| Laser diode(LD)pumped all-solid-state lasers have received extensive attention and research due to their simple and compact structure,stable performance,good beam quality and long service life.After years of development,all-solid-state lasers have played an indispensable role in many fields,such as industrial manufacturing,national defense technology,medicine and scientific research.All-solid-state single-frequency lasers have not only all the advantages of all-solid-state lasers,but also outstanding characteristics like long coherence length,stable frequency,high pulse peak power and narrow spectral line width.Due to their excellent advantages,all-solid-state singlefrequency lasers can be widely used in many fields including high-precision optical measurement,optical detection,fiber communication,high-resolution molecular spectrum analysis and so on.Nd:LuAG crystals have broad application prospects and development potential due to their excellent physical and chemical properties.In this thesis,we studied single-frequency laser characteristics of Nd:LuAG at two representative laser wavelengths of 1.06μm and 1.4μm.The research content mainly includes the following parts:(1)Theoretical research.Study of the generation principle of multi-longitudinal mode and analization of the commonly used single-frequency laser implementation methods;Study of the structure,physicochemical characteristics and spectral characteristics of Nd:LuAG laser crystals;Study of the basic principle of passive Qswitching technology and establishment of passive Q-switching rate equation.(2)Experimental study on preparation of laser cavity-mirror film.According to the theory of optical film design,the laser cavity-mirror film structure required for the experiment was optimized,and all the cavity mirrors used in this experiment were prepared by plasma vacuum sputtering method.(3)Experimental study of 1.06μm continuous wave single-frequency laser.①Using an Nd:LuAG microchip as a laser gain medium,a single-frequency laser was achived through the couple-cavity method.The wavelength of the output laser is 1064.20nm with a line width of 173MHz.The maximum output power is 304mW with a slope efficiency of 10.9%.Its M2 factors in the horizontal and vertical directions are 1.18 and 1.15,respectively.②Using an Nd:LuAG crystal as a laser gain medium,a single-frequency laser was achived by inserting a Brewster plate and a birefringent filter into the cavity for frequency selection.The wavelength of the output laser is 1064.08nm with a line width of 225MHz.The maximum output power is 365.5mW with a slope efficiency of 7.3%.Its M2 factors in the horizontal and vertical directions are 1.18 and 1.15,respectively.(4)Experimental study of 1.06μm passive Q-switched laser.Using a Nd:LuAG microchip as a laser gain medium,a Q-switched pulsed 1064.85nm laser was achieved by inserting a Cr4+:YAG crystal into the cavity as a saturable absorber.The maximum output power is 371mW with a slope efficiency of 6.5%.At the highest output power;the pulse width is 4.2ns;the pulse repetition is 14kHz;the pulse energy is 24.3μJ and the peak pulse power is 5.5kW.(5)Experimental study of 1.4μm continuous wave single-frequency laser.Using a Nd:LuAG crystal as laser gain medium,a single-frequency laser was achived by inserting a Brewster plate and a birefringent filter into the cavity for frequency selection.The wavelength of the output laser is 1442.3 1nm with a line width of 215MHz.The maximum output power is 329mW with a slope efficiency of 7.3%.Its M2 factors in the horizontal and vertical directions are 1.18 and 1.15,respectively.This is the first report of a 1.4μm human eye-safe single-frequency laser,to the best of our knowledge. |
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