Hybrid Computational Simulation and Study of Continuous Wave Terahertz Photomixers

Abstract

A hybrid numerical simulation method is presented to model and analyze integrated terahertz (THz) photomixer antennas. The proposed computational method combines an optoelectronic solver and a full-wave electromagnetic solver to rigorously model continuous wave (CW) THz photomixer sources. In this hybrid computational approach, the photomixer source is modeled in a rigorous manner without any approximation. The optoelectronic solver is used to find absorbed optical intensity and optical carrier generation rate inside the fast photoconductive region through solving an optical scattering problem. Then, the equations governing the charge carrier transport inside the photoconductor are solved to give THz photo-current by considering realistic material parameters. Finally, through a full-wave electromagnetic solver, and using calculated photo-current from the optoelectronic simulator, antenna parameters and radiated THz power are obtained. Using the proposed hybrid simulation method the effects of photomixer parameters on the THz photo-current and radiated power is rigorously investigated for several geometries. Moreover, results of a parametric study on various factors such as carrier lifetime of material, incident optical power density, applied bias voltage, THz beat frequency, and the gap size are presented. The method can be used for accurate design refinement at pre-fabrication stage.

A tunable high-impedance THz antenna array

“…. For maximum input impedance, the total length of each element reads approximately as [4] = = 2 (2) in which and are the plasmonic wavelength and the guided wave number, respectively. If the antenna is wide enough, we can use the following equation to approximate guided wave number [9]…”

“…Generation and detection of THz radiation has therefore been the focus of many academic and industrial research efforts over the last decade. Among the various types of sources and detectors, THz photoconductive antennas are one of the most popular methods for THz generation and detection in established THz experimental setups [2].…”

“…In the photomixer the beams of two single mode lasers or a dual mode laser with different frequencies are mixed. The system is designed such that the difference of the laser frequencies falls in the THz band [2]. Due to the photomixing effect, a continuous wave (CW) photocurrent is generated with the beat frequency in THz range.…”

Graphene-based archimedean spiral THz antenna

“…In recent years, graphene has been exploited in terahertz range of frequencies covering the spectral range of 0.1-10 THz. For example, optical pumping of graphene can exhibit negative-dynamic conductivity in THz range of frequencies, which may bring new types of THz lasers [3].…”

“…THz photoconductive antennas have dominantly been used for THz generation and detection [3]. A typical THz photoconductive antenna consists of an ultrafast photoconductive material called photomixer and two deposing electrodes (usually gold) resembling an antenna.…”