Optical heterodyne microscopy of operating spin Hall nano-oscillator arrays

TL;DR

This paper demonstrates optical heterodyne microscopy techniques to non-invasively characterize high-frequency auto-oscillations in spin Hall nano-oscillator arrays, validating the approach across different materials and configurations.

Contribution

It introduces a robust, phase-resolved optical heterodyne method for spatially mapping spintronic nano-oscillator dynamics, advancing non-invasive characterization tools.

Findings

Optical heterodyne detection effectively characterizes SHNO auto-oscillations.

Material and power influences on SHNO dynamics are systematically studied.

Phase mapping of SHNOs supports potential applications in Ising Machines.

Abstract

Optical heterodyne detection is a powerful technique for characterizing a wide range of physical excitations. Here, we use two types of optical heterodyne detection techniques (fundamental and parametric pumping) to microscopically characterize the high-frequency auto-oscillations of single and multiple nano-constriction spin Hall nano-oscillators (SHNOs). To validate the technique and demonstrate its robustness, we study SHNOs made from two different material stacks, NiFe/Pt and W/CoFeB/MgO, and investigate the influence of both the RF injection power and the laser power on the measurements, comparing the optical results to conventional electrical measurements. To demonstrate the key features of direct, non-invasive, submicron, spatial, and phase-resolved characterization of the SHNO magnetodynamics, we map out the auto-oscillation magnitude and phase of two phase-binarized SHNOs used in Ising Machines. This proof-of-concept platform establishes a strong foundation for further extensions, contributing to the ongoing development of crucial characterization techniques for emerging computing technologies based on spintronics devices