Ultrabroadband and sensitive cavity optomechanical magnetometry

Abstract

Magnetostrictive optomechanical cavities provide a new optically-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/ √ 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-and poly-crystalline 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.

Precision Magnetometers for Aerospace Applications: A Review

“…Possible alternative high-sensitivity instruments include miniaturized atomic magnetometers [ 122 ] and ultra-sensitive integrated magnetostrictive magnetometers [ 11 , 20 , 123 ].…”

“…Magnetostrictive magnetometers [ 11 , 20 , 124 , 125 , 126 , 127 ] rely on the strain induced in a magnetostrictive material (such as galfenol or Terfenol-D) for detection of the magnitude of applied magnetic fields. Depending on the design of the magnetometer, applying a magnetic field to the magnetostrictive material may cause motion, stress, a force or a torque, which can be detected in a number of ways, but are usually read out electronically or optically.…”

“…An example is shown in Figure 7 b [ 131 ]. In most optomechanical magnetometers [ 20 , 123 , 131 , 144 , 145 , 146 , 147 ], the deformation is due to magnetostrictive coatings or fillings that exert a field-dependent force (much like the aforementioned magnetostrictive magnetometers). Related designs [ 145 , 148 , 149 , 150 , 151 , 152 ] respond to the magnetic field gradient via the dipole force, or enhance the magnetostrictive response using ferromagnetic resonance [ 153 ].…”

“…A particular focus of the review is on emerging magnetometer technologies that use optical readout [ 18 , 19 , 20 ], their performance characteristics, and their potential aerospace applications. This is motivated in part by the exponential growth in the use of unmanned aerial vehicles, together with proposals to use magnetometer-equipped drones for extraplanetary exploration [ 21 , 22 , 23 ].…”

“…This is motivated in part by the exponential growth in the use of unmanned aerial vehicles, together with proposals to use magnetometer-equipped drones for extraplanetary exploration [ 21 , 22 , 23 ]. The optical magnetometers considered in this review include atomic magnetometers (see, e.g., in [ 18 ]), magnetometers based on quantum defects in diamond (see, e.g., in [ 19 ]), and optomechanical magnetometers (see, e.g., in [ 20 ]). While each of these kinds of magnetometer have quite different characteristics, in general, a key attraction has been that they offer exquisite sensitivity without requiring cryogenic cooling.…”