Detection of nanomechanical motion by evanescent light wave coupling

Abstract

The authors demonstrate a technique allowing sensitive nanomechanical motion detection based on the evanescent light wave coupling between two photonic nanowires. Any relative motion between the nanowires results in a change in light coupling, providing a means of registering motion. The in-plane vibrations of a 220 nmϫ 400 nmϫ 10 m nanomechanical resonator were recorded using this method. An analysis of the sensitivity reveals the potential of this integrated technique to provide fast and sensitive motion detection. © 2007 American Institute of Physics. ͓DOI: 10.1063/1.2746067͔ Nanoelectromechanical systems ͑NEMSs͒ have received great attention in recent years. Most research has focused on resonant devices for sensor applications. 1,2 Through scaling of the mechanical sensing element from the micron-to the nanoscale, researchers were able to improve the detection limits in force and mass sensing drastically. Devices sensitive enough to measure the magnetic moment of a single electron spin 3 or to perform zeptogram scale mass sensing 4 have resulted from efforts in scaling. A central problem in the development of even more sensitive mechanical sensors is the fast and high-precision detection of motion. In many cases, the performance of the sensor is restricted by the efficiency of the motion detection method employed, more so than by the inherent capabilities of the mechanical element. Much research has been devoted to solving this problem and a myriad of optical and electronic techniques has been developed. 5 Optical motion detection techniques have the inherent advantage that optical signals can be communicated with very large bandwidth. 6-8 Unfortunately, for conventional optical techniques, diffraction effects limit the attainable detection limits when the mechanical devices are scaled. It has been anticipated that these issues can be overcome by integration of mechanical sensors with nanophotonics and by exploiting optical near-field effects. 1,5 Recently, it was shown that motion of micron-scale devices can be monitored through changes in end-to-end alignment of optical waveguides. [9][10][11] In this letter, we propose an integrated and near-field optical motion detection technique that exploits near-field optical evanescent-wave coupling. We demonstrate that the technique works efficiently for nanoscale mechanical resonators, with greater sensitivity than conventional optical techniques.The approach offers potential for applications where robust and sensitive measurement of motion is required and applications requiring remote detection or detection of motion in harsh environments. The integration of the device with photonic circuitry reduces the complexity of addressing large arrays of devices.The detection of nanomechanical motion is achieved through the near-field coupling of light from a photonic waveguide to a mechanical resonator. The mechanical resonator acts as a photonic waveguide; when the evanescent tails of the guided modes of the resonator and waveguide overlap, photons tunnel from one wavegu...

Single laser modulated drive and detection of a nano-optomechanical cantilever

“…The general principles of NOMS detection involve an interaction between the mechanical resonator and a nanophotonic device such as a waveguide [8][9][10] or optical cavity. [11][12][13][14][15][16] The motion of the beam will modulate the optical properties of the nanophotonic structure which is detected as a power modulation at the device output.…”

Strong coupling between two distant electronic spins via a nanomechanical resonator

“…With advances in micro-manufacturing technologies, it is possible to produce nanomechanical resonators (NAMRs) with high quality factors, high resonance frequencies, and small effective masses [5][6][7]. These artificial structures could be utilized for high precision detectors [5,[8][9][10][11][12] and to test quantum phenomena at macroscopic scales [13][14][15][16][17][18][19].…”

Characterization of Strongly Coupled Si-Wire Waveguides for High-Density Optical WDM and Sensing Applications

“…Micro-ring assisted ODCs are shown to have wide range of spectral characteristics [9], but their structures are more sensitive to fabrication imperfections than those without micro-ring. Directional couplers recently have received great attention in optical micro/nano electromechanical systems (MEMS/NEMS) devices as well, and have been implemented as nanomechanical motion detectors [10], [11], phase shifters [12], frequency and wavelength selective components [13], optomechanical switches [14] and interferometric devices [15]. The exponential dependency of the evanescent field bounded by the parallel waveguides on their separation is used to control the gradient forces between the nanomechanical beams [16], [17].…”