Photocurrent detection of the orbital angular momentum of light

Abstract

Applications that use the orbital angular momentum (OAM) of light show promise for increasing the bandwidth of optical communication networks. However, direct photocurrent detection of different OAM modes has not yet been demonstrated. Most studies of current responses to electromagnetic fields have focused on optical intensity–related effects, but phase information has been lost. In this study, we designed a photodetector based on tungsten ditelluride (WTe2) with carefully fabricated electrode geometries to facilitate direct characterization of the topological charge of OAM of light. This orbital photogalvanic effect, driven by the helical phase gradient, is distinguished by a current winding around the optical beam axis with a magnitude proportional to its quantized OAM mode number. Our study provides a route to develop on-chip detection of optical OAM modes, which can enable the development of next-generation photonic circuits.

Ultrafast control of fractional orbital angular momentum of microlaser emissions

“…The vectorial nature of light empowers full control of topological features with spatially phase-variant fields, revealing vortex beams carrying orbital angular momentum (OAM) and spin angular momentum (SAM) in addition to the well-known linear momentum 1 . Owing to the intriguing properties of optical vortices, OAM beams have found numerous applications in particle guiding and trapping, optical communication, quantum computation, holography and high-precision imaging, and novel light-matter interactions with topological materials [2][3][4][5][6][7][8] . Only quite recently have optical beams carrying a fractional orbital angular momentum (FOAM) 9,10 attracted considerable attention for their unusual properties and potential applications 11,12 .…”

Vortex 4.0 on chip

“…Currently, two papers 10,11 have been published in Science side by side to address these challenges in OAMbased optical communication on chip. Zhang et al 10 reported an OAM-tunable vortex microlaser that provides chiral light states of variable topological charges at a single telecommunication wavelength.…”

“…Zhang et al 10 reported an OAM-tunable vortex microlaser that provides chiral light states of variable topological charges at a single telecommunication wavelength. Ji et al 11 demonstrated an OAM photodetector based on tungsten ditelluride (WTe 2 ) to facilitate direct characterization of the topological charge of a vortex beam. These two works provide routes for the development of fourth-generation (4.0) vortex technology on chip.…”

“…These techniques will find applications in on-chip optical communication, computing, and information security in both classical and quantum regimes. Dynamic switching between different OAM modes over time not only enables high-density data transmission but also increases the security of wired and wireless states of the generated vortex light 11 . The non-Hermitian interaction mediated by the externally applied control pump on the bus waveguide can be flexibly switched for the emission of OAM states with desirable chirality from the spin-orbit engineered microring.…”

Terahertz response of monolayer and few-layer WTe_2 at the nanoscale

“…Angle resolved photoemission spectroscopy (ARPES), however, revealed that bi-layers could also be weakly semimetallic with a small negative gap [12]. A combination of inverted bands, strong spin-orbit coupling and low crystal symmetry makes few-layer WTe2 an ideal system for studying topological effects such as the nonlinear anomalous Hall effect [13] [14] [15] and various unusual photogalvanic effects [16] [17] [18]. The goal of the present study is to explore the evolution of the low-energy electrodynamics of WTe2 from monolayer to few-layer variants (Fig.…”