Vergleich von Quencherschaltungen und SPADs

Abstract

In the past years, there has been an increase of interest in the field of uantum information. Quantum objects, such as photons, are used to transfer or encode information in quantum information technologies. Single photon in the visible or near infrared range has extremely small energy, only around 10-19 J. To detect such a small amount of energy, detectors with high sensitivity need to be deployed. Initially, photomultiplier tubes have been used for this purpose, but new detectors and technologies emerged in the recent years, such as superconducting nanowires, frequency up-conversion, quantum-dot phototransistors and single photon avalanche diodes (SPADs). SPADs are probably the mostly used single photon detectors nowadays: they are reliable, offer great quantum efficiency, low dark count rate and high maximal counting rate. Si SPADs are used to detect photons in the visible or near infrared range and are more common, whereas SPADs fabricated from 3-5 semiconductors can be deployed for light detection in the telecommunication wavelength of 1.55 μm. Detector device is, however, not the only component required for single photon light detection. These devices have to be connected to a quenching circuit that ceases the avalanche ignited by the photon and restores the bias voltage to ready the device for another detection. Some of the quenching circuit types are passive quenching circuits, passive quenching circuits with active reset and active quenching circuits, and these circuits can be integrated on a chip together with the SPAD, or produced from discrete components with discrete SPADs. The choice of the detector type, circuit operating principle as well as the specific type of construction affect the performance of the device significantly. It is therefore of high importance to choose the right device and quenching circuit for the application to fulfil the required specifications. In this work, two discrete Si SPADs from two different manufacturers will be compared together with 3 quenching circuits: two passive quenching circuits and one active. In the first chapter, most common detector types are introduced. Second chapter is dedicated to types of quenching circuits, both integrated and discrete. In the third chapter design and measurements of the SPADs and chosen circuits are presented and compared. Fourth chapter describes possible single photon detector applications.