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L2.8.1

Optical Spectroscopy of Silicon-On-Insulator Waveguide Photonic Crystals D. Bajoni, M. Galli, M. Belotti, F. Paleari, M. Patrini, G. Guizzetti, D. Gerace, M. Agio, L.C. Andreani INFM and Dipartimento di Fisica “A. Volta”, via Bassi 6, I-27100 Pavia, Italy Y. Chen Laboratoire de Photonique et de Nanostructures, CNRS, Route de Nozay, 91460 Marcoussis, France Département de Chimie, Ecole Normale Supérieure, 24 Rue Lhomond, 75231 Paris Cedex 05, France ABSTRACT We report on a complete optical investigation on two-dimensional silicon-on-insulator (SOI) waveguide photonic crystals obtained by electron beam lithography and reactive ion etching. The dispersion of photonic modes is fully investigated both above and below the light-line by means of angle- and polarization-resolved micro-reflectance and attenuated total reflectance measurements. The investigated samples consisted in a) large area (300 x 300 µm2) two-dimensional (2D) triangular lattices of air holes containing repeated line–defects; b) small area triangular lattices of holes with different number of periods and /or line defects integrated in a ridge type waveguide structure. In the case of large area samples, variable-angle reflectance and ATR is measured from the sample surface in a wide spectral range from 0.2 to 2 eV both in TE and TM polarizations. The sharp resonances observed in the polarized reflectance and ATR spectra allow mapping of the photonic dispersion of both radiative and guided modes. Experimentally determined and compared to those calculated by means of an expansion on the basis of the waveguide modes. In the case of ridge type waveguide-integrated photonic crystals, transmission is measured in the 0.9-1.7 eV spectral range by an edge-coupling technique. Transmission spectra exhibit significant attenuation corresponding to the photonic gaps along the Γ−Μ and Γ−Κ directions respectively, even when a small number of hole periods is integrated in the ridge waveguide. Good agreement is obtained by comparing the measured transmission spectra with the calculated photonic bands. INTRODUCTION Since the pioneering works from Joannopoulos [1] and Yablonovitch [2], great interest has arosen in photonic crystals (PCs) for their peculiar optical properties. Periodically patterned planar waveguides are emerging as one of the best performing structures for the control of light propagation in three dimensions (3D) [3]-[5]. This is obtained by means of a two-dimansional (2D) photonic lattice embedded in a slab waveguide, which provides additional confinement in the vertical direction by means of total internal reflection. Nanoscale waveguides may be obtained by introducing linear defects in a periodic structure. A common design is the so called W1 waveguide, which consists in a missing row of holes in a triangular lattice along the Γ-Κ symmetry direction. The ω(k) dispersion of the defect- and bulk- photonic modes lies partly above and partly below the dispersion line of light in air. As in conventional dielectric slabs, the former modes can couple wit