Precise optical mode matching is of critical importance to future gravitational wave detectors. Mode mismatching will lead to excess losses, degrading squeezing. Automatic spatial-mode matching schemes have the potential to reduce losses and improve temporal loss stability. We propose a mode-sensing scheme with error signals directly proportional to the mismatch between the recycling cavities...
We demonstrate a novel bipolar Passive Charge Management (PCM) technique using slow photoelectrons generated by a single UV-LED of either 275nm or 295nm, directed at gold-coated floating Test Masses (TM). Slow photoelectrons are defined as having kinetic energies <eV(TM)max, where V(TM)max is the maximum allowable potential for the TM. The slow-photoelectron system requires ≅5minutes to...
The Einstein Telescope will operate with cryogenic mirrors at 10-20K. This temperature needs to be maintained by extracting heat coming from absorption in the substrate and coating and thermal radiation. We present a study of an alternative to tensile suspensions of the Einstein Telescope mirrors. The mirror suspensions presented here tackle the conflicting requirements of being good heat...
DECIGO(DECi-hertz Interferometer Gravitational-wave Observatory)is a space-based gravitational wave detector that has a good sensitivity at low frequencies from 0.1 Hz to 10 Hz. DECIGO can detect gravitational waves from intermediate-mass black hole binary mergers and gravitational wave background. It leads to the verification of the formation scenario of supermassive black holes and inflation...
Here we present the experimental results obtained for backscattered and retro-reflected light from optical components, including uncoated and anti-reflective coated windows and mirrors, using the BARRITON (BAck-scattering and Retro-Reflection by InterferomeTry with lOw cohereNce) instrument. BARRITON is an interferometric set-up based on the Fourier transform spectrometry technique, where the...
Quantum Noise Reduction in Gravitational Wave detectors is mainly limited by the optical losses generated by the mismatch between the vacuum squeezed beam and the resonant cavities of the interferometer. These aberrations must be measured and corrected. For this reason, different efforts have been made to develop wave-front sensing techniques to measure the mismatch between optical cavities....
LIGO Caltech operates a 40-meter prototype interferometer to validate interferometer technologies. The current experimental focus is to conduct testing of the balanced homodyne readout (BHR) scheme before integrating it into aLIGO detectors for O5. With the BHR scheme, the differential arm length signal is obtained by mixing the local oscillator (LO) field and the interferometer output field...
State-of-the-art, high-precision metrology experiments like gravitational wave detectors require carefully stabilized laser sources with exceptionally low relative power noise (RPN). The RPN is fundamentally quantum noise limited by the relative shot noise (RSN) for classical states of light. As the RSN scales inversely with the square root of the optical power, it can be reduced by increasing...
Newtonian noise will likely limit the low-frequency sensitivity of future terrestrial gravitational wave detectors. Commissioning of the third-generation Torsion Pendulum Dual Oscillator (TorPeDO), a sensor for direct detection of Newtonian noise is in progress at the Australian National University. This sensor comprises of two freely suspended perpendicular torsion bars and they...
Coating thermal noise, arising from random Brownian motions of the mirror coating materials, is the main limitation of precision measurements at frequencies below 10 Hz. We proposed a multi cavity transverse mode readout scheme [1] that realises an equivalent thermal noise level of a mesa flat-top beam, which is well known to be efficient at thermal noise reduction compared to a conventional...
Compact displacement sensors with sub-picometer level performance between 0.01Hz and 100Hz are a crucial technology for future detectors, detector upgrades and inertial sensors to reduce noise in suspension control and test-mass sensing. We are investigating sensors based on Deep-Frequency Modulation Interferometry (DFMI) for this purpose at the University of Hamburg and we will present our...
Vault-grade inertial sensors are essential for isolating test masses in gravitational wave detectors from ground motion. In order to achieve excellent noise performance, these sensors are typically big bulky and not vacuum compatible. These features limit the deployment of such sensors and contribute to control noises, which currently prevent the low-frequency performance of LIGO from reaching...
A program dedicated to cryogenic payload development is ongoing at the Amaldi Research Center at the Sapienza University in Rome. We plan to use solid conduction to extract the heat from the test mass and to test the main features of a viable payload, designed to be closely sized to ET targets. The test mass will initially be a dummy body, but all the main parts included in the payload will be...
