Study On The Dual-frequency Microchip Laser For Optical Generation Millimeter-wave

Laser diode pumped dual-frequency microchip lasers are widely used in industrial production, scientific research, information transmission, national defense and many other fields. Especially, as the resources of radio spectrum become increasingly tense, the utilization of millimeter wave spectrum is being put on the agenda. Dual-frequency microchip lasers, of which the generation of millimeter-wave signals is relatively simple and effective, gain high popularity. In recent years scientists from various countries and different fields have showed persistent interests in researches of relevant content of dual-frequency microchip lasers.This thesis mainly focus on characteristics of dual-frequency microchip lasers, which includes researches on features in spectrum and frequency difference of the diode pumped dual-frequency microchip lasers, and the study of laser amplifiers in the case of small-signal input. Specifics include the following aspects:(1) Firstly, this thesis introduces the technology and working principle of how to produce photo-millimeter wave describes the research status of dual-frequency microchip lasers, including researches of LD pumped dual-frequency microchip lasers at home and abroad in recent years; analyses the development of dual-frequency microchip lasers and scientific significance of dual-frequency microchip laser amplification.(2) The thesis elaborates basic principles of dual-frequency microchip lasers, characteristics of the laser crystal and solutions of experiments on microchip crystal, and describes Nd:YVO4 crystal laser characteristics in detail. Meanwhile, from the four-level laser rate equations, which deduce characteristics of dual-frequency microchip laser threshold power, output power and slope efficiency are explored in the case of nearly threshold pumping and pumping light.(3)The thesis provides theoretical analysis of dual-frequency microchip laser resonant cavity mode and the formation conditions of single-frequency and dual-frequency longitudinal modes, conducts the experiments studying the characteristics of laser diode (LD) pumped, tunable frequency difference dual-frequency Nd:YVO4 microchip lasers, in a fixed width of the fluorescence spectrum of the laser gain medium.The output of the laser spectral characteristics is in great relation to pumping power, pumping position, cavity length and other parameters. By controlling the parameters, the relative frequency difference between the dual spectrum peaks of the output laser can be adjusted. Experiment results show that pumping light and the cavity modes can be achieved in a good match when the LD pumped current reach at 14.5A, with excellent stability of dual-frequency operation. The corresponding frequency difference can reach over 90 GHz. When the pump parameters are changed, the corresponding frequency difference can be tuned between 92.22 GHz -94.24 GHz. When increasing the resonator cavity length, the frequency interval of the output longitudinal mode laser reduced and triple-mode operation is achieved. The minimum difference between two frequency peaks was up to 26.5 GHz.(4)The thesis estanlishes a theoretical model of the dual-frequency amplifiers, in the case of small signal gain, starting from the four-level rate equations, researches and analyses the output spectrum and gain width after traveling wave amplifier; by adjusting the parameters. The simulation of the amplifying progress by MATLAB deducts the conclusion:as the gain spectral width is kept unchanged, comparing the changes of the laser spectrum before and after amplifying, it is found that the envelope of dual-frequency amplifying output spectrum is narrower than that of the incident spectrum. When changing the gain spectrum width, it is found that the spectral profile of the laser output is relatively flat if the gain spectral width is enlarged; while the output spectral profile becomes relatively steep, if the gain spectrum width is smaller.