Volume 125, Nº 1 (2025): THEMED SECTION: FUNDAMENTAL PROBLEMS OF GRAVITATIONAL- WAVE ASTRONOMY AND GRAVIMETRY

The possibility of recording high-frequency gravitational waves from cosmological and astrophysical sources through gravitational-optical resonance in Fabry – Perot interferometers is considered. The main characteristics of high-frequency relict gravitational waves necessary for estimating the detector parameters are considered. The characteristics of gravitational wave antennas necessary for recording high-frequency relict gravitational waves are given with taking into account theoretical restrictions on their energy density. A limitation has been found on the frequency of fundamentally registered gravitational waves using the proposed detection method. The optima f~3–10 MHz frequency range for tuning the proposed detector has been determined. Based on the operation of the created prototype of a complex for recording high-frequency gravitational waves, it is shown that the implementation of this scheme involves the correlation of signals from several gravitational wave antennas during the characteristic time required for recording gravitational waves using the proposed method.

In this work, we investigate the possibility of using quantum squeezed light generated during propagation of ultrashort optical pulses in a medium with third-order (Kerr) nonlinearity to increase the sensitivity of interferometric measurements. In a demonstration experiment, using squeezed light states obtained in optical fibers with third-order nonlinearity, we experimentally demonstrated an increase in the interferometer sensitivity by 4 dB beyond the shot noise level, whereas in previous demonstrations, squeezed vacuum states generated in media with quadratic nonlinearity were used to increase the sensitivity. For this purpose, we used an original system based on nonlinear polarization-maintaining fibers to obtain squeezing of the quantum uncertainty of the polarization state of femtosecond pulses better than –5 dB, which has high long-term stability without active stabilization systems.

Monitoring of pulsed disturbances of the ground background of the gravitational gradient generated by both astrophysical and intra-terrestrial cataclysms was performed. The main goal was to register bursts of gravitational radiation from relativistic catastrophes in the Galaxy, as well as hidden explosive processes of the internal terrestrial structures. Experimental studies were carried out using the OGRAN optoacoustical gravitational antenna, the VIRGO gravitational interferometer and auxiliary seismic equipment in the main tunnel of the BNO INR RAS. Measurements of the balance of acoustic, optical and electronic noises of the OGRAN antenna in relation to the noise of the environment were performed. Measurements of the seismic background in the main tunnel of the BNO in the low-frequency range from 0.1 Hz to 10 Hz were carried out. The processing of long-term measurements of low-frequency gravity gradient disturbances on the VIRGO laser gravitational interferometer with a 3 km base was completed. A majorizing estimate of the magnitude of disturbances for oscillations of the inner Earth’s core was obtained. The set of problems solved in this project demonstrates its multidisciplinary nature, providing new knowledge in the fields of: astrophysics (refining the physical processes during stellar mergers and collapses), nuclear physics (refining the equations of state of neutron stars) and geodynamics (processes of the inner earth and seismoacoustics).