Abstract

Since the first proposal by Caves1 that squeezed light could be used to enhance the sensitivity of a gravitational wave interferometric antenna, squeezed states have been demonstrated in the laboratory but not yet used in an actual measurement system. This paper describes a polarization interferometer experiment, operated with a squeezed light source, designed to improve the interferometer sensitivity beyond the standard quantum limit. The interferometer consists of two polarization beam splitters, whose axes are oriented 45° with respect to each other. Linearly polarized incident laser light is transmitted by the first polarizer and split by the second one, which also acts as the splitter for a balanced homodyne detector. A rotation of the polarization between the two polarizers can be detected with quantum-limited sensitivity (e.g., ±1 μrad). The squeezed light entering the other port of the interferometer is produced using a χ² crystal (KTP) in an optical cavity, pumped by a frequency-doubled cw ring Nd:YAG laser. The interferometer sensitivity can thus be increased by a factor depending on the degree of squeezing achieved and on the detector quantum efficiency. Sensitivity increases by factors between 2 and 3 are predicted, and current performance is described.

© 1987 Optical Society of America