Characterisation of complementary metal-oxide-semiconductor compatible single-photon avalanche diode in novel time-resolved applications

Abstract

The Complementary Metal-Oxide Semiconductor (CMOS) compatible Single Photon Avalanche Diodes (SPAD) sensors, are increasingly utilized in various time-resolved applications, including Light Detection And Ranging (LiDAR) and sophisticated biophotonics. The highly sensitive SPAD detectors can identify individual photons and, when integrated with timing circuits, can provide high-resolution time stamps for each detected photon, reaching picosecond precision. In this thesis, an thorough study of CMOS SPAD methodologies is conducted to facilitate the development of innovative designs employing these sensors in novel time-resolved applications. By employing two separate CMOS SPAD sensors, two distinct optical systems were effectively developed and assessed based on their particular objectives and capabilities. The entire process encompasses the incorporation of the sensor into the surrounding electrical and optical systems, execution of firmware and software for managing the optical configuration, and subsequent data processing.

In the first application, a LiDAR system using a 256 × 256 array CMOS SPAD sensor was employed for the first time to evaluate water waves of varying frequencies and amplitudes (leading to an array of wave steepness values (ka)) in a laboratory setting and determining their profile through elevation estimation. The unveiled system holds a distinct edge over numerous other documented methods due to its entirely nonintrusive nature, probable compactness and the absence of any requirement for excessive computational strength to interpret the data. Preliminary results are promising, indicating that superior quality data can be accrued up to a ka value of 0.11. Furthermore, theoretical enhancement of its performance could be achieved through analysis provided by a newly presented optical model in this thesis. The second application showcases the use of a 512 × 16 line sensor in time-resolved fluorescence spectroscopy for achieving concurrent temporal, spectral, and spatial imaging. The systems’ performance is assessed through the analysis of Rodamine and retinal-related fluorophore kinetics. Its high-speed frame rate and capacity to gather further spectral data without necessitating additional frames set the system ahead. These capabilities, while extremely beneficial, are not yet broadly integrated into diagnostics for retinal disorders, positioning it as a potential pioneering tool in Fluorescence Lifetime Imaging Ophthalmoscope (FLIO) domain of retinal imagery.