Enhanced coherent terahertz emission from indium arsenide

We present results showing enhancement of terahertz (THz) emission from indium arsenide (InAs) which demonstrate that at 170 K and magnetic fields (B) up to B = 8 T, increased visible to terahertz conversion efficiencies are possible. With an average total power of 1μW at B = 0 T and 12μW at B = 8 T, we have observed an order of magnitude increase in total conversion efficiency with no visible saturation. The InAs sample was placed within an optical cryostat and illuminated by Ti:Sapphire laser pulses with duration 100 fs. The terahertz powers were recorded using a calibrated He-cooled bolometer. Free space electro-optic sampling (EOS) measurements confirmed the coherent nature of this radiation over the field and temperature range investigated. The optical cryostat could produce magnetic fields of B = 8 T at temperatures from 3 to 300 K. We therefore present a comprehensive study of the terahertz generation as a function of both these variables and a brief comparison with an alternative material system, InSb.