GUEST LECTURE PIERLUIGI DEBERNARDU Pierluigi Debernardi was born in Casale Monferrato, Italy, in 1963. He received the degree in electronics engineering from Politecnico di Torino, Torino, Italy, in 1987 (summa cum laude). Since 1989, he has been with CNR-IEIIT (Institute of Electronics, Information Engineering and Telecommunications, http://www.ieiit.cnr.it/), which has its headquarters in Politecnico di Torino, establishing many collaborations with its researchers. His research interests were initially focused on the modeling of semiconductor materials and devices for optoelectronic applications, especially III–V quantum wells. He was involved in ridge waveguide laser simulation, analysis of the optical bistable behavior of multiple quantum-well devices, and four-wave mixing in semiconductor oscillators and amplifiers. In the last 25 years, his research has been focused on modeling microcavity lasers, photonic bandgap structures, and especially VCSELs (vertical-cavity surface-emitting lasers), with particular attention on their modal properties and their static, dynamical, and noise behavior. He has developed an electromagnetic simulation software, VELM, based on coupled mode theory, which is capable to handle any VCSEL geometry, is fully three-dimensional and vectorial, and is numerically very efficient. He has invented grating VCSELs, capable of keeping a stable polarization over the whole operation range. In the last five years, he has led his research group in the development of an in-house multiphysics VCSEL simulation suite, to be applied to the computer-aided optimization of novel high-power VCSEL architectures. His activity has been and is performed in the framework of several European projects and research contracts with industrial partners. He has contacts and collaborations with several European research institutions and universities. He is the author of two book chapters, two patents, 75 papers on ISI-indexed journals, and 72 conference papers (15 invited).

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Vertical-cavity surface-emitting lasers (VCSELs) are pervasive semiconductor lasers, and nowadays cover 99% of the semiconductor light source datacom and sensing applications, like in the automotive and smartphones markets. VCSELs are composed by hundreds of layers, so that their optical modelling is very challenging. In most applications also polarization stability is of main concern, so that a fully vectorial and three-dimensional approach must be used. Even with nowadays powerful computers, a brute-force numerical solutions based on general-purpose optical solvers such as finite-difference time-domain (FDTD) methods is still not affordable, especially in extensive parametric simulation campaigns, involving hundreds of thousands of different geometries. The course will provide all the details of the model developed during the last 25 years in CNR-IEIIT, at Politecnico di Torino. The first part of the course will present an overview of VCSELs, with particular attention on the reasons of their success, their potential in future applications, their construction details and operation principles. Then, starting from Maxwell’s equations, the reciprocity theorem will be discussed, showing how it is possible to derive the exact equations of coupled mode theory, that is at the basis of VELM, a software that can solve any kind of VCSEL shape, including all relevant anisotropies and temperature/carrier profiles. The sofware and its principles will be described in its general lines. Some real-world structures will also be simulated during the classes, e.g., evaluating the mode profiles also in some non-circular transverse shapes. These are of particular interest, especially in the assessment of the solutions recently proposed for the improvement of polarization stability (gratings), single mode emission (surface relief), and modulation bandwidth.

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P.D.2-2 - Marzo