On-chip detection of spin-selective routing in plasmonic nanocircuits

TL;DR

This paper demonstrates an integrated nanophotonic device that uses spin-orbit interactions in plasmonic circuits to unidirectionally route surface plasmon polaritons based on photon spin, enabling electrical detection of spin states.

Contribution

It introduces a compact on-chip device utilizing spin-orbit interactions for spin-dependent routing and detection of light in plasmonic nanocircuits, advancing integrated nanophotonics.

Findings

Successful unidirectional excitation of surface plasmon polaritons based on photon spin.

Electrical detection of photon spin states using integrated germanium-based photodetectors.

Device size approximately 6 x 18 micrometers.

Abstract

On-chip manipulating and controlling the temporal and spatial evolution of light is of crucial importance for information processing in future planar integrated nanophotonics. The spin and orbital angular momentum of light, which can be treated independently in classical macroscopic geometrical optics, appear to be coupled on subwavelength scales. We use spin-orbit interactions in a plasmonic achiral nano-coupler to unidirectionally excite surface plasmon polariton modes propagating in seamlessly integrated plasmonic slot waveguides. The spin-dependent flow of light in the proposed nanophotonic circuit allows on-chip electrical detection of the spin state of incident photons by integrating two germanium-based plasmonic-waveguide photodetectors. Consequently, our device serves as a compact ($\sim$ 6 $\times$ 18 $\mu$m$^2$) electrical sensor for photonic spin Hall dynamics. The demonstrated configuration opens new avenues for developing highly-integrated polarization-controlled optical devices that would exploit the spin-degree of freedom for manipulating and controlling subwavelength optical modes in nanophotonic systems.