|SCIORTINO GIUSEPPE||Cycle: XXXIII |
Tutor: FIORINI CARLO ETTORE
Advisor: FERRARI GIORGIO Major Research topic
:Multichannel CMOS Integrated Circuits for Spectroscopy ApplicationsAbstract:
Advanced spectroscopy techniques are more and more gaining the interest of the research community because find wide and outspreading applications in many different fields like industrial quality control, tumor analysis and new materials engineering. My thesis contributes to this field by designing and operating Application Specific Integrated Circuits (ASICs) for a fast, yet highly resolved, acquisition of spectra obtained with two powerful techniques, namely broadband Raman scattering microscopy and time-resolved pump and probe spectroscopy. The first ASIC was developed in the framework of VIBRA (Very Fast Imaging by Broadband Coherent Raman), an ERC H2020 project coordinated by Prof. D. Polli of Politecnico di Milano. The challenge of the ERC project is to develop a stimulated Raman scattering microscope, that in real time can distinguish different chemical species with a spatial resolution of about 1μm. The microscope finds its application in the histological field, allowing a fast, safe, contactless, and repeatable tumor analysis. To reach such a result, an ASIC implementing a differential channel readout circuit was designed and integrated in the electronic acquisitions system. The ASIC allows to process in parallel the signals coming from a photodiode arrays with an automatically balanced differential lock-in architecture for a reduction of the optical noise. The developed system acquires a 32 wavelength Raman spectrum in only 100 μs, generating an image of a biological sample in only one second, well beyond the state-of-art for similar applications. Once the ERC goal has been achieved, I dedicated myself to the development of a ground-breaking spectrometer for ultra fast Pump and Probe spectroscopy. The limitations in terms of speed of the current instruments will be overcame using fast repetition rate lasers (1MHz) and a parallel acquisition and processing of many wavelengths (40). These improvements are made possible by a very flexible 20-channels CMOS readout specifically conceived for pump and probe spectroscopy. The chip, based on the switched capacitor technique, acquires the 1MHz pulsed signals and processes them to extract the useful signal with a resolution of few ppm. It strongly relaxes the specification of the following acquisition chain, enabling the development of the full instrument.