Two-photon absorption and stimulated emission in poly-crystalline Zinc Selenide with femtosecond laser excitation  

作　　者：Qianliang Li Walter Perrie Zhaoqing Li Stuart P Edwardson Geoff Dearden 

机构地区：[1]Laser Engineering Group,School of Engineering,University of Liverpool,Liverpool,L693GQ,United Kingdom [2]Laser Processing Research Centre,School of Mechanical,Aerospace and Civil Engineering,University of Manchester,Manchester M139PL,United Kingdom

出　　处：《Opto-Electronic Advances》2022年第1期1-12,共12页光电进展（英文）

摘　　要：The optical nonlinearity in polycrystalline zinc selenide(ZnSe),excited with 775 nm,1 kHz femtosecond laser pulses was investigated via the nonlinear transmission with material thickness and the Z scan technique.The measured two photon absorption coefficientβwas intensity dependent,inferring that reverse saturated absorption(RSA)is also relevant dur-ing high intensity excitation in ZnSe.At low peak intensity I<5 GW cm^(-2),we findβ=3.5 cm GW^(-1) at 775 nm.The spec-tral properties of the broad blueish two-photon induced fluorescence(460 nm-500 nm)was studied,displaying self-ab-sorption near the band edge while the upper state lifetime was measured to be τ_(e)~3.3 ns.Stimulated emission was ob-served when pumping a 0.5 mm thick polycrystalline ZnSe sample within an optical cavity,confirmed by significant line narrowing fromΔλ=11 nm(cavity blocked)toΔλ=2.8 nm at peak wavelength λ_(p)=475 nm while the upper state life-time also decreased.These results suggest that with more optimum pumping conditions and crystal cooling,polycrystal-line ZnSe might reach lasing threshold via two-photon pumping atλ=775 nm.

关 键 词：ZNSE femtosecond laser nonlinear absorption stimulated emission FLUORESCENCE 

分 类 号：TN249[电子电信—物理电子学] TN15