Development Of Balanced Homodyne Detector

Quantum noise is ubiquitous in the physical world. Different from the classical noise of the light field, it is limited by the basic principle of quan-tum mechanics and can not be eliminated physically. It is important and dif-ficult in the research area of quantum optics that finding a way to break the limit of quantum noise. Experimental studies of the squeezed states of light in the last twenty years have shown that it’s able to overcome and breakthrough the standard quantum limit, so the first task of researching squeezed light is how to detect it.Balanced homodyne detection is an important technical method to detect quantum noise of squeezed states. In the former detection system we need to use a pair of photo-detectors with symmetric performance. Firstly, we have to select the devices with symmetric performance which makes it very hard to produce a pair of detectors completely symmetric. Inspired by the kirchhoff current law, we have designed and produced the new balanced homodyne de-tector. By the way of series two photodiodes, we can avoid producing a pair of symmetric detectors while getting current difference signal and improve the common-mode rejection ratio (CMRR) of detection system.After introducing the related theoretical knowledge of squeezed light, in this paper we describe the principle and structure in designing balanced ho-modyne detector with the knowledge of semiconductor electronics and the performance of the detector was tested. The experimentally measured CMRR of detector is39dB at the modulation frequency of2MHz.The detector with well linear gain in AC/DC has the saturated optical power of18mW.These indicators can satisfy the requirements of quantum experiments for balanced homodyne detector very well.