Waveguide-integrated and portable optomechanical magnetometer

TL;DR

This paper introduces a scalable, integrated optomechanical magnetometer on a silicon chip that uses a waveguide for excitation and readout, achieving high sensitivity with portable electronics in ambient conditions.

Contribution

It presents the first waveguide-integrated, portable optomechanical magnetometer with on-chip excitation and readout, maintaining high sensitivity and quality factors.

Findings

High sensitivity and dynamic range in ambient conditions

Retention of high-quality optical whispering gallery modes

Effective operation with portable electronics

Abstract

Optomechanical magnetometers enable highly sensitive magnetic field sensing. However, all such magnetometers to date have been optically excited and read-out either via free space or a tapered optical fiber. This limits their scalability and integrability, and ultimately their range of applications. Here, we present an optomechanical magnetometer that is excited and read out via a suspended optical waveguide fabricated on the same silicon chip as the magnetometer. Moreover, we demonstrate that thermomechanical noise limited sensitivity is possible using portable electronics and laser. The magnetometer employs a silica microdisk resonator selectively sputtered with a magnetostrictive film of galfenol (FeGa) which induces a resonant frequency shift in response to an external magnetic field. Experimental results reveal the retention of high quality-factor optical whispering gallery mode resonances whilst also demonstrating high sensitivity and dynamic range in ambient conditions. The use of off-the-shelf portable electronics without compromising sensor performance demonstrates promise for applications.