| The ultrafast pulse laser with picosecond duration and nanosecond energy has the characteristics of high pulse energy,narrow pulse width,and high peak power,making it a vital research direction in the field of laser technology.It has promising applications in laser processing,laser ranging,medical beauty,environmental monitoring,marine communication,and optical switching.The passive Q-switched microchip laser pumped by a laser diode(LD)has become the main technical means for obtaining high-energy nanosecond lasers due to its compact structure,small size,high stability,excellent beam quality,and low cost.This study focuses on the key scientific and technological problems of large energy and miniaturized passive Q-switched microchip lasers for industrial processing and optical switching excitation applications.The YAG/Nd:YAG/Cr4+:YAG bonded crystal was selected as the research object,and pulsed LD pumping technology was used.The laser output characteristics of the 1064 nm passive Q-switched microchip laser oscillator,laser amplifier,nonlinear frequency conversion,and microchip laser under high repetition frequency were systematically studied theoretically and experimentally.This research provides theoretical and data support for developing compact high-energy nanosecond lasers.Specifically,the research content of this paper includes:The first chapter introduces the characteristics of sub-nanosecond microchip lasers and their applications in fields such as laser medical treatment,laser processing,laser ranging,laser ignition,laser-induced breakdown spectroscopy,and optical switching.The research progress of sub-nanosecond lasers both domestically and internationally is summarized,and the main research content of this dissertation is outlined.The second chapter discusses the pumping method,gain medium,and characteristics of saturable absorbers for microchip lasers,as well as the passive Q-switching process.Measures to alleviate crystal thermal effects are also listed.A rate equation model for passive Q-switching of YAG/Nd:YAG/Cr4+:YAG microchip lasers pumped by pulsed LDs is established,and the impact of pump power and pulse width on pulse width,pulse count,single pulse energy,and other parameters is numerically solved and simulated under pulsed pumping conditions.In experiments,a pulsed laser with a single pulse energy of 1.2 mJ,a pulse width of 574 ps,an M2 beam quality of 1.21,and a power stability of 1.08%was obtained.The third chapter analyzes the impact of the pump beam spot and initial transmittance of the microchip crystal on laser performance at a pump repetition frequency of 100 Hz.A pulsed laser output with a single pulse energy of 2.4 mJ,a pulse width of 575 ps,and an M2 beam quality of 1.61 was achieved.Using this microchip laser as a seed source,an end-pumped double-pass solid-state laser amplifier was designed to obtain a 1064 nm high-energy subnanosecond laser output with a single pulse energy of 7.7 mJ.Nonlinear frequency doubling and triple frequency conversion were achieved using KTP and LBO crystals,respectively,resulting in green light and ultraviolet laser outputs with single pulse energies of 3.2 mJ and 1.05 mJ,respectively.High-reliability engineering design and system integration were carried out,and a prototype of a miniaturized high-energy sub-nanosecond laser was developed.The fourth chapter explores the impact of microchip laser repetition frequency and pump beam duty cycle on sub-nanosecond laser output parameters.A prototype of a miniaturized 1 kHz microchip laser was designed and developed,and a sub-nanosecond laser output with a single pulse energy of 0.3 mJ,a pulse width of 568 ps,and an M2 beam quality of 1.76 was obtained at a repetition frequency of 1 kHz.The fifth chapter summarizes the main research achievements,innovations,and shortcomings of this dissertation,and provides prospects for the optimization and development of miniaturized sub-nanosecond lasers. |
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