We review the field of cavity optomechanics, which explores the interaction between electromagnetic radiation and nano- or micromechanical motion This review covers the basics of optical cavities and mechanical resonators, their mutual optomechanical interaction mediated by the radiation pressure force, the large variety of experimental systems which exhibit this interaction, optical measurements of mechanical motion, dynamical backaction amplification and cooling, nonlinear dynamics, multimode optomechanics, and proposals for future cavity quantum optomechanics experiments In addition, we describe the perspectives for fundamental quantum physics and for possible applications of optomechanical devices

Cavity Optomechanics

This paper presents a review of silicon micromachined accelerometers and gyroscopes. Following a brief introduction to their operating principles and specifications, various device structures, fabrication, technologies, device designs, packaging, and interface electronics issues, along with the present status in the commercialization of micromachined inertial sensors, are discussed. Inertial sensors have seen a steady improvement in their performance, and today, microaccelerometers can resolve accelerations in the micro-g range, while the performance of gyroscopes has improved by a factor of 10/spl times/ every two years during the past eight years. This impressive drive to higher performance, lower cost, greater functionality, higher levels of integration, and higher volume will continue as new fabrication, circuit, and packaging techniques are developed to meet the ever increasing demand for inertial sensors.

/pdf/micromachined-inertial-sensors-esf6197vdc.pdf

Micromachined inertial sensors

http://cds.cern.ch/record/503806/files/0106045.pdf

New developments in the Casimir effect

Nanoelectromechanical systems (NEMS) hold promise for a number of scientific and technological applications. In particular, NEMS oscillators have been proposed for use in ultrasensitive mass detection, radio-frequency signal processing, and as a model system for exploring quantum phenomena in macroscopic systems. Perhaps the ultimate material for these applications is a carbon nanotube. They are the stiffest material known, have low density, ultrasmall cross-sections and can be defect-free. Equally important, a nanotube can act as a transistor and thus may be able to sense its own motion. In spite of this great promise, a room-temperature, self-detecting nanotube oscillator has not been realized, although some progress has been made. Here we report the electrical actuation and detection of the guitar-string-like oscillation modes of doubly clamped nanotube oscillators. We show that the resonance frequency can be widely tuned and that the devices can be used to transduce very small forces.

A tunable carbon nanotube electromechanical oscillator

The micromachining technology that emerged in the late 1980s can provide micron-sized sensors and actuators. These micro transducers are able to be integrated with signal conditioning and processing circuitry to form micro-electromechanical-systems (MEMS) that can perform real-time distributed control. This capability opens up a new territory for flow control research. On the other hand, surface effects dominate the fluid flowing through these miniature mechanical devices because of the large surface-to-volume ratio in micron-scale configurations. We need to reexamine the surface forces in the momentum equation. Owing to their smallness, gas flows experience large Knudsen numbers, and therefore boundary conditions need to be modified. Besides being an enabling technology, MEMS also provide many challenges for fundamental flow-science research.

/pdf/micro-electro-mechanical-systems-mems-and-fluid-flows-44x8s6duky.pdf

Micro-electro-mechanical-systems (mems) and fluid flows

A micromechanical resonator device and a micromechanical device utilizing same are disclosed based upon a radially or laterally vibrating disk structure and capable of vibrating at frequencies well past the GHz range. The center of the disk is a nodal point, so when the disk resonator is supported at its center, anchor dissipation to the substrate is minimized, allowing this design to retain high-Q at high frequency. In addition, this design retains high stiffness at high frequencies and so maximizes dynamic range. Furthermore, the sidewall surface area of this disk resonator is often larger than that attainable in previous flexural-mode resonator designs, allowing this disk design to achieve a smaller series motional resistance than its counterparts when using capacitive (or electrostatic) transduction at a given frequency. Capacitive detection is not required in this design, and piezoelectric, magnetostrictive, etc. detection are also possible. The frequency and dynamic range attainable by this resonator makes it applicable to high-Q RF filtering and oscillator applications in a wide variety of communication systems. Its size also makes it particularly suited for portable, wireless applications, where, if used in large numbers, such a resonator can greatly lower the power consumption, increase robustness, and extend the range of application of high performance wireless transceivers.

