Measurement and Analysis of THz Radiation from Bulk Semiconductors

Abstract

When illuminated by femtosecond laser pulses, where the photon energy lies above the optical absorption bandedge, GaAs emits pulsed submillimeter-wave (THz) radiation via ultrafast photocarrier transport. The radiation emitted from the semiconductor surface has both forward (transmitted direction) and backward (psoudoroflected diroction) components. This radiation has been used to coherently probe the ultrafast electronic properties of the semiconductor. However due to technical difficulties associated with THz beam measurements, there are still many unanswered questions. For example, a detailed comparison and analysis of amplitude and phase of the forward and backward THz radiation has not reported. In this talk, we present recent measurements and analysis of the amplitude and phase of both forward and backward THz radiation via ultrafast photocarrier transport. Based on these results we are able to qualitatively and quantitatively explain anomalous THz emission from metal/semiconductor interfaces. All these interesting results which have not been reported before will improve our understanding of THz emission from semiconductors.