Terahertz emission from metal nanoparticle array

Abstract

We demonstrate theoretically that ultrafast heating of metal nanoparticles by the laser pulse should lead to the generation of coherent terahertz (THz) radiation during the heat redistribution process. It is shown that after the femtosecond laser pulse action, the time-dependent gradient of the electronic temperature induces low-frequency particle polarization with the characteristic timescale of about fractions of a picosecond. In the case of the directed metallic pattern, the THz pulse waveform can be controlled by changing the geometry of the particle. The proposed THz generation mechanism can be the basis for interpretation of recent experiments with metallic nanoparticles and nanostructures.

Optical excitation of surface plasmons and terahertz emission from metals

“…We performed numerical study of the discussed mechanism of THz field generation on the basis of hydrodynamic equations for free electrons in metal and Maxwell equations. The computational scheme was similar to the one used in previous studies of optical-to-THz conversion on flat metal surfaces and in arrays of nanoparticles [10,16]. First of all, numerical modeling demonstrates fairly good agreement with the analytical formula for the generated THz field given by Eq.…”

Metallic and dielectric metasurfaces in photoconductive terahertz devices: a review

“…[133][134][135][136] In this case, the THz generation occurs due to nonlinear optical processes 134 as well as the heat redistribution inside metal due to electron heating by an optical excitation. 137,138 However, the emitted THz power of the standalone metal metasurface is relatively low compared with the plasmonic PCA 69 and even to the surface photo-Dember THz emitter 136 and amounts, on average, to 0.15 mW, corresponding to an optical-to-THz conversion efficiency of up to 0.01% at 5.8 THz. 135 Furthermore, both metallic and dielectric metasurface configurations can be designed to effectively interact with THz radiation and thus can be used in ultrasensitive THz sensors, THz absorbers, highly selective THz detectors, tunable THz field modulators, [139][140][141][142] and THz mirrors, 143 as well as to control a wavefront at THz frequency, 144 etc.…”

Numerical simulation of 2D electrodynamic problems with unstructured triangular meshes

“…From discreet energy conservation law (10) it follows that • all eigenvectors of M operator are real; • every two eigenvectors with different eigenvalues are orthogonal in the scope of metric (7). With the above conclusions we can use "complex time" method to find eigenvectors and eigenvalues.…”

“…Being normalized at each step at some point any random initial vector will converge to first eigenvector since all other solutions will not survive due to lower eigenvalues. Next eigenvectors can be found using the fact that all eigenvectors with different eigenvalues are orthogonal in metric (7). So we can withdraw found eigenvector from any initial vector and start from it.…”