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Opt Express ; 25(19): 23035-23044, 2017 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-29041607


We demonstrate low-loss GaN/AlGaN planar waveguides grown by molecular beam epitaxy on sapphire substrates. By using a proper AlGaN cladding layer and reducing surface roughness we reach <1dB/cm propagation losses at 633nm. These low propagation losses allow an efficient second harmonic generation using modal phase matching between a TM0 pump at 1260nm and a TM2 second harmonic at 630nm. A maximal power conversion of 2% is realized with an efficiency of 0.15%·W-1cm-2. We provide a modelling that demonstrates broadband features of GaN/AlGaN platform by showing second harmonic wavelengths tunability from the visible up to the near-infrared spectral region. We discuss drawbacks of modal phase matching and propose a novel solution which allows a drastic improvement of modal overlaps with the help of a planar polarity inversion. This new approach is compatible with low propagation losses and may allow as high as 100%·W-1cm-2 conversion efficiencies in the future.

Opt Express ; 17(20): 17868-73, 2009 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-19907575


We propose a new mode adapter which allows more efficient launching of the optical power selectively in the fundamental mode of a multimode waveguide. Theoretical and experimental results confirm that such a mode adapter increases the performances in terms of coupling efficiency, coupling tolerances and transmitted power with respect to previously proposed solutions. Proof of principle of device operation is obtained with a simple Coupled Mode Theory model. Experimental results are obtained at a wavelength of 840 nm in Lithium Niobate Soft Proton Exchanged waveguides and agree very well with theoretical predictions.

Nióbio/química , Dispositivos Ópticos , Óxidos/química , Refratometria/instrumentação , Desenho Assistido por Computador , Desenho de Equipamento , Análise de Falha de Equipamento , Luz , Reprodutibilidade dos Testes , Espalhamento de Radiação , Sensibilidade e Especificidade
Appl Opt ; 41(7): 1418-23, 2002 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-11900022


We present the measurements of hemispherical elastic scattering of light guided by different modes of a planar LiNbO3 waveguide. It is shown that the fundamental and the lowest-order modes are more sensitive to the scattering properties of the air-core interface, whereas higher-order modes are more sensitive to the optical inhomogeneities of the core-substrate interface. We also demonstrate that because of static polarization of LiNbO3 crystal, the air-core interface is sensitive to the presence of dust particles in air, which causes a change in the scattered light based on time of observation. This sensitivity could be used to elaborate compact sensors of air contamination.

Opt Express ; 10(19): 990-5, 2002 Sep 23.
Artigo em Inglês | MEDLINE | ID: mdl-19451955


A theoretical method and an original numerical procedure to calculate the light spectra generated by optical parametric florescence (OPF) in a periodically polled medium is presented. This efficient procedure allows us to precisely study the generation in a periodically poled lithium niobate crystal. As an example, the evolution of the OPF spectra as a function of the pump frequency is presented as an animation. Furthermore, we show that OPF spectra can be generated when the pump frequency goes below the degeneracy.