MOLECULAR SPECTROSCOPY WITH A HIGH-RESOLUTION, FREQUENCY-CALIBRATED TERAHERTZ SPECTROMETER BASED ON OPTICAL PHOTOMIXING IN LOW-TEMPERATURE-GROWN GaAs

Abstract

An all-solid-state, fully fiber-coupled THz spectrometer based on photomixing of near-infrared radiation in low-temperature-grown (LTG) GaAs has been developed. The optical pumping system consists of three 850 nm diode lasers; lasers \#1 and \#2 are locked to different longitudinal modes of a Fabry-Perot cavity via the Pound-Drever-Hall method and the third laser is offset-locked to laser \#2. The primary outputs of lasers \#1 and \#3 are injected into a maser-oscillator power amplifier (MOPA). The two simultaneously amplified beams are focused onto a LTG GaAs photomixer to generate THz radiation. The free-spectral-range of our ultra-low-expansion. Fabry-Perot cavity can be precisely determined, allowing absolute calibration of the THz radiation. High-resolution molecular spectroscopy performed with this spectrometer will be presented.