ratio of the Bi source to the first solvent is (0.1-0.2) g:1L; the temperature of the first solvothermal reaction is 195-205°C, further 200°C; the time of the first solvothermal reaction is 10-14h, further 12h; The Sb source, the second Te source, the second reducing agent and the second surfactant are dissolved in the second solvent, and then mixed evenly with the Bi2Te3 suspension, a second solvent thermal reaction is carried out, and a Bi2Te3 / Sb2Te3 lateral heterojunction material is obtained after washing and drying; wherein, the molar ratio of Sb to Te in the Sb source and the second Te source is 1:(1.4-1.6), further 1:1.5; the molar ratio of the Sb source to the second reducing agent is 1:(8-12), further 1:10; the molar ratio of the Sb source to the second surfactant is 1:(0.01-0.015); the amount ratio of the Sb source to the second solvent is (0.1-0.2) g:1L; the temperature of the second solvent thermal reaction is 195-205°C, further 200°C; the time of the second solvent thermal reaction is 14-18h, further 16h; the washing method is repeated washing with deionized water and anhydrous ethanol.

[0017] More specifically, the molar ratio of Bi to Sb in the Bi source and the Sb source is 1:(3-5), and further 1:4.

[0018] More specifically, the Bi source is at least one of bismuth chloride, bismuth nitrate, and bismuth oxide.

[0019] More specifically, the Sb source is at least one of antimony chloride, potassium antimony tartrate, and antimony oxide.

[0020] More specifically, the first Te source and the second Te source are at least one of elemental tellurium, Na2TeO3, and K2TeO3.

[0021] More specifically, the first reducing agent and the second reducing agent are at least one of hydrazine hydrate, ammonia water, sodium hydroxide, hydroxylamine, and ethylenediamine.

[0022] More specifically, the first surfactant and the second surfactant are at least one of cetyltrimethylammonium bromide (CTAB), sodium dodecylbenzene sulfonate (SDBS), and polyvinylpyrrolidone (PVP).

[0023] More specifically, the first solvent and the second solvent are at least one of ethylene glycol, water, and isopropanol.

[0024] In this embodiment, the Bi2Te3 / Sb2Te3 lateral heterojunction material accounts for 0.1-1% of the mass of the polymer matrix, and further 0.4%.

[0025] In this embodiment, the thickness of the saturable absorption layer is 200-350 nm.

[0026] In this embodiment, the substrate is quartz glass.

[0027] In a second aspect, the present invention provides a method for preparing a saturable absorber based on Bi2Te3 / Sb2Te3, comprising the following steps: S1, dispersing Bi2Te3 / Sb2Te3 lateral heterojunction material and polymer into an organic solvent to obtain a film-forming solution; S2. Apply the film-forming liquid to the surface of the substrate, and obtain a saturable absorber of Bi2Te3 / Sb2Te3 after drying.

[0028] In this implementation, step S1 includes: S11, dispersing the Bi2Te3 / Sb2Te3 lateral heterojunction material into a first organic solvent to obtain a Bi2Te3 / Sb2Te3 dispersion; S12, dispersing the polymer in a second organic solvent to obtain a polymer solution; S13, uniformly mix the Bi2Te3 / Sb2Te3 dispersion and the polymer solution to obtain a film-forming solution.

[0029] Specifically, the concentration of the Bi2Te3 / Sb2Te3 dispersion is 0.4-0.6 mg / mL.

[0030] Specifically, the first organic solvent is at least one of ethanol, toluene, dichloromethane and acetone.

[0031] Specifically, Bi2Te3 / Sb2Te3 is ultrasonically dispersed into the first organic solvent by ultrasonic dispersion.

[0032] More specifically, during the ultrasonic dispersion process, the ultrasonic dispersion time is 2-6 hours, further 2 hours.

[0033] Specifically, the second organic solvent is at least one of ethanol, toluene, dichloromethane and acetone.

[0034] Specifically, the mass fraction of the polymer solution is 4-6%, more specifically 5%.

[0035] Specifically, the polymer is dispersed in the second organic solvent by stirring and dispersing.

[0036] More specifically, during the stirring and dispersing process, the temperature is 50-70° C., further 60° C.; the stirring time is 2-6 h, further 2 h.

