Terahertz radiation from narrow-gap semiconductors photoexcited by femtosecond laser pulses

Large increase of the emitted terahertz power has been observed for p-InAs samples with the p-doping levels of ≈1016-1017 cm−3. This increase was explained by a large surface depletion layer and an electric-field-induced optical rectification effect in the layer. Terahertz fields radiated by the samples of all three investigated CdxHg1 − xTe layers was of the same order of magnitude. No azimuthal angle dependence of the radiated signal was detected, what evidences that linear current surge effect is dominating over nonlinear optical rectification. Azimuthal angle and magnetic fields emission witness that it is caused by linear photo-Dember type processes.