UV, IR, and terahertz optics

Features of terahertz radiation generation and interaction with sodium acid phthalate (NaAP) crystal

Ph. A. Kozhevnikov^a, V. L. Manomenova^b, E. B. Rudneva^b, N. N. Kozlova^b, A. S. Sinko<sup>ab

a</sup> Lomonosov Moscow State University
^b National Research Centre "Kurchatov Institute", Moscow

Abstract: A novel terahertz molecular crystal, sodium acid phthalate (NaAP), has been investigated. The high-Q infrared (IR) and Raman-active vibrational modes of NaAP crystal in the terahertz frequency range enable the generation of narrowband terahertz radiation when the medium is excited by ultrashort laser pulses. It has been established that the spectral characteristics of absorption and refraction in the terahertz range strongly depend on temperature and crystal orientation. The obtained results suggest that NaAP crystal is a promising nonlinear optical material for terahertz photonics and optoelectronics.

Keywords: terahertz radiation, molecular crystal, terahertz spectroscopy, nonlinear optical generation.

Received: 02.07.2025
Revised: 27.08.2025
Accepted: 19.09.2025

DOI: 10.61011/OS.2025.09.61768.8346-25