[0037] Specifically, the volume ratio of the Bi2Te3 / Sb2Te3 dispersion to the polymer solution is 1:(1-3), specifically 1:2.

[0038] In this embodiment, in step S2, the film-forming liquid is applied to the surface of the substrate by spin coating.

[0039] Specifically, during the spin coating process, the rotation speed of the coating machine is 800-2000 rpm, and the spin coating time is 10-30s.

[0040] In this embodiment, the drying temperature is room temperature, and the drying time is 6-12 h.

[0041] In a third aspect, the present invention provides an all-solid-state passively Q-switched mode-locked pulse laser, comprising a pump source 1, an optical fiber 2, a coupling system 3, an input mirror 4, a laser gain medium 5, a first reflector 6, a second reflector 7, a saturable absorber 8, and an output mirror 9 which are sequentially connected; wherein the input mirror 4, the first reflector 6, the second reflector 7 and the output mirror 9 together constitute a resonant cavity; the saturable absorber 8 is a saturable absorber based on Bi2Te3 / Sb2Te3 provided in one aspect of the present invention.

[0042] The present invention uses the above-mentioned Bi2Te3 / Sb2Te3-based saturable absorber as a Q-switched mode-locked starting element in an all-solid-state laser, based on a Z-cavity structure, to achieve stable passive Q-switched mode-locked laser operation with a wavelength of 1064 nm. The obtained pulsed laser output has high peak power and narrow pulse width, excellent beam quality, and high stability, which solves the problem that the saturated absorption efficiency of a single material is low and the Q-switched mode-locked performance is limited, which limits its wide application in high-performance pulsed lasers. The introduction of this lateral heterojunction material provides new ideas and options for the design of lasers and other optoelectronic devices, and helps promote the development and application of related technologies.

[0043] In the present invention, the pump light is input into the laser gain medium 5 through the coupling system 3 and the input mirror 4, and then reflected by the first reflector 6 and the second reflector 7 in sequence, passes through the saturable absorber 8, and finally outputs the Q-switched mode-locked laser through the output mirror 9.

[0044] In this embodiment, the pump source 1 is a fiber-coupled output laser diode, and the central wavelength of the pump source is 808 nm.

[0045] In this embodiment, the input mirror 4 is a concave mirror with a curvature radius of 50-150 mm, specifically 100 mm; the end of the input mirror 4 away from the pump source is coated with a high-reflection film with an output wavelength of 1064 nm, and the end close to the pump source is coated with an anti-reflection film with a pump center wavelength of 808 nm.

[0046] In this embodiment, the laser gain medium 5 is a neodymium-doped yttrium vanadate (Nd:YVO4) crystal, specifically 0.1-0.5 at.% Nd:YVO4 crystal, more specifically 0.3 at.% Nd:YVO4 crystal.

[0047] In this embodiment, the first reflector 6 and the second reflector 7 are both plane mirrors, and the mirror surfaces are coated with a 1064 nm high-reflection film.

[0048] In this embodiment, the output mirror 9 is a plane mirror, and its transmittance to the 1064nm wavelength laser is 2-5%, specifically 3%.

[0049] In this embodiment, the resonant cavity adopts a Z-shaped cavity, and the total cavity length is about 45-60 cm, specifically 52 cm.

[0050] In this embodiment, the all-solid-state passively Q-switched mode-locked pulse laser further includes: a power meter 10, a photodiode 11 and an oscilloscope 12; wherein the output mirror 9 is connected to the power meter 10 and the photodiode 11 respectively, and the photodiode 11 is connected to the oscilloscope 12.

[0051] In the present invention, the output power of the Q-switched mode-locked laser outputted through the output mirror 9 is measured by a power meter, and a laser pulse signal is obtained through a photodiode 11 and an oscilloscope 12 .

[0052] To avoid redundancy, in the following embodiments and comparative examples of the present invention, the preparation methods of Bi2Te3 / Sb2Te3 lateral heterojunction material, Bi2Te3 single material, and Sb2Te3 single material are as follows: Preparation of Bi2Te3 / Sb2Te3 lateral heterojunction materials: (1) Pour 315 mg of bismuth chloride, 332 mg of sodium tellurite, 400 mg of sodium hydroxide and 500 mg of polyvinyl pyrrolidone (PVPK-30) into a beaker and add 40 ml of ethylene glycol. Stir until completely dissolved. Transfer the precursor solution into the polytetrafluoroethylene liner (specification 50 ml) of the high-pressure reactor with a filling degree of 80%. Place the reactor in a 200 °C drying oven and react at a constant temperature for 12 hours to obtain a Bi2Te3 suspension. After the reaction is completed and cooled to room temperature, it is set aside without any treatment.

