Low frequency signals of large scale GW-interferometers

Abstract

Application of the large scale gravitational wave interferometers for measurement of geophysical signals at very low frequencies is considered. Analysis is concentrated on the mechanism of penetration of quasistatic geophysical perturbation through the main interferometer output. It is shown that it has a parametrical nature resulted in slow variations of the optical transfer function of the interferometer. Geophysical modulation index is calculated for any harmonical component of the output spectrum, but mainly for a photon circulation frequency appeared in the case of stochastic illumination of modes neighbour to the central resonance. Value of the effect is estimated for different operational regimes of the device. For improvement of geophysical signal readout a modernization of the instrument with using of two component resonance optical pump is proposed and a correspondent calculation is carried out. Numerical estimations for different regimes of the setup are given together with discussion of possible application for measuring some weak gravitational effects.

On the Possible Detection of Low Frequency Periodic Signals in Gravitational Wave Interferometers

“…In previous attempts to explain the modulation of the fsr power, macroscopic mirror motion was often considered [2,3,4]. Such motion, however, is compensated by the tidal servo and any remaining displacement is corrected by the interferometer controls.…”

“…The modulation of the signal at the fsr sideband frequency, ν f sr was observed by the LIGO collaboration and has been discussed in the past [1,2]. Attempts to address the issue analytically can be found in [3,4]. However, given the complexity of the optical fields in GW interferometers, it is advisable to carry out a numerical simulation such as presented here.…”

Searching for photon-sector Lorentz violation using gravitational-wave detectors

“…The power at f + is thus modulated at the frequencies of harmonic changes in ∆n. In short, when the carrier frequency is used to lock the interferometer, the sideband at the fsr frequency can be used to measure the low-frequency signals from Lorentz violation [15,16].…”

Observation of long-term changes in the effective refractive index of light

“…When an fsr sideband circulates in the interferometer it is modulated by mirror motion, just as is the carrier. This leads to a detectable signal if only a single sideband circulates [17]. Serendipitously, such a sideband was present in the H1 interferometer because the large test masses (the mirrors of the arms) have a mechanical resonance near 37.890 kHz which is excited by the ambient thermal energy.…”