arXiv subjects

Matteo Barsuglia

Publications and source records attributed to Matteo Barsuglia.

At least 19 recordsLinked to original sources

arXiv2026

Modeling Newtonian noise of acoustic origin in the Virgo gravitational wave detector

Since the first gravitational-wave (GW) detection of September 14th 2015 and with hundreds of gravitational-wave sources identified by the LIGO-Virgo-KAGRA network, GW have produced many important results in astrophysics and fundamental physics. Along with planned new data takings, current detectors will be upgraded and new project, such as Einstein Telescope and Cosmic Explorer, are under study. Among noises limiting low frequency sensitivity, vibro-acoustic noises are particularly important. In this work, we focus on the gravity gradient noise (also called Newtonian noise) of acoustic origin, which refers to the small fluctuations in the gravity field resulting from the acoustic pressure field present in the experimental areas of the detector. The induced noise is quantified in an original way, using a detailed nu- merical acoustic model of the experimental room, when the pressure field is excited by the air conditioning system. The method is used for Virgo, but it can be easily extended for future detectors and used to guide the design of caverns and experimental areas.

physics.class-ph↗

arXiv2026

Sensitivity of Laguerre-Gaussian Modes to Misalignment and Mode Mismatch in Gravitational-Wave Detectors

Higher-order Laguerre-Gaussian (LG) modes have broader and more uniform transverse intensity distributions than the fundamental Gaussian mode, making them attractive for precision optical applications. In gravitational-wave detectors, their enhanced spatial averaging of thermally driven test-mass fluctuations can reduce thermal noise. Their implementation, however, requires efficient coupling of the injected beam to the target cavity eigenmode. Residual misalignment and mode mismatch couple power out of the desired mode, reducing intracavity power buildup and degrading detector sensitivity. Here, we analytically and numerically evaluate the coupling loss induced by misalignment and mode mismatch for a generic $\mathrm{LG}_{p,\ell}$ beam. We show that the leading-order loss due to angular or lateral misalignment scales as $2p+|\ell|+1$, whereas that due to waist size or waist position mismatch scales as $2p^2+2p+(2p+1)|\ell|+1$. Although sensitivity to imperfect coupling generally increases with mode order, the donut-shaped $\mathrm{LG}_{0,\ell}$ family exhibits favorable mode mismatch scaling: its loss factor reduces to $|\ell|+1$ and therefore increases only linearly with the azimuthal index. This robustness, together with their broad intensity profiles and central dark regions that permit selective mirror masking, provides additional practical motivation for using $\mathrm{LG}_{0,\ell}$ modes in precision interferometers, including gravitational-wave detectors.

astro-ph.IM↗

arXiv2026

Improving Beam Quality in Gravitational-Wave Interferometers Illuminated by Higher-Order Laguerre-Gaussian Modes

Higher-order Laguerre-Gaussian (LG) laser modes have been proposed to reduce test-mass thermal noise in laser interferometric gravitational-wave detectors, owing to their more homogeneous intensity profiles compared to the currently employed fundamental Gaussian beam. However, LG beams such as the LG$_{3,3}$ mode suffer significant beam quality degradation in Fabry-Perot arm cavities in GW detectors with realistic state-of-the-art mirror surface figure errors, due to scattering into degenerate modes of the same order, which are resonantly enhanced by shared cavity resonance conditions. In this work, we investigate an alternative ''donut-shaped'' LG$_{0,\ell}$-like mode, specifically the LG$_{0,6}$ mode, and demonstrate strategies to improve its performance. These include the introduction of a tailored circular mirror mask with anti-reflective coating in the central region, which selectively increases the losses of parasitic degenerate modes while minimally impacting the LG$_{0,6}$ mode due to its limited overlap with the masked area. We further assess the marginal benefits of anticipated improvements in mirror surface figure errors and the potential reduction of cavity finesse. We demonstrate that these strategies can reduce the average contrast defect by more than two orders of magnitude and lower the mode loss by nearly a factor of five, achieving performance at or below the typical values observed in current detectors. This work opens up new research and development pathways for employing LG$_{0,\ell}$-type modes that achieve significant thermal noise reduction while maintaining beam quality and optical performance comparable to current gravitational-wave interferometers.