[0053] (2) Pour 228 mg of antimony chloride, 332 mg of sodium tellurite, 400 mg of sodium hydroxide, and 500 mg of polyvinyl pyrrolidone (PVPK-30) into a beaker and add 32 mL of ethylene glycol. Stir until completely dissolved.

[0054] (3) Take 8 mL of the Bi2Te3 suspension from step (1), mix it with the solution from step (2), stir it ultrasonically for 0.5 hours, transfer it into the polytetrafluoroethylene liner (specification 50 ml) of the high-pressure reactor, and fill it to 80%. Place the reactor in a drying oven at 200°C and react at constant temperature for 16 hours to obtain a Bi2Te3 / Sb2Te3 lateral heterojunction suspension. The suspension is repeatedly washed with deionized water and anhydrous ethanol for 3-5 times, and vacuum dried to obtain a black powder.

[0055] Preparation of Bi2Te3 single material: Pour 315 mg of bismuth chloride, 332 mg of sodium tellurite, 400 mg of sodium hydroxide and 500 mg of polyvinyl pyrrolidone (PVP K-30) into a beaker and add 40 ml of ethylene glycol, stir until completely dissolved, transfer the precursor solution into the polytetrafluoroethylene liner (specification 50 ml) of the high-pressure reactor, with a filling degree of 80%, place the reactor in a 200 ° C drying oven, and react at a constant temperature for 12 hours to obtain a Bi2Te3 suspension. The suspension was repeatedly washed with deionized water and anhydrous ethanol for 3-5 times, and vacuum dried to obtain Bi2Te3 powder.

[0056] Preparation of Sb2Te3 single material: Pour 228 mg of antimony chloride, 332 mg of sodium tellurite, 400 mg of sodium hydroxide, and 500 mg of polyvinyl pyrrolidone (PVPK-30) into a beaker and add 40 mL of ethylene glycol, stir until completely dissolved, transfer the precursor solution into the polytetrafluoroethylene liner of a 50 mL high-pressure reactor with a filling degree of 80%, place the reactor in a 200 ° C drying oven, and react at a constant temperature for 16 hours to obtain a Sb2Te3 suspension. The suspension was repeatedly washed with deionized water and anhydrous ethanol for 3-5 times, and vacuum dried to obtain Sb2Te3 powder.

[0057] Example 1 This embodiment provides a method for preparing a saturable absorber based on Bi2Te3 / Sb2Te3, comprising the following steps: (1) Bi2Te3 / Sb2Te3 powder was dispersed in ethanol at a concentration of 0.4 mg / mL, and a Bi2Te3 / Sb2Te3 dispersion was obtained after ultrasonic treatment for 2 h. (2) Dissolve PMMA with a molecular weight of 30,000 in toluene, control the mass fraction to 5%, heat and stir at 60 °C for 2 h until it becomes clear, and obtain a PMMA toluene solution; (3) uniformly mixing the Bi2Te3 / Sb2Te3 dispersion obtained in step (1) and the PMMA toluene solution obtained in step (2) in a volume ratio of 1:2 to obtain a mixed solution; (4) The mixed solution obtained in step (3) is spin-coated at 2000 rpm for 15 s to form a film, and dried at room temperature to obtain a saturable absorber based on Bi2Te3 / Sb2Te3; wherein the substrate is quartz glass.

[0058] Comparative Example 1 The only difference from Example 1 is that the Bi2Te3 / Sb2Te3 dispersion obtained in step (1) is spin-coated at 2000 rpm for 15 s to form a film.

[0059] See also Figure 1 , Figure 1 AFM images of saturable absorbers based on Bi2Te3 / Sb2Te3; (a) is Comparative Example 1, and (b) is Example 1. Figure 1 It can be seen that if Bi2Te3 / Sb2Te3 is not mixed with PMMA, the coverage of nanosheets on the surface of the saturable absorber is relatively low and uneven, which greatly reduces its optical performance; on the surface of the saturable absorber prepared by mixing Bi2Te3 / Sb2Te3 with PMMA, nanosheets can be observed to overlap to form a large-size film with a thickness of about 200-350 nm and a surface coverage of more than 80%. The thickness of a single heterostructure nanosheet is about 25 nm.

