|MADONINI FRANCESCA||Cycle: XXXV |
Tutor: GERACI ANGELO
Advisor: VILLA FEDERICA ALBERTA Major Research topic
:Single Photon Avalanche Diode arrays for quantum-enhanced microscopyAbstract:
Many microelectronic and biomedical applications involve the detection of transparent media for which classical light microscopes are often unsuitable to acquire high-contrast images without damaging the sample or introducing measurement artefacts. Quantum-enhanced microscopy is a quantum physics field that exploits non-classical states of light to reach unprecedented sensitivity in the non-invasive and low light (single-photon) detection.
A first real-word implementation of quantum imaging is envisioned by the Horizon-2020 project Q-MIC (Quantum-enhanced on-chip interference MICroscopy) which aims at developing a miniaturized on-chip interferometric microscope without lenses and illuminated by short wavelength entangled photon pairs. From the detection standpoint, Q-MIC is based on a Single-Photon Avalanche Diodes (SPADs) image sensor array able to detect single photon coincidences. Indeed, in the last years, SPADs have become an enabling technology for many applications demanding ultimate light quanta sensitivity, microchip compactness, device ruggedness, ease of operation and cost-effectiveness. Silicon integrated SPADs usually trade off photonic performance for compatibility with microelectronic transistors and circuits, thus enabling on-chip coexistence of both.
This unique combination of features will extend the impact well beyond the scientific interests and lead to portable, high throughput, non-invasive, and label free sensing of transparent objects, such as cells, microorganisms, viruses and proteins. For example, microarrays of biomarkers with millions of spots could be read in a single shot, with no need of fluorescence marking. Other applications include the detection of small particles in the microelectronics industry and inline quality control of transparent substrates for roll-to-roll production of flexible optoelectronic devices.
The present PhD research aims to conceive, design and validate very dense SPADs imagers that integrate on the same die high efficiency sensors that can be operated at room temperature along with in-pixel sensing and event processing able to detect the arrival of strictly correlated in-time photons and provide their relative position in the array. With a huge number of pixels, a large field-of-view can be reached and resolution is boosted. However, the major breakthrough will be the ability to detect photon coincidences spread over the entire array directly on chip and to locate the involved pixels only when a coincidence is detected, thanks to a novel event-driven logic. Digital processing and data readout will be tailored to match the specific features of the entangled photon sources used by Q-MIC consortium. Moreover, this research activity will develop compact end-user systems, including the aforementioned SPAD arrays with microlenses and off-chip processing through FPGA platforms, in order to interface the SPAD detection module with the quantum source and the optics of the microscope.