Precise and accurate control of the ellipticity of THz radiation using a photoconductive pixel array

Mosley, C.D.W. and Deveikis, J. and Lloyd-Hughes, J. (2021) Precise and accurate control of the ellipticity of THz radiation using a photoconductive pixel array. Applied Physics Letters, 119 (12): 121105. ISSN 0003-6951

Abstract

Full control of the ellipticity of broadband pulses of THz radiation, from linear to left- or right-handed circular polarization, was demonstrated via a four-pixel photoconductive emitter with an integrated achromatic waveplate. Excellent polarization purity and accuracy were achieved, with Stokes parameters exceeding 97% for linear and circular polarization, via a robust scheme that corrected electrically for polarization changes caused by imperfect optical elements. Furthermore, to assess the speed and precision of measurements of the THz polarization, we introduced a figure of merit, the standard error after one second of measurement, found to be 0.047° for the polarization angle.