astro-ph.IM↗

arXiv2026

Demonstration of length control for a filter cavity with coherent control sidebands

For broadband quantum noise reduction of gravitational-wave detectors, a frequency-dependent squeezed vacuum field realized using a filter cavity is the most promising technique and will be implemented in Advanced LIGO and Advanced Virgo in the fourth observing run. To obtain the benefit of frequency-dependent squeezing, the length and alignment of the filter cavity with respect to the squeezed vacuum field must be accurately controlled. To this purpose, a new length and alignment control scheme for a filter cavity, using coherent control sidebands, was suggested [Phys. Rev. D 102, 042003 (2020)]. The coherent control sidebands are already used to control the squeezing angle in squeezed vacuum sources for gravitational-wave detectors. As both the squeezed vacuum field and coherent control sidebands have the same mode-matching conditions and almost the same frequency, the length and alignment of the filter cavity with respect to the squeezed vacuum field can be accurately controlled with this scheme. In this paper, we experimentally demonstrate the new control scheme for a filter cavity with coherent control sidebands. In addition to the conventional filter cavity control with the green field, we succeed in controlling the length of a 300-m filter cavity with coherent control sidebands and reduce the filter cavity length noise (rms) from 6.8 to 2.1 pm.

physics.ins-det↗

arXiv2026

Simultaneous Misalignment and Mode Mismatch Sensing in Optical Cavities Using Intensity-Only Measurements

Precise sensing and control of spatial mode content is essential for the performance of precision optical systems, particularly interferometric gravitational-wave detectors, where misalignment and mode mismatch can lead to significant optical losses and degraded quantum noise suppression. Conventional approaches, including heterodyne wavefront sensing and phase camera techniques, are effective but can be limited by hardware complexity and systematic uncertainties arising from restricted reference-beam overlap. This paper presents a novel two-step deep learning pipeline for robust beam diagnostics based solely on beam intensity images. In the first stage, a multi-intensity-image convolutional neural network (CNN) performs accurate mode decomposition, recovering the complex modal content of distorted beams. In the second stage, the predicted mode coefficients are fed into a downstream regression network that simultaneously estimates all eight degrees of freedom (DoFs) associated with misalignment and mode mismatch, including beam tilt, lateral offset, and waist size and position mismatches in both transverse directions. The proposed CNN-based framework achieves a mean absolute error (MAE) of 0.0034 in the mode decomposition stage, which propagates to a total MAE of 0.0062 in the recovered beam imperfection parameters at the final stage. This corresponds to an average residual optical loss of 39 ppm per DoF (310 ppm total). This approach relies only on standard CCD imaging and is robust to random intensity noise, eliminating the need for complex interferometric hardware. The results demonstrate that the proposed deep learning pipeline enables real-time, high-accuracy wavefront sensing and mode-mismatch diagnostics, providing a scalable and hardware-efficient tool for improving the stability and sensitivity of precision optical systems.

astro-ph.IM↗

arXiv2025

Performance of multiple filter-cavity schemes for frequency-dependent squeezing in gravitational-wave detectors

Gravitational-wave detectors use state-of-the-art quantum technologies to reduce the noise induced by vacuum fluctuations, via injection of squeezed states of light. Future detectors, such as Einstein Telescope, may require the use of two filter cavities or a 3-mirror coupled filter cavity to achieve a complex rotation of the squeezing ellipse, in order to reduce the quantum noise over the whole detector bandwidth. In this work, we compare the theoretical feasibility and performances of these two optical layouts and their resilience with respect to different degradation sources (optical losses, mismatching, locking precision), analytically and numerically. We extend previous analysis on squeezing degradation and find that the coupled cavity scheme provides similar or better performances than the two-cavity option, in terms of resilience with respect to imperfections and optical losses. We further highlight the role of mode-mismatch phases in limiting squeezing. Finally, we propose a possible two-step implementation scheme for Einstein Telescope using a single filter cavity that can be possibly upgraded into a coupled filter cavity.

