Infrared wavelength and temperature dependence of optically induced terahertz radiation from InSb

Results of the temperature and infrared wavelength (0.8, 1.4, and 1.9 μm) dependence of terahertz radiation generated from both undoped and Te-doped InSb irradiated with ≊125 fs laser pulses are reported. Undoped InSb shows a substantial change in the spectral content of the terahertz radiation between 80 and 260 K, while the spectrum of Te-doped InSb remains nearly unchanged, an effect attributed to its mobility being dominated by impurity scattering. Also, the terahertz radiation from undoped InSb at 80 K is dependent on the irradiating wavelength, with both a higher frequency spectrum and much larger amplitude generated at longer wavelengths. No such effect is observed at 260 K.