Laser intensity profile based terahertz field enhancement from a mixture of nano-particles embedded in a gas.

P Varshney,M Kundu,A P Singh,K Gopal

doi:10.1007/s11082-022-03597-9

Abstract

Nano-particle embedded system plays an importance in developing of future terahertz (THz) radiation source for real-world applications. The laser interactions with nanoparticle embedded system can produce a wide range of THz radiation due to plasma oscillations excitation. We investigate THz field generation from the laser-beat wave interaction with a mixture of spherical and cylindrical graphite nanoparticles in argon gas. Different laser intensity distributions such as Gaussian, cosh-Gaussian, flat-top and ring shape laser pulses have been studied in this work. The relevant plasmon resonance conditions with appropriate symmetry of spherical nanoparticles and cylindrical nanoparticles are discussed. THz field is enhanced upto the order of 10^{2} when the laser intensity redistributes along the polarization direction for a ring shape field envelope.

Highlights

IntroductionTerahertz (THz) radiation lies in between microwave and infrared range of electromagnetic (EM) wave spectrum
We have considered the redistribution of laser intensity considering the field profile that has beam decentred parameter; this parameter allows the intensity redistribution in space
Since transverse current is a key source for radiation generation, laser intensity redistribution is treated as a significant parameter in present numerical calculations to estimate the properties of THz radiations

Summary

Introduction

Terahertz (THz) radiation lies in between microwave and infrared range of electromagnetic (EM) wave spectrum. Linearmode conversion (Sheng et al 2005b) has been another way to produce THz radiation in non-uniform plasmas, where laser wakefield is converted into electromagnetic radiation with conversion efficiency scaling as ~ T , where T and L are the terahertz and laser L wave frequency, respectively. Properties of THz radiation can be tuned using the laser intensity and the scale-length of the non-uniform plasmas (Sheng et al 2005a). Nonlinear mixing of laser beat wave with non-uniform plasmas can generate THz fields under appropriate phase matching conditions (Singh and Sharma 2013; Varshney et al 2018). Electron photoemission and ponderomotive acceleration through surface enhanced optical fields can produce THz radiation from gold nano-rods when illuminated by intense laser pulses with different central wavelength (Takano et al 2019).

Physical model and THz field calculation

Findings

Result and discussion

Conclusion