Experimental characterization of frequency dependent squeezed light

TL;DR

This paper demonstrates broadband frequency-dependent squeezed light with stable locking and characterization, crucial for enhancing sensitivity in gravitational wave detectors like GEO600.

Contribution

It presents the first stable locking and detailed characterization of frequency-dependent squeezed light using quantum state tomography.

Findings

Achieved stable locking of carrier frequency and quadrature angle.

Measured Wigner functions of squeezed states.

Demonstrated potential application in gravitational wave detectors.

Abstract

We report on the demonstration of broadband squeezed laser beams that show a frequency dependent orientation of the squeezing ellipse. Carrier frequency as well as quadrature angle were stably locked to a reference laser beam at 1064nm. This frequency dependent squeezing was characterized in terms of noise power spectra and contour plots of Wigner functions. The later were measured by quantum state tomography. Our tomograph allowed a stable lock to a local oscillator beam for arbitrary quadrature angles with one degree precision. Frequency dependent orientations of the squeezing ellipse are necessary for squeezed states of light to provide a broadband sensitivity improvement in third generation gravitational wave interferometers. We consider the application of our system to long baseline interferometers such as a future squeezed light upgraded GEO600 detector.