gr-qc↗

arXiv2022

Improving the stability of frequency dependent squeezing with bichromatic control of filter cavity length, alignment and incident beam pointing

Frequency dependent squeezing is the main upgrade for achieving broadband quantum noise reduction in upcoming observation runs of gravitational wave detectors. The proper frequency dependence of the squeezed quadrature is obtained by reflecting squeezed vacuum from a Fabry-Perot filter cavity detuned by half of its linewidth. However, since the squeezed vacuum contains no classical amplitude, co-propagating auxiliary control beams are required to achieve the filter cavity's length, alignment, and incident beam pointing stability. In our frequency dependent squeezing experiment at the National Astronomical Observatory of Japan, we used a control beam at a harmonic of squeezed vacuum wavelength and found visible detuning variation related to the suspended mirrors angular drift. These variations can degrade interferometer quantum noise reduction. We investigated various mechanisms that can cause the filter cavity detuning variation. The detuning drift is found to be mitigated sufficiently by fixing the incident beam pointing and applying filter cavity automatic alignment. It was also found that there is an optimal position of the beam on the filter cavity mirror that helps to reduce the detuning fluctuations. Here we report a stabilized filter cavity detuning variation of less than 10$\,$Hz compared to the 113$\,$Hz cavity linewidth. Compared to previously published results [Phys. Rev. Lett. 124, 171101 (2020)], such detuning stability would be sufficient to make filter cavity detuning drift induced gravitational wave detector detection range fluctuation reduce from $11\%$ to within $2\%$.

physics.ins-det↗

arXiv2022

Next Generation Observatories -- Report from the Dawn VI Workshop; October 5-7 2021

The workshop Dawn VI: Next Generation Observatories took place online over three days, 5-7 October, 2021. More than 200 physicists and astronomers attended to contribute to, and learn from, a discussion of next-generation ground-based gravitational-wave detectors. The program was centered on the next generation of ground-based gravitational-wave observatories and their synergy with the greater landscape of scientific observatories of the 2030s. Cosmic Explorer (CE), a concept developed with US National Science Foundation support, was a particular focus; Einstein Telescope (ET), the European next generation concept, is an important complement and partner in forming a network. The concluding summary of the meeting expressed the sentiment that the observational science accessible to CE and ET, also in combination with data from other non-GW observatories, will stimulate a very broad community of analysts and yield insights which are exciting given the access to GWs from the entire universe. The need, and desire, for closer collaboration between ET and CE was expressed; a three-detector network is optimal for delivering much of the science. The science opportunities afforded by CE and ET are broad and compelling, impacting a wide range of disciplines in physics and high energy astrophysics. There was a consensus that CE is a concept that can deliver the promised science. A strong endorsement of Cosmic Explorer, as described in the CE Horizon Study, is a primary outcome of DAWN VI.

astro-ph.IM↗

arXiv2020

Frequency-Dependent Squeezed Vacuum Source for Broadband Quantum Noise Reduction in Advanced Gravitational-Wave Detectors

The astrophysical reach of current and future ground-based gravitational-wave detectors is mostly limited by quantum noise, induced by vacuum fluctuations entering the detector output port. The replacement of this ordinary vacuum field with a squeezed vacuum field has proven to be an effective strategy to mitigate such quantum noise and it is currently used in advanced detectors. However, current squeezing cannot improve the noise across the whole spectrum because of the Heisenberg uncertainty principle: when shot noise at high frequencies is reduced, radiation pressure at low frequencies is increased. A broadband quantum noise reduction is possible by using a more complex squeezing source, obtained by reflecting the squeezed vacuum off a Fabry-Perot cavity, known as filter cavity. Here we report the first demonstration of a frequency-dependent squeezed vacuum source able to reduce quantum noise of advanced gravitational-wave detectors in their whole observation bandwidth. The experiment uses a suspended 300-m-long filter cavity, similar to the one planned for KAGRA, Advanced Virgo and Advanced LIGO, and capable of inducing a rotation of the squeezing ellipse below 100 Hz.

astro-ph.IM↗

arXiv2020

Estimation of losses in a 300 m filter cavity and quantum noise reduction in the KAGRA gravitational-wave detector

