He Jun, Qu Yingli, Li Heping, Mi Jun, Ji Wei
Opt Express. 2005 Nov 14;13(23):9235-47. doi: 10.1364/opex.13.009235.
We report a systematic investigation of both three-photon absorption (3PA) spectra and wavelength dispersions of Kerr-type nonlinear refraction in wide-gap semiconductors. The Z-scan measurements are recorded for both ZnO and ZnS with femtosecond laser pulses. While the wavelength dispersions of the Kerr nonlinearity are in agreement with a two-band model, the wavelength dependences of the 3PA are found to be given by (3Ephoton/Eg-1)5/2(3Ephoton/Eg)-9. We also evaluate higher-order nonlinear optical effects including the fifth-order instantaneous nonlinear refraction associated with virtual three-photon transitions, and effectively seventh-order nonlinear processes induced by three-photon-excited free charge carriers. These higher-order nonlinear effects are insignificant with laser excitation irradiances up to 40 GW/cm2. Both pump-probe measurements and three-photon figures of merits demonstrate that ZnO and ZnS should be a promising candidate for optical switching applications at telecommunication wavelengths.
我们报告了对宽带隙半导体中的三光子吸收（3PA）光谱和克尔型非线性折射的波长色散的系统研究。使用飞秒激光脉冲对ZnO和ZnS进行了Z扫描测量。虽然克尔非线性的波长色散与双带模型一致，但发现3PA的波长依赖性由(3E光子/Eg - 1)^5/2(3E光子/Eg)^-9给出。我们还评估了高阶非线性光学效应，包括与虚拟三光子跃迁相关的五阶瞬时非线性折射，以及由三光子激发的自由电荷载流子引起的有效七阶非线性过程。在高达40 GW/cm2的激光激发辐照度下，这些高阶非线性效应不显著。泵浦 - 探测测量和三光子品质因数均表明，ZnO和ZnS应是电信波长光开关应用的有前途的候选材料。
