Terahertz Magneto Optical Polarization Modulation Spectroscopy
  We report the development of new terahertz techniques for rapidly measuring the complex Faraday angle in systems with broken time-reversal symmetry using the cyclotron resonance of a GaAs two-dimensional electron gas in a magnetic field as a system for demonstration of performance. We have made polarization modulation, high sensitivity (< 1 mrad) narrow band rotation measurements with a CW optically pumped molecular gas laser, and by combining the distinct advantages of terahertz (THz) time domain spectroscopy and polarization modulation techniques, we have demonstrated rapid broadband rotation measurements to < 5 mrad precision. 
D. K. George, A. V. Stier, C. T. Ellis, B. D. McCombe, J. \v{C}erne   and A. G. Markelz
cond-mat.mtrl-sci physics.optics