High-sensitivity monitoring of micromechanical vibration using optical whispering gallery mode resonators

The inherent coupling of optical and mechanical modes in high finesse optical microresonators provide a natural, highly sensitive transduction mechanism for micromechanical vibrations. Using homodyne and polarization spectroscopy techniques, we achieve shot-noise limited displacement sensitivities of 10^(-19) m Hz^(-1/2). In an unprecedented manner, this enables the detection and study of a variety of mechanical modes, which are identified as radial breathing, flexural and torsional modes using 3-dimensional finite element modelling. Furthermore, a broadband equivalent displacement noise is measured and found to agree well with models for thermorefractive noise in silica dielectric cavities. Implications for ground-state cooling, displacement sensing and Kerr squeezing are discussed.Comment: 25 pages, 8 figure

Non-tilting out-of-plane mode high-Q mechanical silicon oscillator

Abstract A single-crystal silicon oscillator with a non-tilting out-of-plane vibrational mode and high-quality factor for the mechanical resonance was designed, fabricated and characterized. The finite-element method (FEM) was utilized before the fabrication process to simulate the oscillator behavior and give guidance in optimizing the design. At low pressure p =10 −3 mbar and at room temperature, the resonance frequency and Q value were measured to be f 0 = 26 526 Hz and Q = 100 000, respectively. The measured resonance frequency was in a good agreement with the simulated one, f 0,FEM = 26 787 Hz. The actual mode pattern was verified by measurements and compared with the simulation result. An interferometric laser beam was scanned over the oscillator surface and position-dependent oscillation amplitudes were stored with the phase-sensitive detection. The oscillation was proved to occur effectively in a pure non-tilting out-of-plane mode. We propose to use this kind of micromechanical probe in various measurement schemes, where one needs to approach the surface with a single non-torsional plane. In addition, such an oscillator can be utilized as an optical mirror so that the optical mode can be kept the same when moving the mirror

Progress Report on Closing the Quantum Metrological Triangle

Quantum Metrological Triangle is made out of three components: Josephson voltage standard, Quantum Hall resistance standard and an accurate current pump. Closing the Triangle consists of applying Ohm's law with great accuracy on the three devices, which are based on fundamental physical phenomena and quantities, such as Planck's constant and electron charge. The first two devices are already accepted international metrological standards. We will report on our recent progress in developing an accurate current pump, based on a hybrid single electron transistor, and compare it with other current pumps. We will also report on new ideas in developing the low noise current amplifier, needed for testing the Ohm's law, and describe our overall plans for closing the Triangle along with the expected uncertainties