This paper describes a setup aimed at measuring the so-called Tilt-To-Length (TTL) coupling in the optical benches of the LISA mission. The TTL is the coupling of the angular jitter of any optical setup into the optical path length between its input and output pupils. This might be deleterious in laser ranging experiments and must be evaluated for further compensation. The setup is made of two laser beams, one features an angular jitter that mimics the input beam as seen from the jittering bench under test (BUT), the other is aligned to the optical axis of the BUT and provides a phase reference for the jittering beam. The induced phase variations between both beams detected at the BUT's output pupil gives access to the TTL coupling. The "TTL probe" must feature a negligible residual TTL coupling which implies a micrometric accuracy in the centering of the setup pupil, the beams and the angular jitter associated pivot point. The setup integrates optical masks as a link between the setup optical reference frame to its mechanical reference frame, together with position memories and servo-loops for the beam's alignment. We show that the stability, the accuracy, and the noise floor of the setup is compliant with the LISA specifications for the TTL mitigation, although it makes use of off-the-shelf components and is operated in a standard environment laboratory.

Advanced LIGO and Advanced Virgo are actively monitoring the sky and collecting gravitational-wave strain data with sufficient sensitivity to detect signals routinely. In this paper we describe the data recorded by these instruments during their first and second observing runs. The main data products are the gravitational-wave strain arrays, released as time series sampled at 16384 Hz. The datasets that include this strain measurement can be freely accessed through the Gravitational Wave Open Science Center at http://gw-openscience.org, together with data-quality information essential for the analysis of LIGO and Virgo data, documentation, tutorials, and supporting software.

Second generation of laser interferometer gravitational wave detectors can now detect the fusion of compact stellar object pair weekly. To increase the sensitivity, an important change of design between first and second generation gravitational wave detectors is the use of homodyne detection instead of heterodyne. This modification has strongly increased the requirement on laser power stabilization for Advanced VIRGO [1] . The relative intensity noise (RIN) requirement depends on the effective defects of the interferometer mirrors and its operational state. It spans between 10 -8 Hz -1/2 and 1.2×10 -9 Hz -1/2 at 30 Hz for the most sensitive future configuration (2024).

Summary form only given. VIRGO is a 3-km-arm laser interferometer for gravitational wave detection in the 20 Hz-5 kHz frequency band. Its second-generation version, Advanced VIRGO, aims at reducing the detector noise by a factor of ten compared to the first generation, with the progressive deployment of new technologies and equipment [1]. The first detections of gravitational waves with VIRGO were made in August 2017 [2]. For its next scientific observations with an increased sensitivity, a pre-stabilized laser system twice as powerful has been developed. It comprises a new 100-W solid-state amplifier pumped at 878.7 nm. It is the first time such amplifier is integrated in a gravitational wave detector, LIGO detectors using a 70 W amplifier pumped at 808 nm. Power noise, long term power stability, frequency noise, beam jitter and transverse mode quality have been extensively studied and compared to Advanced VIRGO requirements. The pre-stabilized laser system, emitting a continuous wave at 1064 nm, is based on a 17 W laser oscillator, injection locked onto a low frequency noise 500 mW source, followed by the new 100 W amplifier and a 1.6-mperimetre bow -tie shape Fabry-Perot cavity acting as a spatial and temporal mode cleaner. The optical amplifier, manufactured by neoLASE, is based on four Nd 3+ :YVO 4 crystals pumped longitudinally each with 50 W at 878,7 nm coming from volume Bragg grating diode lasers. The pump light is transported by 20 meters of multi mode fi bers deployed between two separate rooms for acoustic and electromagnetic contamination reasons. The fi rst test and characterization campaign was performed in Nice in 2017 followed by the integration at the VIRGO site. The system has been working continuously for commissioning for more than one year. The amplifier delivers 96 W with 17 W input and reaches 100 W with increased input power. No global decrease of the amplifier output power has been so far observed. The relative intensity noise spectrum (Fig. 1-a) is below 10 -4 x(10 Hz/f) 1 / 2 Hz -1 / 2 in the detection band and limited by 13 mA photocurrent shot noise (5x 10 Hz 1/2 ) in the 5-10 MHz band used for modulation. Further power noise reduction is realized by combining passive fi ltering from Fabry-Perot mode cleaners and active power stabilization with an acousto-optic modulator in transmission to reach 2x 10 -9 Hz -1 / 2 in the detector band. The spectrum of the frequency noise added by the amplifier (Fig. 1-b) was measured with a heterodyne interferometer and is lower than 3x 10 -1 Hz/Hz 1 / 2 , far below the master laser oscillator. Those performances are compliant with Advanced VIRGO specifications [1].

Stable low-noise high-power lasers are indispensable in advancing the strain sensitivity of interferometric gravitational wave detectors. Advanced LIGO and Advanced Virgo are currently under commissioning and require about 200 W of single-frequency laser power, while the future detector design may require up to the order of 500 W. In this Letter, we present the design and, to the best of our knowledge, the first experimental demonstration of the laser system for Advanced Virgo that is based on coherently combined fiber laser amplifiers. We show the long-term performance of two 40 W fiber laser amplifiers, as well as their characterization in terms of beam quality, power noise, phase noise, and beam pointing. Moreover, a simple and compact setup utilizing fibered modulators and actuators for the coherent beam combination of these two fiber laser amplifiers is reported. A combination efficiency of about 96% was achieved, and no spurious noise was observed.

Nous avons concu et construit un systeme optique de synthese d’ondes hyperfrequences, millimetriques et submillimetriques a tres bas bruit de phase. Les resultats preliminaires montrent une densite spectrale de bruit de phase a 10 kHz de la porteuse d’une onde a 9 GHz limitee par l’appareil de mesure. Pour les bruits plus pres de la porteuse, le bruit de phase est limite par une modulation d’amplitude residuelle : le systeme est en cours de modifications.

We report on the design of an ultra stable microwave/THz oscillator and on the realization and the characterization of its laser source. The tunable oscillator is expected to show below -150 dB rad2/Hz phase instability at an offset frequency of 10 kHz for a 30 GHz carrier frequency, as well as 18 GHz, 100 GHz, 400 GHz and 1 THz carrier frequencies.