Designing And Testing Of The Bell-state Photodetector For Quantum Optics Experiments

In order to measure the shot noise and its non-classical charateristics effectively in quantum optics experiments, the photodetector should be low-noise and high-sensitity intended. Especially for the measurement of optical Bell-states, the power of the input 1064nm laser is around 50μW and the shot noise is rather weak. In order to avoid the weak shot noise being overwhelmed by the photodetector electronic noise, the measured shot noise should be lOdB higher than the electronic noise at 2MHz. Therefore, much effort has been put onto designing and testing Bell-state photodetectors with characteristics on low-noise and high-gain.The mechanisms of optoelectric detection、know-hows for high signal-to-noise ration, methods to reduce the electronic noise of photodetectors, etc, are included in this master thesis. When the input laser is around 51μW@1064nm, the avaible signal-gain is better than reported results, which meets the demand of Bell-state detection. And the main contents and new ideas are arranged as follows:1. Based on the SPICE model of circuits, quatitive analysis and circuit simulations are carried out for low-noise and high-gain photodetectors.2. Through the detailed research of low-noise cicuits, it’s clear that: the key to designing a low-noise and high-gain Bell-state photodetector is reducing the input noise voltage and input capacitance in the transimpedance amplifer(TIA).3. The bootstrap effect on photodiode is elegantly applied in the newly designed Bell-state photodetector by a JFET (junction gate field-effect transistor). And the electronic noise at 2MHz is effectly reduced by 8.8dB.4. Parameters of the newly designed Bell-state photodetector meet the demand for the measurments of Bell-states. The shot noise is 13dB above the electronic noise at 2MHz when 51μW laser (1064nm) is focused onto the photodetector, which is better than reported results. And the bandwidth reaches around 5MHz with excellent linearities for both dc and ac amplifications when the input laser power is changed from 12.5μW to 1.52mW linearlily.The newly designed Bell-state photodetector is simple-debugging and reliable oriented with more available components, which could function well for the measurement of optical Bell-states with high precision.