Brillouin scattering in planar waveguides. II. Experiments
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Data
2003-10-15
Autores
Chiasera, A.
Montagna, M.
Moser, E.
Rossi, F.
Tosello, C.
Ferrari, M.
Zampedri, L.
Caponi, S.
Goncalves, R. R.
Chaussedent, S.
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American Institute of Physics (AIP)
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Silica-titania planar waveguides of different thicknesses and compositions have been produced by radio-frequency sputtering and dip coating on silica substrates. Waveguides were also produced by silver exchange on a soda-lime silicate glass substrate. Brillouin scattering of the samples has been studied by coupling the exciting laser beam with a prism to different transverse-electric (TE) modes of the waveguides, and collecting the scattered light from the front surface. In multimode waveguides, the spectra depend on the m mode of excitation. For waveguides with a step index profile, two main peaks due to longitudinal phonons are present, apart from the case of the TE0 excitation, where a single peak is observed. The energy separation between the two peaks increases with the mode index. In graded-index waveguides, m-1 peaks of comparable intensities are observed. The spectra are reproduced very well by a model which considers the space distribution of the exciting field in the mode, a simple space dependence of the elasto-optic coefficients, through the value of the refraction index, and neglects the refraction of phonons. A single-fit parameter, i.e., the longitudinal sound velocity, is used to calculate as many spectra as is the number of modes in the waveguide. (C) 2003 American Institute of Physics.
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Journal of Applied Physics. Melville: Amer Inst Physics, v. 94, n. 8, p. 4882-4889, 2003.