Enhanced THz emission from unmagnetized plasma using quadratically chirped HChG laser pulse

Abstract

Terahertz (THz) radiation generation through laser-plasma interactions has emerged as a promising approach for producing high-intensity, broadband THz sources. In this study, we investigate the enhancement of THz emission by employing a quadratically chirped Hermite-Cosh-Gaussian laser beam interacting with an underdense plasma. The purpose of this study is to investigate the enhancement of THz emission by employing a quadratically chirped Hermite-Cosh-Gaussian laser beam interacting with an underdense plasma. Tailoring the chirp profile significantly amplifies asymmetric electron motion and transient nonlinear currents, resulting in the generation of stronger and more tunable THz radiation. The results reveal that there is a significant relation between the THz field profile and laser parameters like the chirp parameter $b$, decentred parameter $d$, and mode index $m$ of the Hermite function. Numerical analysis demonstrates that quadratic chirping optimizes the phase matching between the driving beam and the plasma response, resulting in an increased THz yield and a broader spectral bandwidth compared to conventional linear chirping. Our results reveal that the application of quadratic chirp improves temporal phase matching, enhances nonlinear electron motion, and leads to a notable increase in THz field amplitude. We observe that higher-order spatial modes and optimal decentering further amplify the THz yield, and the maximum enhancement is achieved at lower chirp values compared to linear chirping. There is a significant enhancement of THz amplitude at a lower value of the chirp parameter, i.e. $b=0.0099$.These findings underscore the efficacy of chirp engineering as a strategic tool for designing next-generation THz sources based on laser–plasma platforms. The proposed framework holds significant promise for applications in broadband spectroscopy, secure wireless communication, medical diagnostics, and ultrafast material characterization.