322 research outputs found
Design of continuously variant metasurfaces for conformal transformation optics
No full textMetasurfaces optics and structured light represent two emerging paradigms which are revolutionizing optics in a wide range of fields, from imaging to telecommunications, both in the classical and single-photon regimes. In this work, we present and describe a method for the design of high-resolution geometric-phase metasurfaces in the form of continuously variant sub-wavelength gratings, and we demonstrate how this technique is suitable for harmonic phase masks implementing conformal optical transformations. In this framework, we revisit the metasurface design of blazed gratings and spiral phase plates, the so-called q-plates, and we extend the method to the metasurface implementation of two conformal mappings, the log-pol and the circular-sector transformation, which have been exploited successfully to perform the generation, sorting and manipulation of structured light beams carrying orbital angular momentum
Compact demultiplexing of optical vortices by means of diffractive transformation optics
No full textOrbital angular momentum (OAM) states of light have been recently considered in new mode-division multiplexing techniques in order to increase the bandwidth of today's optical networks. Many optical architectures have been presented and exploited in order to sort the different OAM channels. Here we present a diffractive version of the sorting technique based on log-pol optical transformation and we further improve the miniaturization level by integrating the two components into a single diffractive optical element. Samples have been fabricated with high-resolution electronbeam lithography and characterized in the optical range. The presented design is promising for integration into nextgeneration optical platforms performing optical processing of OAM modes, for applications both in free-space and optical fibers
Nanofabrication and test of novel diffractive optics for OAM-mode division multiplexing in optical fibers
No full textFunctionalized SU-8 patterned with X-ray Lithography
No full textIn this work we demonstrate the feasibility of x-ray lithography on SU-8 photoresist doped with the laser dye Rhodamine 6G, while retaining the photoactive properties of the embedded dye. Two kinds of structures are fabricated via soft x-ray lithography and characterized: a laser and in amplified spontaneous emission light source that couples out light normal to the chip plane. In addition we examine the influence of the x-ray irradiation on the fluorescence of thin films of dye doped SU-8. The dye embedded in the SU-8 is optically excited during, characterization by an external light source tuned to the absorption band of the dye. (c) 2005 American Iaviuon SocietY
Tempi e opere di Luigi Orione
No full textProfilo storico-biografico di Luigi Orione centrato sui momenti fondamentali della sua vita: il modernismo, il terremoto di Messina e quello di Avezzano, la fondazione di una congregazione religiosa oggi diffusa in tutto il mondo, i contatti con alcuni dei personaggi più significativi della storia italiana novecentesca: Tommaso Gallarati Scotti, Ignazio Silone, Giuseppe De Luca
Multiplication and division of the orbital angular momentum of light with diffractive transformation optics
No full textWe present a method to efficiently multiply or divide the orbital angular momentum (OAM) of light beams using a sequence of two optical elements. The key element is represented by an optical transformation mapping the azimuthal phase gradient of the input OAM beam onto a circular sector. By combining multiple circular-sector transformations into a single optical element, it is possible to multiply the value of the input OAM state by splitting and mapping the phase onto complementary circular sectors. Conversely, by combining multiple inverse transformations, the division of the initial OAM value is achievable by mapping distinct complementary circular sectors of the input beam into an equal number of circular phase gradients. Optical elements have been fabricated in the form of phase-only diffractive optics with high-resolution electron-beam lithography. Optical tests confirm the capability of the multiplier optics to perform integer multiplication of the input OAM, whereas the designed dividers are demonstrated to correctly split up the input beam into a complementary set of OAM beams. These elements can find applications for the multiplicative generation of higher-order OAM modes, optical information processing based on OAM beam transmission, and optical routing/switching in telecom
Absorption profile modulation by means of 1D digital plasmonic gratings
No full textOptical simulations of 1D digital plasmonic gratings on a Silicon substrate are performed by means of the Finite Elements Method and a modal analysis. The different mechanisms of transmission of the light are elucidated. The absorption profile in Silicon can be modulated and controlled changing the geometry. Configuration maps allow to determine the different optical regimes. Surface Plasmon Polaritons and cavity-mode resonances are shown to be effectively exploitable to enhance NIR-light absorption in different shallower regions of the underlying Silicon
Multipole-phase division multiplexing
No full textThe control of structured waves has recently opened innovative scenarios in the perspective of radiation propagation, advanced imaging, and light-matter interaction. In information and communication technology, the spatial degrees of freedom offer a wider state space to carry many channels on the same frequency or increase the dimensionality of quantum protocols. However, spatial decomposition is much more arduous than polarization or frequency multiplexing, and very few practical examples exist. Among all, beams carrying orbital angular momentum gained a preeminent role, igniting a variety of methods and techniques to generate, tailor, and measure that property. In a more general insight into structured-phase beams, we introduce here a new family of wave fields having a multipole phase. These beams are devoid of phase singularities and described by two continuous spatial parameters which can be controlled in a practical and compact way via conformal optics. The outlined framework encompasses multiplexing, propagation, and demultiplexing as a whole for the first time, describing the evolution and transformation of wave fields in terms of conformal mappings. With its potentialities, versatility, and ease of implementation, this new paradigm introduces a novel playground for space division multiplexing, suggesting unconventional solutions for light processing and free-space communications
Da Knoblecher a Comboni. Il contributo missionario all'esplorazione del bacino del Nilo
No full textLa scoperta delle sorgenti del Nilo fu uno dei maggiori problemi esplorativi e politici della storia ottocentesca. Le sorgenti del Nilo erano infatti nel cuore dell'Africa nera e il loro possesso implicava il controllo del continente. Nella corsa alla scoperta delle sorgenti, un ruolo fondamentale e non ancora riconosciuto ebbero i missionari cattolici del Vicariato apostolico dell'Africa Centrale, con sede a Khartoum. Il saggio analizza minutamente tale ruolo e indica i missionari le cui esplorazioni resero possibile l'individuazione dell'origine del fiume: Knoblecher, Vinco, Beltrame, Kaufmann, Morgan, Comboni
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