A broadband silicon quarter-wave retarder for far-infrared spectroscopic   circular dichroism
  The high brightness, broad spectral coverage and pulsed characteristics of infrared synchrotron radiation enable time-resolved spectroscopy under throughput-limited optical systems, as can occur with the high-field magnet cryostat systems used to study electron dynamics and cyclotron resonance by far-infrared techniques. A natural extension for magnetospectroscopy is to sense circular dichroism, i.e. the difference in a material's optical response for left and right circularly polarized light. A key component for spectroscopic circular dichroism is an achromatic 1/4 wave retarder functioning over the spectral range of interest. We report here the development of an in-line retarder using total internal reflection in high-resistivity silicon. We demonstrate its performance by distinguishing electronic excitations of different handednesses for GaAs in a magnetic field. This 1/4 wave retarder is expected to be useful for far-infrared spectroscopy of circular dichroism in many materials. 
Xiaoxiang Xi, R.J. Smith, T.N. Stanislavchuk, A.A. Sirenko, S.N.   Gilbert, J.J. Tu, G.L. Carr
cond-mat.mtrl-sci cond-mat.mes-hall