[0060] See also Figure 2-4 , Figure 2-4 The near-infrared nonlinear transmittance curves of Sb2Te3, Bi2Te3, and Bi2Te3 / Sb2Te3 used in the present invention are shown respectively. Figure 2-4 It can be seen that Bi2Te3 / Sb2Te3 is beneficial to the increase of modulation depth and saturation intensity due to the synergistic effect between different materials, and optimizes the saturable absorption performance.

[0061] Example 2 This embodiment provides an all-solid-state passively Q-switched mode-locked pulse laser, specifically: a saturable absorber based on Bi2Te3 / Sb2Te3 is set in the resonant cavity of the all-solid-state laser to form an all-solid-state passively Q-switched mode-locked pulse laser, and its structure is as follows: Figure 5 As shown. Among them, the pump source 1 is a fiber-coupled output laser diode with a central wavelength of 808 nm, and the gain medium 5 is a 0.3 at.% Nd: YVO4 crystal. The first reflector 6, the second reflector 7 and the output mirror 9 are plane mirrors. The first reflector 6 and the second reflector 7 are coated with a 1064nm high-reflection film, and the saturable absorber 8 is through Bi2T e3 / Sb2Te3-PMMA is deposited on the surface of quartz glass. The transmittance of output mirror 9 to 1064nm laser is 3%. Input mirror 4 is a concave mirror with a radius of curvature of 100mm. One end is coated with a high-reflection film with an output wavelength of 1064nm, and the other end is coated with an anti-reflection film with a pump center wavelength of 808nm. The total length of the resonant cavity is about 52 cm. The pump light is incident into the crystal through a coupling system. Using a Bi2T e3The saturable absorber of / Sb2Te3 realizes the Q-switched mode-locking characteristics of Nd:YVO4 laser with high peak power, narrow pulse width, excellent beam quality and high stability. The test results are as follows Figure 6-11 .

[0062] See also Figure 6 , Figure 6 This is a spectrum diagram of the all-solid-state passively Q-switched mode-locked pulse laser in Example 2 of the present invention. Figure 6 It can be seen that the central wavelength of the pulsed laser is at 1064 nm.

[0063] See also Figure 7 , Figure 7 The figure is a graph showing the relationship between the average output power and pulse energy of the Q-switched envelope of the all-solid-state passively Q-switched mode-locked pulse laser and the pump power in Example 2 of the present invention. Figure 7 It can be seen that when the pump power is 1.5W, a stable passively Q-switched mode-locked pulse is obtained; when the pump power is 5.5W, a stable pulse laser output with a maximum output power of 910mW (close to the watt level) and a pulse energy of 10.8μJ in the Q-switched envelope is obtained.

[0064] See also Figure 8-10 , Figure 8-10 : is a pulse sequence diagram of the all-solid-state passively Q-switched mode-locked pulse laser in Example 2 of the present invention, with scanning times of 10 μs, 500 ns and 20 ns respectively. Figure 8-10 It can be seen that the measured width of the Q-switched envelope is 1.8 μs, the repetition frequency is 83.81 kHz, and the amplitude fluctuation between pulse envelopes is within the range of ±1%. The interval between mode-locked pulses under the Q-switched envelope is 3.2 ns, the repetition frequency is 312.8 MHz, and the pulse width is about 505 ps. The modulation depth of the mode-locked pulse is close to 100%.

[0065] See also Fig.11 , Fig.11 1 is the laser beam quality diagram of the all-solid-state passively Q-switched mode-locked pulse laser in Example 2 of the present invention. It can be seen from 11 that the output laser beams in the x-direction and the y-direction are both Gaussian beams, and the beam quality factor and They are 1.10 and 1.21 respectively, both <1.3, and the beam waist radius is about 0.29 m, indicating that the working state of the laser is stable, the stability of the output beam is high, and the quality of the laser beam is very close to the ideal Gaussian beam, thereby generating high energy density.

[0066] See also Fig.12 , Fig.122D and 3D intensity diagrams of the laser beam of the all-solid-state passively Q-switched mode-locked pulse laser in Example 2 of the present invention. As can be seen from 12, the pulsed laser beam exhibits a good Gaussian intensity distribution on the horizontal axis and the vertical axis, further indicating that the output light is a Gaussian pulse light of good quality.

