Theory of helicity-sensitive terahertz radiation detection by field effect transistors

Abstract

Within the two antenna model, we develop a theory of the recently observed helicity-sensitive detection of terahertz radiation by FETs. The effect arises because of the mixing of the ac signals produced in the channel by the two antennas. We calculate the helicity-dependent part of the photoresponse and its dependence on the antenna impedance, gate length, and gate voltage.

Nonlinear photoresponse of field effect transistors terahertz detectors at high irradiation intensities

“…In the case of low radiation intensity (V tr ( u T , where u T is the thermal voltage), Eqs. (11a), (12), and (13) simplifies to Eq. (14a) and DU is proportional to I ir .…”

“…11)). Additional interesting properties of the FET detector were recently discovered, where the photoresponse exhibits sensitivity to radiation helicity 10,12 making FETs promising for the all-electric detection of the radiation Stokes parameters. However, there have been very few studies of THz FET detectors at high radiation intensities.…”

Plasmonic Helicity‐Driven Detector of Terahertz Radiation

“…. They were predicted to be absent for zero loading impedances . Below, we use hydrodynamic approach to study the resonant regime of TeraFET operation.…”

“…Hence, the ac signals at the source and drain have equal frequencies but can have different amplitudes and be shifted by phase with the shift magnitude θ determined by antenna design and have different amplitudes. Importantly, the phase shift θ arises for any antennas and/or contact pads configuration which are asymmetric with respect to the direction of the induced dc current . Taking into account that the radiation induces a dc voltage drop V across the sample, we write the BC as follows …”

“…In the case, when the device is excited by a circularly polarized wave, θ changes sign with changing the helicity of the polarization . We focus on the helicity‐driven effects, that is, on the contribution to the current, which changes sign with replacing θ with − θ or, equivalently, with (for definiteness we put below ).…”