A one-dimensional dielectric grating, based on a simple geometry, is proposed and investigated to enhance light absorption in a monolayer graphene exploiting guided mode resonances. Numerical findings reveal that the optimized configuration is able to absorb up to 60% of the impinging light at normal incidence for both TE and TM polarizations resulting in a theoretical enhancement factor of about 26 with respect to the monolayer graphene absorption (≈2.3%). Experimental results confirm this behavior showing CVD graphene absorbance peaks up to about 40% over narrow bands of a few nanometers. The simple and flexible design points to a way to realize innovative, scalable and -easy-to fabricate-graphene-based optical absorbers.

We report theoretical and experimental investigations of the optical response of two-dimensional periodic arrays of rectangular gold nanopatches grown on a monolayer graphene placed on a glass substrate. We discuss the numerical analysis and optical characterization by means of reflection spectra and show that rectangular nanopatches display a polarization-dependent response, at normal incidence, which leads to double plasmonic resonances due to the Wood anomaly. We detail the fabrication process highlighting how the resist primer and the adhesion layer can reduce and impede the graphene doping due to the environment and to the nanopatches, respectively, by means of Raman spectroscopy.

We theoretically investigate the amplification of extraordinary optical transmission (EOT) phenomena in periodic arrays of subwavelength apertures incorporating gain media. In particular, we consider a realistic structure consisting of an opaque silver film perforated by a periodic array of slits and clad on each side by an optically pumped dielectric thin film containing rhodamine dye molecules. By solving the semiclassical electronic rate equations coupled to rigorous finite-element simulations of the electromagnetic fields, we show how the resonant electric-field enhancement associated with EOT properties enables complete ohmic loss compensation at moderate pump intensity levels. Furthermore, our calculations show that, as a consequence of the strong spatial hole-burning effects displayed by the considered structures, three separate regimes of operation arise: the system can behave as an absorber, an optical amplifier or a laser, depending on the value of the pump intensity. A discussion on the feasibility of reaching the lasing regime in the considered class of structures is also presented.

We report on the formation of plasmonic bandgaps in two-dimensional periodic arrangements of gold patches.Orthogonal arrays of subwavelength slits with different periodicities have been studied by means of a threedimensional finite-difference time-domain (FDTD) code, changing incident polarization and geometrical parameters. Spectral response of gold patches having different a form factor and surrounded by different media have been also investigated and compared in order to give a full description of bandgap shifts paving the way for the design of polarization-sensitive devices.

Mesoscopic self-collimation (MSC) in mesoscopic photonic crystals with high reflectivity is exploited to realize a novel high Q-factor cavity by means of mesoscopic PhC planar mirrors. These mirrors efficiently confine a mode inside a planar Fabry-Perot-like cavity, that results from a beam focusing effect that stabilizes the cavity even for small beam sizes, resembling the focusing behavior of curved mirrors. Moreover, they show an improved reflectivity with respect to their standard distributed Bragg reflector counterparts that allows higher compactness. A Q-factor higher than 10⁴ has been achieved for an optimized 5-period-long mirror cavity. The optimization of the Q-factor and the performances in terms of energy storage, field enhancement, and confinement are detailed.

This paper summarizes all research advancements obtained by the Polytechnic of Bari through the RES NOVAE Project activities in the field of the smart district. In this context it is important to investigate and apply new efficient technologies solutions for the building management in order to optimize the energy usage and to improve the inhabitants’ comfort. The integration of the ICT technologies and the building automation systems together with innovative renewables energy solutions is studied. Moreover, suitable control algorithms, communication protocols and measurement devices are proposed and tested to improve the efficiency of the building energy management systems.

A highly compact 2 × 2 photonic crystal (PhC) passive wavelength router (λ-router) is proposed. The proposed λ- router exploits two photonic crystal ring resonators (PCRRs) having a 3.2 μmdiameter and a broadband PhC waveguide crossing. The router topology, allowing assembly into higher-order matrices capable of connecting multiple transmitters with multiple receivers, can be exploited as a basic building block for the design, through a compositional approach, of more complex photonic integrated networks. The design criteria, derived by applying the finite difference time domain and the plane wave expansion methods, are reported. Moreover, the analysis of a 4 × 4 λ-router configuration, obtained by assembling four 2 × 2 basic switching elements, is reported to highlight the potentiality of the basic routing element to be assembled into compact higher-order matrices that exhibit small footprints of 24 μm × 24 μm and a maximum crosstalk between the ports equal to −20.1 dB.

We propose a simple, fast, and accurate method to design complex layered photonic crystal structures that exhibit mesoscopic self-collimation. We apply this method to the control of the overall reflectivity of such structures, and we numerically demonstrate high transmissivity (>99%) self-collimating waveguides and high-reflectivity (>99%) self-collimating Bragg mirrors.