Research On All-solid-state Pulsed Laser Based On The Saturable Absorption Properties Of MoS₂ Two-dimensional Materials

In the context of the new era of "smart manufacturing" and "Internet+",because of its simple structure,robustness,convenient maintenance,low cost,high output power,strong pulse energy,high repetition frequency,good spot quality,wide selectable wavelength range and other characteristics,all-solid-state pulsed lasers have been widely used in scientific research,national defense,medical,mechanical processing,and precision manufacturing fields.At the same time,this also poses new challenges for easier and more convenient methods to obtaining high-quality lasers.Laser passive Qswitching technology is an important method to obtain excellent pulsed lasers,and saturable absorption devices play the most critical role in this technology.In recent years,with the emergence of various new two-dimensional materials,graphene,transition metal dichalcogenide(TMDs),topological insulators(TIs),and black phosphorus(BP)have been successfully applied in the field of saturable absorber optimization of pulsed solid-state lasers,owing to their stable chemical properties,fast recovery time,high damage threshold and wide adaptive spectrum.Based on this background,this dissertation works around saturable absorption devices.MoS2 saturable absorbers are prepared by CVD method,Ta2O5 protective film is evaporated by EBE method,and it is applied to Q-switched experiments of all solidstate pulsed lasers.The main work of the thesis includes:1.Based on the basic theory of two-dimensional materials,the lattice stacking method.band structure,and optical characteristics of layered MoS2 are deeply explored.As the number of layers decreases,the band gap width of MoS2 two-dimensional materials will continue to increase,and The indirect band gap is converted to a direct band gap,thereby improving its photoelectric characteristics.Secondly,the growth mechanism of MoS2 material prepared by CVD is investigated in this paper,and the influence of process parameters such as carrier gas mass flow rate,reactant dosage ratio and growth temperature on film formation quality is analyzed.The MoS2 thin films with different morphologies were successfully prepared by reducing MoO3 with excess sublimation sulfur powder under a constant temperature of 775? for 14min with an atmosphere of 20sccm argon.2.After summarizing the research progress and preparation process of Ta2O5 thin films,Ta2O5 crystals were bombarded and melted with 310mA small spot electron beam by EBE method in the laboratory.The crystals were successfully deposited on a 300?substrate after gasification.The thickness of the film was 157.5nm.After the film was thermally annealed,a ?-Ta2O5 high-temperature phase polycrystalline structure was generated at 900?,and the band gap of the film was increased to 4.46eV,so that the film was flatter and denser,and the optical transmittance was higher.It provides experimental support for Ta2O5 film as a saturable absorber protective film.3.Using the thin film prepared in this thesis as a saturable absorption device and Nd3+:YAG as the working substance,a transmission short straight-cavity Q-switched pulse experiment was performed in an all-solid-state laser.Successfully obtained 57mW stable 1064nm Q-switched pulsed laser output with a pulse width of 513.4ns,a repetition frequency of 571.14kHz,a single pulse energy of 99.8nJ,and a peak power of 194.39mW.