The sensitivity of present ground-based gravitational wave antennas is too low to detect many events per year. It has, therefore, been planned for years to build advanced detectors allowing actual ...astrophysical observations and investigations. In such advanced detectors, one major issue is to increase the laser power in order to reduce shot noise. However, this is useless if the thermal noise remains at the current level in the 100 Hz spectral region, where mirrors are the main contributors. Moreover, increasing the laser power gives rise to various spurious thermal effects in the same mirrors. The main goal of the present study is to discuss these issues versus the transverse structure of the readout beam, in order to allow comparison. A number of theoretical studies and experiments have been carried out, regarding thermal noise and thermal effects. We do not discuss experimental problems, but rather focus on some theoretical results in this context about arbitrary order Laguerre-Gauss beams, and other “exotic” beams.
Various noise sources limit the sensitivity of current interferometric gravitational wave detectors, including seismic noise, thermal noise of the optical components and suspension elements and ...photon shot noise. Plans are in place for a suite of hardware upgrades which should increase the sensitivity of these detectors by reducing the various noise sources. With these designs for 2nd generation detectors mature, techniques for further improvement of detector sensitivity by a factor of approximately 10 are under study. A particular challenge is the reduction of the thermal noise associated with the interferometer mirrors and their suspensions. We review the current status of research on thermal noise in interferometric gravitational wave detectors. Aspects of possible techniques for use in future ‘3rd generation detectors’ such as cryogenics and diffractive optics are discussed.
The aim of the Laser Interferometer Space Antenna (LISA) is to detect gravitational waves through a phase modulation in long (2.5 Mkm) laser light links between spacecraft. Among other noise sources ...to be addressed are the phase fluctuations caused by a possible angular jitter of the emitted beam. The present paper follows our preceding one (Vinet et al 2019 Class. Quant. Grav. 36, 205 003) based on an analytical study of the far field phase. We address here a numerical treatment of the phase, to first order in the emitted wavefront aberrations, but without any assumptions on the static bias term. We verify that, in the phase change, the higher order terms in the static mispointing are consistent with the results found in our preceding paper.
We present a direct and very fast calculation of the low frequency tail of the spectral density of thermal noise due to the thermal motion of matter in the cylindrical mirrors generally used in ...gravitational wave interferometric detectors. This calculation is based on the method recently proposed by Levin, that we extend to the case of finite mirrors, allowing one to study the aspect ratio dependence of the noise. Results are found in good agreement with those found in heavier preceding approaches, and provide a useful cross-check.
PDF
