1,721,084 research outputs found
Theoretical performance analysis of an integrated optic filter made of glass waveguides and POLICRYPS holographic gratings
No full textWe present the theoretical study and the simulation of the optical field propagation in a guided wave tuneable optical filter using a composite material grating. A numerical analysis of the optical propagation has been performed by using a 3D semivectorial BPM (Beam Propagation Method) based software and the results have been compared with a matrix-transfer approach based on the effective index
method. The dependency of the filter response on the index modulation depth (Dn), the length and the thickness of the grating have been also analyzed. Performance of chirped and apodized gratings were also studied. The optical filter reflection and transmission spectral responses in terms of full width at half maximum(FWHM) have been calculated
Polymeric zone plates for THz focusing
No full textA conventional binary zone plate for terahertz focusing is compared with a proposed new configuration in which two zone plates are stacked, showing an increased focusing efficiency. The field intensity in the focal spot is enhanced by employing a low-loss cyclo-olefin polymer instead of more conventional materials
Liquid crystal waveguide technologies for a new generation of low-power photonic integrated circuits
No full textIn this paper we show two approaches to fabricate photonic channels on different substrate technology platforms, in particular silicon and polydimethylsiloxane (PDMS), for flexible photonic integrated circuits. The electro-optic effect and nonlinear optical properties of liquid crystals (LC) allow the realization of low cost and low energy consumption optoelectronic devices operating at both visible and near-infrared wavelengths. High extinction ratio and large tuning range guided wave devices will be presented to be used for both optofluidic and datacom applications, in which both low realization costs and low power consumption are key features. In particular we will show our recent results on polarization independent light propagation in waveguides whose core consists of LC infiltrated in PDMS channels (LC: PDMS waveguides) fully compatible with optofluidic and lab-on-chip microsystems
High-resolution binary zone plate in double-sided configuration for terahertz radiation focusing
No full textA double-sided phase-reversal binary zone plate is numerically investigated and experimentally characterized at the frequency of 1 THz.The double-sided zone plate has a novel design based on a binary phase-reversal zone plate, in which the total zone thickness is split into two halves located at a distance optimized by means of numerical simulations.The samples are fabricated by a three-axis milling technique on slabs of an ultralow-loss cyclo-olefin polymer.The lenses' characterization at the frequency of 1 THz is performed by means of a terahertz time-domain spectrometer, in terms of both focal length and spatial resolution.The focusing properties of the double-sided zone plate are compared with those of a conventional binary zone plate.The double-sided zone plate features smaller focal spot, higher focusing efficiency, and an approximately longer depth of field than the conventional binary configuration
Design-flow of Fabry-Perot cavity leaky-wave antennas based on homogenized metasurfaces
No full textIn this work, a design flow for leaky-wave antennas based on metasurfaces is proposed. In particular, the possibility to extract the surface impedance of partially reflecting surfaces (PRS) for which homogenization formulas are not yet available in the literature has been exploited by means of numerical tools. The knowledge of the surface impedance in a PRS-based Fabry-Perot cavity leaky-wave antenna (FPC-LWA) allows for accurately evaluating the radiating performance by means of simple analytical formulas. A fishnet-like metasurface is designed to validate the proposed approach and its implementation as a partially reflective sheet for a highly-directive FPC-LWA working at terahertz frequencies is discussed
Systematic design of THz leaky-wave antennas based on homogenized metasurfaces
Full text linkIn this paper, a systematic design of Fabry-Perot cavity antennas based on leaky waves is proposed in the THz range. The use of different topologies for the synthesis of homogenized metasurfaces shows that a specific fishnetlike unit cell is particularly suitable for the design of efficient THz radiating devices. Accurate full-wave simulations highlight the advantages and disadvantages of the proposed geometries, thoroughly considering the bounds dictated by technological constraints and the homogenization limit as well. The radiative performance of different designs for achieving theoretical directivities ranging from 15 to 30 dB is evaluated with reliable analytical and numerical methods, and completely validated with full-wave simulations. The relevant results corroborate the proposed systematic design, consolidating the validity and the usefulness of the leaky-wave approach, well established at microwave frequencies, to the more challenging and still unexplored THz range
Liquid crystal display panel
No full textDisplay panel based on the use of a liquid crystal (8) which modulates a light emitted by a backlighting light source (electrodes 2, 4 and emitting layer 3) based on organic electroluminescent materials and directly fabricated onto one of the sublayers (1) thereof. Preferably, the electroluminescent material consits of liquid crystalline polymers emitting polarized light
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Polarization-independent nematic liquid crystal waveguides for optofluidic applications
No full textWe present the fabrication and the characterization of waveguides made of a nematic liquid crystal infiltrated in poly(dimethylsiloxane) channels. They are made by means of cast and molding technique and patterned using soft photolithography. The orientation of the nematic liquid crystal molecules induced by the poly(dimethylsiloxane) inner surfaces of the channels allows a polarization independent optical propagation. Optical transmission measurements showed an average of just 0.35 dB variation of light transmission versus input polarization orientation
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