Simultaneous measurement of circular dichroism and Faraday rotation at terahertz frequencies utilizing electric field sensitive detection via polarization modulation

摘要

A far-infrared system measures the full complex Faraday angle, the rotation as well as the ellipticity, with an unprecedented accuracy of 10 μrad/T. The system operates on several far-infrared laser lines in the spectral range from 0.3 to 6 THz and produces results as a continuous function of temperature from 10 to 310 K and applied fields between ±8 T. Performance of the instrument is demonstrated by measurements on a GaAs two-dimensional electron gas heterostructure and Bi2Sr2CaCu2O8+x single crystal. © 2010 American Institute of Physics Article Outline INTRODUCTION INSTRUMENT OVERVIEW CRITICAL COMPONENTS AND DESIGN ISSUES Étalons and multiple reflections Sample design and mounting considerations Magnet Laser system Mechanical rotator Detectors, mirrors, polarizers, and beam splitter Electronics INSTRUMENT CALIBRATION AND OPERATION Electronics Lock-in amplifiers: Harmonic analysis and setting the phase Detector frequency roll-off Δβ and ΔΓ from FTIR spectroscopy Δβ and ΔΓ in situ calibration: Polarizer as sample Calibration of Im(θF) : Inserting a waveplate or 2DEG as a reference sample INSTRUMENT PERFORMANCE: MEASUREMENTS ON BI-2212