Terahertz pulse generation from (111)-cut InSb and InAs crystals when illuminated by 1.55-μm femtosecond laser pulses.

Terahertz (THz) pulse generation from p-InAs, p-InSb, and n-InSb epitaxial layers are investigated using 1.55-μm wavelength femtosecond laser pulses for photoexcitation. The samples are of (111) crystallographic orientation resulting in anisotropic photoconductivity. Experiments have shown that THz generation in InAs is mainly due to anisotropic photocurrent in the surface electric field while a dominant mechanism in InSb is optical rectification. At high optical excitation fluencies, InSb is more efficient than p-InAs. In the presence of an external magnetic field, (111) InSb has exhibited promising viability as an alternative to the photoconductive antenna emitter in a THz time-domain-spectroscopy (THz-TDS) system.