Laser Interferometric Gravitational Wave Detectors Research Articles

Black hole spectroscopy with ground-based atom interferometer and space-based laser interferometer gravitational wave detectors

Gravitational wave (GW) detection allows us to test general relativity in entirely new regimes. A prominent role takes the detection of quasi-normal modes (QNMs), which are emitted after the merger of a binary black hole (BBH) when the highly distorted remnant emits GWs to become a regular Kerr black hole (BH). The BH uniqueness theorems of Kerr black hole solutions in general relativity imply that the frequencies and damping times of QNMs are determined solely by the mass and spin of the remnant BH. Therefore, detecting QNMs offers a unique way to probe the nature of the remnant BH and to test general relativity. We study the detection of a merging BBH in the intermediate-mass range, where the inspiral–merger phase is detected by space-based laser interferometer detectors TianQin and LISA, while the ringdown is detected by the ground-based atom interferometer (AI) observatory AION. The analysis of the ringdown is done using the regular broadband mode of AI detectors as well as the resonant mode optimizing it to the frequencies of the QNMs predicted from the inspiral–merger phase. We find that the regular broadband mode allows constraining the parameters of the BBH with relative errors of the order 10−1 and below from the ringdown. Moreover, for a variety of systems considered, the frequencies and the damping times of the QNMs can be determined with relative errors below 0.1 and 0.2, respectively. We further find that using the resonant mode can improve the parameter estimation for the BBH from the ringdown by a factor of up to three. Utilizing the resonant mode significantly limits the detection of the frequency of the QNMs but improves the detection error of the damping times by around two orders of magnitude.

Experimental demonstration of frequency- downconverted arm-length stabilization for a future upgraded gravitational wave detector.

Ground-based laser interferometric gravitational wave detectors (GWDs) consist of multiple optical cavity systems whose lengths need to be interferometrically controlled. An arm-length stabilization (ALS) system has played an important role in bringing these interferometers into an operational state and enhancing their duty cycle. The sensitivity of these detectors can be improved if the thermal noise of their test mass mirror coatings is reduced. Crystalline AlGaAs coatings are a promising candidate for this. However, the current ALS system with a frequency-doubled 532 nm light is no longer an option with AlGaAs coatings because the 532 nm light is absorbed by AlGaAs coatings due to the narrow bandgap of GaAs. Therefore, alternative locking schemes must be developed. In this Letter, we describe an experimental demonstration of a novel ALS scheme, to the best of our knowledge, which is compatible with AlGaAs coatings. This ALS scheme will enable the use of AlGaAs coatings in current and future terrestrial gravitational wave detectors.

Effects of mirror birefringence and its fluctuations to laser interferometric gravitational wave detectors

Effects of mirror birefringence and its fluctuations to laser interferometric gravitational wave detectors

Prophetic detection and discovery of gravitational waves

Einstein's general relativity theory includes the gravitational wave as a key prediction. One of the most crucial areas of contemporary physics is gravitational wave detection. A fantastic addition to conventional electromagnetic radiation astronomy, gravitational wave astronomy is a brand-new field of study based on the discovery of gravitational waves. In this paper, the prediction and characteristics of gravitational waves are discussed, and the detection methods of gravitational waves are given, such as the limitations of the resonant rod of gravitational waves, the working principle and basic structure of the gravitational wave probe, the laser interferometer. The gravitational wave signal of the binary black hole merger detected by the LIGO laser interferometer gravitational wave detector in the United States for the first time on September 14, 2015, which opens a new "gravitational wave window" for human astronomy research. It is foreseeable that in the near future gravitational wave research will explore the unknown information of the universe from various gravitational wave frequency bands.

