Light scattering issues specific to high performance optical components have received considerable attention over the last decade for several reasons.
Firstly, the manufacturing processes of interference filters have benefited from technological breakthroughs which today allows the routine manufacture of stacks with several hundreds of thin films on substrates with extreme polishes. Such...
Back-scattered light results in parasitic modulations of the output light of gravitational-wave observatories. It constitutes a major noise source at low audio-band frequencies. Modulations due to the back-scattered light appear both in phase and amplitude quadratures of the output light. It is proposed to use dual-homodyne detection to measure both quadratures and to discriminate between GW...
The interferometric detection of tiny ripples in the fabric of spacetime called gravitational waves require extreme noise sensitive operating conditions for detectors such LIGO, Virgo, KAGRA, as well as the future planned LISA and ET. One such instrument noise source is scattered light from optical components, that can induce phase noise in the output signal by recombining with the main...
A peculiar kind of stray light that can affect the performance of a squeezing-enhanced gravitational-wave interferometer is the light that travels backwards along the squeezed light injection path. After being amplified by the nonlinear process inside the optical parametric oscillator (OPO), the backscattered light eventually reaches the readout photodiode of the interferometer with a random...
As straylight is a dominating limitation for the sensitivity of gravitational wave detectors, we investigate the use of tunable coherence in the form of phase modulation following a pseudo-random-sequence on the interferometer laser to break the coherence of the delayed straylight. Thereby, we aim to reduce its intrusive impact on the measurement by effectively realizing a pseudo white-light...
As part of the second phase of Advanced Virgo update program, instrumented baffles are being constructed to be installed around the end mirrors in the main FP cavities, in continuation of what has been implemented for the input mode cleaner end mirror during phase I. According to the current design, these baffles will be equipped with more than 200 photosensors, allowing for real-time...
Scattered light is one of the problems that most limits the performance of current gravitational wave detectors.
Simulating stray light is still computationally complicated. Therefore, in order to estimate the amount of scattered light from the optical elements, we built at LAPP an interferometric scattermeter with which the BRDF of the desired elements is measured.
In parallel, in Virgo we...
Stray light is suspected to be a major culprit for the excess noise measured in present gravitational wave interferometers, and is projected to be even more dangerous for the next generation of instruments which will attempt to further push the sensitivity limits. Stray light originating in different areas of the detectors and through various mechanisms can impact the performance either...
