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.
We present techniques to model and design membrane phononic crystals with low-mass defects, optimized for force sensing. Further, we identify the importance of the phononic crystal mass contrast as it pertains to the size of acoustic bandgaps and to the dissipation properties of defect modes. In particular, we quantify the tradeoff between high mass contrast phononic crystals with their associated robust acoustic isolation, and a reduction of soft clamping of the defect mode. We fabricate a set of phononic crystals with a variety of defect geometries out of high stress stoichiometric silicon nitride membranes, and measured at both room temperature and 4 K in order to characterize the dissipative pathways across a variety of geometries. Analysis of these devices highlights a number of design principles integral to the implementation of low-mass, low-dissipation mechanical modes into optomechanical systems.
Thin vapor chambers provide a novel solution to thermal management in mobile electronics. In the pursuit of vapor chamber optimization, characterization of the wicking structure can allow for a better understanding of the limitations of the device. This paper presents two novel testing methods: one for measuring the permeability of various wicking structures and another for measuring the capillary pressure. We find that the permeability of the mesh used in the wicking structure and hybridization of wicking-structures can impact what geometries limit performance, besides impacting performance directly. Specifically, while the permeability of a mesh-pillar hybrid wick follows the weighted average of the mesh and pillar permeability, the capillary pressure is determined by the capillary pore size of just the pillars or just the mesh, whichever is larger.
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