Application of Newtonian approximate model to LIGO gravitational wave data processing

With the observation of a series of ground-based laser interferometer gravitational wave (GW) detectors such as LIGO and Virgo, nearly 100 GW events have been detected successively. At present, all detected GW events are generated by the mergers of compact binary systems and are identified through the data processing of matched filtering. Based on matched filtering, we use the GW waveform of the Newtonian approximate (NA) model constructed by linearized theory to match the events detected by LIGO and injections to determine the coalescence time and utilize the frequency curve for data fitting to estimate the parameters of the chirp masses of binary black holes (BBHs). The average chirp mass of our results is , which is very close to provided by GWOSC. In the process, we can analyze LIGO GW events and estimate the chirp masses of the BBHs. This work presents the feasibility and accuracy of the low-order approximate model and data fitting in the application of GW data processing. It is beneficial for further data processing and has certain research value for the preliminary application of GW data.

Measurement of the temperature dependence of mechanical losses induced by an electric field in undoped silicon disk resonators

Test masses of future laser interferometric gravitational-wave detectors will be made of high-purity silicon and cooled, in particular, to 123 K in the LIGO Voyager project. Electrostatic actuators are supposed to be used to tune the test mass position. Capacitive coupling of the actuator electrodes with the silicon test mass results in the mechanical loss caused by electric currents flowing in silicon having a finite resistivity. This loss is a cause of additional thermal noise. In this study, we present the results of temperature dependence of the electric field induced loss in the bending vibration mode of commercial disk-shaped undoped silicon wafers in the temperature range of 100–295 K.

The laser interferometric gravitational wave detector calibrator suspension: First attempt

AbstractIn 2015 the first detection of gravitational waves (GW) was made; such detection was made by kilometer size interferometer detectors. The calibration of such a detector is still a challenge then a calibrator was proposed. This calibrator is a resonant mass gravitational wave detector that operates at frequencies where the GW have been detected. This work shows part of the challenges of making a suspension for this device. The device has its vibration mode simulated in Finite Element Methods, then the parts of the device which have less movement were chosen to connect the suspension. Other simulations were made with the complete system and the results were analyzed.

Boosting the sensitivity of high-frequency gravitational wave detectors using PT -symmetry

The kilo-Hertz gravitational waves radiated by the neutron star merger remnants carry rich information about the physics of high-density nuclear matter states, and many important astrophysical phenomena such as gamma-ray bursts and black hole formation. Current laser interferometer gravitational wave detectors, such as LIGO, VIRGO, and KAGRA have limited signal response at the kilo-Hertz band, thereby unable to capture these important physical phenomena. This work proposes an alternative protocol for boosting the sensitivity of the gravitational wave detectors at high frequency by implementing an optomechanical quantum amplifier. With the auxiliary quantum amplifier, this design has the feature of Parity-Time (PT) symmetry so that the detection band will be significantly broadened within the kilo-Hertz range. In this work, we carefully analyze the quantum-noise-limited sensitivity and the dynamical stability of this design. Based on our protocol, our result shows that the quantum-noise-limited sensitivity will be improved by one order of magnitude around 3kHz, which indicates the potential of our design for a future search of neutron star merger signals.

Can the phase of radiation pressure fluctuations be flipped in a single path for laser interferometric gravitational wave detectors?

Radiation pressure (RP) noise, one component of quantum noise, can limit the sensitivity of laser interferometric gravitational wave (GW) detectors at lower frequencies. We conceived a possible RP noise cancellation method, using phase flipped ponderomotive-squeezed light (FPSL) incident on free-mass mirrors in interferometers' arms. This possibility is investigated under the constraint that the method is for space-based GW detectors in a broad frequency band lower than 1 Hz without using a long optical cavity. Considering various patterns in a single path small-scale case to generate the FPSL, we proved that no configuration exists in the single path case.

Suspension and vibration isolation systems of the ground-based laser interferometric gravitational wave detectors

To successfully detect the ultrasmall gravitational wave signal ($\sim$$10^{-19}$ m), the ground-based laser interferometric gravitational wave detector should reduce all kinds of noise. This study summarizes the seismic noise that affects gravitational wave detection and the basic principle and method for mitigating the seismic noise. At present, a multistage suspension system and an active vibration isolation system are combined to further reduce seismic noise. We investigate and analyze the application of passive and active vibration isolation methods in ground-based gravitational wave detectors by reviewing the suspension and vibration isolation systems of current gravitational wave detectors, including LIGO, Virgo, KAGRA, and GEO600.