Micromechanical resonator device and micromechanical device utilizing same

VHF and UHF MEMS-based vibrating micromechanical resonators equipped with new solid dielectric (i.e., filled) capacitive transducer gaps to replace previously used air gaps have been demonstrated at 160 MHz, with Q's ~ 20,200 on par with those of air-gap resonators, and motional resistances (Rx's) more than 8times smaller at similar frequencies and bias conditions. This degree of motional resistance reduction comes about via not only the higher dielectric constant provided by a solid-filled electrode-to-resonator gap, but also by the ability to achieve smaller solid gaps than air gaps. These advantages with the right dielectric material may now allow capacitively-transduced resonators to match to the 50-377 Omega impedances expected by off-chip components (e.g., antennas) in many wireless applications without the need for high voltages. In addition to lower motional resistance, the use of filled-dielectric transducer gaps provides numerous other benefits over the air gap variety, since it (a) better stabilizes the resonator structure against shock and microphonics; (b) eliminates the possibility of particles getting into an electrode-to-resonator air gap, which poses a potential reliability issue; (c) greatly improves fabrication yield, by eliminating the difficult sacrificial release step needed for air gap devices; and (d) potentially allows larger micromechanical circuits (e.g., bandpass filters comprised of interlinked resonators) by stabilizing constituent resonators as the circuits they comprise grow in complexity

/pdf/vibrating-micromechanical-resonators-with-solid-dielectric-4al27z82hk.pdf

Vibrating micromechanical resonators with solid dielectric capacitive transducer gaps

A completely monolithic high-Q oscillator, fabricated via a combined CMOS plus surface micromachining technology, is described, for which the oscillation frequency is controlled by a polysilicon micromechanical resonator to achieve stability and phase noise performance comparable to those of quartz crystal oscillators. It is shown that the closed-loop, steady-state oscillation amplitude of this oscillator can be controlled through the DC-bias voltage applied to the capacitively driven and sensed /spl mu/resonator. Measurements indicate a phase noise density level of -168 dBm/Hz at 5 kHz offset frequency for an oscillator carrier power of -14.5 dBm. >

CMOS micromechanical resonator oscillator

A vacuum package based on localized aluminum/silicon-to-glass bonding has been successfully demonstrated. With 3.4 watts heating power, /spl sim/0.2 MPa applied contact pressure, and 90 minutes wait time before bonding, vacuum encapsulation at 25 mtorr can be achieved. Folded-beam comb drive /spl mu/-resonators are encapsulated and used as pressure monitors. Long-term testing of un-annealed vacuum-packaged /spl mu/-resonators with a Q of 2500 has demonstrated stable operation after 20 weeks. A /spl mu/-resonator with Q of /spl sim/9600 has been vacuum encapsulated and shown to be stable after 7 weeks.

Vacuum packaging technology using localized aluminum/silicon-to-glass bonding

A flexural-mode, micromechanical resonator utilizing a non-intrusive support structure to achieve measured Q's as high as 8,400 at VHF frequencies from 30-90 MHz is manufactured using polysilicon surface micromachining technology. Also, a method for extending the operating frequency of the resonator as well as other types of micromechanical resonators is disclosed. One embodiment of the method is called a differential-signaling technique. The other embodiment of the method is called a dimple-down technique. The support structure includes one or more torsional-mode support springs (16) in the form of beams that effectively isolate a resonator beam from its anchors (18) via quarter-wavelength impedance transformations, minimizing anchor dissipation and allowing the resonator to achieve high Q with high stiffness in the VHF frequency range. The resonator also includes one or more spacers (26) in the form of dimples formed on the flexural resonator beam (12) or the substrate. In operation, the dimples (26) determine a capacitive-transducer gap of the resonator. When a large DC-bias voltage is applied between a drive electrode (20) and the resonator beam (12), the dimples (26) provide a predetermined minimum distance between the flexural resonator beam (12) and the drive electrode (20).

Clark T.-C. Nguyen

Papers

Micromechanical resonator device and micromechanical device utilizing same

Vibrating micromechanical resonators with solid dielectric capacitive transducer gaps

CMOS micromechanical resonator oscillator

Vacuum packaging technology using localized aluminum/silicon-to-glass bonding

Device including a micromechanical resonator having an operating frequency and method of extending same