Spin detection with a micromechanical trampoline: towards magnetic resonance microscopy harnessing cavity optomechanics

Abstract

We explore the prospects and benefits of combining the techniques of cavity optomechanics with efforts to image spins using magnetic resonance force microscopy (MRFM). In particular, we focus on a common mechanical resonator used in cavity optomechanics-high-stress stoichiometric silicon nitride (Si 3 N 4 ) membranes. We present experimental work with a 'trampoline' membrane resonator that has a quality factor above 10 6 and an order of magnitude lower mass than a comparable standard membrane resonators. Such high-stress resonators are on a trajectory to reach 0.1 aN Hz force sensitivities at MHz frequencies by using techniques such as soft clamping and phononic-crystal control of acoustic radiation in combination with cryogenic cooling. We present a demonstration of force-detected electron spin resonance of an ensemble at room temperature using the trampoline resonators functionalized with a magnetic grain. We discuss prospects for combining such a resonator with an integrated Fabry-Perot cavity readout at cryogenic temperatures, and provide ideas for future impacts of membrane cavity optomechanical devices on MRFM of nuclear spins.

Fractal-like Mechanical Resonators with a Soft-Clamped Fundamental Mode

“…This boundary loss suppression does not require the structure to extend beyond one acoustic wavelength and therefore can enhance the quality factor of the fundamental resonator mode, as well as of a multitude of other low-order modes at the same time. Our results are relevant to the design of beam [21][22][23] and tethered-membrane [19,28] nanomechanical resonators, as well as the suspensions of macroscopic test masses [24,25]. The example nanoresonator design presented in this work should be amenable to nanofabrication using conventional techniques for patterning and suspending high-stress films.…”

Analysis of Membrane Phononic Crystals with Wide Band Gaps and Low-Mass Defects

“…However, under conditions where both these devices are radiation-loss dominated, device A has the potential to outperform device C in force sensitivity due to its robust acoustic isolation, or equivalently achieve equal radiation isolation with a smaller number of unit cells. The low mass trampoline defect archetype also incorporates high stress tethers, which can be readily utilized to deposit metallic or magnetic materials for further device functionalization [25].…”

“…For designs in this work, we specifically have in mind applications where high force sensitivity is desired for MHz-scale membrane resonators simultaneously coupled to an optical mode and a spin or electrical degree of freedom [24][25][26]. For these functionalization purposes, we considered a few design constraints.…”

Influence of clamp-widening on the quality factor of nanomechanical silicon nitride resonators

“…Additional studies have been made employing the same arXiv:1905.06730v2 [physics.app-ph] 28 May 2019 trampoline geometry for ultralow-noise sensors 26 and magnetic resonance force microscopy 27 . While large Qs are observed in these cases as well, they can be explained through the framework of dissipation dilution.…”