Lu Baozhu, Torchinsky Darius H
Opt Express. 2018 Dec 10;26(25):33192-33204. doi: 10.1364/OE.26.033192.
We describe a novel scheme of detecting rotational anisotropy-second harmonic generation (RA-SHG) signals using a lock-in amplifier referenced to a fast scanning RASHG apparatus. The method directly measures the nth harmonics of the scanning frequency corresponding to SHG signal components of Cn symmetry that appear in a Fourier series expansion of a general RA-SHG signal. GaAs was used as a test sample allowing comparison of point-by-point averaging with the lock-in based method. When divided by the C signal component, the lock-in detected data allowed for both self-referenced determination of ratios of Cn components of up to 1 part in 10 and significantly more sensitive measurement of the relative amount of different Cn components when compared with conventional methods.
我们描述了一种新颖的检测旋转各向异性二次谐波产生（RA-SHG）信号的方案，该方案使用与快速扫描RA-SHG装置参考的锁相放大器。该方法直接测量与一般RA-SHG信号的傅里叶级数展开中出现的Cn对称性的SHG信号分量相对应的扫描频率的n次谐波。使用砷化镓作为测试样品，以便将逐点平均与基于锁相的方法进行比较。当除以C信号分量时，锁相检测到的数据既允许对高达1/10的Cn分量比率进行自参考测定，又与传统方法相比，能更灵敏地测量不同Cn分量的相对量。