[0067] Compared with the prior art, the beneficial effects of the present invention also include: (1) Improving the processing performance of materials: By mixing Bi2Te3 / Sb2Te3 lateral heterojunction materials with PMMA, the processing and manufacturing performance of the materials are improved, making it easier to prepare into the desired shape and structure, thereby improving production efficiency.

[0068] (2) Enhanced optical adaptability of materials: Lateral heterojunction materials exhibit better optical adaptability and adjustability, enabling them to be used in a wider range of laser systems and meet different performance requirements.

[0069] (3) Reduce costs: PMMA, as a relatively economical material, can reduce the overall manufacturing cost, thereby making lateral heterojunction materials more economical in commercial applications.

[0070] (4) Improving the thermal stability of materials: Combining with PMMA can improve the thermal stability of lateral heterojunction materials, making them more reliable in high-power laser applications and reducing performance degradation caused by thermal effects.

[0071] (5) Promote the development of new lasers: The obtained Q-switched pulse envelope and mode-locked sub-pulses have high repetition rate and narrow pulse width, which is of great significance for optical applications requiring high precision and high resolution.

[0072] (6) Improving system integration: The introduction of lateral heterojunction materials may improve the integration of laser systems, making system design more compact and efficient.

[0073] These beneficial effects have jointly promoted the advancement of high-performance pulsed lasers and expanded the application areas of laser technology.

[0074] The specific implementation of the present invention described above does not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A saturable absorber based on Bi2Te3 / Sb2Te3, characterized in that: The structure includes: A substrate and a saturable absorption layer disposed on the surface of the substrate; wherein, The saturable absorption layer includes: a polymer matrix and a Bi2Te3 / Sb2Te3 lateral heterojunction material, and the Bi2Te3 / Sb2Te3 lateral heterojunction material is doped in the polymer matrix; the Bi2Te3 / Sb2Te3 lateral heterojunction material has a lateral heterostructure with Bi2Te3 in the middle and Sb2Te3 around.

2. The saturable absorber based on Bi2Te3 / Sb2Te3 according to claim 1, characterized in that: The preparation steps of the Bi2Te3 / Sb2Te3 lateral heterojunction material are as follows: Dissolving a Bi source, a first Te source, a first reducing agent, and a first surfactant into a first solvent, and then performing a first solvothermal reaction to obtain a Bi2Te3 suspension; The Sb source, the second Te source, the second reducing agent, and the second surfactant are dissolved in the second solvent, and then uniformly mixed with the Bi2Te3 suspension, and a second solvent thermal reaction is performed, and after washing and drying, a Bi2Te3 / Sb2Te3 lateral heterojunction material is obtained; wherein, The molar ratio of Bi to Te in the Bi source and the first Te source is 1:(1.4-1.6); and / or, The molar ratio of the Bi source to the reducing agent is 1:(8-12); and / or, The molar ratio of the Bi source to the first surfactant is 1:(0.01-0.015); and / or, The usage ratio of the Bi source to the first solvent is (0.1-0.2) g:1 L; and / or, The temperature of the first solvent thermal reaction is 195-205° C., and the time of the first solvent thermal reaction is 10-14 h; and / or, The molar ratio of Sb to Te in the Sb source and the second Te source is 1:(1.4-1.6); and / or, The molar ratio of the Sb source to the second reducing agent is 1:(8-12); and / or, The molar ratio of the Sb source to the second surfactant is 1:(0.01-0.015); and / or, The usage ratio of the Sb source to the second solvent is (0.1-0.2) g:1 L; and / or, The temperature of the second solvent thermal reaction is 195-205° C., and the time of the second solvent thermal reaction is 14-18 hours; and / or, The molar ratio of Bi to Sb in the Bi source and the Sb source is 1:(3-5); and / or, The Bi source is at least one of bismuth chloride, bismuth nitrate and bismuth oxide; and / or, The Sb source is at least one of antimony chloride, potassium antimony tartrate, and antimony oxide; and / or, The first Te source and the second Te source are at least one of elemental tellurium, Na2TeO3, and K2TeO3; and / or, The first reducing agent and the second reducing agent are at least one of hydrazine hydrate, ammonia water, sodium hydroxide, hydroxylamine, and ethylenediamine; and / or, The first surfactant and the second surfactant are at least one of cetyltrimethylammonium bromide, sodium dodecylbenzenesulfonate, and polyvinylpyrrolidone; and / or, The first solvent and the second solvent are at least one of ethylene glycol, water, and isopropanol.

