Abstract

The THz optoelectronics field is now maturing and semiconductor-based THz antenna devices are becoming more widely implemented as analytical tools in spectroscopy and imaging [1]. Photoconductive (PC) THz switches/antennas are driven optically typically using either an ultrashort-pulse laser or an optical signal composed of two simultaneous longitudinal wavelengths which are beat together in the PC material at a THz difference frequency. This allows the generation of (photo)carrier pairs which are then captured over ultrashort timescales (τ_c < 1ps) usually by defects and trapping sites throughout the active material lattice. Defect-implanted PC materials with relatively high bandgap energy such as LT-GaAs ($E_g^{GaAs}\approx 1.42eV$) are typically used and many parameters such as carrier mobility and PC gain are greatly compromised. We demonstrate here the implementation of low bandgap energy InAs ($E_g^{InAs}\approx 0.98eV$) quantum dots (QDs) embedded in standard crystalline GaAs as both the PC medium and the ultrafast capture mechanism [2] in a PC THz antenna. This semiconductor structure is grown using standard MBE methods and allows the device to be optically driven efficiently at wavelengths up to ~1.3 µm, in this case by a single tunable dual-mode QD diode laser.

© 2013 IEEE