# Prof. Dr. Costantino DE ANGELIS

Costantino De Angelis, Director of the Department of Information Engineering of the University of Brescia, Italy, is visiting the Faculty of Physics and Astronomy as an Abbe School of Photonics Visiting Professor in July 2012. During his stay he will give two lectures.

Costantino De Angelis (CDA) obtained the Laurea Degree in Electronics Engineering from the University of Padova in 1989 (110/110 cum laude) and the PhD in Telecommunication Engineering from the University of Padova in 1993. He has been lecturer at the Department of Mathematics and Statistics of the University of New Mexico in 1993. He has been assistant professor at the University of Padova between 1994 and 1997 and invited professor at the University of Limoges in 1998.

In 1998 CDA has been appointed by the Department of Electronics for Automation of the University of Brescia to establish a team responsible for teaching and research activities in the area of electromagnetic fields and photonics. Today the team (Electromagnetic Fields and Photonics Group, http://nora.ing.unibs.it) is a ten people team, well known both at the national and at the international level for its achievements in the area of Nonlinear Optics and Nanophotonics. The team is now attracting an average funding rate of roughly 200 k€ per year.

Since 2004 CDA is Full Professor of Electromagnetic Fields at the University of Brescia. In 2010 and 2011 CDA has been appointed as a visiting professor at the Massachusetts Institute of Technology in Boston. Since 2010 CDA is serving as Director of the Department of Information Engineering of the University of Brescia.

The research activity of CDA over the past 20 years has led to the publication of more than 130 papers on international refereed journals, over 150 contributions at international conferences, including more than 20 invited presentations. Some of his papers have contributed to the early stage of new research developments in the field of discrete nonlinear photonic periodic structures and related devices.**Research Interests:**

- Nonlinear Optics: areas of interest include soliton propagation sustained by second and third order nonlinear effects, submicron structuring of domain inverted ferroelectric based devices (in particular PPLN), harmonic generation and frequency conversion in periodic structures, with an emphasis on second harmonic generation.
- Nanophotonics and optical antennas: areas of interest include novel photonic crystal based devices for telecommunications and sensing applications, negative index materials, photonic crystal fibers design and characterization, optical nanowires, optics of metals, computational electromagnetism.

website of Costantino De Angelis

## Lecture 1: Binary plasmonic waveguide arrays: energy localization, modulational stability and gap solitons in a gapless system

**Time: July 16, 2012, 13:00Place: Seminar room, Institute of Applied Physics, Albert-Einstein-Straße 15, 07745 Jena**

We first obtain solitary-wave solutions of a model describing light propagation in binary (linearly and nonlinearly) waveguide arrays. This model describes energy localization and transport in various physical settings, ranging from metal-dielectric (i.e., plasmonic) to photonic crystal waveguides. The solitons exist for focusing, defocusing, and even for alternating focusing-defocusing nonlinearity. We also consider a model consisting of two subsystems coupled exclusively by nonlinear terms. We show the existence of bright-dark gap solitons of both the discrete system and its continuous long wavelength limit, in spite of the absence of a gap in the linear (i.e. plane wave) spectrum. We find that these solitons are always modulationally unstable in the continuous limit, whereas they can be stable in the discrete system if the amplitude of the background component exceeds a certain threshold.

## Lecture 2: Modeling of broadband optical pulse propagation in quadratic media

**Time: July 18, 2012, 14:00Place: Seminar room, Institute of Applied Physics, Albert-Einstein-Straße 15, 07745 Jena**

We outline the derivation of a nonlinear envelope equation (NEE) to describe the propagation of broadband optical pulses in second order nonlinear materials. Our approach goes beyond the usual coupled wave description of c(2) phenomena and provides an accurate modeling of the evolution of broadband pulses also when the separation into different coupled frequency bands is not possible or not profitable. The analysis of optical pulse propagation typically involves the definition of a complex envelope "slowly" varying with respect to the oscillation of a carrier frequency. Different authors showed how to extend the validity of the envelope equation to pulse duration down to the single optical oscillation cycle and to the generation of high order harmonics. When second order nonlinearities are considered, the usual approach is to write coupled equations for the separated frequency bands relevant for the process. However if ultra-broadband c(2) phenomena take place, the different frequency bands might merge, generating a single broad spectrum, as observed in recent experiments and in these cases the coupled NEE description fails due to the overlapping between different frequency bands.

We derive here a single wave envelope equation to describe ultra-broadband c(2) interactions; moreover our equation can be solved with a modest computational effort and can be easily generalized to include other kind of nonlinearities such as Kerr or Raman.