title: Design and performance of reflective terahertz air-biased-coherent-detection for time-domain spectroscopy.
abstract: When a sample being tested is optically opaque or has a high absorption coefficient, a reflective measurement is often more suitable than a transmission measurement. We report the design and evaluation of a reflective terahertz time-domain spectroscopy (R-THz-TDS), using air as THz wave emitter and sensor, together with air-biased-coherent-detection (ABCD) method for the first time. With an 85 fs pulse amplified laser, we demonstrate a usable bandwidth from 0.5 THz to 12 THz, together with a peak dynamic range (DR) better than 2000:1 and a peak THz electrical field greater than 30 kV/cm. With a 32 fs pulse amplified laser, the usable bandwidth is remarkably expanded to a continuous 35 THz. Several far-infrared optical properties in various samples are reported. Furthermore, the time-resolved optical pump-THz probe experiment is performed. Finally, the uniqueness and advantage of this spectrometer are comprehensively compared with traditional THz-TDS and Fourier transform infrared (FTIR) spectroscopy.
authors.affiliation: Center for Terahertz Research, Rensselaer polytechnic Institute, Troy, NY 12180-3590, USA.
authors.forename: I-Chen
authors.initials: IC
authors.lastname: Ho
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Guo
authors.forename: X-C
authors.initials: XC
authors.lastname: Zhang