Characterization and evasion of backscattered light in the squeezed-light enhanced gravitational wave interferometer GEO 600.

Squeezed light is injected into the dark port of gravitational wave interferometers, in order to reduce the quantum noise. A fraction of the interferometer output light can reach the OPO due to sub-optimal isolation of the squeezing injection path. This backscattered light interacts with squeezed light generation process, introducing additional measurement noise.

Frequency noise stabilisation of a 1550 nm external cavity diode laser with hybrid feedback for next generation gravitational wave interferometry.

Longer wavelength lasers will be needed for future gravitational wave detectors that use cryogenic cooling of silicon based test-mass optics. Diode lasers with a 1550 nm wavelength output are potential seed light sources for such a detector, however diode laser devices have a different spectral profile and higher frequency noise than the solid state lasers used in current detectors. We present a frequency stabilisation system for a 1550 nm external cavity diode laser capable of reducing the laser frequency noise to a level of 0.

Direct limits for scalar field dark matter from a gravitational-wave detector.

The nature of dark matter remains unknown to date, although several candidate particles are being considered in a dynamically changing research landscape. Scalar field dark matter is a prominent option that is being explored with precision instruments, such as atomic clocks and optical cavities. Here we describe a direct search for scalar field dark matter using a gravitational-wave detector, which operates beyond the quantum shot-noise limit.

First Demonstration of 6 dB Quantum Noise Reduction in a Kilometer Scale Gravitational Wave Observatory.

Photon shot noise, arising from the quantum-mechanical nature of the light, currently limits the sensitivity of all the gravitational wave observatories at frequencies above one kilohertz. We report a successful application of squeezed vacuum states of light at the GEO 600 observatory and demonstrate for the first time a reduction of quantum noise up to 6.03±0.

Crown Taper Angles Achieved by Dental Students: A Systematic Review.

The aim of this systematic review was to examine the literature on clinical taper angles achieved by dental students during crown preparation to determine the theoretical and clinically acceptable values identified in research studies. Medline, Embase, Web of Knowledge, the Cochrane Library, the , and the were searched to identify relevant studies. Studies were included if they were in vivo research on full crown preparations by dental students and published in English.

High power and ultra-low-noise photodetector for squeezed-light enhanced gravitational wave detectors.

Current laser-interferometric gravitational wave detectors employ a self-homodyne readout scheme where a comparatively large light power (5-50 mW) is detected per photosensitive element. For best sensitivity to gravitational waves, signal levels as low as the quantum shot noise have to be measured as accurately as possible. The electronic noise of the detection circuit can produce a relevant limit to this accuracy, in particular when squeezed states of light are used to reduce the quantum noise.

Interferometer Techniques for Gravitational-Wave Detection.

Several km-scale gravitational-wave detectors have been constructed world wide. These instruments combine a number of advanced technologies to push the limits of precision length measurement. The core devices are laser interferometers of a new kind; developed from the classical Michelson topology these interferometers integrate additional optical elements, which significantly change the properties of the optical system.

Automatic beam alignment for the mode-cleaner cavities of GEO 600.

The automatic alignment system for the two suspended, triangular mode-cleaner cavities of the gravitational wave detector GEO 600 has been in continuous operation since the spring of 2001. A total of 20 angular degrees of freedom are controlled by feedback loops with almost no manual alignment having been required since installation. Error signals for the eight most important degrees of freedom are obtained with the differential wave-front sensing technique.

Sensing and control in dual-recycling laser interferometer gravitational-wave detectors.

We introduce length-sensing and control schemes for the dual-recycled cavity-enhanced Michelson interferometer configuration proposed for the Advanced Laser Interferometer Gravitational Wave Observatory (LIGO). We discuss the principles of this scheme and show methods that allow sensing and control signals to be derived. Experimental verification was carried out in three benchtop experiments that are introduced.