3. The saturable absorber based on Bi2Te3 / Sb2Te3 according to claim 1, characterized in that: The Bi2Te3 / Sb2Te3 lateral heterojunction material accounts for 0.1-1% of the mass of the polymer matrix; and / or, The thickness of the saturable absorption layer is 200-350 nm.

4. The saturable absorber based on Bi2Te3 / Sb2Te3 according to claim 1, characterized in that: The material of the polymer matrix is ​​polymethyl methacrylate; and / or, The substrate is quartz glass.

5. A method for preparing a saturable absorber based on Bi2Te3 / Sb2Te3 as claimed in any one of claims 1 to 4, characterized in that: The following steps are involved: Dispersing Bi2Te3 / Sb2Te3 lateral heterojunction material and polymer in an organic solvent to obtain a film-forming solution; The film-forming liquid is spin-coated onto the surface of a substrate, and after drying, a saturable absorber of Bi2Te3 / Sb2Te3 is obtained.

6. The method for preparing a saturable absorber based on Bi2Te3 / Sb2Te3 according to claim 5, characterized in that: The preparation steps of the film-forming solution include: Dispersing the Bi2Te3 / Sb2Te3 lateral heterojunction material into a first organic solvent to obtain a Bi2Te3 / Sb2Te3 dispersion; dispersing the polymer in a second organic solvent to obtain a polymer solution; The Bi2Te3 / Sb2Te3 dispersion and the polymer solution are mixed evenly to obtain a film-forming solution; wherein, The concentration of the Bi2Te3 / Sb2Te3 dispersion is 0.4-0.6 mg / mL; and / or, The first organic solvent is at least one of ethanol, toluene, dichloromethane and acetone; and / or, The mass fraction of the polymer solution is 4-6%; and / or, The second organic solvent is at least one of ethanol, toluene, dichloromethane and acetone; and / or, The volume ratio of the Bi2Te3 / Sb2Te3 dispersion to the polymer solution is 1:(1-3).

7. The method for preparing a saturable absorber based on Bi2Te3 / Sb2Te3 according to claim 5, characterized in that: The film-forming liquid is applied to the substrate surface by spin coating; wherein, During the spin coating process, the rotation speed of the coating machine is 800-2000 rpm, and the spin coating time is 10-30s.

8. An all-solid-state passively Q-switched mode-locked pulse laser, characterized in that: It includes a pump source, an optical fiber, a coupling system, an input mirror, a laser gain medium, a first reflector, a second reflector, a saturable absorber, and an output mirror that are sequentially connected; wherein, The input mirror, the first reflector, the second reflector and the output mirror together form a resonant cavity; The saturable absorber is the Bi2Te3 / Sb2Te3-based saturable absorber according to any one of claims 1 to 4.

9. The all-solid-state passively Q-switched mode-locked pulse laser according to claim 8, characterized in that: The pump source is a fiber-coupled output laser diode, and the central wavelength of the pump source is 808 nm; and / or, The input mirror is a concave mirror, and the curvature radius of the input mirror is 50-150 mm; and / or, The end of the input mirror away from the pump source is coated with a high-reflection film with an output wavelength of 1064 nm, and the end of the input mirror close to the pump source is coated with an anti-reflection film with a pump center wavelength of 808 nm; and / or, The laser gain medium is a neodymium-doped yttrium vanadate crystal; and / or, The first reflector and the second reflector are both plane mirrors, and the mirror surfaces thereof are coated with a 1064nm high-reflection film; and / or, The output mirror is a plane mirror, and its transmittance to 1064nm wavelength laser is 2-5%; and / or, The resonant cavity adopts a Z-shaped cavity, and the total cavity length is 45-60 cm.

10. The all-solid-state passively Q-switched mode-locked pulse laser according to claim 8, further comprising: power meter, photodiode and oscilloscope; among them, The output mirror is connected to the power meter and the photodiode respectively, and the photodiode is connected to the oscilloscope.

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