Bridging the TeraHertz Gap

In recent times the so called ‘Terahertz (THz) gap’, the region between Microwave and Infrared radiation, has become accessible mainly due to availability of ultrafast lasers. THz spectroscopy has immense potential of probing numerous physical, chemical, and biological processes occurring in the picosecond timescale and with energies in meV, such as intra and intermolecular vibrations in molecules and molecular assemblies, charge carriers and lattice vibrations in crystalline solids, relaxation dynamics in liquids and biomolecules. 
In our lab at IISER-Pune, we use an air-plasma based technique for the generation and detection of THz light to achieve high power-high bandwidth regime (0.5 to 15 THz). In addition to time-domain THz (THz-TDS) and time-resolved THz spectroscopy (TRTS), we also use optical Kerr effect (OKE) spectroscopy that provides collective response of depolarized Raman modes in a transparent condensed medium. In this talk, I will present a general introduction to THz spectroscopy; followed by discussion on how the air-plasma based technique works in generation and detection, and present some of our experimental results on lead-halide perovskites and non-ideal liquid mixture employing these techniques.

References: 

1) Sneha Banerjee, Gurivireddy Yettapu, Sohini Sarkar, Pankaj Mandal, Broadband Terahertz Spectroscopy, Springer Nature, vol. 13, 117-142 (2021).

2) Gurivi Reddy Yettapu, Debnath Talukdar, Sohini Sarkar, Abhishek Swarnkar, Angshuman Nag, Prasenjit Ghosh, and Pankaj Mandal, Nano Letters 16 (8), 4838-4848 (2016).