Research On High Performance Photodetector In Preparation Of Squeezed Light Field In Low Frequency Band

Squeezed states of light is a significant non-classical optical field in quantum optics,which was obtained for the first time through experimental preparation in 1985.Because of its ability to break through the limit of quantum noise and squeeze quantum noise,it plays a key role in precision measurement.Recently,the squeezed light have been used for gravitational wave detection,the LIGO experimental team injected squeezed vacuum states from the dark port of the detector,which greatly improved its sensitivity.The high or low sensitivity depends on the squeezing degree of the injected squeezed light.The main limiting factors for improving squeezing degree include loss and phase jitter.In order to apply squeezed light with the high squeezing degree to the actual precision measurement simultaneously,the high requirements are put forward for the stability and size of the experimental system.The preparation of squeezed light source with miniaturization and high stability has become the future trend.The preparation of squeezed light source with miniaturization not only requires miniaturization of mechanical parts such as lens frame and cavity,but also a reasonable layout of the optical path.Among them,in order to match the design of balanced homodyne detector with high common mode rejection ratio,the triangular layout of the squeezed light balance detection part occupies a relatively large area.The occupied area can be reduced to a great extent by miniaturizing the balanced homodyne detector,which plays a vital role in miniaturizing the squeezed light source.In addition,in order to make the squeezed source work stably for a long time,not only the stability of the mechanical structure should be improved,but also the cavity length offset and phase jitter should be reduced by active feedback.Active feedback technology specifically adopts PDH locking technology,which is the most mature and best performance locking technology at present.In PDH locking technology,the performance of the whole locking loop is determined by the photodetector in the first stage of the feedback loop,and the accuracy and stability of locking are determined by whether the error signal of high signal-to-noise ratio can be obtained.Traditional broadband detectors cannot achieve high gain in a wide bandwidth range due to the limitation of the gain bandwidth product of the integrated chip.By adopting a resonant structure,the resonant detector implemented in this paper can achieve high gain at high frequency.When the length of the optical cavity and the phase of the two beams are stably locked by the optimized resonant detector,the designed miniaturized and highperformance balanced homodyne detector is used to achieve the measurement of low frequency and high squeezing degree,which verifies the excellent performance of the two detectors.The main research contents are as follows:1.Developed a resonant photodetector with high quality factor(Q),analyzed the circuit schematic diagram of the existing resonant detector in detail,and established multiple amplifier circuit models using the circuit simulation software,Multisim,and simulated the circuit by setting the correlation element parameters.Then the schematic diagram and PCB board are drawn,and finally a resonance type photodetector with high quality factor is realized.The detector can be used to lock cavity length offset and phase jitter simultaneously in the PDH locking technology,which greatly improves the stability of the squeezed light source and lays a solid foundation for the preparation of high-performance continuous variable squeezed and entangled light fields.2.Developed a miniaturized low-frequency balanced homodyne detector,which reduced the area of the detection part to 1/3 of the original area,and the lowest detectable frequency reached 40 k Hz.By quantitatively analyzing the noise of the balanced homodyne detector,the appropriate electronic components are selected,and the circuit that simultaneously amplifies both AC and DC is designed to avoid the loss of AC information at low frequencies.Moreover,the detection part is separated from the power supply part in the PCB layout,and only the detection part is placed in the squeezed light source,which greatly reduces the area occupied by the detection part in the squeezed source and greatly promotes the practical process of the squeezed light source.