Optical Reading of Nanoscale Magnetic Bits in an Integrated Photonic Platform

TL;DR

This paper introduces a hybrid plasmonic-photonic device capable of optically reading nanoscale magnetic bits beyond the diffraction limit, enhancing magneto-optical detection for integrated photonic and spintronic applications.

Contribution

The paper presents a novel integrated hybrid plasmonic-photonic device that enables nanoscale magnetic bit detection beyond diffraction limits using enhanced magneto-optical effects.

Findings

Detects magnetic bits down to ~100x100 nm²

Achieves >0.5% intensity contrast for 200x100 nm² bits

Simulates effective magneto-optical read-out in integrated platform

Abstract

In this paper, we propose a compact integrated hybrid plasmonic-photonic device for optical reading of nanoscale magnetic bits with perpendicular magnetic anisotropy in a magnetic racetrack on top of a photonic waveguide on the indium phosphide membrane on silicon platform. The hybrid device is constructed by coupling a doublet of V-shaped gold plasmonic nanoantennas on top of the indium phosphide waveguide. By taking advantage of the localized surface plasmons, our hybrid device can enable detection of the magnetization state in magnetic bits beyond the diffraction limit of light and enhance the polar magneto-optical Kerr effect (PMOKE). We further illustrate how combining the hybrid device with a plasmonic polarization rotator provides magneto-optical read-out by transforming the PMOKE-induced polarization change into an intensity variation of the waveguide mode. According to the simulation results based on a three-dimensional finite-difference time-domain method, the hybrid device can detect the magnetization states in targeted bits in a magnetic racetrack medium down to ~ 100x100 nm2, regardless of the magnetization state of the rest of the racetrack with a relative intensity contrast of greater than 0.5% for a ~ 200x100 nm2 magnetic bit. We believe our hybrid device can be an enabling technology that can connect integrated photonics with nanoscale spintronics, paving the way toward ultrafast and energy efficient advanced on-chip applications.