Quantum spin Hall effect in bound states in continuum

Moving the polarization of the incident wave along a meridian of the Poincaré sphere, experimentally we show that the coupling with the fundamental Bloch's surface waves of the mode, provide a spatially coherent, macroscopic spinmomentum locked propagation along the symmetry axes of the PhCM. This novel mechanism of light-spin manipulation enables a versatile implementation of spin-optical structures that may pave the way to novel strategies for light spin technology and photonic multiplatform implementations

Playing with light in diatoms: microalgae with a natural photonic crystal structure

Complex micro- and nano-structured materials for photonic applications are designed and fabricated using top technologies. A completely different approach to engineering systems at the sub-micron-scale consists in recognizing the nanostructures and morphologies that nature has optimized during life’s history on earth. In fact, biological organisms could exhibit ordered geometries and complex photonic structures which often overcome the products of the best available fabrication technologies [1]. An example is given by diatoms, microalgae with a peculiar cell wall consisting of amorphous hydrated silica valves reciprocally interconnected in a structure called the frustule. Valve surfaces exhibit specie-specific patterns of regular arrays of chambers, called areolae, developed into the frustule depth. Areolae range in diameter from few hundreds of nanometers up to few microns, and can be circular, polygonal or elongate [2]. The formation of these patterns can be modeled by self-organised, genetically controlled processes. Despite of the high level of knowledge on the genesis and morphology of diatom frustules, their functions are not completely understood [2]. In this work, we show that the silica valves of marine diatoms, characterized by a photonic crystal-like structure, have surprising optical properties, being capable of filtering and focalizing light, as well as exhibiting optical sensing capabilities

Frontiers of light manipulation in natural, metallic, and dielectric nanostructures

AbstractThe ability to control light at the nanoscale is at the basis of contemporary photonics and plasmonics. In particular, properly engineered periodic nanostructures not only allow the inhibition of propagation of light at specific spectral ranges or its confinement in nanocavities or waveguides, but make also possible field enhancement effects in vibrational, Raman, infrared and fluorescence spectroscopies, paving the way to the development of novel high-performance optical sensors. All these devices find an impressive analogy in nearly-periodic photonic nanostructures present in several plants, animals and algae, which can represent a source of inspiration in the development and optimization of new artificial nano-optical systems. Here we present the main properties and applications of cutting-edge nanostructures starting from several examples of natural photonic architectures, up to the most recent technologies based on metallic and dielectric metasurfaces

Observation of resonant states in negative refractive photonic crystals

In this paper, experimental evidences about the resonance phenomena in a negative 2D photonic crystal are shown. Localized plasmon-like modes and guided mode resonances are detected in the reflectivity spectrum of a photonic crystal slab irradiated with out-of-plane incident radiation. The strong confinement of the radiation, in addition to the field enhancement, make photonic crystals a very appealing alternative to plasmonic substrates, avoiding the limits of absorption losses in metals

New perspectives in silicon micro and nanophotonics

In the last two decades, there has been growing interest in silicon-based photonic devices for many optical applications: telecommunications, interconnects and biosensors. In this work, an advance overview of our results in this field is presented. Proposed devices allow overcoming silicon intrinsic drawbacks limiting its application as a photonic substrate. Taking advantages of both non-linear and linear effects, size reduction at nanometric scale and new two-dimensional emerging materials, we have obtained a progressive increase in device performance along the last years. In this work we show that a suitable design of a thin photonic crystal slab realized in silicon nitride can exhibit a very strong field enhancement. This result is very promising for all photonic silicon devices based on nonlinear phenomena. Moreover we report on the fabrication and characterization of silicon photodetectors working at near-infrared wavelengths based on the internal photoemission absorption in a Schottky junction. We show as an increase in device performance can be obtained by coupling light into both micro-resonant cavity and waveguiding structures. In addition, replacing metal with graphene in a Schottky junction, a further improve in PD performance can be achieved. Finally, silicon-based microarray for biomedical applications, are reported. Microarray of porous silicon Bragg reflectors on a crystalline silicon substrate have been realized using a technological process based on standard photolithography and electrochemical anodization of the silicon. Our insights show that silicon is a promising platform for the integration of various optical functionalities on the same chip opening new frontiers in the field of low-cost silicon micro and nanophotonics

The square Thue-Morse tiling for photonic application

International audienceThe photonic properties of a two-dimensional photonic aperiodic crystal based on the Thue-Morse substitutional sequence were investigated theoretically. Differently from the traditional photonic quasicrystals based on the Penrose tiling, these structures were obtained by removing the lattice points from a square arrangement, following the inflation rules emerging from the Thue-Morse sequence. The resulting structure does not exhibit the typical translational symmetry of a photonic crystal. In particular, it is well known that the Thue-Morse sequence has a singular continuous Fourier transform. This property was transferred directly on the two-dimensional Thue-Morse photonic aperiodic crystal represented by an array of pillars in air. The electromagnetic field distribution can be described as a quasi-localized state, with characteristics lying between the localized states, corresponding to the defect state in a photonic crystal, and the Bloch states, as in case of the eigenmode in a photonic crystal. The photonic bandgap formation was explored as a function of pillar radius. Furthermore a preliminary investigation of the defect behaviour in square Thue-Morse tiling was carried out. The electric field in the defect state revealed to be strictly localized in the defect pillar. These structures provide interesting properties which could be used to design novel optical devices

Le Stenosi laringo-tracheali nell'infanzia. Esperienza personale mediante trattamento chirurgico endoscopico

Viene dettagliata l'esperienza personale acqusisita nel trattamento chirurgico endoscopicodelle stenosi laringo-tracheali nell'infanzia