Fortunato Tito Arecchi
Emeritus of Physics, University of Firenze, and Scientific Associate of Istituto Nazionale di Ottica (INO) del CNR
Dip. di Fisica - Università di Firenze and INO, Largo E. Fermi, 6 - 50125 Firenze (Italy)
Tel.: +39-055-229328, Fax: +39-055-2337755, E-mail: email@example.com
Date and place of birth:
11/12/1933, Reggio Calabria, Italy
1957: PhD in Electrical Engineering at Politecnico di Milano
1957-60: Researcher in Nuclear Electronics at CISE, Milano,
1960-62: Research Associate on Lasers, Dept. EE, Stanford University,
1962-70: Leader Research Group on Lasers at CISE Milano,
1963-70: Associate Professor of Physics, Milan University,
1970-77: Chair of Physics, University of Pavia;
1977-2009: Chair of Physics, University of Firenze;
2001-present: Scientific Associate of INO
2009-present: Professor Emeritus of Physics, University of Firenze
1968-69: IBM Res. Lab. Ruschlikon (CH);
1978 and 1985: IBM Res. Lab. San Jose, (CA);
1969-70: Visiting Professor, Dept. of Phys., MIT;
1975-2000 : President of Istituto Nazionale di Ottica (INO)
Member of: - Italian Physical Society (SIF) and Italian Society of Optics and Photonics (SIOF);
- Academie Internationale de Philosophie des Sciences (AIPS) (Bruxelles);
- Academia Europaea
- Accademia Colombaria (Firenze)
Fellow of: Optical Society of America (OSA)
Main scientific contributions:
1) Cooperative effects in quantum optics,
2) Photon statistics and laser fluctuations,
3) Deterministic chaos in optics,
4) Pattern formation in extended media,
5) Complex phenomena and cognitive processes,
(see the enclosed comment and selected list of papers)
Max Born 1995 Medal of OSA
Enrico Fermi 2007 Prize SIF (Italian Physical Society)
Honorary Editor: Chaos (American Institute of Physics)
Honorary Member: Scientific Committee for Physics of Solvay Institute (Bruxelles)
Vice-Director: Nuovo Cimento (Italy) 1976-1998;
Editor in Chief: European Physical Journal -D (1999-2003);
Editor: Chaos (AIP-U.S.A.) (1991-2016);
Formerly Editorial Board: Optics Communications, (North Holland); Int. J. Bifurcation and Chaos (World Scientific); J. Phys. B (IOP- U.K.); Int. J. Nonlinear Optical Physics (World Scientific); Cognitive Processing (Pabst)
Member of the Commissions de Publications Francaises de Physique and Acta Physica Polonica;
- Scientific papers: more than 450.
- Communications to scientific meetings: more than 300.
1-Laser Handbook, vol. 1 and 2. (with E. Schulz Du Bois), North Holland 1972;
2-Instabilities and Chaos in Quantum Optics (with R.G. Harrison), Springer 1987;
3-I simboli e la realtà,(with I. Arecchi), Jaca Book, Milano 1990;
4-Optical chaos (selected papers on) (with R.G. Harrison), SPIE Opt. Eng. Press 1994;
5-Lexicon of Complexity (with A. Farini), Firenze 1996;
6-Coerenza,Complessità, Creatività , S.Di Renzo,Roma2007;
also Co-Editor of several Proceedings of International Conferences or Schools.
MAIN SCIENTIFIC CONTRIBUTIONS (numbers refer to the selected list of papers):
- Cooperative effects in quantum optics
- 1964: Theory of a laser amplifier which extended Lamb theory to account for space dependence. This was the first formulation of the coupled field-matter equations with space dependence (later called "Maxwell-Bloch equations"). It predicted invariant pulses propagating at the light speed (the nonlinearity compensating for dispersion). These results were later applied to absorbing media (self induced transparency).
- 1969: Introduced a fundamental parameter of the resonant interaction that is, the correlation length in the cooperative spontaneous emission of atoms prepared incoherently in an excited state. It does not depend on boundary conditions (as the mirrors in a laser), nor on an external field (as in coherent spectroscopy), but it is an intrinsic parameter of many body optical interactions.
- 1970: Theory of the atomic coherent states as a basis for a statistical description of coherent phenomena in resonant spectroscopy.
- 1978: Theory of the two photon optical bistability, observed four years later.
- Photon statistics and laser fluctuations (reviewed in [R1-R2])
- 1965: First experimental evidence of the statistical difference between a laser and a random field[2,3]. It was obtained by photon statistics, and it included evidence of the bunching phenomenon for Gaussian sources already explored by Hanbury-Brown and Twiss, but also of the absence of such a bunching for a laser field. These experiments provided a physical ground for Glauber's theory of coherence.
- 1966-67: Application of the above methods to laser fluctuations at threshold, providing the first experimental evidence of critical fluctuations and slowing down in a "phase transition out of equilibrium", as called later.
- 1967: Transient statistics of a laser switched from below to above threshold: a new phenomenon was discovered, i.e. a transient enhancement of the photon variance.
- 1989: The time statistics permits an accurate calibration of the initial photon number giving rise to the amplified chain in a laser. This method has been called "statistical microscope" because it provides measurement of a small photon number not by electron multiplication (as in usual photomultipliers) but by photon multiplication.
