Kirill Dzhikirba | Searcharxiv

arXiv2026

Visibility function and Stokes parameter analysis for non-ideal quarter-wave plates in a polarization contrast scheme

The match of the fourth power of the normalized third Stokes parameter for a single non-ideal quarter-wave plate (QWP) and the visibility function of the polarization contrast measured using a polarimetric setup with parallel polarizers and two identical QWPs was examined and observed. The behavior of the Stokes parameters of a single QWP and the visibility function of the polarization contrast scheme were investigated theoretically using the Fourier-modal method (FMM) and described within the Jones matrix formalism. This analysis was then generalized to a realistic case, accounting for the transmission anisotropy, phase deviation, and misalignment of optical components from their ideal orientations. An analytical expression for the visibility function of the polarization contrast scheme in terms of the normalized Stokes parameters was derived, along with the asymptotic expansions in terms of small parameters representing the phase deviation, transmission anisotropy, and angular misalignment of the polarization contrast scheme. For the investigated silicon-grating-based QWP, good quantitative agreement between the FMM-calculated fourth power of the normalized third Stokes parameter, and the visibility function (FMM-calculated and experimentally measured) was demonstrated over almost the entire investigated frequency range of 200-700 GHz.

physics.optics↗

arXiv2022

Ultralow-noise terahertz detection by p-n junctions in gapped bilayer graphene

Graphene shows a strong promise for detection of terahertz (THz) radiation due to its high carrier mobility, compatibility with on-chip waveguides and transistors, and small heat capacitance. At the same time, weak reaction of graphene's physical properties on the detected radiation can be traced down to the absence of band gap. Here, we study the effect of electrically-induced band gap on THz detection in graphene bilayer with split-gate p-n junction. We show that gap induction leads to simultaneous increase in current and voltage responsivities. At operating temperatures of ~25 K, the responsivity at 20 meV band gap is from 3 to 20 times larger than that in the gapless state. The maximum voltage responsivity of our devices at 0.13 THz illumination exceeds 50 kV/W, while the noise equivalent power falls down to 36 fW/Hz^0.5. These values set new records for semiconductor-based cryogenic terahertz detectors, and pave the way for efficient and fast terahertz detection.

cond-mat.mes-hall↗