研究目的
Investigating the excess noise in homodyne detection originating from distributed photocarrier generation in photodiodes and its impact on high-accuracy quantum measurement.
研究成果
The distributed photon absorption in photodiodes causes excess noise in the high-frequency region of continuous-wave light detection, which can be treated as a frequency-dependent optical loss in homodyne detection. This excess loss is a critical limitation in the bandwidth of homodyne detection, becoming non-negligible above 100 MHz for Si photodiodes and 1 GHz for (In,Ga)As photodiodes. The experimental results agree with the theoretical model, providing new design criteria for high-efficiency photodiodes.
研究不足
The study is limited by the technical challenges of maintaining a high signal-to-noise ratio of the shot noise over 1 GHz and the slight error in power calibration. The model's assumptions may not accurately describe the gain characteristics around the negative peak frequency due to simplifications in the photocurrent transfer functions.
1：Experimental Design and Method Selection:
The study employs two experimental methods to evaluate the excess loss in homodyne detection: comparison of signal gain and shot-noise gain of one-port homodyne detection, and balanced homodyne detection of squeezed light at a 500-MHz sideband.
2：Sample Selection and Data Sources:
Uses 860-nm CW light and a Si-PIN photodiode S5971SPL (Hamamatsu Photonics) with near-unity quantum efficiency at 860 nm.
3：List of Experimental Equipment and Materials:
Includes Ti:sapphire laser MBR-110, photodetector composed of low-noise amplifiers HMC8410 and ZFL-1000LN+, spectrum analyzer E4402B, network analyzer E5080A, and waveguide intensity modulator.
4：Experimental Procedures and Operational Workflow:
Detailed procedures for shot-noise spectrum measurement and squeezed light measurement are described, including the setup for homodyne detection and data acquisition.
5：Data Analysis Methods:
The excess loss is calculated from the shot-noise measurement and estimated from the squeezed light measurement, with theoretical curves compared to experimental data.
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