- Recently, this research line has been recently revisited in two directions, aiming at
- i) providing evidence of quantum interference between macroscopic distinct states,
- ii) exploring the coherence properties of the Bose Einstein condensate and the atom laser.
- Deterministic chaos in optics
- 1978: Theoretical introduction of a mechanism of laser turbulence, consisting of a cavity including a lasing medium and a second harmonic crystal. A pair of laser photons are converted to a second harmonic photon and this photon is reconverted into a pair of laser photons of different frequencies, thus inducing a type of chaos observed later (in 1986).
- 1982: First experimental evidence of deterministic chaos in a laser, starting a research line the main results of which are:
- i) 1982-87: characterization of low dimensional laser chaos by different means, that is, loss modulation, injection of an external field, two counter propagating fields in a ring cavity, and feedback.
- ii) 1982: first evidence of generalized multistability, which is the coexistence of many attractors.
- iii) 1984: classification of lasers in classes A,B,C depending on the time scales of their dynamical variables. This classification has now become of general use.
- iv) 1987: evidence of the mechanism of competing instabilities leading to homoclinic chaos (Shil'nikov chaos) characterized by the statistics of the return times to a given reference point in phase space. Characterizing chaos by times rather than by geometry is conceptually similar to what done in transient statistics and it is an essential tool whenever chaos does not induce appreciable geometric irregularities, as in most heteroclinic connections; synchronization of homoclinic chaos appears as a universal avenue for biological clocks and biological communication.
- v) 1993: adaptive recognition of chaos and its control.
- vi) 2004: Mixed Mode Oscillations = coexistence of two temporal regimes in chaotic semiconductor lasers.
- Pattern formation in extended media (reviewed in [R3-R4])
- High-dimensional optical dynamics results from the competition of many degrees of freedom, either space-like as in extended media, or time-like as in delayed dynamics. In both cases competition gives rise to patterns similar to those observed in fluids, hence the name of "dry hydrodynamics".
- 1990: The gradual transition from a small to a high number of competing modes is denoted by the passage from periodic and chaotic alternation (PA, CA) where one single mode per time is present, to space time chaos (STC) where many modes coexist at the same time. These phenomena, first observed in, have been explained in terms of cavity symmetries in.
- 1991: A heterodyne method introduced to detect phase singularities or vortices of the optical field allows the description of optical pattern formation in terms of vortex statistics. The different scaling of the vortex statistics with the cavity size provides a discrimination between two regimes, one in which patterns are imposed by the boundary and one where patterns are intrinsic of the medium, as in chemical Turing morphogenesis.
- 1992: A different way to study high dimensional chaotic systems is to still refer to a strongly confined medium as a single mode laser cavity, but introducing a feedback with a delay longer than the intrinsic correlation time of the laser dynamics.
- 1995-1997: Morphogenetic mechanisms analogous to those of fluid mechanics, are shown by the onset of different crystal and quasi-crystal symmetries, depending on the boundary constraints. As the system is driven far away from threshold, many of these "pure" symmetries are excited simultaneously, but rather than quenching each other, they coexist in different regions, giving rise to a multidomain structure or they lock into a single super-structure.
- 1999: Ref. reports the scaling behaviour of defects after a rapid passage from below to above threshold in a nonlinear optical system. This corresponds to the rapid passage from many uncorrelated domains to an asymptotic single coherence area; however the asymptotic state is reached for long times, and immediately at the end of the switch pulse one finds a collection of frozen defects, due to the critical slowing down at the transition point. Such a feature is common to all extended critical phenomena; it had been hypothesized for cosmological defects and observed in liquid helium, however here we provided the first quantitative evidence of the scaling.
- 2009: First evidence of Rogue Waves in a nonlinear optical cavity.
- Physics of cognitive processes (reviewed in [R5])
- The methods developed to recognize and control chaos and patterns can be extended to biological phenomena as e.g. cardiac and brain signals. The adaptive methods can not only be extended from discrete to continuous dynamical systems, but they can also control a delayed system. Now, the delayed feedback method corresponds to embedding a physical system with a small number of degrees of freedom into a space with a larger number of dimensions.
Hence, this appears as a good analogy of the cognitive strategy used in any perceptual task, whereby we build holistic perceptions upon partial information (think e.g. of a deteriorated photography).
- 2004-2009: A new type of chaotic behaviour, called HC (homoclinic chaos) consisting of spike trains separated by chaotic time intervals ,first observed in CO2 lasers, displays features common to brain neurons. It has been demonstrated to display a high propensity to organise in large synchronized networks, hence it appears as the most plausible dynamical model for the build up of “feature binding” through the synchronization of large neuron arrays in the brain.
- Rather than tracing the individual neuron behavior, a collective way of describing cognitive tasks is by Bayes inference. Bayes inference characterizes perceptual processes, whereby a sensorial input elicites an adequate motor reaction; it requires a pre-assigned algorithm. On the contrary, in linguistic tasks, humans compare a piece of a text with a previous one, recalled by the short-term memory. The comparison gives rise to a new algorithm, via a process called inverse Bayes.
- The role of language vs perception in decision tasks is being actively explored, as reported in the review R5.