The DECi-hertz Interferometer Gravitational-Wave Observatory (DECIGO) is a space gravitational wave (GW) detector. One of the most important DECIGO’s goals is the observation of the primordial GW background (PGW). To increase the possibility of PGW observation, we need to improve the sensitivity of DECIGO, which is limited by quantum noise.
Standard squeezing used in ground-based detectors...
Researches on cosmology and astrophysics have revealed that more than 80% of the matter in the universe consists of an unknown substance, or dark matter. The nature of dark matter is still unknown and many searches have been conducted for various dark matter candidates. Axion-like particles (ALPs) are undiscovered particles that are well-motivated candidates for ultralight dark matter. The...
The current GW detectors (LIGO, Virgo and KAGRA) are Dual Recycled Fabry Perot Michelson Interferometers which are all controlled to operate in a broadband, Resonant Sideband Extraction (RSE) configuration. By changing the microscopic length of the Signal Recycling mirror, one obtains a Detuned RSE (DRSE) setup. It has been previously shown that a lossless DRSE configuration presents unique...
Phase cameras are devices which perform differential wavefront sensing at high spatial resolutions. The intended purpose of these devices is to provide high resolution amplitude & phase maps of the various RF control sidebands for diagnostic purposes during commissioning. The increased spatial resolution allows the sensing of high order modes which may be key to understanding unsolved...
The Einstein Telescope (ET) is a planned third-generation gravitational-wave detector that includes a low-frequency (LF) and a high-frequency (HF) laser interferometer.
Cryogenic operation of ET-LF is imperative for exploiting the full scientific potential of ET, with mirrors operated at temperatures of $10\,\mathrm{K}$ to $20\,\mathrm{K}$ in order to limit thermal noise.
Thermal shielding...
After the first detection of gravitational waves in 2015, a new era in understanding the universe took off. To make such detection, gravitational wave detectors are required to operate in an ultra-stable environment that can be obtained only by isolating them from external disturbances. Active isolation control is a major approach in this context, it was successfully implemented in LIGO's...
This study investigates the use of strong lensed gravitational waves (GWs) to constrain the mass of the graviton, a crucial parameter in fundamental physics. By simulating lensing by point mass lenses of various masses (400, 4000, and 4000000 solar masses) and a singular isothermal sphere (SIS) model with a mass of 4000000 solar masses, we calculate the strain of GWs and show that the...
Faraday isolators are needed in various areas of the gravitational-wave detectors, either requiring very low-loss (in the squeezer area), or high-power operation (in the input area), all while maintaining excellent optical isolation and low-noise performance.
Ultra-low-loss Faraday isolators have been built for the A+ output and squeezer isolators, and have shown excellent performance...
Suspended optics in gravitational wave (GW) observatories are susceptible to alignment perturbations and, in particular, to slow drifts over time due to variations in temperature and seismic levels. Such misalignments affect the coupling of the incident laser beam into the optical cavities, degrade both circulating power and optomechanical photon squeezing, and thus decrease the astrophysical...
The Gravitational Wave Data Manager (GWdama) is a Python package that aims at providing an easy way to access Gravitational Wave data and output well-organized datasets, that can be then used for various purposes, including the data management of multichannel data coming from different instruments as well as the development of new data analysis methods, such as Machine Learning.
GWdama...
Coating thermal noise is one of the dominant noise sources in current gravitational wave detectors and ultimately limits their sensitivity to signals from weaker or more distant astronomical sources.
Here we present investigations into the promising candidate high-n coating material for future detectors: TiO2:GeO2. Specifically a mixture of 44% TiO2 / 56% GeO2, as well as pure SiO2...
As part of the upgrade program towards Advanced Virgo+ that started after the end of O3, instrumented baffles are being installed in the detector. These baffles are equipped with photosensors in order to monitor the distribution of scattered light in the cavities in real time and help with beam alignment. A first instrumented baffle was installed in the input mode cleaner (IMC) cavity in 2021...
Improvement of the sensitivity of gravitational waves (GWs) at lower frequencies is important for 3rd-generation detectors. While space-based detectors, such as DECIGO and LISA, remove seismic noise and suspension thermal noise on account of the free-fall state of mirrors, these noises limit the sensitivity of the ground-based detectors, such as Einstein Telescope and Cosmic Explorer. One of...
