CIOP   05384
CENTRO DE INVESTIGACIONES OPTICAS
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
RECONSTRUCTION OF LOW CONTRAST WAVEGUIDE INDEX PROFILE CONSIDERING THE EVANESCENT FIELD
Autor/es:
D. BIASETTI; M.R. TEJERINA; G.A. TORCHIA
Lugar:
Sevilla
Reunión:
Congreso; EUROMAT; 2013
Resumen:
In last years, a substantial amount of works have been published about the reconstruction of waveguide index profile, many of them are based on the inversion of the scalar wave equation [1] for TE propagation modes and measuring the near field. In our work, we also use this equation but we consider the evanescent field as a key experimental data to be acquired and analyzed. From this, it is possible to obtain a better fitting of the real low contrast waveguides index profile, and get more important information allowing us to determine at the same time the effective index and the shape of the cross guidance section. In particular we investigated waveguides fabricated bydirect writing [2,3] technique using femtosecond laser pulses on fused silica and LiNbO3 crystals. In order to achieve a good fitting of the waveguide?s shape, it is necessary to improve either the spatial and intensity resolution of the near field. In this sense, we study the way under which experimental conditions can minimize the error in the numerical determination of the refractive index profile after processing experimental data. So to do that, it is required a CCD camera of ten bit at least to register the near field especially due the low SNR in the evanescent field region. Additionally, an adequate optical zoom to register the guided mode in the CCD is also considered in this work. Finally, we test a fit algorithm of reconstruction with the simulated data of TE propagation modes. From this and comparing with real data it seems to be possible, in a self-consistent way, enhance the accuracy of the retrieval information corresponding to the transversal shape of these kinds of waveguides. This procedure allows us obtaining the effective and absolute refractive index profile, instead of a relative determination of these values, usually reported in the literature.