Amorphous silicon nitride deposited by an NH3-free plasma enhanced chemical vapor deposition method for the coatings of the next generation laser interferometer gravitational waves detector

Cryogenic mechanical loss of the mirror coatings will result in thermal noise and limit the sensitivity of the next generation laser interferometer gravitational wave detectors operated at cryogenics. Amorphous silicon nitride (aSiN) films deposited by NH3 plasma enhanced chemical vapor deposition (NH3-PECVD), a coating method with potential in large area uniform coatings for the next generation detectors, were found previously to have a low cryogenic mechanical loss and without loss peaks that are common in current coatings for room temperature detectors. A positive correlation between N–H bond density and cryogenic mechanical loss in the aSiN films has been observed previously, and the existence of an N–H bond-related asymmetrical two-level system was postulated to account for the cryogenic mechanical loss. In this report, we studied an NH3-free PECVD process to reduce the N–H bond concentration and hence reducing the cryogenic mechanical loss. The N–H bond density of all films deposited by the NH3-free PECVD method was reduced to below the detection limit (<1020 cm−3). The composition of the optimized film is SiN0.33H0.58 which shows the lowest extinction coefficient (1.21 × 10−5 @ 1550 nm), a high refractive index (2.68 @ 1550 nm), and excessively low stress (20.8 MPa), respectively. From 10 K to 120 K, cryogenic mechanical loss of the as-deposited SiN0.33H0.58 varies from 5 × 10−5 to 8 × 10−5 which is two to three times lower than that of the best NH3-PECVD silicon nitride previously obtained. No distinctive cryogenic loss peak was found as well.

Unsupervised learning architecture for classifying the transient noise of interferometric gravitational-wave detectors

In the data obtained by laser interferometric gravitational wave detectors, transient noise with non-stationary and non-Gaussian features occurs at a high rate. This often results in problems such as detector instability and the hiding and/or imitation of gravitational-wave signals. This transient noise has various characteristics in the time–frequency representation, which is considered to be associated with environmental and instrumental origins. Classification of transient noise can offer clues for exploring its origin and improving the performance of the detector. One approach for accomplishing this is supervised learning. However, in general, supervised learning requires annotation of the training data, and there are issues with ensuring objectivity in the classification and its corresponding new classes. By contrast, unsupervised learning can reduce the annotation work for the training data and ensure objectivity in the classification and its corresponding new classes. In this study, we propose an unsupervised learning architecture for the classification of transient noise that combines a variational autoencoder and invariant information clustering. To evaluate the effectiveness of the proposed architecture, we used the dataset (time–frequency two-dimensional spectrogram images and labels) of the Laser Interferometer Gravitational-wave Observatory (LIGO) first observation run prepared by the Gravity Spy project. The classes provided by our proposed unsupervised learning architecture were consistent with the labels annotated by the Gravity Spy project, which manifests the potential for the existence of unrevealed classes.

Can the Phase of Radiation Pressure Fluctuations Be Flipped in a Single Path for Laser Interferometric Gravitational Wave Detectors?

Can the Phase of Radiation Pressure Fluctuations Be Flipped in a Single Path for Laser Interferometric Gravitational Wave Detectors?

Can the Phase of Radiation Pressure Fluctuations Be Flipped in a Single Path for Laser Interferometric Gravitational Wave Detectors?

Can the Phase of Radiation Pressure Fluctuations Be Flipped in a Single Path for Laser Interferometric Gravitational Wave Detectors?

Model-independent time-delay interferometry based on principal component analysis

With a laser interferometric gravitational-wave detector in separate free flying spacecraft, the only way to achieve detection is to mitigate the dominant noise arising from the frequency fluctuations of the lasers via postprocessing. The noise can be effectively filtered out on the ground through a specific technique called time-delay interferometry (TDI), which relies on the measurements of time delays between spacecraft and careful modeling of how laser noise enters the interferometric data. Recently, this technique has been recast into a matrix-based formalism by several authors, offering a different perspective on TDI, particularly by relating it to principal component analysis (PCA). In this work, we demonstrate that we can cancel laser frequency noise by directly applying PCA to a set of shifted data samples, without any prior knowledge of the relationship between single-link measurements and noise, nor time delays. We show that this fully data-driven algorithm achieves a gravitational-wave sensitivity similar to classic TDI.