Juggled Interferometer is a Michelson-type interferometer aiming at improving the sensitivity of earthbound GW detectors at 0.1–10 Hz. This improvement can be achieved with repeatedly free-falling test masses (juggling), which decouples test masses from the seismically noisy environment and avoids suspension thermal noise. With this improved sensitivity, a Juggled Interferometer would be...
The $10\,\mathrm{m}$-Prototype Interferometer of the Albert-Einstein-Institute Hannover will test new techniques to surpass the Standard Quantum Limit. The required displacement sensitivity of the Fabry-Perot Michelson interferometer is below $10^{-19}\,\mathrm{m / \sqrt{Hz}}$ at $200\,\mathrm{Hz}$. The $100\,\mathrm{g}$ test mass mirrors are designed as triple suspensions, where the last...
We present a laser-interferometric detector for axions (LIDA) which is, on the one hand, a testbed for several effects relevant for gravitational-wave (GW) detectors, and, on the other hand, a proposed future application of the LIGO facilities in the 3G era. Our detector is based on the polarisation-sensitive readout of a high-finesse cavity at up to 200kW of circulating power. We will be able...
To preserve the unquestionable improvements deriving by cooling down the mirrors at cryogenic temperature (LT), the methods adopted to mitigate all possible noise sources for gravitational wave detection need to be compliant with cryogenics.
Electrostatic charging is an already known limiting noise source. At room temperature, a mitigation method proposed by the LIGO collaboration has been...
Glitches are short-duration, transient noises that can affect data quality and mask astrophysical signals. Therefore, it is extremely important to characterize them to understand their origin and mitigate them. A key step in this process is to characterize the different glitch families, that are thought to be linked to their different production mechanisms.
Glitches can be classified...
In present gravitational wave (GW) detectors, the limiting noise at mid-frequency range is due to the Brownian thermal noise in the multilayer reflective coating, in particular the intrinsic dissipation of the high refractive index material. The anelastic behavior of amorphous materials is explained by the presence of metastable states that are separated by an energy barrier.
To reduce...
It has become critical to understand and develop effective Thermal Compensation System (TCS) schemes in order to achieve design sensitivity in current and next generation gravitational wave detectors. A full-scale TCS test facility has been proposed and funded for construction at the University of Adelaide. This facility will allow thermal compensation systems to be tested at full scale before...
Even at cryogenic temperature the thermo-elastic effect can hinder mechanical loss measurements of coatings deposited on crystalline substrates by coupling the different contributions, from the substrate and from the coating itself, to the loss angle. We show here that a careful choice of the geometry of the substrate can drastically reduce this effect allowing more accurate measurements of...
The absorption of laser power in the core optics of ground-based gravitational wave detectors induces thermoelastic deformations and changes of the optical path length, that add up to mirror manufacturing defects causing deviations from the ideal optical configuration of the interferometer and worsening its performances. To mitigate these distortions a thermal compensation system (TCS) has...
In the upcoming Advanced Virgo+ upgrade, the goal is to reduce quantum noise across the detector's entire bandwidth by introducing a frequency-dependence using a 300m long cavity (Filter Cavity). However, there can be a mismatch between the fundamental mode of the squeezed vacuum field and the cavity-supported mode that can lead to optical losses. This mismatch is described in terms of the...
Squeezed light is central to the success of future GW detectors, such as Einstein Telescope, but it's also very susceptible to various sources of loss. One of the most important and at the same time less understood sources is mode mismatch between different cavities in the interferometer. Not only it affects the squeezing directly as usual loss, but also couples in anti-squeezing, if the...
Bichromatic control schemes are used to control Fabry-Perot cavities used as filter cavity for frequency dependent squeezing and to acquire the lock of kilometric arm cavities. In the Advanced Virgo+ filter cavity, we observed that the phases of different colors of light are subject to temperature changes in the mirrors. Here we report the evidence of this thermal detuning and its...
The next generation ground-based gravitational wave detectors will expand our view of the Universe. The Einstein Telescope, expected to be built in Europe in the next decade, will be an order of magnitude more sensitive than Advanced Virgo and LIGO and expand its frequency range down to 3 Hz. This low-frequency sensitivity will allow the detection of high-redshift black hole coalescences and...
