|Thesis abstract: |
The measurement of fast-changing and very faint light signals in the visible and near-infrared wavelength range with picosecond timing resolution has proven to be an effective technique to study different physical and biological structures like biological tissues in functional brain imaging, optical mammography and molecular imaging, not to mention Fluorescence Lifetime Imaging, Fluorescence Correlation Spectroscopy, Quantum Information, LIDAR and many others. Single-Photon Avalanche Diodes (SPADs) are some of the most used detectors to measure fast light pulses at single-photon level.
SPAD detectors are becoming increasingly widespread thanks to their good Photon Detection Efficiency (PDE) (up to 50% in the visible range) and low timing jitter (few tens of picoseconds). Moreover, a SPAD can be gated from OFF to ON in few hundreds of picoseconds by modulating its bias voltage. Detector gating is an effective way to keep the detector blind during intense photon fluxes, while enabling its single photon sensitivity only during desired gate-ON time windows.
My PhD topic consists in the development, characterization and experimental exploitation of a fast-gated SPAD detector module intended to operate different Silicon SPADs (built in a CMOS or custom process, with different active areas and structures) in the fast-gated regime with ON and OFF transitions below 200 ps.
The detector has been employed in different scientific collaborations ranging from diffuse optical spectroscopy, STED microscopy, study of the fluorescence of isoelectronic traps in GaAs etc
Furthermore, by exploiting the technical background acquired during the development of fast-gated SPAD detectors, different other scientific instruments and setups have been built and characterized like: a two-window gated counter, a fast pulse generator, a sinusoidally-modulated InGaAs/InP SPAD detector etc.