Optical multi/demultiplexer device, optical wavelength selective filter and method of making filter

Optical multi/demultiplexer (4) device comprising a substrate, a plurality of wave guides (45, 46, 47, 48) on a surface of said substrate, a plurality of selective wavelength filters (452, 462, 472, 482). Each of said plurality of filter is able to transmit a first predetermined band of wavelengths (PB') and to reflect a second predetermined band (SB'). Each one of said plurality of filter comprising a plurality of transverse cuts (4521, 4522, 4523) provided on said waveguide disposed in predetermined positions. Said cuts forms a plurality of transmissive couple providing said first predetermined band and a plurality of reflective couple providing said second predetermined band. Said transm…

Second-harmonic generation in surface periodically poled lithium niobate waveguides:On the role of multiphoton absorption

Second harmonic generation is investigated in lithium niobate channels realized by proton exchange and quasi-phase-matched by surface periodic-poling. The reduction in conversion efficiency at high powers is interpreted in terms of multi-photon absorption via two-color terms, yielding an estimate of the dominating three-photon process.

Optical band splitter/combiner and apparatus comprising the same

An optical device for splitting/combining a first and a second continuous optical wavelength bands, each wider than 10 nm, has a first, a second, a third, a fourth and a fifth optical splitting devices optically coupled in cascade and a first, a second, a third and a fourth optical differential delay devices optically coupled to, and interleaved between, the optical splitting devices. A suitable choice of the coupling angles of the splitting devices and of the differential delays of the optical differential delay devices gives to the structure flattened passbands and stopbands and makes the optical device tolerant to fluctuations of the structural parameters. An apparatus includes the optic…

Duplicazione di frequenza e tuning non lineare in guide d’onda in niobato di litio con poling periodico superficiale

Analysis of Lithium Niobate Surface Layer after Electric Field Periodic Poling and Proton Exchange

DUAL BAND OPTICAL MUX/DEMUX AND APPARATUS COMPRISING THE SAME

An optical device for splitting/combining a first and a second optical wavelength band has a first, a second and a third optical splitting device optically coupled in cascade and a first and a second differential optical delay device optically coupled to, and interleaved between, the optical splitting devices. This structure together with a suitable choice of the coupling coefficients of the splitting devices and of the differential delays of the differential optical delay devices achieves flattened pass bands and stop-bands and makes the optical device tolerant fluctuations of the structural parameters. An apparatus comprising the optical device is also disclosed for use in fiber-to-the-pr…

Integrated optic surface plasmon resonance measurements in a borosilicate glass substrate

The surface plasmon resonance (SPR) technique is a well-known optical method that can be used to measure the refractive index of organic nano-layers adsorbed on a thin metal film. Although there are many configurations for measuring biomolecular interactions, SPR-based techniques play a central role in many current biosensing experiments, since they are the most suited for sensitive and quantitative kinetic measurements. Here we give some results from the analysis and numerical elaboration of SPR data from integrated optics experiments in a particular borosilicate glass, chosen for its composition offering the rather low refractive index of 1.4701 at 633 nm wavelength. These data regard the…

Bloch analysis of finite periodic microring chains

We apply Bloch analysis to the study of finite periodic cascading of microring resonators. Diagonalization of the standard transfer matrix approach not only allows to find an exact analytic expression for transmission and reflection, but also to derive a closed form solution for the field in every point of the structure. To give more physical insight we analyze the main features of the transmission resonances in a finite chain and we give some hints for their experimental verification

Duplicazione di frequenza in guide d'onda in Niobato di Litio con poling periodico: ruolo dell'assorbimento multifotoni

MATCHING THIN LAYER FOR SURFACE PLASMON RESONANCE TUNING ON LITHIUM NIOBATE WAVEGUIDES

University of Palermo: Exploiting the Optical Quadratic Nonlinearity of Zinc-Blende Semiconductors for Guided-Wave Terahertz Generation: A Material Comparison