The sensitivity of the gravitational-wave detector KAGRA, presently under construction, will be limited by quantum noise in a large fraction of its spectrum. The most promising technique to increase the detector sensitivity is the injection of squeezed states of light, where the squeezing angle is dynamically rotated by a Fabry-Pérot filter cavity. One of the main issues in the filter cavity design and realization is the optical losses due to the mirror surface imperfections. In this work we present a study of the specifications for the mirrors to be used in a 300 m filter cavity for the KAGRA detector. A prototype of the cavity will be constructed at the National Astronomical Observatory of Japan, inside the infrastructure of the former TAMA interferometer. We also discuss the potential improvement of the KAGRA sensitivity, based on a model of various realistic sources of losses and their influence on the squeezing amplitude.

astro-ph.IM↗

arXiv2018

Measurement of optical losses in a high-finesse 300 m filter cavity for broadband quantum noise reduction in gravitational-wave detectors

Earth-based gravitational-wave detectors will be limited by quantum noise in a large part of their spectrum. The most promising technique to achieve a broadband reduction of such noise is the injection of a frequency dependent squeezed vacuum state from the output port of the detector, whit the squeeze angle rotated by the reflection off a Fabry-Perot filter cavity. One of the most important parameters limiting the squeezing performance is represented by the optical losses of the filter cavity. We report here the operation of a 300 m filter cavity prototype installed at the National Astronomical Observatory of Japan (NAOJ). The cavity is designed to obtain a rotation of the squeeze angle below 100 Hz. After achieving the resonance of the cavity with a multi-wavelength technique, the round trip losses have been measured to be between 50 ppm and 90 ppm. This result demonstrates that with realistic assumption on the input squeeze factor and on the other optical losses, a quantum noise reduction of at least 4 dB in the frequency region dominated by radiation pressure can be achieved.

astro-ph.IM↗

arXiv2018

Impact of infrasound atmospheric noise on gravity detectors used for astrophysical and geophysical applications

Density changes in the atmosphere produce a fluctuating gravity field that affect gravity strainmeters or gravity gradiometers used for the detection of gravitational-waves and for geophysical applications. This work addresses the impact of the atmospheric local gravity noise on such detectors, extending previous analyses. In particular we present the effect introduced by the building housing the detectors, and we analyze local gravity-noise suppression by constructing the detector underground. We present also new sound spectra and correlations measurements. The results obtained are important for the design of future gravitational-wave detectors and gravity gradiometers used to detect prompt gravity perturbations from earthquakes.

astro-ph.IM↗

arXiv2010

Higher-order Laguerre-Gauss mode generation and interferometry for gravitational wave detectors

We report on the first experimental demonstration of higher-order Laguerre-Gauss (LGpl) mode generation and interferometry using a method scalable to the requirements of gravitational wave (GW) detection. GW detectors which use higher-order LGpl modes will be less susceptible to mirror thermal noise, which is expected to limit the sensitivity of all currently planned terrestrial detectors. We used a diffractive optic and a mode-cleaner cavity to convert a fundamental LG00 Gaussian beam into an LG33 mode with a purity of 98%. The ratio between the power of the LG00 mode of our laser and the power of the LG33 transmitted by the cavity was 36%. By measuring the transmission of our setup using the LG00, we inferred that the conversion efficiency specific to the LG33 mode was 49%. We illuminated a Michelson interferometer with the LG33 beam and achieved a visibility of 97%.

gr-qc↗

arXiv2003

Detection of a close supernova gravitational wave burst in a network of interferometers, neutrino and optical detectors

Trying to detect the gravitational wave (GW) signal emitted by a type II supernova is a main challenge for the GW community. Indeed, the corresponding waveform is not accurately modeled as the supernova physics is very complex; in addition, all the existing numerical simulations agree on the weakness of the GW emission, thus restraining the number of sources potentially detectable. Consequently, triggering the GW signal with a confidence level high enough to conclude directly to a detection is very difficult, even with the use of a network of interferometric detectors. On the other hand, one can hope to take benefit from the neutrino and optical emissions associated to the supernova explosion, in order to discover and study GW radiation in an event already detected independently. This article aims at presenting some realistic scenarios for the search of the supernova GW bursts, based on the present knowledge of the emitted signals and on the results of network data analysis simulations. Both the direct search and the confirmation of the supernova event are considered. In addition, some physical studies following the discovery of a supernova GW emission are also mentioned: from the absolute neutrino mass to the supernova physics or the black hole signature, the potential spectrum of discoveries is wide.

