Research On Few Hundreds KHz All-solid-state Picosecond Regenerative Amplifier

In recent decades,laser technology has been developing rapidly and become more and more important in various fields.Especially ultrashort pulse laser has been a wide range of fields,such as high-speed optical communications,optical holographic storage technology,laser fusion,precision machining,laser ranging,laser radar,biological areas of science,laser spectroscopy,optical sampling technique,blinding weapons and so on.Laser Diode?LD?pumped all-solid-state picosecond laser can output high-peak power,narrow-pulse-width,high-beam-quality pulse laser.In order to meet precision machining's speed required for material processing.High pulse repetition frequency?PRF?picosecond lasers should be used.Energy extraction period would become much smaller than the energy upper state lifetime of laser gain media at high-repetition-rate regenerative amplifier,so output laser contains two-different-energy pulse which is generally described as a period doubling bifurcation phenomenon.In this paper,theoretical analysis and numerical simulation of the corresponding experiment were analyzed.This full paper was divided into four chapters.In the first chapter,application value of all-solid-state high-repetition-rate in precision machining and laser ranging was expounded;the history and actualities of the ultrafast laser regenerative amplifier and multi-pass amplifier were introduced.In addition,the main content and research sources were also introduced.In the second chapter,in order to improve the regenerative amplifier output power and laser beam quality,two kinds of pumping methods of semiconductor lasers were analyzed and compared.LD end pump Nd:YVO₄ crystal in 888 nm was used because of Nd:YVO₄ crystal's advantages.Then,the absorption coefficient,short cavity power and thermal stress of Nd:YVO₄ crystal with doping concentration of 0.5 at.%in 4 mm×4mm×30 mm size were measured.In the third chapter,mode-locked laser principle with a semiconductor saturable absorber mirror?SESAM?was expounded.And Nd:YVO₄ mode locked laser with SESAM was also set up.Corresponding experiment was made at the PRF of 100 kHz,the two-different-energy in output laser pulses was found,which was generally described as a period doubling bifurcation phenomenon.When the PRF was more than250 kHz,it can avoid the period doubling bifurcation phenomenon.And when the absorbed pump laser was 70W,PRF between 250 and 500kHz picosecond laser was obtained.The pulse width was 12ps,the maximum output average power was 18 W at500 kHz,and the maximum single pulse energy was 72?J at 250 kHz.In the forth chapter,dynamics features of high PRF continuously pumped solid-state regenerative amplifiers were studied numerically.Pulses'simulative computation of the dynamic process from the regenerative amplifier in different PRF was conducted.