Content synopsis of the following paper: Matteo Cherchi, Alberto Taormina, Alessandro C. Busacca, Roberto L. Oliveri, Saverio Bivona, Alfonso C. Cino, Salvatore Stivala, Stefano Riva Sanseverino, and Claudio Leone, "Exploiting the Optical Quadratic Nonlinearity of Zinc-Blende Semiconductors for Guided-Wave Terahertz Generation: A Material Comparison", IEEE Journal of Quantum Electronics, Vol. 46, N. 3, March 2010

Nanopatterned ferroelectric crystals for parametric generation

We report on recent results by surface periodic poling on lithium niobate and lithium tantalate. Such approach allows periodic inversion of the second order susceptibility with nanoscale features using insulating masks. We achieved a world-best 200 nm feature size, as well as good compatibility with alpha-phase proton exchanged channel waveguides in lithium niobate. Preliminary results of surface periodic poling in lithium tantalate also show similar characteristics. Surface poling is best suited for integrated optics devices in technologically-demanding configurations such as backward second harmonic generation and counter propagating optical parametric amplification

Exact analytic expressions for electromagnetic propagation and optical nonlinear generation in finite one-dimensional periodic multilayers.

Translation Matrix Formalism has been used to find an exact analytic solution for linear light propagation in a finite one-dimensional (1D) periodic stratified structure. This modal approach allows to derive a closed formula for the electric field in every point of the structure, by simply imposing a convenient form for the boundary conditions. We show how to apply this result to Second Harmonic Generation (SHG) in the undepleted pump regime.

Design scheme for Mach–Zehnder interferometric coarse wavelength division multiplexing splitters and combiners

I propose an analytical approach to design flattened wavelength splitters with cascaded Mach–Zehnder inter- ferometers when wavelength dependence of the directional couplers cannot be neglected. I start from a geo- metrical representation of the action of a doubly point-symmetrical filter, assuming no wavelength dependence of the couplers. Next I derive the analytical formulas behind its working principle and extend them to the wavelength-dependent case. I also show how the geometrical representation allows one to broaden the class of working structures. © 2006 Optical Society of America

Exact analytic expressions for electromagnetic propagation in a finite one-dimensional periodic multilayer

Translation Matrix Formalism has been used to find an exact analytic solution for light propagation in a finite one-dimensional (1-D) periodic stratified structure. This modal approach allows to derive a closed formula for the electric field in every point of the structure, by simply imposing a convenient form for the boundary conditions. As an example it is also shown how to extend this result to gratings featuring defects.

Analysis of Lithium Niobate Surface after Electric Field Periodic Poling and Proton Exchange

The role of nonlinear optical absorption in narrowband difference-frequency terahertz-wave generation

We present a general analysis of the influence of nonlinear optical absorption on terahertz generation via optical difference frequency generation, when reaching for the quantum conversion efficiency limit. By casting the equations governing the process in a suitably normalized form, including either two-photon- or three-photon-absorption terms, we have been able to plot universal charts for phase matched optical-to-terahertz conversion for different values of the nonlinear absorption coefficients. We apply our analysis to some experiments reported to date, in order to understand to what extent multiphoton absorption could have played a role and also to predict the maximum achievable conver…

Surface Periodic Poling in Lithium Niobate and Lithium Tantalate

Periodic Poling of Lithium Niobate crystals (PPLN) by means of electric field has revealed the best technique for finely tailoring PPLN structures and parameters, which play a central role in many current researches in the field of nonlinear integrated optics. Besides the most studied technique of bulk poling, recently a novel technique where domain inversion occurs just in a surface layer using photoresist or silica masks has been devised and studied. This surface periodic poling (SPP) approach is best suited when light is confined in a thin surface guiding layer or stripe, as in the case of optical waveguide devices. Also, we found that SPP respect to bulk poling offers two orders of magn…

Universal charts for optical difference frequency generation in the terahertz domain

We present a universal and rigorous approach to study difference frequency generation in the terahertz domain, keeping the number of degrees of freedom to a minimum, through the definition of a suitable figure of merit. The proposed method relies on suitably normalized charts, that enable to predict the optical-to-terahertz conversion efficiency of any system based on wave propagation in quadratic nonlinear materials. The predictions of our approach are found to be in good agreement with the best experimental results reported to date, enabling also to estimate the d22 nonlinear coefficient of high quality GaSe.

