Marble Christopher B, Sanderson Carl R, Ballmann Charles W, Yakovlev Vladislav V
Department of Physics and Astronomy, Texas A&M University, College Station, Texas 77843, USA.
Systems Management and Production Center, The University of Alabama in Huntsville, Huntsville, Alabama 34899, USA.
Appl Phys Lett. 2023 Jun 19;122(25):251105. doi: 10.1063/5.0147756. Epub 2023 Jun 21.
High harmonic generation (HHG) in semiconductors has been extensively studied recently in the high-intensity limit using middle infrared (mid-IR) femtosecond laser pulses resulting in emission spectra of self-phase modulated harmonics resting on top of a broadband continuum. In this report, a different approach to HHG in polycrystalline zinc selenide (poly-ZnSe) was explored utilizing a relatively low power regime (1-40 GW/cm) and much longer (30 ps) mid-IR laser pulses. Through a combination of low power, picosecond excitation, and narrowband (<10 nm full width at half maximum) mid-IR excitation, the nonlinear optical effects in poly-ZnSe could be isolated and studied independently. From the clearly distinguishable HHG peaks, harmonic conversion efficiencies of 10-10 for second to ninth harmonic in poly-ZnSe were measured, and the relationship between the Nth harmonic intensity and excitation intensity (I) was found to follow a power law, I with x ≤ N/2, as a result of the random quasi-phase matching process.
近年来，利用中红外（mid-IR）飞秒激光脉冲在高强度极限下对半导体中的高次谐波产生（HHG）进行了广泛研究，其产生的自相位调制谐波发射光谱位于宽带连续谱之上。在本报告中，探索了一种在多晶硒化锌（poly-ZnSe）中实现HHG的不同方法，该方法利用了相对较低的功率范围（1-40 GW/cm）和更长（30 ps）的中红外激光脉冲。通过低功率、皮秒激发和窄带（半高宽<10 nm）中红外激发的组合，可以分离并独立研究poly-ZnSe中的非线性光学效应。从清晰可辨的HHG峰中，测量了poly-ZnSe中二次到九次谐波的谐波转换效率为10-10，并且由于随机准相位匹配过程，发现第N次谐波强度与激发强度（I）之间的关系遵循幂律，即I与x≤N/2。
