Integrated optic planar waveguides fabricated by sol-gel method by doping Neodymium (Nd3+) in glass were studied for gain properties. To our knowledge, this is the first time that a theoretical model based on atomic susceptibility (χas) is applied to the study of sol- gel based Nd-glass waveguide amplifier. Single pass amplification through these waveguides using this theory correlates well with the experimental results. As we see a strong dependence of χas in the observed gain coefficient, it is also possible to extend this theory to the case of inhomogeneously distributed Nd-atomic clusters in the gain medium. Studies on the absorption spectra of the samples showed a strong peak at λ equals 585 nm, which was used as the wavelength for pumping the waveguide. We note that a net gain of over 15 dB is achievable over a few cm's of the waveguide, assuming a homogeneous dispersion of the dopant ions in the medium. The precursors for the sol were TEOS (Tetraethyl orthosilicate) and TPOT (Titanium(IV) isopropoxide) in the ratio of 4:1 and Nd2O3 was used as the dopant. The concentration of the Nd3+ in the waveguide was 2.5 at. %. On a clean glass substrate, with typical dimensions of 2 cm x 1 cm, spincoated films comprising of multi-layers, produced a thickness of approximately 4 micrometers and a refractive index change of 0.0476 as revealed by the m-line measurements using the prism coupling technique. The samples supported two modes at λ=633 nm.
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