Broadband Terahertz Spectroscopy
Sneha Banerjee, Gurivireddy Yettapu, Sohini Sarkar, and Pankaj Mandal
Abstract Terahertz (THz) spectroscopy is a non-contact technique to probe properties and dynamics of molecules and materials in the meV energy range and
picosecond timescales. This chapter describes different popular methods of generation and detection of broadband THz pulses, experimental technique, and data analysis procedures of THz time-domain and time-resolved THz spectroscopy. We have
also reviewed some recent representative works utilizing these methods.
Keywords Terahertz spectroscopy · THz-TDS · TRTS · Picosecond dynamics
1 Introduction
Terahertz (THz) radiation occupies the region between the microwave (<100 GHz)
and the far-infrared band (>10 THz) of the electromagnetic spectrum (Fig. 1). The
term ‘terahertz’ became popular only in the mid-1970s when it was used by spectroscopists to describe the region below the far-infrared [1, 2]. Today, THz spectroscopy
roughly spans from 0.1 to 20 THz, where 1 THz is equivalent to a wavelength of
300 μm, 33.3 cm
−1 in wavenumber, and 4.14 meV in energy. The THz spectral
range bridges the so-called “THz gap” in the electromagnetic spectrum between the
electronics region, which can be described classically, and the photonics, where the
quantum nature of light comes into play.
Terahertz radiation is abundant in our universe. Most objects emit THz radiation above 10 K as part of black body radiation [3], but the emitted waves from
these sources are feeble and go unnoticed. Initially, THz technology was used by
chemists, astronomers, earth, planetary, and space scientists to characterize rotational and vibrational resonances, measure, and map the thermal emission lines of
S. Banerjee · G. Yettapu · P. Mandal (B)
Department of Chemistry, Indian Institute of Science Research and Education, Pune, Maharashtra
411008, India
e-mail: pankaj@iiserpune.ac.in
S. Sarkar
Department of Chemistry, University of Southern California, Los Angeles, CA 90089-0482, USA
© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021
D. K. Singh et al. (eds.), Modern Techniques of Spectroscopy, Progress in Optical Science
and Photonics 13, https://doi.org/10.1007/978-981-33-6084-6_5
117
Sneha Banerjee, Gurivireddy Yettapu, Sohini Sarkar, and Pankaj Mandal
Abstract Terahertz (THz) spectroscopy is a non-contact technique to probe properties and dynamics of molecules and materials in the meV energy range and
picosecond timescales. This chapter describes different popular methods of generation and detection of broadband THz pulses, experimental technique, and data analysis procedures of THz time-domain and time-resolved THz spectroscopy. We have
also reviewed some recent representative works utilizing these methods.
Keywords Terahertz spectroscopy · THz-TDS · TRTS · Picosecond dynamics
1 Introduction
Terahertz (THz) radiation occupies the region between the microwave (<100 GHz)
and the far-infrared band (>10 THz) of the electromagnetic spectrum (Fig. 1). The
term ‘terahertz’ became popular only in the mid-1970s when it was used by spectroscopists to describe the region below the far-infrared [1, 2]. Today, THz spectroscopy
roughly spans from 0.1 to 20 THz, where 1 THz is equivalent to a wavelength of
300 μm, 33.3 cm
−1 in wavenumber, and 4.14 meV in energy. The THz spectral
range bridges the so-called “THz gap” in the electromagnetic spectrum between the
electronics region, which can be described classically, and the photonics, where the
quantum nature of light comes into play.
Terahertz radiation is abundant in our universe. Most objects emit THz radiation above 10 K as part of black body radiation [3], but the emitted waves from
these sources are feeble and go unnoticed. Initially, THz technology was used by
chemists, astronomers, earth, planetary, and space scientists to characterize rotational and vibrational resonances, measure, and map the thermal emission lines of
S. Banerjee · G. Yettapu · P. Mandal (B)
Department of Chemistry, Indian Institute of Science Research and Education, Pune, Maharashtra
411008, India
e-mail: pankaj@iiserpune.ac.in
S. Sarkar
Department of Chemistry, University of Southern California, Los Angeles, CA 90089-0482, USA
© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021
D. K. Singh et al. (eds.), Modern Techniques of Spectroscopy, Progress in Optical Science
and Photonics 13, https://doi.org/10.1007/978-981-33-6084-6_5
117