TEMPERATURE-DEPENDENCE OF TERAHERTZ PULSES PRODUCED BY DIFFERENCE-FREQUENCY MIXING IN INSB

Terahertz radiation emitted from (111) InSb illuminated with focused 1 .4 mu m laser pulses is due to both difference-frequency mixing and de pletion field driven current. By rotating an undoped (111) InSb sample at a temperature of 80 K about its surface normal, we were able to se parate the relative contribution of the azimuthally dependent differen ce-frequency mixing (DFM) signal from the total terahertz wave form. C ontrary to expectations, it was found that the azimuthally dependent s pectrum appears nearly identical to the azimuthally independent spectr um. From this, it is concluded that the spectrum of the current surge signal blue shifts as the pump is focused. Also, a strong similarity e xists between the temperature dependence of the DFM and current surge signals. (C) 1995 American Institute of Physics.