Knowledge of changes in distance, known as displacement sensing, is crucial for detecting gravitational waves. In addition to detecting test-mass motion in inertial sensors, we also want to monitor unwanted displacements in suspension systems to increase detector sensitivity.
This poster presents the idea of using optical cavities for displacement sensing, and introduces a heterodyne...
In VnEXT, the evolution of Virgo beyond the AdV+ project, the sensitivity is expected to improve by a factor of 10 compared to O5. The increasingly high power stored in the interferometer will require high-precision thermal control of the cavity mirrors to cope with the optical aberrations induced by thermal effects resulting from a circulating power up to 1.5 MW.
The Thermal Compensation...
The DECi-hertz Interferometer for Gravitational-wave Observatory(DECIGO) aims mainly at the detection of primordial gravitational waves (PGWs) originating from inflation. Recent observations by the Planck satellite and others have lowered the upper limit of PGWs. Thus, it is necessary to improve the target sensitivity of DECIGO. A newly proposed method to reduce the quantum noise of DECIGO is...
The seismically excited motion of high-Q pendula in gravitational-wave observatories sets a sensitivity limit to sub-audio gravitational-wave frequencies. Here, we report on the use of machine learning to successfully predict the motion of a high-Q pendulum with a resonance frequency of 1.4 Hz that is driven by natural seismic activity. We achieve a reduction of the displacement power spectral...
The DECi-hertz Interferometer Gravitational-wave Observatory (DECIGO) is a gravitational wave antenna, which is designed to have the optimum sensitivity in the low-frequency band for detection of primordial gravitational waves. Detections of primordial gravitational waves are expected to reveal various unsolved problems, such as proof of cosmic inflation. However, the original design of DECIGO...
Scattered light that re-couples with the main beam of current gravitational wave detectors is a major limitation of their sensitivity, particularly at low frequencies. The detector noise depends on the amount of produced scattered light and the relative motion between the scattering objects and the interferometer. To address this issue in Virgo, we estimated the amount of scattered light...
The DECi-hertz Interferometer Gravitational wave Observatory (DECIGO) project is the future Japanese space mission, which aims at detecting primordial gravitational waves (PGWs) produced in the inflation period. Three arm cavities with 1,000 km compose one cluster of Michelson laser interferometers. We theoretically proposed a quantum locking with optical spring to improve DECIGO’s...
Thulium-doped silica fibre (TDF) lasers have a broad emission band near 2 $\mu$m, making them attractive for use with next-generation cryogenic-silicon gravitational wave detectors. We have demonstrated single-frequency, polarised 2 $\mu$m TDF distributed Bragg reflector (DBR) lasers at wavelengths between 1900 nm and 2050 nm. A high Tm concentration allows the use of a short cavity length,...
For high quality optical surfaces used in gravitational wave detectors, the quantization and reduction of light scattered by localized defects is a challenge. The defects are less than a micron in size, are caused by the manufacturing process (polishing, coating, storage, assembly), and are sparsely distributed (less than one defect per 100 micrometers of diameter). In gravitational wave...
The generation of strongly squeezed vacuum states is a key technology for future ground-based gravitational wave detectors to reach sensitivities beyond their classical quantum noise limit. Due to increased noise at sub-audio frequencies, the generation and subsequent characterization of such states are particularly challenging in the low-frequency range addressed by the Einstein Telescope...
Proposed future gravitational wave detectors place high demands on their stabilized laser system. Especially the proposed interferometers operating with cryogenically cooled silicon mirrors demand another laser wavelength than current detectors. In addition, some of these detectors are expected to be sensitive to gravitational waves down to a few hertz.
We present a prototype for a...
The heating, ventilation and air conditioning (HVAC) systems for the experimental halls of the Virgo interferometer generate considerable low-frequency noise of seismic, acoustic and electromagnetic nature that could affect detector sensitivity. This was experienced several times in the Virgo detector lifetime and most recently during the third science run. In preparation for the fourth run,...
The LISA space interferometer aims at GW detection with ~3x10^-20/√Hz strain sensitivity, resulting in a displacement sensitivity of 11pm/√Hz over a path length of 2.5x10^9 m in the frequency range from 3x10^-5 to 1 Hz.
