Pereira Mauro Fernandes
Department of Physics, Khalifa University of Science and Technology, Abu Dhabi 127788, United Arab Emirates.
Institute of Physics, Czech Academy of Sciences, 18221 Prague, Czech Republic.
Nanomaterials (Basel). 2022 Apr 28;12(9):1504. doi: 10.3390/nano12091504.
Semiconductor superlattices are proven nanomaterials for THz nonlinear optics by means of high order harmonic generation. Seminal approaches leading to a perfectly antisymmetric current-voltage (I-V.) curve predict the generation of odd harmonics only in the absence of a bias. However, even harmonics at high orders have been detected in several experiments. Their generation has been explained by considering deviations from the current flow symmetry that break the exact antisymmetry of the I-V. curve. In this paper, we focus on another issue found experimentally that has also not been explained, namely the harmonic power output asymmetry from negative to positive applied bias. Once more, breaking the I-V. flow symmetry explains the experiments and leads to a further tool to design the power output of these materials. Furthermore, a new approach for the Boltzmann Equation under relaxation-rate approximation eliminates numerical difficulties generated by a previous theory. This leads to very efficient analytical expressions that can be used for both fundamental physics/optics/material sciences and realistic device development and simulations.
半导体超晶格通过高次谐波产生被证明是用于太赫兹非线性光学的纳米材料。导致完美反对称电流 - 电压（I - V）曲线的开创性方法预测，仅在无偏置的情况下才会产生奇次谐波。然而，在几个实验中已经检测到了高阶偶次谐波。通过考虑与电流流动对称性的偏差来解释它们的产生，这种偏差打破了I - V曲线的精确反对称性。在本文中，我们关注实验中发现的另一个尚未得到解释的问题，即从负向正向施加偏置时谐波功率输出的不对称性。再次强调，打破I - V流动对称性解释了这些实验，并导致了一种设计这些材料功率输出的新工具。此外，在弛豫率近似下对玻尔兹曼方程的一种新方法消除了先前理论产生的数值困难。这导致了非常有效的解析表达式，可用于基础物理/光学/材料科学以及实际器件开发和模拟。
