DIODE-PUMPED TERAHERTZ PHOTOMIXING SPECTRAMETER

Abstract

We previously demonstrated a high-resolution terahertz $spectrometer^{b}$ by mixing dye lasers in a fast low-temperature-grown (LTG)-GaAs photoconductor with submicron interdigital electrodes feeding a broadband complementary spiral antenna which radiates the coherent terahertz beat through a sample gas cell to a composite Si bolometer. We have upgraded the system efficiency, range and sensitivity by replacing the dye lasers with near-infrared diode,.lasers, using lower capacitance photomixers and detecting the far-ir radiation with a faster response hot-electron InSb bolometer. The fixed-tuned laser is a single-frequency $(\lambda \approx 852 nm)$ distributed-Bragg-reflector (DBR)GaAIAs diode, self-locked to a confocal interferometer and the tunable diode laser is a broadband quantum-well $(828 \leq \lambda \leq 858 nm)$ single-mode Littman-Metcalf external-cavity oscillator and a tapered planar amplifier, with precision linear piezoelectric tuning of up to 60 GHz and complete spectral coverage from 0.1 to 2 THz. Sample spectra will be given.