Broadband Terahertz Emission Based on the Femtosecond Laser Pulses

The characteristics of terahertz (THz) radiation from the surface of InN excited by the femtosecond laser pulses are presented. The effect of intensity and central wavelength of the excited laser pulse on THz emission are studied experimentally. THz radiations from the surface emission of Mg-doped InN and InAs are compared. The results show the stronger dependence of THz radiation on the different intensity and central wavelength of the excitation pulses. THz radiation from InAs than InN has higher emission efficiency. However, the strong enhancement of THz emission is observed from InN with appropriate Mg concentrations. The mechanism of THz emission from InN is found to be the photo-Dember effect and the emission intensity is inversely proportional to the conductivity, which is beneficial to investigate THz source based on InN.