gr-qc↗

arXiv2003

Coincidence and coherent data analysis methods for gravitational wave bursts in a network of interferometric detectors

Network data analysis methods are the only way to properly separate real gravitational wave (GW) transient events from detector noise. They can be divided into two generic classes: the coincidence method and the coherent analysis. The former uses lists of selected events provided by each interferometer belonging to the network and tries to correlate them in time to identify a physical signal. Instead of this binary treatment of detector outputs (signal present or absent), the latter method involves first the merging of the interferometer data and looks for a common pattern, consistent with an assumed GW waveform and a given source location in the sky. The thresholds are only applied later, to validate or not the hypothesis made. As coherent algorithms use a more complete information than coincidence methods, they are expected to provide better detection performances, but at a higher computational cost. An efficient filter must yield a good compromise between a low false alarm rate (hence triggering on data at a manageable rate) and a high detection efficiency. Therefore, the comparison of the two approaches is achieved using so-called Receiving Operating Characteristics (ROC), giving the relationship between the false alarm rate and the detection efficiency for a given method. This paper investigates this question via Monte-Carlo simulations, using the network model developed in a previous article.

gr-qc↗

arXiv2003

Comparison of filters for detecting gravitational wave bursts in interferometric detectors

Filters developed in order to detect short bursts of gravitational waves in interferometric detector outputs are compared according to three main points. Conventional Receiver Operating Characteristics (ROC) are first built for all the considered filters and for three typical burst signals. Optimized ROC are shown for a simple pulse signal in order to estimate the best detection efficiency of the filters in the ideal case, while realistic ones obtained with filters working with several ``templates'' show how detection efficiencies can be degraded in a practical implementation. Secondly, estimations of biases and statistical errors on the reconstruction of the time of arrival of pulse-like signals are then given for each filter. Such results are crucial for future coincidence studies between Gravitational Wave detectors but also with neutrino or optical detectors. As most of the filters require a pre-whitening of the detector noise, the sensitivity to a non perfect noise whitening procedure is finally analysed. For this purpose lines of various frequencies and amplitudes are added to a Gaussian white noise and the outputs of the filters are studied in order to monitor the excess of false alarms induced by the lines. The comparison of the performances of the different filters finally show that they are complementary rather than competitive.

gr-qc↗

arXiv2003

An elliptical tiling method to generate a 2-dimensional set of templates for gravitational wave search

Searching for a signal depending on unknown parameters in a noisy background with matched filtering techniques always requires an analysis of the data with several templates in parallel in order to ensure a proper match between the filter and the real waveform. The key feature of such an implementation is the design of the filter bank which must be small to limit the computational cost while keeping the detection efficiency as high as possible. This paper presents a geometrical method which allows one to cover the corresponding physical parameter space by a set of ellipses, each of them being associated to a given template. After the description of the main characteristics of the algorithm, the method is applied in the field of gravitational wave (GW) data analysis, for the search of damped sine signals. Such waveforms are expected to be produced during the de-excitation phase of black holes -- the so-called 'ringdown' signals -- and are also encountered in some numerically computed supernova signals.

gr-qc↗

arXiv2001

Detection in coincidence of gravitational wave bursts with a network of interferometric detectors (I): Geometric acceptance and timing

Detecting gravitational wave bursts (characterised by short durations and poorly modelled waveforms) requires to have coincidences between several interferometric detectors in order to reject non-stationary noise events. As the wave amplitude seen in a detector depends on its location with respect to the source direction and as the signal to noise ratio of these bursts are expected to be low, coincidences between antennas may not be so likely. This paper investigates this question from a statistical point of view by using a simple model of a network of detectors; it also estimates the timing precision of a detection in an interferometer which is an important issue for the reconstruction of the source location, based on time delays.

gr-qc↗