Recent developments in terahertz spectroscopy
Abstract
Terahertz (THz) spectroscopy and sensing are attracting much attention because of their potential application to various fields. In this talk, the basics of THz-TDS and recent developments in THz-TDS are reviewed. The topics include
- The basics of THz-TDS (the sources and detector),
- Polarization sensitive measurements, and
- THz imaging based on THz-TDS.
In topic (1), recent developments of THz emitters are also briefly reviewed. For example, the four-wave mixing in the laser-induced plasma is reported to be a powerful THz source. One of the key devices in the THz spectroscopy is photoconductive (PC) antennas, which are used in the THz-TDS as the emitter and detector. For the polarization sensitive measurements (the topic (2)), multi-contacts PC antennas are used as the polarization modulator or polarization detector. Birefringence and stress-induced birefringence measurements are presented as examples of the polarization sensitive measurements. THz imaging, the topic (3), is attracting much attention because of its potential use in the non-destructive sensing for security purposes. For practical applications, however, fast imaging techniques are required. The two-dimensional electro-optic (2D-EO) sampling is one of the solutions. A 2DEO sampling system with a high-frame rate CMOS camera operated in a dynamic subtraction scheme is presented in the talk.
