BBO晶体中级联非线性效应的实验研究

采用800 nm和400 nm两束飞秒激光脉冲在BBO晶体中同时满足相位匹配条件,产生差频、和频及其级联效应.实验运用了中心波长800 nm、重复频率10 Hz、脉宽60 fs及光斑直径7 mm的钛蓝宝石再生放大飞秒激光,输出约为10 mJ的能量以7:3分束.其中7 mJ光脉冲用一块非线性晶体BBO倍频至400 nm获得1.45 mJ能量,然后与另一束800 nm的3 mJ基频激光以非共线方式注入到另一块BBO中,在兼顾和频与差频的相位匹配条件下,即晶体对于和频与差频相位匹配状态同时存在少量失谐时,会同时产生267 nm与800 nm的和频与差频效应,新产生光波与原入射激光脉冲又经过进一步非线性混频作用,最终得到多达10余束可见、紫外的一维列阵.分析了此级联非线性效应的产生机理并讨论了入射光强度,啁啾,延迟等因素对级联效果的影响.

Experimental Research of Cascading Nonlinear Effect in BBO Crystal

The sum frequency , difference frequency and corresponding cascading nonlinear effect were reported with 800 nm and 400 nm femtosecond light beams satisfying the phase-matching condition in BBO crystal. We obtain sum-frequency 267 nm and difference-frequency 800 nm waves simultaneously, taking account of phase matching of sum frequency and difference frequency. The laser pulses are with 10 Hz repetition rate, 800 nm central wavelength, 60 fs pulse width and 7 mm spot diameter. The 10 mJ output energy of the Ti∶sapphire regenerative amplifier are split into two beams, and 70% energy is frequency doubled to 1.45 mJ of 400 nm by the first nonlinear crystal BBO and then injected into the second one with 3 mJ, 800 nm laser beam. For both of them there exists a small amount of detuning. When the new pulses mix frequency with input waves further, one-dimensional array of more than 10 beams including ultraviolet, visible bands can be observed. The mechanism and influencing factors of the input light intensity, chirp, relative time delay on the cascading nonlinear effect are investigated in details.