论文标题
高阶（n = 4-6）多光子吸收和间隙，ZNSE，GASE和ZGP晶体中的中红外Kerr非线性
High-order (N=4-6) multi-photon absorption and mid-infrared Kerr nonlinearity in GaP, ZnSe, GaSe, and ZGP crystals
论文作者
论文摘要
我们报告了一项研究高阶多光子吸收，非线性折射及其各向异性的研究，该研究使用Z-扫描方法和2.35-μmfemtosecond的峰值脉冲，在200 GW/CM的峰值中，使用Z-SCAN方法和2.35-μmfemtosecond脉冲。我们发现，非线性吸收遵守n = 4至6的多光子吸收（MPA）顺序的扰动模型，与晶体的带镜很好地吻合。对自由载体吸收的作用的研究，通过改变30至70 fs的脉冲持续时间进行，同时保持恒定的峰强度表明，在我们的强度水平下，在MPA吸收过程中产生的自由载体比从线性吸收横截面中预期的要强得多。可能的机制包括高场效应，例如传统带中的谷体散射以及吸收到较高的带状带中。使用（i）封闭的孔径z扫描和（ii）由于自相度调制而宽阔的光谱扩展，两种方法彼此吻合良好。
We report a study of high-order multi-photon absorption, nonlinear refraction, and their anisotropy in four notable mid-infrared \c{hi}(2) crystals: GaP, ZnSe, GaSe and ZGP using the Z- scan method and 2.35-μm femtosecond pulses with peak intensity in excess of 200 GW/cm2. We found that the nonlinear absorption obeys a perturbation model with multi-photon absorption (MPA) orders from N = 4 to 6, in good agreement with the bandgaps of the crystals. A study of the role of free carrier absorption, performed by varying the pulse duration between 30 and 70 fs while maintaining a constant peak intensity showed that at our intensity levels, free carriers generated in the process of MPA absorb much stronger than would be expected from their linear absorption cross section. Possible mechanisms include high-field effects, such as intra-valley scattering in the conduction band and absorption to higher lying bands. Nonlinear refractive indices were measured using (i) closed aperture Z-scan and (ii) spectral broadening due to self-phase modulation, both methods agreeing well with each other.
