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Silvano Donati

Prof. Silvano  Donati

Professor Emeritus
Department of Electronics
Chair in Optoelectronics
Faculty of Engineering, University of Pavia

v. Ferrata, 1 I-27100

tel: +39 0382 985 204
fax: +39 0382 422 582
E-mail: silvano.donati@unipv.it
Web: http://www.unipv.it/donati

Area of Expertise

optoelectronic instrumentation for engineering and biophysical measurements; chaos and chaos cryptography; photodetectors for single photon and 3-D applications


Silvano Donati graduated in Physics cum laude in 1966 at University of Milan, Italy. In 1980 he became a full Professor of Optoelectronics at the Department of Electronics, Faculty of Engineering, University of Pavia, Italy, where he leads the Group of Optoelectronics active on photodetector and noise, and electro-optical instrumentation (gyroscopes, interferometry, etc.). He is the credited inventor of self-mixing interferometry and of chaos-shift-keying (CSK) cryptography, the topics acknowledged in his Fellow citation and the subject covered in his Distinguished Lecture given in 21 LEOS Chapters in two terms, 2007/08 and 2007/08.

Author of two books, ‘Photodetectors’ published by Prentice Hall, 1999, and ‘Electro-Optical Instrumentation’, published by Prentice Hall, 2004, this last translated in Chinese (Jiao Tong University Press, 2006) and available as paperback and e-book (2008). He authored or co-authored about 300 papers on peer-reviewed Journals He was the founder (1996) and the past Chairman (1997-01) of the Italian LEOS Chapter. Has been LEOS Vice President Region 8 Membership (2002-04), LEOS Board of Governors Elected Member (2004-06), Treasurers of the Italian LEOS Chapter (2002-06), Counselor of the IEEE Student Branch in Pavia (2001-07) and LEOS Distinguished Lecturer. Member of the Nanotechnology Council Fellow Board. Has been chairing the IEEE Italy Section on the term 2008/09.

He acted as Guest Editor of several Special Issues, on Fiber Optics and Passive Components (JSTQE Sept. 1999), on Laser Interferometry (J. Optics A 1998 and 2002, Opt. Engineer. 2001) for a Feature Issue of IEEE Journal Quantum Electronics, Sept. 2002, on Optical Chaos and Applications to Cryptography and of one on Photodetectors (2004).

He has been a Visiting Professor at National Taiwan University (2005) and National Sun Yat Sen University (2007, 200, 2010)

He is a Member of SPIE, Life Fellow of the IEEE, Meritorios Member of AEIT, and Fellow of OSA.

Lecture Title(s)

Self-Mixing Interferometry: a Universal Yardstick to Measure Almost Everything
we start with a theoretical introduction to mutual- and self-coupling phenomena in laser oscillator, and then describe in details the principle of operation of self-mixing interferometer, a new coherent configuration for the measurement of dimensional and kinematic quantities such as: displacement, distance, vibration amplitude, thickness, and angle, and also physical quantities like: coupling factors, line width, alfa-facto index of refraction. In the measurement arrangement, the laser undergoes self-injection at weak level, leading to an amplitude and frequency modulation driven by external optical path length. Then we will describe the developments of a displacement-measuring instrument, first by using the up/down counting of mode hops, then extending the principle of measurement to the case of a diffuse target, reflecting back a field affected by the speckle-pattern statistics. Third, we will report on the successful implementation of two-channel (or, referenced) vibrometer, based on analogue processing of the self-mix signal, in which the speckle-related amplitude errors are removed thanks to a servo-loop concept, and the instrument is capable of true differential operation, on diffuse surface, like a normal optical interferometer operates on legs ending with reflective surfaces. A survey of perfomances achieved in different design will conclude the talk. (60 slides, 45-60 min.)

From Order to Chaos and back: High-Level Coupling for Optical Cryptography
After a theoretical introduction to mutual- and self-coupling in laser oscillator, we describe the application to optical chaos and cryptography. Chaos is generated by the laser source at strong level of coupling, in the mutual or self-injection regime. The mutual regime displays a rich dynamics of multi-periodicity and chaos found between the first and the final locking, and the associated time, frequency and state diagrams. We point out that, by injecting the chaos-generated signal into a slave system, we can drive the latter to the same chaos, or, be able to synchronize it. Synchronization is the crucial issue leading to cryptography of the message, and two possible schemes are then developed: ACM (additive Chaotic Masking) and CSK (Chaos Shift Keying). Of these schemes, we discuss the block diagram and the performance parameters.We then strive to find the most viable and robust configuration to implement cryptography, and develop chaos generators based a self-injected semiconductor laser. We show how to adapt the mutual-injected concept of chaos generation to this case, and how they may be regarded as equivalent. Last, we describe the experimental development of chaos-based transmission, reporting on in-field trial experience. (55 slides, 45 min.)

Single-Photon Imaging Sensor with SPAD Arrays for Industrial and Bio-applications
We first review Single-Photon Detectors stuctures and performances, mainly PMTs (Photo-multipliers) versus APDs (avalanche photodiode) and SPADs, and point out how a fully solid-state PMT with true single-photon detection capability can nowa-days be implemented by paralleling the outputs of an array of individual SPADs (the APD working at infinity gain). Then, as an evolution of the concept, we present a new solid-state image sensor capable of performing single-photon counting and time-of-arrival measurement and classification. The sensor has 32x32-pixel dimeansionality, each pixel consisting in a single-photon avalanche photodiode, a counter, and a chronometer. Each pixel operates independently and simultaneously, generating one time-interval measurement every 2 ms with a time resolution of <100 ps. The photosensitive area is a small 6-mm diameter, internal to a pixel allocating the electronics circuits for time measurement, occupaying 50-mm by side. One problem is recovering the loss due to the area fill-factor, and we use an array of plano-convex microlenses, one for each pixel, of 50-mm diameter. The microlens array boosts the power density by a factor ≈30, thus recovering almost completely the loss of efficiency due to the area-ratio, given by a factor 40. The sensor has been fully characterized and tested in a number of industrial and bio-setups and examples will be described. (40 slides, 30-40 min.)

Developing 3-D Imaging Sensors: Problems and Technologies
We discuss the technology available for 3-D imaging-taking cameras, starting from the basic configurations used to build single-point laser rangefinders, that is, triangulation, sinewave and pulsed techniques, and analyzing the system requirements on parameters like: covered range, illumination power, detector noise, stray light. We consider SPAD-based 3D camera and its application to sophisticated, single-photon and high speed applications. Then we report an example of development of the design concept for a minimal part-count, 3-D camera based on standard CMOS Silicon Technology and intended for use in robotics. The camera is based on a conceptually new CMOS photo-detector which combines in a single device the two functions of optical detection and of signal demodulation, as it is required by the sine-wave modulated rangefinder approach. We discuss detail of the circuit design and implementation in a 180-nm CMOS process. We end up with a 6x6 mm chip integrating all the 3-D camera functions, covering a distance range from 1 to a few m with a resolution of a few cm. (34 slides, 25-35 min.)

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