Research On Passively Mode-locked Nd:YVO₄ Lasers With In-band Pumping At 914nm

Mode-locked laser has the advantages of ultrashort pulse duration,high peak power and broad spectrum.Recently,with the development of laser diode(LD),LD pumped high power mode-locked lasers have been widely used and played an important role in optical communication,micromachining,high-density information storage,laser spectroscopy,nonlinear optics,laser ranging,all optical network,laser medical etc.However,due to thermal effects,the development of high efficiency and high power mode-locked laser has been greatly limited.For solid-state lasers with Nd3+ doped,in band pumping can reduce the heat generation fundamentally,thereby reduce the influence of thermal effect on the performance of laser.Therefore,in order to achieve high power and high efficiency mode-locked lasers,passively mode-locked Nd: YVO4 lasers with in-band pumping at 914 nm are of great value.In this paper,the main contents and innovations are as follows:1.The passively Q-switched mode-locked Nd:YVO4 laser based on Cr4+:YAG pumped by 914 nm LD is studied.The mode-locking principle and rate equation of Cr4+:YAG are studied.The thermal effect of Nd: YVO4 is analyzed.The cavity of the laser is calculated by using MATLAB and optimized to achieve the modelocking operation.The maximum absorpted pump power is 26 W,the highest average output power is 5.37 W with the conversion efficiency of 20.7% and the slope efficiency of 23.3%.The mode-locked pulse repetition frequency is 1.1GHz and the pulse duration is 322 ps.2.A 914 nm LD-pumped passively mode-locked Nd: YVO4 laser based on SESAM is designed.A five-mirror Z-shaped cavity is optimized and the cavity of the laser is calculated by MATLAB.The highest average output power is 6.23 W,the corresponding absorpted pump power is 16.9W,the optical-optical conversion efficiency is 36.9% and the slope efficiency is 44.4%.The mode-locked pulse repetition frequency is about 88.7 MHz and the pulse duration is about 52 ps.A stable mode-locked pulse train is realized,which effectively suppresses the Qswitched mode-locking.3.A compact high efficiency actively Q-switched self-Raman Nd: YVO4 laser with 914 nm in-band pumped is investigated.The average output power of 1.51W(20 °C)and 2.11W(30 °C)were obtained at different crystal temperatures with two Nd: YVO4 crystals(1.0-at.% and 2.0-at.%)respectively.The corresponding opticaloptical efficiency was 28.5% and 35.2%,respectively,and the conversion efficiency of the absorbed pump laser was 42.7% and 39.0%,respectively.It provides a theoretical basis for the 914 nm pumped self-Raman mode-locked Nd: YVO4 laser which will be researched in the future.