LIGO Seminar

During the last decade the technology for generating squeezed vacuum has reached maturity. Tests showed a remarkable interferometer sensitivity improvement, promising an increase of more than a factor of three in the observable event rate. This sensitivity gain is also available as significant risk mitigation in case excessive optical absorption and thermal lensing prevents full power operations. It does however require minimal optical losses on the squeezed light path.

For a gravitational wave interferometer a significant chunk of the losses are due the mode matching into the output mode cleaner. Those losses are particularly worrisome for two reasons. First, the initial static mode matching is a challenge because the relevant mode, namely the mode resonant in the arm cavities, is not necessarily identical with the total light visible at the interferometerʼs dark port. Second, the arm optical mode will be affected by thermal lensing inside the interferometer. Such lensing is expected to occur at the full input power level of the Advanced LIGO design, and can also effect the interferometer optical gain. For that reason the Advanced LIGO design anticipated the need for thermal lens correction actuators in the recycling cavities, but the project currently does not include adaptive correction of the mode matching into the output mode cleaner. A squeezer upgrade for Advanced LIGO will thus put adaptive mode matching into the output mode cleaner on the critical path.

This talk will discuss the work done so far for designing an adaptive mode-matching actuator capable of correcting up to about 10% mode-mismatch in any Gouy phase.

We plan to broadcast this talk using SeeVogh.