Higher-Order Spatially Squeezed Beam for Enhanced Spatial Measurements

Abstract

A scheme is proposed to realize high-precision spatial measurement of laser beams beyond quantum limit using a novel quantum state called the (Formula presented.) order spatially squeezed state, which is the combination of a bright (Formula presented.) mode coherent state and squeezed vacuum (Formula presented.) mode state. An effective technique for the generation of a rectangular shape higher-order mode squeezed light with a maximum mode order of 5 is experimentally demonstrated using a doubling resonated optical parametric amplifier. Furthermore, the fourth order tilt- and displacement-squeezed beams are constructed and used to perform spatial tilt and displacement measurements, thereby improving the signal-to-noise ratio by 10 and 8.6 dB compared to the (Formula presented.) mode. The results indicate that high-order spatially squeezed states enhance measurement precision beyond the shot noise limit and are more prominent in back-action noise reduction. High-precision spatial measurement has potential practical applications in high-sensitivity atomic force microscope and super-resolution quantum imaging.