TITLE:
Generation of Higher Terahertz Harmonics in Nonlinear Paraelectrics under Focusing in a Wide Temperature Range
AUTHORS:
Volodymyr Grimalsky, Jesus Escobedo-Alatorre, Christian Castrejon-Martinez, Yered Gomez-Badillo
KEYWORDS:
Terahertz Wave Beams, Nonlinear Crystalline Paraelectrics, Different Temperatures, Generation of Harmonics, Initial Focusing
JOURNAL NAME:
Journal of Electromagnetic Analysis and Applications,
Vol.15 No.4,
April
28,
2023
ABSTRACT: It is theoretically investigated the generation of higher harmonics of two-dimensional and three-dimensional terahertz electromagnetic beams in nonlinear crystals. The attention is paid to crystalline paraelectrics like SrTiO3 under the temperatures 60 - 200 K, these crystals possess the cubic nonlinearity. The bias electric field is applied to provide the dominating quadratic nonlinearity. The initial focusing of the beams not only increases the efficiency of generation of higher harmonics, but alto makes possible to select maxima of different higher harmonics at some distances from the input. At lower temperatures the nonlinearity behaves at smaller input amplitudes, whereas at higher temperatures the harmonic generation can be observed at higher frequencies up to 1.5 THz. In three-dimensional beams the peak amplitudes of higher harmonics can be bigger than in two-dimensional beams, but the ratios of these peak values to the maximum values of the focused first harmonic are smaller than in two-dimensional beams.