Improving The SNR Of Weak Measurement Via Power Recycling

Weak measurement is widely used in researching the amplification and detection of small signals. For example:the measurement of the beam deflection, the small phase shift and short time delay. A generic shortcoming of weak-value-related metrological techniques is the fact that only a small fraction of the events are "post-selected," while the vast majority of events are intentionally thrown away, which will lead to a small signal-to-noise ratio (SNR). How to improve the SNR has become a pressing task.Our analysis begins with the beam deflection measurement setup, using the power recycling to re-inject the optical signal that is not selected by the post-selection in the interferometer, thereby enhancing the strength of the signal detected and promoting the SNR. We used partially transmitting mirror in the experiment to build a power recycling cavity. We based on the resonant cavity theory to deduce the SNR expression of the experiment. We use PDH technology to lock the cavity length to ensure the stability of the experiment. Finally, the single photon detectors instead of the quadrant detector in the experiment to eliminate the influence of gain noise. The signal strength increased 2.36 times via power recycling. The final results showed that SNR has been promoted and broke through the SNR limit of the standard weak measurement system by using the power recycling.