A special focus of research is the formation of self-organised and self-confined structures in the transverse profile of the coherent field (transverse, i.e., with respect to the optical axis of the system). This topic in the last decade has indeed originated a new branch of Optics (Transverse Non-linear
Optics). Within this framework a mainstream of activities was activated on modelling and studying semiconductorbased optical devices, which stimulated to promotion of a number of projects on national and European scales. Most relevant is the ESPRIT LTR P.I.A.N.O.S. Project n.28235, devoted to the demonstration and exploitation of cavity solitons (see below) in optical information treatment. To this respect, paper n.26 in the list was the theoretical prediction of the new class of dissipative solitons and properties thereof, it has been considered as an Excellence milestone by INFM and included in the volume “INFM Highlights 1997” as one of the 5 representative and outstanding researches of the Institute in the field of Non-linear Optics. 

The joint description and confirmation of cavity solitons as dissipative self-confined structures and at the same time plastic, addressable pixel, appeared in Nature in 2002 and was the first-timer in this field as for semiconductor-based devices.
The FET-STREP project FunFACS was the natural prosecution of the former, and within this framework new first-time predictions were developed concerning total three-dimensional confinement of radiation in optical nonlinear systems.
The largest part of the research has been performed in close collaboration with broadly acknowledged experimental groups, with the precise aim of providing modelistic interpretation of evidences, or conversely to stimulate experiments confirming theoretical predictions. Many of the publications listed in this CV stem from those collaborations. In the few cases where no experimental activity was available on the subject, the treatment has been particularly steered, so to provide useful indications for an eventual experiment. It thus happened that experiments came later, supporting the predictions.
After the appointment of a permanent position (Researcher, in Dec. 1995), the activities were carried on within the group of Nonlinear and Quantum Optics of the joint University and Polytechnic Department of Physics. It should be stressed that up to that period there did not exist any structured theoretical activity. In the course of the first four years, adequate numerical resources have been acquired (a RISC workstation, a net of post-processing PCs, appropriate software resources) and access to greater resources has been granted via national and international collaborations. In the following years the nucleated group attained international status as witnessed by scientific production and project
encadrement. The various research issues have been opened to graduating and Ph.D. students
and financial resources have been acquired, funding several men-years at postdoc level.
The research bias then moved towards the studies of pattern formation and dynamics in n.l.o.s. with high Fresnel number, where the number of contributing transverse modes becomes very large and boundary effect are ineffective in the pattern selection process; the system in general exhibits a translational symmetry in the transverse plane. In such conditions, optical systems show similarities with other (e.g. hydrodynamical) systems, well-known to exhibit spontaneous morphogenesis (Rayleigh-Benard convection, defect-mediated turbulence, etc.). In these systems the formation of global, spatially modulated structures has been predicted, such as rolls, hexagonal or honeycomb lattices, more complicated non-stationary structures. An extremely interesting feature, theoretically predicted by several groups including ours and experimentally confirmed in “slow” optical systems, is the occurrence of non diffracting, self-confined structures which appear as bright peaks of light in the transverse profile of the coherent field. Such self-organised “pixels” are now currently called Cavity Solitons (CS) and are excellent candidates for optical information treatment. As it emerges from theoretical indications , CS can be caused to drift in a controlled manner across the device’s transverse section. Thus, at difference from presently used arrays of microlasers or S.E.E.D.s , the self-organisation of CS allows us to conceive classes of all-optical reconfigurable matrices, serial to parallel converters, commutators which can couple more efficiently to the “silicon” part of optoelectronical devices.
Relevant results in this issue are:
– The first prediction of stable CS in theoretical models (originally developed) in semiconductor heterostructured microresonators. The models contemplated both “passive” devices (where the carrier generation relies on externally injected optical fields) and “active” ones, wherein pumping electrical currents cause the device to operate as an amplifier. These results stimulated experimental activities on CS beyond pristine “slow” optical systems (liquid crystal light valves, organic absorbers, etc.). After the consolidation of the indications, the PIANOS project was activated and funded, with the precise aim to observe CS in microdevices and to demonstrate basic processing features based on CS.
– On the grounds of CS properties as they emerged from the basic research, it was possible to show how they can be used for all-optical signal amplification with large differential gains, with contextual signal commutation operation. Architectures have been suggested to show the principles of all-optical logic gate( AND, OR, NOT) operation with CS. It is worthwhile to stress the recent experimental results obtained at the Nonlinear Optics group at the Westfälische Wilhelms-Universität in Münster (D), which confirm the predictions about the
possibility of achieving a differential gain by optically modulating a CS, even in a passive system.
Experiments have been performed in a Sodium cell and presently appear in excellent agreement with the general theoretical indications.
– The existence and manipulability of CS in VCSEL devices, as predicted in 1997, has been achieved in 2001 and the joint theoretical and experimental results appeared in the journal “Nature” in 2002. The achieved evidences determined the successful conclusion of the PIANOS Project.
Since 2012 new research interests were developed in the field of QCL dynamics and self-mixing laser devices. In conjunction with experimental groups. The main achievements are
– the prediction of QCL operation where coherent and spontaneous locking of modes provides regularly oscillating dynamics
– the prediction and confirmation of regimes of absolute stability for QCL with feedback, due to removal of relaxation oscillation amplification
– the realization of all-photodesigned THz metamaterials, written by NIR beams and acting as QCL modulators in the THz regime
– the imaging of carriers in semiconductors via self-mixing interferometry (s.m.i.) in QCLs
– the prediction of several sensing schemes based on s.m.i. for multiparametric or multitarget measurements.

Most significant articles