Optical properties of azo (EO) chromophore (DR1) doped in poly amic acid (PAM)
In this work, we studied the effects of annealing on the structural and optical properties of an azo electro optic (EO) polymer, Disperse Red1 (DR1), doped in Poly Amic Acid (PAM). Thin films were deposited on glass substrates by spin coating technique. The films were annealed at 195°C. The Structural and optical properties of the doped films were investigated by using UV-VIS spectra, Atomic Force Microscopy (AFM) and Prism Coupling technique. The number of modes, angles of coupling, thickness and refractive index were compared before and after annealing. The experimental results, showed 24nm blue shift in the photon absorption peak and number of modes and surface roughness of thin films decreased after annealing. Thickness was reduced about 1um and refractive index was increased by 0.03.
High-performance electro-optic modulators realized with a commercial side-chain DR1-PMMA electro-optic copolymer
Several high-performance polymeric electro-optic modulators have been demonstrated in the last decade. Most of them have been elaborated using specific high-performance electro-optic polymers designed for their exceptional electro-optic response and their thermal stability. In this paper we report the high performance of electro-optic modulators made of a commercial side-chain electro-optic copolymer DR1-PMMA as the active core material and of a passive epoxy polymer NOA73 as cladding material. The electro-optic polymer used in these modulators is a Disperse Red 1- poly-methylmethacrylate (DR1-MMA) side-chain copolymer with relative molar concentrations of DR1-substituted (resp. MMA unsubstituted) groups equal to 30% (resp. 70%). We have designed, elaborated and tested phase modulator and pushpull Mach-Zehnder modulators in order to optimize their figure of merit VπL. A push-pull Mach-Zehnder modulator with 2 cm-long electrodes and an inter-electrode distance of 8.8 μm displays a half-wave voltage of 2.6 V at 1550 nm, corresponding to a figure of merit of 5.2 V.cm. This result was obtained with a moderate poling electric field of 75 V/μm applied to the core of the modulator waveguide. We report here the best figure of merit which has never been observed in a modulator realized with a commercial side-chain electro-optic polymer.
RDF Keyword Search based on Keywords-To-SPARQL Translation
In this paper, we present a summary of our work on RDF keyword search. Given a set of keywords, our method automatically generates a set of candidate SPARQL queries, and their natural language description, to be evaluated on the RDF data graph. We discuss our approach, highlighting current and future directions.