Biomedical subjects

Andrea Melloni

Publications and source records attributed to Andrea Melloni.

5 recordsLinked to original sources

PubMed2004

Polarization conversion in ring resonator phase shifters.

The effect of the polarization rotation induced by curved waveguides on the spectral behavior of phase shifter ring resonators is investigated both theoretically and experimentally. At resonance the polarization rotation that takes place in curved waveguides is strongly enhanced. The effect can be detrimental, or it can be exploited for new devices. The ring vectorial transfer function is derived, together with the conditions for the total conversion of TE polarization into TM polarization. These conditions are verified experimentally.

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PubMed2004

Experimental confirmation of matched bends.

Modal conversion between the fundamental mode and the first-order (leaky) mode has been experimentally investigated in high-index-contrast integrated-optical bent waveguides. The matched bend condition has been experimentally confirmed on cascaded bends, and the effect of both matched and unmatched bends on Y branches has been investigated. Good agreement between theoretical predictions and experimental results for both monomode and multimode waveguides is achieved. It is demonstrated that, in bent waveguides, the modal conversion between the fundamental mode and the first (leaky) mode can be accurately controlled to avoid additional losses and transfer function impairments.

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PubMed2003

Ring-resonator filters in silicon oxynitride technology for dense wavelength-division multiplexing systems.

The design and characterization of ring-resonator-based filters with free spectral ranges of 100 and 50 GHz by use of SiO(x)N(y) technology is presented. Fiber-to-fiber insertion losses of 4.4 dB on the drop port and 2.1 dB on the through port have been achieved for a single-ring filter. An interleaver filter for a 25-GHz spaced dense wavelength-division multiplexing system with two cascaded rings is demonstrated. The filter has a 7.4-GHz bandwidth at -1 dB and an extinction ratio of 15 dB and is polarization independent.

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PubMed2003

Design of curved waveguides: the matched bend.

A new criterion for the optimum design of curved dielectric waveguides is proposed. The bends designed according to this model are named matched bends. In the matched bend, the suitable choice of both bending radius and bending angle reduces the total losses of the bend and avoids the leaky-mode excitation at the end of the bend. For a given angle, a discrete number of bending radii that satisfy the matched bend criterion can be analytically determined. With respect to the lateral offset, matched bends are more robust to both fabrication tolerances and wavelength and can be realized in every technology. The reduction of the leaky-mode excitation at the output of the bend is a fundamental property when two or more components are cascaded. Ghost images in the spectral response, cross talk, and asymmetries of the transfer function are successfully reduced. Some examples that use buried, rib, ridge, and diffused waveguides are presented and discussed.

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PubMed2003

Equivalent circuit of Bragg gratings and its application to Fabry-Pérot cavities.

An equivalent circuit of both uniform and apodized symmetrical Bragg gratings is proposed, consisting of an ideal partially reflecting mirror placed between two wavelength-dependent uniform propagating sections. The model is simple, exact, and valid for every wavelength; it can be combined with other port-based models and is of great aid in the analysis and design of devices containing two or more Bragg gratings. As an application, the synthesis of dispersive Bragg gratings based Fabry-Pérot cavities is demonstrated. The conditions under which a Bragg-grating-based Fabry-Pérot cavity behaves exactly as an ideal dispersive Fabry-Pérot cavity are discussed. Experimental results that confirm the theoretical spectral response calculated by using the equivalent circuit are reported.

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