The squeeze laser and its applications in quantum sensing

Abstract

Laser interferometers are able to measure relative optical length changes and to analyze material properties, surface structures, and density fluctuations of fluids and gases. As these setups approach the quantum limit in sensitivity, employing quantum squeezed light becomes a crucial method to enhance the signal-to-noise ratio without increasing the optical power. Squeeze lasers, which produce these squeezed states, have been successfully improved for almost three decades and were implemented in gravitational wave detectors as a first user application. As quantum squeezing finds more practical applications, conventional squeeze lasers, which take up a full optical table, become impractical. The need for compact, robust, and versatile devices rises. Here, I designed, built, and set up two squeeze lasers on breadboards with footprints of 80cm*80cm and 60cm*40cm and with squeezing values at a Fourier-frequency of 5MHz of (10.70+-0.18)dB and (10.06+-0.14)dB respectively. One of this setups was used for a laser Doppler vibrometer experiment at the Clausthal University of Technology. My squeeze laser increased the sensitivity of the heterodyne readout of the motion of a oscillating mirror at 1MHz by (2.77+-0.61)dB. As another practical application of squeeze lasers, I report on the squeezed-light enhanced detection and characterization of ultrasonic sound waves in air between 4.2-7.2MHz via a Mach-Zehnder interferometer at 1550nm. Squeezed light allowed to enhance the sensitivity of the setup by more than 10dB, enabling the detection of sound waves up to (0.12+-0.02)mPa/sqrt(Hz). The work in this thesis demonstrates practical uses of the squeeze laser and opens the path for a new generation of applications for squeezed light.