Short Pulse Generation Of LD-Pumped Microchip Laser And Its Output Characteristics

LD-pumped microchip lasers combine many advantages such as compactness, reliability, high beam quality, high efficiency and long lifetime. They are of great interest in the field of laser radar, biomedicine, micro-mechanism, range finder, remote sensing, pollution detection and space optical communication, etc. They have been a hot point in laser technology and devices.To get stable and controllable laser pulses with short duration and high repetition rate for a seed source in MOPA system, the dissertation focuses on two important technology to generate short pulses: passive Q-switching and gain-switching. The theory analyses, simulation calculations, experiment researches and parameters optimization have been made. Some new methods and opinions have been presented for enhancing the output characteristics of LD-pumped microchip lasers.During the solution process of the rate equations of Cr~4+ doped passive Q-switched lasers, many parameters of resonance cavity and saturable absorber are integrated into two synthesis parameters. The relationship of and the energy, peak power and duration of Q-switched laser pulses with the synthesis parameters are calculated.Using pre-pumping technique, the highly stable Q-switched laser pulses with repetition rate from 1Hz to 4kHz was acquired in a Cr~4+,Nd~3+:YAG microchip laser. The two-section Cr~4+:YAG-Nd~3+:YAG laser was studied and the self-Q-switched laser pulses with duration of 10ns and 10kHz repetition-rate were acquired. The experimental results accord well with the theory calculations.In the dissertation, the gain-switching model of four-level lasers is established. For the first time, the variation of the laser output characteristics with LD pump direct current, pump pulse current and pump pulse width was calculated by numerically solving the model. Furthermore the optimal LD pump parameters were acquired aiming to get maximum peak power and minimum pulse duration. By the optimization of pump parameters, the duration of output laser pulse was compressed to 16ns.A monolithic small Nd~3+:YVO4 gain-switched laser was developed. Stable laser pulses with repetition rate varied in a large range of lHz-25kHz were acquired with homemade modulation signal generator.A Cr~4+,Nd~3+:YAG microchip laser was primarily explored in experiments under dual mechanism of gain-switching and Q-switching taking effect together. Stable laser pulses with duration of 6ns and repetition rate of lHz-25kHz were obtained.