Photocurrent at oblique illumination and reconstruction of wavefront direction with 2d photodetectors

TL;DR

This paper demonstrates that symmetric metal-2DES photodetectors can determine the direction of oblique light incidence through photocurrent measurements, enabling wavefront reconstruction.

Contribution

It introduces a novel method for reconstructing light incidence direction using photocurrent in symmetric junctions of metals and 2DES, including angle quantification via plasmon resonance.

Findings

Photocurrent occurs at oblique incidence independent of rectification.

Photocurrent direction indicates the quadrant of light incidence.

Angle determination is enhanced by 2D plasmon resonance.

Abstract

Many contemporary photodetectors operate beyond the readout of light intensity and enable the reconstruction of spectrum and polarization at the single-pixel level. However, the determination of light incidence direction with reconstructive detectors has not been realized so far. We show that photodetectors based on symmetric junctions of metals and 2d electron systems (2DES) enable (1) zero-bias photocurrent at oblique light incidence (2) reconstruction of incidence direction based on photocurrent measurements at variable carrier density. The former effect is based on peculiar electrodynamics of metal-contacted 2DES, where spatial variations of incident field phase translate into strong variations of local field amplitude. The local absorbances at two opposite metal-2DES junctions at oblique incidence are dissimilar, which results in finite photocurrent independent of microscopic rectification mechanism at these junctions. The direction of photocurrent uniquely determines the quadrant of light incidence. Quantitative determination of incidence angle becomes possible under conditions of 2d plasmon resonance at variable carrier density. In such a case, obliquely incident radiation excites the asymmetric plasmon modes, which amplitude carries unique information about angle of incidence.