Generazione di seconda armonica per quasi accordo di fase in guide a canale su LiNbO3 periodicamente polato in superficie.

Ultraviolet quasi-phase-matched second harmonic generation in surface periodically poled Lithium Niobate optical waveguides

Nanotecnologie in Niobato di Litio per la conversione di frequenza in ottica integrata nel campo UV.

Guided-wave frequency doubling in surface periodically poled lithium niobate: competing effects

We carried out second-harmonic generation in quasi-phase-matched ? -phase lithium niobate channel waveguides realized by proton exchange and surface periodic poling. Owing to a limited ferroelectric domain depth, we could observe the interplay between second-harmonic generation and self-phase modulation due to cascading and cubic effects, resulting in a nonlinear resonance shift. Data reduction allowed us to evaluate both the quadratic nonlinearity in the near infrared as well as the depth of the uninverted domains. © 2007 Optical

Role of nonlinear absorption during frequency doubling in lithium niobate waveguides.

Proton exchange channel waveguides compatible with surface domain engineering in Lithium Niobate crystals

First experiments of proton exchange channel waveguides compatible with electric field surface periodic poling of congruent lithium niobate crystals are addressed. Picosecond nonlinear copropagating QPM-SHG measurements have been carried out on such structures.

Generazione di luce UV per interazione QPM/SHG in guida ottica di niobato di litio congruente

Wavelength-flattened directional couplers for mirror-symmetric interferometers

In the context of guided optics, we derive, analytically and geometrically, a rigorous general criterion to design wavelength insensitive interferometers with mirror symmetry, which are needed for wavelength multiplexing/demultiplexing. The criterion is applied to a practical case, resulting in an interferometer that works on a band wider than 70 nm.

Exploiting the optical quadratic nonlinearity of zinc-blende semiconductors for guided-wave terahertz generation: A material comparison

We present a detailed analysis and comparison of dielectric waveguides made of CdTe, GaP, GaAs and InP for modal phase matched optical difference frequency generation (DFG) in the terahertz domain. From the form of the DFG equations, we derived the definition of a very general figure of merit (FOM). In turn, this FOM enabled us to compare different configurations, by taking into account linear and nonlinear susceptibility dispersion, terahertz absorption, and a rigorous evaluation of the waveguide modes properties. The most efficient waveguides found with this procedure are predicted to approach the quantum efficiency limit with input optical power in the order of kWs.

Optical Bloch-mode-induced quasi phase matching of quadratic interactions in one-dimensional photonic crystals

We examine in detail the quasi-phase-matching process obtained as a stationary modulation of the fundamental field at the band edge of a finite one-dimensional photonic crystal. The treatment is carried out in terms of the structure Bloch waves and fully explains the behavior of second-harmonic generation in the grating. An integrated microstructured AlGaAs mesa waveguide is proposed that gives efficient second-harmonic and difference-frequency generation in virtue of the combined presence of a periodic modulation of the fundamental-field amplitude and of the photonic bandgap edge.

Frequency doubling in surface periodically-poled lithium niobate waveguides: role of cascading and nonlinear absorption

Guide d’onda a scambio protonico in cristalli ferroelettrici con domini ingegnerizzati superficialmente

Frequency doubling in surface periodically poled lithium niobate waveguides: Competing effects

We fabricated α-phase pro ton-exchanged (PE) lithium niobate (LN) channel waveguides quasi phase-matched (QPM) via surface periodic poling (SPP) and carried out the first experimental demonstration of second harmonic generation (SHG) in such devices.[1] Experiments were performed by employing an optical parametric amplifier/oscillator producing 25 ps pulses in the range 1.1-1.6 μm with a line-width less than 2cm−1 and a repetition rate of 10Hz. SHG measurements were performed either at a fixed wavelength by varying the fundamental frequency (FF) input power or by scanning the FF wavelength, ratioing the second harmonic (SH) output to the FF input to obtain the conversion efficiency. By repe…