OPTICAL MEASUREMENTS OF WEAK ABSORPTION BEYOND SHOT-NOISE LIMIT

摘要

The optical measurement of weak absorption beyond the shot-noise limit (SNL) has been achieved by employing quantum-correlated twin beams from a nondegenerate optical parametric oscillator operating above threshold. An improvement in signal-to-noise ratio of 2.5dB relative to SNL is obtained for the weak absorption measurements. Semi classical theoretical analyses demonstrate that the minimum detectable absorptance is able to trend toward zero through the proposed regime if the intensity difference squeezing between the twin beams is perfect.