Tunable photoconducting emitters and detectors of free space terahertz radiation

Abstract

In recent years, various optoelectronic techniques have been developed to generate and coherently detect broadband pulses of terahertz (THz) radiation in free space [1]. While the power of these methods for far-infrared spectroscopy has been amply demonstrated, certain measurements such as of nonlinear interactions in the far-infrared would clearly benefit from a scheme of spectral control of both the generation and detection of THz radiation. Recently, we reported a new scheme of producing quasi-sinusoidal modulation of optical radiation at tunable THz frequencies [2]. This was accomplished by mixing two linearly chirped broadband optical pulses with a variable delay τ between one another and led to the production of tunable narrowband THz radiation. In this summary, we demonstrate the applicability of the chirped pulse beating technique to incorporate spectral selectivity in the phase-coherent detector, as well as the emitter, of THz radiation. We have developed and carefully characterized a THz system composed of photoconducting dipole emitters and detectors independently tunable from ~60 GHz to ~0.8 THz [3]. In addition, we report our results on the possibility of circumventing the saturation effects normally encountered in generating high-intensity THz radiation from photoconducting antennas by the use of the chirped pulse mixing scheme.