Heterodyne detection at 337 micrometers in epitaxial GaAs

Optical heterodyne detection at 337 micrometers has been measured using a HCN laser and an epitaxial n-type GaAs photoconductor. The donor concentration, obtained from spectral curves given by Stillman et al. (1970), was 150 trillion/cu cm; the acceptor concentration was half of this value. The signal power of the fourfold frequency shifted signal was found to be 1.1 times ten to the minus fourteenth W/Hz. The improvement of this value over the results reported by Summers et al. (1970) are probably the result of an increased local oscillator power (25 microWatts) and the use of a low noise cryogenic preamplifier with a matched imput impedance.