Ultralight dark matter searches with KAGRA gravitational wave telescope

Among various dark matter candidates, bosonic ultralight fields with masses below 1eV are well motivated. Recently, a number of novel approaches have been put forward to search for ultralight dark matter candidates using laser interferometers at various scales. Those include our proposals to search for axion-like particles (ALPs) and vector fields with laser interferometric gravitational wave detectors. ALPs can be searched for by measuring the oscillating polarization rotation of laser light. Massive vector fields weakly coupled to the standard model sector can also be searched for by measuring the oscillating forces acting on the suspended mirrors of the interferometers. In this paper, the current status of the activities to search for such ultralight dark matter candidates using a gravitational wave detector in Japan, KAGRA, is reviewed. The analysis of data from KAGRA’s observing run in 2020 to search for vector dark matter, and the installation of polarization optics to the arm cavity transmission ports of the interferometer to search for ALPs in future observing runs are underway.

A nonparametric method to assess the significance of events in the search for gravitational waves with false discovery rate

AbstractWe present a consistent procedure to assess the significance of gravitational wave events observed by laser interferometric gravitational wave detectors based on the background distribution of the detection statistic. We propose a non-parametric method to estimate the p-value. Based on the estimated p-values, we propose a new procedure to assess the significance of a particular event with a q-value which is the minimum false discovery rate that can be attained when calling the event significant. The q-value gives us a criterion on the significance of events which is different from Pastro as used in the LIGO–Virgo analysis and others. The proposed procedure is applied to the 1-OGC and 2-OGC catalogs. For most of the events which were claimed significant in these catalogs, we obtain the same results. However, there are differences in the significance for several marginal events. Since the proposed procedure does not require any assumptions on signal and noise, it is very simple and straightforward. The procedure is also applicable to other searches for gravitational waves whose background distribution of the detection statistic is difficult to know.

The electromagnetic field in gravitational wave interferometers * *Preprint UWThPh-2021-11

We analyse the response of laser interferometric gravitational wave detectors using the full Maxwell equations in curved spacetime in the presence of weak gravitational waves. Existence and uniqueness of solutions is ensured by setting up a suitable boundary value problem. This puts on solid ground previous approximate calculations. We find consistency with previous results obtained from eikonal expansions at the level of accuracy accessible to current gravitational wave detectors.

The response of laser interferometric gravitational wave detectors beyond the eikonal equation

The response of Michelson interferometers to weak plane gravitational waves is computed at one order of accuracy beyond the eikonal equation. The modulation of the electromagnetic field amplitude and polarisation are taken into account by solving the transport equations of geometrical optics with boundary conditions adapted to laser interferometry. Considering both DC and balanced homodyne readout schemes, explicit formulae for the interferometer output signals are derived. These signals comprise perturbations of the optical path length, frequency and amplitude, and are shown to be insensitive to polarisation perturbations.

Revealing optical loss from modal frequency degeneracy in a long optical cavity.

Optical loss plays a significant role in optical experiments involving optical cavities such as recycling cavities and filter cavities in laser interferometer gravitational-wave detectors. For those cavities, modal frequency degeneracy, where the fundamental and a higher order mode resonate inside the cavity simultaneously, is a potential mechanism which may bring extra optical loss to the cavity thus degrade detection sensitivity. In this paper, we report observation of modal frequency degeneracy in a large-scale suspended Fabry-Pérot cavity. The cavity g-factor is tuned by a CO2 laser heating one test mass, and the cavity finesse is obtained from a ring-down measurement of the transmitted light. We demonstrate that the modal frequency degeneracy can cause a reduction of the cavity finesse by up to ∼30%, corresponding to a ∼2-fold increase in total optical loss. To minimize optical loss in gravitational-wave detectors, the effect of modal frequency degeneracy needs to be taken into account in the design and operation of the detector.