The Padova-Trento Virgo group: Experimental Activity in Virgo

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3 Experimental Activity in Virgo


Partial view of the optoelectronic system at the EGO site for the production of a light squeezed vacuum state for Advanced Virgo: the photo details one of the subsystems developed by the Padova-Trento group. The beam of a 1W infrared laser source (red-black box on the right) is coupled to the Second Harmonic Generation (SHG) cavity (metal-black part at the left of the laser source), which converts the infrared radiation into visible green light.

Padova-Trento group is co-chairing the Virgo working group on the squeezed light upgrade for Advanced Virgo. The motivations of the use of squeezed light in Advanced Virgo are two-fold: a mitigation of the risk related to high power operation of the detector and a significant improvement of the detector sensitivity. The former is a short term goal, achievable with a squeezed light source and injection systems analogous to what already tested on the LIGO Hanford and GEO detectors. The latter instead is a longer-term goal, since it requires the development of an additional system to adapt the squeezed light phase as a function of frequency, which has not been operated yet in a gravitational wave detector. Current activities include the preparation of a Technical Design Report on the squeezed light source and its injection system in the frequency independent configuration, targeting a near future upgrade of the Advanced Virgo detector. In addition, the group contributes to and coordinates the realization at the Virgo site of a squeezed light source prototype and low loss optical components for the injection system, following the design described in the Technical Design Report, in collaboration with other Virgo groups. In particular, for this project, the group has developed:

Padova-Trento is currently addressing the implementation of the coherent control loop for the stabilization of the squeezing ellipse and is contributing to the integration the entire squeezed light source. Another ongoing activity in collaboration with the EGO optical group is the construction of a low loss Faraday isolator operating in vacuum, which is a required component of the squeezed light injection system in Advanced Virgo.

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