Terahertz Transients: Generation and Applications

Abstract

The recent advances in terahertz (THz) science and technology – encompassing various spectroscopic and imaging techniques – have enriched all the disciplines of fundamental and applied sciences. In the current research scenario, most of the techniques of generation and detection of electromagnetic THz radiation are based on infrared femtosecond lasers. A rapid growth in THz technology for more than a decade emanates from a parallel development of ultrafast lasers and efficient THz emitters and detectors. In this chapter, I will briefly review some well-established tabletop techniques of THz generation and detection based on modulated current density in semiconductors, optical rectification, and electro-optic sampling in nonlinear crystals and intersubband transition-induced intense emission in semiconductor superlattices called THz quantum cascade lasers. The applications of THz technology, i.e., time-domain spectroscopy and imaging, will be discussed in particular context of condensed matter physics. The two main facets of these applications are the realization of ultrafast carrier, spin and polarization dynamics using THz emission spectroscopy and the understanding of the low-energy dynamics/excitations arising from strong correlations probed by the THz time-domain spectroscopy.