Study Of Shot-Noise-Limited Phase-Sensitive Heterodyne Detection Of Low-Frequency Signals

The detection of low-frequency signals(10 Hz and lower frequency)at the shot noise limit plays an important role in fundamental physics research,such as gravitational-wave detection,observation of magnetic-field induced vacuum birefringence.On account of potential high sensitivity in low-frequency signal detection,phase-sensitive heterodyne detection has attracted worldwide interest.However,as a new detection method,phase-sensitive heterodyne detection needs to be studied deeper both in theory and in experiment.This dissertation presents theoretical and experimental research on shot-noise-limited phase-sensitive heterodyne detection of low-frequency amplitude signal produced by a Mach-Zehnder interferometer and low-frequency phase signal created by a Fabry-Perot interferometer.Through theoretical calculation,scheme design,experimental realization,data acquisition,process and noise analysis,we have achieved the following results:(1)The sensitivity in detecting low-frequency amplitude signal reaches the shot noise limit around 10 Hz(0.2 Hz is the lowest);(2)the sensitivity of detecting low-frequency phase signal around 1 Hz is close to the shot noise limit,mainly limited by electronics noise.With frequency-synthesized light for Fabry-Perot cavity locking,we have experimentally demonstrated suppression of residual amplitude modulation(RAM)fluctuations between 0.3-100 m Hz by two orders of magnitude and 10 d B below the RAM noise of a traditional phase-modulated light,when a simple RAM servo is activated.The research of phase-sensitive heterodyne detection in this dissertation should have laid a theoretical and experimental base for detecting low-frequency signals(10 Hz and lower frequencies)at the shot noise limit,and hopefully has a positive impact on scientific research,especially gravitational-wave detection.