R. Schilling

The GEO 600 gravitational wave detector

The GEO 600 laser interferometer with 600 m armlength is part of a worldwide network of gravitational wave detectors. Due to the use of advanced technologies like multiple pendulum suspensions with a monolithic last stage and signal recycling, the anticipated sensitivity of GEO 600 is close to the initial sensitivity of detectors with several kilometres armlength. This paper describes the subsystems of GEO 600, the status of the detector by September 2001 and the plans towards the first science run.

Resonant sideband extraction: a new configuration for interferometric gravitational wave detectors

Abstract We introduce a new Fabry-Perot based interferometric gravitational wave detector that, compared with previous designs, greatly decreases the amount of power that must be transmitted through optical substrates to obtain a given light power in its arms. This significantly reduces the effects of wavefront distortions caused by heating due to absorption in the optics, and allows an improved broadband sensitivity to be achieved.

A Mode Selector to Suppress Fluctuations in Laser Beam Geometry

Our development of a gravitational wave detector requires a Michelson interferometer of extreme sensitivity capable of measuring 10-16 m (i.e. some 10-10 of a wavelength λ of the illuminating laser light). Even after painstaking alignment of the interferometer components, and after considerable improvement of the laser stability, noise contributions much in excess of this goal were observed, due partly to fluctuations of the laser beam geometry. The two most obvious types of geometric beam fluctuations are a lateral beam jitter and a pulsation in beam width; these lead to spurious interferometer signals if the interfering wavefronts are misaligned in their tilts or in their curvatures respectively. The geometry of the laser beam can be considerably stabilized by passing it through an optical resonator. The geometric beam fluctuations, as viewed from this resonator, can be described by a well-centred ground mode TEMoo, contaminated by transverse modes TEM mn , with amplitudes decreasing rapidly with the mo...

The LTP interferometer and phasemeter

The LISA Technology Package (LTP), to be launched by ESA in 2006/2007, is a technology demonstration mission in preparation for the LISA space-borne gravitational wave detector. A central part of the LTP is the optical metrology package (heterodyne interferometer with phasemeter) which monitors the distance between two test masses with a noise level of 10 pm Hz−1/2 between 3 mHz and 30 mHz. It has a dynamic range of >100 µm without any actuators for the pathlength. In addition to the longitudinal measurements, it provides alignment measurements with an expected noise level of <10 nrad Hz−1/2. While the basic design has been described previously by Heinzel et al (2003 Class. Quantum Grav. 20 S153–61), this paper gives new details on the laser stabilization, the phasemeter and recent prototype results.

Status of the GEO600 detector

Of all the large interferometric gravitational-wave detectors, the German/British project GEO600 is the only one which uses dual recycling. During the four weeks of the international S4 data-taking run it reached an instrumental duty cycle of 97% with a peak sensitivity of 7 × 10−22 Hz−1/2 at 1 kHz. This paper describes the status during S4 and improvements thereafter.

Frequency-domain interferometer simulation with higher-order spatial modes

FINESSE is a software simulation allowing one to compute the optical properties of laser interferometers used by interferometric gravitational-wave detectors today. This fast and versatile tool has already proven to be useful in the design and commissioning of gravitational-wave detectors. The basic algorithm of FINESSE numerically computes the light amplitudes inside an interferometer using Hermite–Gauss modes in the frequency domain. In addition, FINESSE provides a number of commands for easily generating and plotting the most common signals including power enhancement, error and control signals, transfer functions and shot-noise-limited sensitivities. Among the various simulation tools available to the gravitational wave community today, FINESSE provides an advanced and versatile optical simulation based on a general analysis of user-defined optical setups and is quick to install and easy to use.

Thermal lensing in recycling interferometric gravitational wave detectors

Thermal lensing limits the performance of advanced interferometric gravitational wave detectors that use high light powers. We evaluate the effects of thermal lensing in such systems and estimate their gravitational wave sensitivity assuming that fused silica optical substrates are employed. Although useful sensitivity can be achieved with established designs, the new technique of resonant sideband extraction is most promising for wideband detectors.

The status of GEO 600

The GEO 600 laser interferometer with 600m armlength is part of a worldwide network of gravitational wave detectors. GEO 600 is unique in having advanced multiple pendulum suspensions with a monolithic last stage and in employing a signal recycled optical design. This paper describes the recent commissioning of the interferometer and its operation in signal recycled mode.

LISA and its in-flight test precursor SMART-2

LISA will be the first space-home gravitational wave observatory. It aims to detect gravitational waves in the 0.1 MHz+1 Hz range from sources including galactic binaries, super-massive black-hole binaries, capture of objects by super-massive black-holes and stochastic background. LISA is an ESA approved Cornerstone Mission foreseen as a joint ESA-NASA endeavour to be launched in 2010-11. The principle of operation of LISA is based on laser ranging of test-masses under pure geodesic motion. Achieving pure geodesic motion at the level requested for LISA, 3×10^(−15) ms^(−2)/√Hz at 0.1 mHz, is considered a challenging technological objective. To reduce the risk, both ESA and NASA are pursuing an in-flight test of the relevant technology. The goal of the test is to demonstrate geodetic motion within one order of magnitude from the LISA performance. ESA has given this test as the primary goal of its technology dedicated mission SMART-2 with a launch in 2006. This paper describes the basics of LISA, its key technologies, and its in-flight precursor test on SMART-2.

An argon laser interferometer for the detection of gravitational radiation

The instrument described is used to locate and study various noise sources and other disturbances, which would restrict signal perceptibility. From an analysis of these disturbances, the demands on apparatus components are estimated. Some constructional details are given, as well as suggestions for improvement aimed at a future interferometer of increased base length, with the prospect of successful operation.