Time-to-digital converters for reconfigurable photon-counting detectors

Measuring time with a picosecond resolution is a complicated process, especially when employing non-specialized hardware. This thesis focuses on the development of a system with a time resolution of roughly 18 ps, with optimizations to reduce its non-linearities and increase the system scalability. A firmware-based time-to-digital converter array is designed and fully implemented in an Artix 7 FPGA from Xilinx. This array is coupled to a single-photon imaging sensor with 23 pixels, enabling photon arrival time measurements with picosecond resolution. A novel approach is taken in the firmware design by enabling a sliding scale measurement principle, drastically reducing the non-linearities. The timestamps are read out through a USB3 connection to be processed in real-time in a C++ software interface. The system has been extensively characterized in terms of its bin size or resolution (∼18 ps), non-linearities (±0.3 LSB) and the system jitter including the SPADs (120 ps). Comparisons with literature show that this system can meet state-of-the-art timestamping performance in FPGAs and excels especially in its linearity. Such a system is the perfect candidate to be equipped in, for example, scanning microscopes and perform time-resolved single photon measurements. These include, among others, fluorescence lifetime microscopy (FLIM) and fluorescence correlation spectroscopy (FCS).