Preliminary studies related to balanced homodyne detection of squeezed light

Abstract

The objective of this project is to investigate experimental requirements for quantum noise limited balanced homodyne detection at 1064 nm, with the long term goal of supporting future squeezed light measurements for precision interferometry and gravitational wave detection. The work focuses on developing a low noise balanced detection platform capable of resolving quantum noise above the electronic background. The main experimental work consisted of photon shot noise and vacuum noise measurements using balanced photodetectors. Initial measurements with a fiber-coupled balanced photodetector showed the expected increase of noise with optical power, but the results exhibited relatively large fluctuations and incomplete suppression of classical noise. Improved performance was obtained using a free-space balanced photodetector. In the balanced configuration, the measured voltage noise spectral density showed close agreement with the theoretical shot noise prediction and significantly reduced measurement scatter, indicating effective rejection of common mode classical noise. Vacuum noise measurements in a balanced homodyne configuration further showed that the clearance above the electronic dark noise floor improved from about 1.43 dB at 50 μWlocal oscillator power to about 5.4 dB at 440 μW. These results demonstrate that the present detection system provides a practical foundation for future squeezed light measurements at the few-dB level. Keywords: photon shot noise, vacuum fluctuations, balanced homodyne detection, squeezed light, balanced photodetector.