Cavity Optomechanical Magnetometer

Abstract

A cavity optomechanical magnetometer is demonstrated. The magnetic field induced expansion of a magnetostrictive material is resonantly transduced onto the physical structure of a highly compliant optical microresonator, and read-out optically with ultra-high sensitivity. A peak magnetic field sensitivity of 400 nT Hz −1/2 is achieved, with theoretical modeling predicting the possibility of sensitivities below 1 pT Hz −1/2 . This chipbased magnetometer combines high-sensitivity and large dynamic range with small size and room temperature operation.Ultra-low field magnetometers are essential components for a wide range of practical applications including geology, mineral exploration, archaeology, defence and medicine [1]. The field is dominated by superconducting quantum interference devices (SQUIDs) operating at cryogenic temperatures [2]. Magnetometers capable of room temperature operation offer significant advantages both in terms of operational costs and range of applications. The state-of-the-art are magnetostrictive magnetometers with sensitivities in the range of fT Hz −1/2 [3, 4], and atomic magnetometers which achieve impressive sensitivities as low as 160 aT Hz −1/2 [5] but with limited dynamic range due to the nonlinear Zeeman effect [2,6]. Recently, significant effort has been made to miniaturize room temperature magnetometers. However both atomic and magnetostrictive magnetometers remain generally limited to millimeter or centimeter size scales. Smaller microscale magnetometers have many potential applications in biology, medicine, and condensed matter physics [7,8]. A particularly important application is magnetic resonance imaging, where by placing the magnetometer in close proximity to the sample both sensitivity and resolution may be enhanced [9], potentially enabling detection of nuclear spin noise [10], imaging of neural networks [7], and advances in areas of medicine such as magneto-cardiography[1, 6] and magneto-encephalography [11].In the past few years, rapid progress has been achieved on NV center based magnetometers. They combine sensitivities as low as 4 nT Hz −1/2 with room temperature operation, optical readout and nanoscale size [12] and are predicted theoretically to reach the fT Hz −1/2 range [13]. This has allowed three-dimensional magnetic field imaging at the micro scale using ensembles of NV-centers [7], and magnetic resonance [14] and field imaging[13] at the nanoscale using single NV centers. In spite of these extraordinary achievements applications are hampered by fabrication issues and the intricacy of the read-out schemes [15]. Furthermore miniaturization is limitied by the bulky read-out optics, the magnetic field coils for state preparation and the microwave excitation device [7].In this letter we present the concept of a cavity optomechanical field sensor which combines room temperature operation and high sensitivity with large dynamic range and small size. The sensor leverages results from the emergent field of cavity optomechanics where ultra-sensitive force and positi...

Microphotonic Forces from Superfluid Flow

“…In cavity optomechanics, in particular, optical forces enable cooling and control of microscale mechanical oscillators that can be used for ultrasensitive detection of forces, fields and mass [7][8][9], quantum and classical information systems [10], and fundamental science [11,12]. Recent progress has seen radiation pressure used for coherent state swapping [13], ponderomotive squeezing [14], and ground state cooling [15], while static gradient forces have enabled all-optical routing [16] and nonvolatile mechanical memories [17].…”

Ultrahigh Q-frequency product for optomechanical disk resonators with a mechanical shield

“…The interaction of light with mechanical motionoptomechanics [1][2][3] and its related concepts-is now investigated in a wide variety of experimental settings. Optomechanical resonators of various size and geometry continue to be developed and optimized for applications like weak force sensing 4,5 or optical cooling of mesoscopic mechanical systems down to the quantum regime. 6,7 For most of these applications, high mechanical frequency f, strong optomechanical coupling g 0 , and low optical/mechanical dissipation are desirable.…”

Optimal quantum parameter estimation in a pulsed quantum optomechanical system

“…With the rapid advance of technology, quantum cavity optomechanics [17][18][19], in which the mechanical resonator is coupled to the optical field by radiation pressure or photothermal force, has excited a burst of interest [20] due to the following two reasons: On one hand, the cavity optomechanical system provides a new platform to investigate the fundamental questions on the quantum behavior of macroscopic system [21] and even the quantum-to-classical transition [22,23]; On the other hand, it brings a novel quantum device for applications in ultra-high precision measurement [24][25][26][27][28], gravitation-wave detection [29], quantum information processing [30] and quantum illumination [31]. Many interesting researches in cavity optomechanical systems, such as optomechanically induced transparency [32,33], ground-state cooling of the mechanical resonator [34][35][36][37][38], optomechanical entanglement [39,40], optimal state estimation [41], have been reported.…”