Improved sensitivity of terahertz detection by GaAs photoconductive antennas excited at 1560 nm

The terahertz detection by photoconductive antennas (PCAs) based on low-temperature grown (LTG) GaAs with 1.5 mu m pulse excitation was revisited. We found that the detection efficiency can be improved by a factor of 10 (20 dB) by reducing the excitation spot size and the gap length of the PCA, maintaining the low noise feature of the PCA on LTG GaAs. As a result, the signal-to-noise ratio higher than 50 dB was obtained at a reasonable incident power of 9.5 mW, suggesting that the scheme is promising for the detection of terahertz waves in practical time domain systems. (C) 2010 American Institute of Physics. [doi:10.1063/1.3519480]