Ultrasensitive measurement of microcantilever displacement below the shot-noise limit

Journal Article · Thu Apr 23 00:00:00 EDT 2015 · Optica

DOI:https://doi.org/10.1364/OPTICA.2.000393· OSTI ID:1185444

Pooser, Raphael C. ^[1]; Lawrie, Benjamin J. ^[1]

---

1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

The displacement of micro-electro-mechanical-systems (MEMs) cantilevers is used to measure a variety of phe- nomena in devices ranging from force microscopes for single spin detection[1] to biochemical sensors[2] to un- cooled thermal imaging systems[3]. The displacement readout is often performed optically with segmented de- tectors or interference measurements. Until recently, var- ious noise sources have limited the minimum detectable displacement in MEMs systems, but it is now possible to minimize all other sources[4] so that the noise level of the coherent light eld, called the shot noise limit (SNL), becomes the dominant source. Light sources dis- playing quantum-enhanced statistics below this limit are available[5, 6], with applications in gravitational wave astronomy[7] and bioimaging[8], but direct displacement measurements of MEMS cantilevers below the SNL have been impossible until now. Here, we demonstrate the rst direct measurement of a MEMs cantilever displace- ment with sub-SNL sensitivity, thus enabling ultratrace sensing, imaging, and microscopy applications. By com- bining multi-spatial-mode quantum light sources with a simple dierential measurement, we show that sub-SNL MEMs displacement sensitivity is highly accessible com- pared to previous eorts that measured the displacement of macroscopic mirrors with very distinct spatial struc- tures crafted with multiple optical parametric ampliers and locking loops[9]. We apply this technique to a com- mercially available microcantilever in order to detect dis- placements 60% below the SNL at frequencies where the microcantilever is shot-noise-limited. These results sup- port a new class of quantum MEMS sensor whose ulti- mate signal to noise ratio is determined by the correla- tions possible in quantum optics systems.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: ORNL LDRD Director's R&D; USDOE
• Grant/Contract Number: AC05-00OR22725
• OSTI ID: 1185444
• Journal Information: Optica, Journal Name: Optica Journal Issue: 5 Vol. 2; ISSN 2334-2536
• Publisher: Optical Society of America
• Country of Publication: United States
• Language: English

Related Subjects

47 OTHER INSTRUMENTATION
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
quantum optics
squeezed states