Acharya Shankar, Collier Brian, Geerts Wilhelmus
Department of Physics, Texas State University, San Marcos, Texas 78666, USA.
Rev Sci Instrum. 2019 Dec 1;90(12):123001. doi: 10.1063/1.5117304.
A dual beam magneto-optical setup employing a dual axis photoelastic modulator (PEM) and an intensity-stabilized laser was designed and constructed. The beam transmitted through or reflected of the sample is split by a Wollaston prism into two orthogonal high-quality linearly polarized beams. Two photodetectors are used to measure the DC and 2ω components of each beam's intensity. Theoretical calculations using Jones matrices show that the difference between the 2ω signals, i.e., ΔI, is linearly proportional to the Kerr or Faraday rotation of the sample. Different from I of a traditional single beam setup, the ΔI does not contain an offset caused by the Fabry Perot interference in the PEM's optical head, making the setup less sensitive for small sample movements and laser drifts including intensity, wavelength, and beam direction drifts all originating from mainly temperature fluctuations in the lab.
设计并构建了一种采用双轴光弹调制器（PEM）和强度稳定激光器的双光束磁光装置。透过样品或从样品反射的光束由沃拉斯顿棱镜分成两束正交的高质量线偏振光束。使用两个光电探测器测量每束光强度的直流分量和二次谐波（2ω）分量。利用琼斯矩阵进行的理论计算表明，2ω信号之间的差值，即ΔI，与样品的克尔旋转或法拉第旋转成正比。与传统单光束装置的光强I不同，ΔI不包含由PEM光学头中的法布里-珀罗干涉引起的偏移，这使得该装置对小样品移动和激光漂移（包括强度、波长和光束方向漂移，这些主要源于实验室中的温度波动）不太敏感。
