10 research outputs found
Nanoparticle detection in an open-access silicon microcavity
We report on the detection of free nanoparticles in a micromachined,
open-access Fabry-P\'erot microcavity. With a mirror separation of m,
a radius of curvature of mm, and a beam waist of m, the mode
volume of our symmetric infrared cavity is smaller than pL. The small
beam waist, together with a finesse exceeding 34,000, enables the detection of
nano-scale dielectric particles in high vacuum. This device allows monitoring
of the motion of individual nm radius silica nanospheres in real time.
We observe strong coupling between the particles and the cavity field, a
precondition for optomechanical control. We discuss the prospects for optical
cooling and detection of dielectric particles smaller than nm in radius
and amu in mass.Comment: 4 pages, 3 figure
MOEMS Based Single Chip Lorentz Force Magnetic Gradiometer
The functional principle of an optical gradient magnetic field sensor consisting of two independent laterally oscillating masses on a single chip is reported. These oscillations are caused by the Lorentz forces resulting from an alternating current through the masses interacting with a static magnetic field. Light is modulated by relative in-plane movement of the masses and a fixed frame and subsequently detected by two photodiodes. Evaluation of magnitude and phase of the output signal reveals information about the uniformity of the magnetic field. The sensor is capable of detecting uniaxially strength and direction of magnetic gradient fields, offset gradient fields and homogeneous fields
Responsitivity Measurement of a Lorentz Force Transducer for Homogeneous and Inhomogeneous Magnetic Fields
This paper reports a MEMS gradiometer consisting of two independent, laterally oscillating masses on a single chip with integrated optical readout featuring a responsitivity of 35V/T at resonant operation. The symmetrical design of the two masses offers high accuracy and low cost by using conventional MEMS batch fabrication technology. The sensing principle is based on lateral displacement of the masses actuated by Lorentz forces which modulates a light flux passing through a stationary mask and the moving mask integrated in the masses. Phase and intensity detected by photodiodes reveal information about the uniformity of an external applied magnetic field, hence, enables the measurement of gradient-, homogeneous- and offset gradient magnetic fields
Dual Resonator MEMS Magnetic Field Gradiometer
Accurate knowledge of the spatial magnetic field distribution is necessary when measuring field gradients. Therefore, a MEMS magnetic field gradiometer is reported, consisting of two identical, but independent laterally oscillating masses on a single chip. The sensor is actuated by Lorentz force and read out by modulation of the light flux passing through stationary and moving arrays of the chip. This optical readout decouples the transducer from the electronic components. Both phase and intensity are recorded which reveals information about the uniformity of the magnetic field. The magnetic flux density is measured simultaneously at two points in space and the field gradient is evaluated locally. The sensor was characterised at ambient pressure by performing frequency and magnitude response measurements with coil and various different permanent magnet arrangements, resulting in a responsivity of 35.67 V/T and detection limit of 3.07 µT/ Hz (@ 83 Hz ENBW). The sensor is compact, offers a large dynamic measurement range and can be of low-cost by using conventional MEMS batch fabrication technology
Silicon microcavity arrays with open access and a finesse of half a million
Optical resonators are increasingly important tools in science and
technology. Their applications range from laser physics, atomic clocks,
molecular spectroscopy, and single-photon generation to the detection, trapping
and cooling of atoms or nano-scale objects. Many of these applications benefit
from strong mode confinement and high optical quality factors, making small
mirrors of high surface-quality desirable. Building such devices in silicon
yields ultra-low absorption at telecom wavelengths and enables integration of
micro-structures with mechanical, electrical and other functionalities. Here,
we push optical resonator technology to new limits by fabricating
lithographically aligned silicon mirrors with ultra-smooth surfaces, small and
wellcontrolled radii of curvature, ultra-low loss and high reflectivity. We
build large arrays of microcavities with finesse greater than F = 500,000 and a
mode volume of 330 femtoliters at wavelengths near 1550 nm. Such high-quality
micro-mirrors open up a new regime of optics and enable unprecedented
explorations of strong coupling between light and matter