The LISA France Collaboration is in charge of the ground optical tests of the MOSA (Moving Optical Sub-Assembly), including the Optical Bench, Telescope and Gravitational...
The Einstein Telescope (ET) is a third generation gravitational wave detector, combining a low-frequency (LF) and a high-frequency (HF) laser interferometer. Cryogenic operation of ET-LF in the temperature range of 10-20 K is essential to suppress the suspension thermal noise (STN), which dominates the detection sensitivity at frequencies below 10 Hz. The minimization of the STN requires...
Amorphous Ta2O5 thin films are at the heart of the mirrors of gravitational wave interferometers. Their mechanical and optical properties determine the noise floor of the whole instrument in its most sensitive frequency range and thus the portion of the observable Universe.
Those optical coatings are deposited in their amorphous form by PVD processes. It is then customary to expose the...
Since the first detection of gravitational waves, new data analysis algorithms and methods have emerged. However, to be developed and tested, these new methods require simulated datasets to compensate for the lack of large numbers of real events currently available. Furthermore, upgrades of existing detectors and planning for next-generation instruments, like the Einstein Telescope or Cosmic...
Third generation ground-based gravitational wave detectors as the Einstein Telescope will expand our view of the Universe. In the meantime, upgrade programs as Virgo_nEXT are planned to boost the sensitivity of existing detectors such as Advanced Virgo in the post-O5 time frame. In this context, improving seismic noise attenuation is particularly promising to enhance the sensitivity at low...
In 2027, the Advanced Virgo Plus (AdV+) gravitational-wave detector will enter Phase II, a thermal noise reduction upgrade involving the increase of the terminal mirror masses from 42 kg to 104 kg. Both the terminal SuperAttenuators will thus have their load increased and their parts upgraded in such a way to keep the natural oscillation frequencies unchanged.
This requires a revision of all...
Torsion-Bar Antenna (TOBA) is a ground-based gravitational-wave detector using a torsion pendulum. The resonant frequency of torsional motion is $\sim 1\, \mathrm{mHz}$, therefore TOBA has good design sensitivity in low frequency, specifically $10^{-19} \, /\sqrt{\mathrm{Hz}}$ at $0.1\, \mathrm{Hz}$. TOBA can detect intermediate-mass black hole binary mergers, Newtonian noise, and so on. A...
Silicon is one of the candidates for the construction of monolithic mirror suspensions of 3rd generation GW detectors. In this context, one of the open challenges is the realization of the interfaces between the suspension fibers and the rest of the system. Having a technology that allows the welding of two crystalline components is therefore a first crucial step. With this aim, we decided to...
Future detectors, such as NEMO, Voyager, & Cosmic Explorer, will likely use Silicon optics, ~2000nm lasers, cryogenic temperatures, active mode control, high-circulating power & AlGaAs coated mirrors. We present progress & plans towards a prototype coupled cavity that combines these technologies. This poster presents an overview of the experimental topology and status updates.
On input...
To reduce thermal noise, KAGRA and 3G gravitational waves detectors will operate at cryogenic temperature. This requires the use of crystalline test-masses which could be birefringent. This birefringence leads to several issues from characterization to detector performances. We are now developping a quick method to measure and compensate birefringence as well as a new alignment control scheme...
The DECi-hertz Interferometer Gravitational wave Observatory (DECIGO) is an interferometer with a frequency band between 0.1 and 10 Hz. One of the main objectives of
DECIGO is to detect primordial gravitational waves (PGW) originating from inflation. However,
recent observations of cosmic microwave background lowered the upper limits of normalized
gravitational wave energy density for...
The gravitational waves detectors of the LIGO, Virgo and Kagra collaborations use a mirror actuator using the radiation pressure of a laser as a reference for the calibration. This actuator is called the photon calibrator (PCal). The displacement of the mirror induced by the PCal is estimated from a measurement of the power of the laser reflected by the mirror. Thus, the calibration of the...
Currently, the sensitivity of the second generation Gravitational-Wave (GW) detectors is limited in the low and mid frequency range by Thermal Noise (TN) and Seismic Noise (SN).
Major improvements in GW instrumentation science are expected from the Thermal Noise (TN) reduction in the mid-frequency range of the detectors, achievable also by cooling down the mirrors to $10$ K.
In order to...
