Biological samples are often highly photosensitive and optical damage is a limiting factor in many biophysical experiments. For this reason, many biological applications exploit single-photon detectors for lowering the light power excitation, thus reducing unwanted phenomena such as photo-bleaching. Imagers based on Single-Photon Avalanche Diode (SPAD) arrays, thanks to their quantum-level sensitivity, low noise, and the possibility of being activated in well-defined time-slots, provide further significant advantages compared to other more traditional detectors. This work presents the development and the validation of three SPAD camera systems, based on three different array chips, namely with 8x8, 128x1, and 32x32 CMOS SPAD pixels, suitable for fluorescence spectroscopy, quantum microscopy, and other biological applications. The chips, previously developed by the SPADlab, provide the possibility to either measure the number of incoming photons or time-stamp the arrival of the first photon hitting each pixel. The latter modality enables the application of the camera in many quantum experiments where it is necessary to detect the coincidences of photons from entangled pairs impinging on the array. The developed cameras are designed and implemented in order to be extremely versatile and to allow the acquisition of both two-dimensional “intensity” images and three-dimensional “timing” maps (two spatial dimensions plus the photon arrival time information) by exploiting the TCSPC technique. The 32x32 SPAD camera implemented in this thesis work has been validated in preliminary tests for the H2020 “Q-MIC” project, in collaboration with ICFO (the Institute of Photonic Sciences, in Barcelona). This camera will enable the Q-MIC project to develop a super-sensitive microscope for photosensitive highly-transparent samples (e.g. cells, micro-organisms, viruses, proteins). Thanks to the exploitation of quantum phenomena, like entanglement and superposition of states, this new technology will reach super-sensitivity with low input light power and large field-of-view. The results of such preliminary tests and the prospective developments conclude this thesis.
Danni causati da una troppo elevata potenza ottica sono spesso un fattore limitante negli esperimenti biofisici, in quanto molti campioni biologici sono fotosensibili. Per questo motivo molte applicazioni in questo campo sfruttano l’elevata sensibilità dei rivelatori a singolo fotone per poter minimizzare l’intensità della luce che interagisce con il campione. Dispositivi basati su array di Single-Photon Avalanche Diode (SPAD), rispetto a rivelatori più tradizionali, offrono estrema sensibilità, basso rumore e la possibilità di attivare con estrema precisione temporale il sensore. Questa tesi presenta lo sviluppo e la validazione di tre sistemi basati su tre chip, con rispettivamente 8x8, 128x1 e 32x32 CMOS SPAD pixel, adatti a misure di spettroscopia di fluorescenza, quantum microscopy e ad altre applicazioni biologiche. I chip, sviluppati in precedenza dallo SPADlab, permetto di contare il numero di fotoni che collidono su ogni pixel o, alternativamente, di misurare il tempo di arrivo di ciascun fotone. Quest'ultima modalità rende i chip adatti ad applicazioni quantistiche dov'è richiesto di riconoscere coppie i cui fotoni incidono simultaneamente su diversi pixel della matrice. Le camere sviluppate durante questo lavoro di tesi sono state realizzate puntando a un’estrema versatilità di utilizzo e permettono sia di acquisire immagini 2D o 3D, sia di applicare la tecnica TCSPC per la ricostruzione di segnali ottici. La camera 32x32 è stata utilizzata, in collaborazione con l’istituto di ricerca ICFO (Institute of Photonic Sciences, in Barcellona), durante i test preliminari del progetto H2020 “Q-MIC”. Il progetto ha come scopo lo sviluppo un microscopio adatto all’analisi di campioni fotosensibili e trasparenti come, ad esempio, cellule e microrganismi. Sfruttando fenomeni quantistici, come l’entangelment e la sovrapposizione degli stati, che permettono di superare i limiti di risoluzione dalla microscopia con luce classica, questa nuova tecnologia potrà fornire ampio FOV e super-risoluzione contendendo la potenza ottica. I risultati di questi test preliminari e le possibili implementazioni future concludono la tesi.
Time-resolved single-photon cameras for quantum microscopy applications
CUSINI, IRIS
2018/2019
Abstract
Biological samples are often highly photosensitive and optical damage is a limiting factor in many biophysical experiments. For this reason, many biological applications exploit single-photon detectors for lowering the light power excitation, thus reducing unwanted phenomena such as photo-bleaching. Imagers based on Single-Photon Avalanche Diode (SPAD) arrays, thanks to their quantum-level sensitivity, low noise, and the possibility of being activated in well-defined time-slots, provide further significant advantages compared to other more traditional detectors. This work presents the development and the validation of three SPAD camera systems, based on three different array chips, namely with 8x8, 128x1, and 32x32 CMOS SPAD pixels, suitable for fluorescence spectroscopy, quantum microscopy, and other biological applications. The chips, previously developed by the SPADlab, provide the possibility to either measure the number of incoming photons or time-stamp the arrival of the first photon hitting each pixel. The latter modality enables the application of the camera in many quantum experiments where it is necessary to detect the coincidences of photons from entangled pairs impinging on the array. The developed cameras are designed and implemented in order to be extremely versatile and to allow the acquisition of both two-dimensional “intensity” images and three-dimensional “timing” maps (two spatial dimensions plus the photon arrival time information) by exploiting the TCSPC technique. The 32x32 SPAD camera implemented in this thesis work has been validated in preliminary tests for the H2020 “Q-MIC” project, in collaboration with ICFO (the Institute of Photonic Sciences, in Barcelona). This camera will enable the Q-MIC project to develop a super-sensitive microscope for photosensitive highly-transparent samples (e.g. cells, micro-organisms, viruses, proteins). Thanks to the exploitation of quantum phenomena, like entanglement and superposition of states, this new technology will reach super-sensitivity with low input light power and large field-of-view. The results of such preliminary tests and the prospective developments conclude this thesis.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/148573