Waveguide-integrated and portable optomechanical magnetometer

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.Comment: 9 pages, 4 figure

Ultrabroadband and sensitive cavity optomechanical magnetometry

Magnetostrictive optomechanical cavities provide a new optical readout approach to room-temperature magnetometry. Here we report ultrasensitive and ultrahigh bandwidth cavity optomechanical magnetometers constructed by embedding a grain of the magnetostrictive material Terfenol-D within a high quality (Q) optical microcavity on a silicon chip. By engineering their physical structure, we achieve a peak sensitivity of 26 pT/root Hz comparable to the best cryogenic microscale magnetometers, along with a 3 dB bandwidth as high as 11.3 MHz. Two classes of magnetic response are observed, which we postulate arise from the crystallinity of the Terfenol-D. This allows single crystalline and polycrystalline grains to be distinguished at the level of a single particle. Our results may enable applications such as lab-on-chip nuclear magnetic spectroscopy and magnetic navigation. (c) 2020 Chinese Laser Pres

Precision Magnetometers for Aerospace Applications: A Review

Aerospace technologies are crucial for modern civilization; space-based infrastructure underpins weather forecasting, communications, terrestrial navigation and logistics, planetary observations, solar monitoring, and other indispensable capabilities. Extraplanetary exploration—including orbital surveys and (more recently) roving, flying, or submersible unmanned vehicles—is also a key scientific and technological frontier, believed by many to be paramount to the long-term survival and prosperity of humanity. All of these aerospace applications require reliable control of the craft and the ability to record high-precision measurements of physical quantities. Magnetometers deliver on both of these aspects and have been vital to the success of numerous missions. In this review paper, we provide an introduction to the relevant instruments and their applications. We consider past and present magnetometers, their proven aerospace applications, and emerging uses. We then look to the future, reviewing recent progress in magnetometer technology. We particularly focus on magnetometers that use optical readout, including atomic magnetometers, magnetometers based on quantum defects in diamond, and optomechanical magnetometers. These optical magnetometers offer a combination of field sensitivity, size, weight, and power consumption that allows them to reach performance regimes that are inaccessible with existing techniques. This promises to enable new applications in areas ranging from unmanned vehicles to navigation and exploration