Rapid-scan broadband frequency-domain terahertz spectroscopy via dynamic optical phase lock

Abstract

Frequency-domain terahertz (THz) spectroscopy using photomixing devices has unique advantages such as high dynamic range and high spectral resolution. Thus, many applications for solid-state and gas-phase spectroscopy have been proposed. In this study, we developed a feedback controlled technique to dynamically compensate for the optical phase accompanied by frequency sweep, enabling both fast and high-resolution data acquisition across a wide frequency region. From gas-phase THz spectroscopy measurements of dilute acetonitrile gas in a wide frequency range up to 1.1 THz, fine structures with linewidths less than 10 MHz were clearly resolved, while the data acquisition rate was improved by two orders compared to the previously reported value.