Optomechanical Magnetometry with a Macroscopic Resonator

Abstract

We demonstrate a centimeter-scale optomechanical magnetometer based on a crystalline whispering gallery mode resonator. The large size of the resonator allows high magnetic field sensitivity to be achieved in the hertz to kilohertz frequency range. A peak sensitivity of 131 pT Hz −1/2 is reported, in a magnetically unshielded non-cryogenic environment and using optical power levels beneath 100 µW. Femtotesla range sensitivity may be possible in future devices with further optimization of laser noise and the physical structure of the resonator, allowing applications in high-performance magnetometry.

Quantum enhanced optomechanical magnetometry

“…Cavity optomechanics [1][2][3] has attracted increasing research interest for both fundamental studies and practical applications. Strong radiation pressure coupling between high quality mechanical and optical resonances has enabled the demonstration of a range of interesting quantum behaviors, such as ground state cooling of macroscopic mechanical oscillators [4][5][6][7], quantum squeezing of mechanical motion [8][9][10][11], and the production of squeezed light [12,13], while the combination of resonance enhanced mechanical and optical response [14] has enabled precision sensors [15] ranging from kilometer-sized laser interferometer gravitational wave detectors [16,17] to micro/nanoscale siliconchip-based force [18], mass [19], acceleration [20,21], and magnetic field [22][23][24][25] sensors.…”

Phone-sized whispering-gallery microresonator sensing system

“…However, till now all the demonstrations were implemented in optical laboratories with well-set equipment on bulky optical tables, which limit the practical applications of WGM microresonators, e.g., various kinds of sensing, including sensing of single nanoparticle [4][5][6][7], biomolecule [21,22], magnetic field [23,24], angular velocity [25][26][27], gas [28,29], etc. The obstacles of practical applications for WGM sensors lie on two factors: i) the challenge of long-term stability for tapered fiber coupling of cavity modes outside the laboratory, and ii) bulky commercial equipment needed for testing cavity modes, including not only a laser source and a detector but also a function generator and an oscilloscope.…”

Ultrabroadband and sensitive cavity optomechanical magnetometry

“…The resonant enhancement of both optical and mechanical response in a cavity optomechanical system [1,2] has enabled precision sensors [3] of displacement [4,5], force [6], mass [7], acceleration [8,9], ultrasound [10], and magnetic fields [11][12][13][14][15][16]. Cavity optomechanical magnetometers are particulary attractive, promising stateof-the-art sensitivity without the need for cryogenics, with only microwatt power consumption [11][12][13][14]16], and with silicon chip based fabrication offering scalability [15]. For instance, cavity optomechanical magnetometers working in the megahertz frequency range have been demonstrated by using a magnetostrictive material Terfenol-D, either manually deposited onto a microcavity [11,12,14] with a reported peak sensitivity of 200 pT/ √ Hz [12], or sputter coated onto the microcavity with a reported peak sensitivity of 585 pT/ √ Hz [15].…”