Eur. Phys. J. Plus (2020) 135: 85
https://doi.org/10.1140/epjp/s13360-019-00094-z

Regular Article

Comparison of full-wave models of terahertz photoconductive antenna based on ordinary differential equation and Monte Carlo method

¹ Department of Mathematical Modeling, Vilnius Gediminas Technical University, 10223, Vilnius, Lithuania
² Department of Physical Technologies, Center for Physical Sciences and Technology, 10257, Vilnius, Lithuania
³ Department of Optoelectronics, Center for Physical Sciences and Technology, 10257, Vilnius, Lithuania

^* e-mail: gediminas.slekas@ftmc.lt

Received: 15 October 2019
Accepted: 31 December 2019
Published online: 17 January 2020

Abstract

The investigation and comparison of two full-wave models of photoconductive terahertz antenna, made from low-temperature grown gallium arsenide, is performed. One model solves simple approximation of drift-diffusion equations another uses Monte Carlo simulation for estimation of the electrical current in the active region of antenna. Simulation results revealed that the simple model can be useful in the cases when the duration of photoexcitation is relatively long (FWHM  250 fs). In a case of shorter laser pulses (FWHM  130 fs), electron recombination (or trapping) time should be in the order of 0.1 ps, which is characteristic of highly compensated semiconductors. In other cases, transient dynamics of electron drift velocity at sub-picosecond timescales makes significant impact to the growth speed of the photocurrent. This leads to the overestimation of electric field amplitude in the high-frequency range when the simple model is used. Full-wave simulation shows good agreement with experimental results when the detectors’ response is included in the calculation. The calculated results were confirmed experimentally which increases the reliability of the full-wave model presented in the paper.