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Integrated optic planar waveguides fabricated by sol-gel method by doping neodymium $(Nd^{3+})$ in glass were studied for gain properties. To our knowledge, this is the first time that a theoretical model based on atomic susceptibility $(X_{as})$ 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 $X_{as}$ 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 $\lambda=585 nm$, 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 $Nd_2O_3$ was used as the dopant. The concentration of the $Nd^{3+}$ 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 in-line measurements using the prism coupling technique. The samples supported two modes at $\lambda=633 nm$.

In this paper, we present an analysis of optical amplification properties of Nd-doped planar waveguides on glass substrates fabricated by sol-gel process. Modified gain characteristics are determined from the susceptibility profile and the waveguide dispersion properties. The waveguide dispersion properties are represented by the propagation coefficient variation with optical frequency, \beta(\omega). This is determined by solving the non-linear dispersion equation using the waveguide structural parameters, such as, the transverse refractive index profile, the waveguide film thickness and the operating optical frequency. The susceptibility profile, \chi(\omega), is determined using the measured absorption spectra from the fabricated waveguide samples. The analysis is facilitated by fitting an appropriate Gaussian distribution to the measured absorption spectra at the resonant frequency. It is observed that the gain profile is modified asymmetrically by the waveguide parameters

Incorporation of active materials, such as neodymium $(Nd^{3+})$ and erbium $(Er^{3+})$ in suitable host media has potential applications in lasers and amplifiers. We have fabricated composite planar waveguides on glass substrates doped with $Nd^{3+}$ and $Er^{3+}$ ions using the sol-gel process. The composite sol-gel was prepared using polyvinylpyrrolidone as the organic part, while tetraethyl orthosilicate and titanium isopropoxide formed the inorganic part. The samples were prism coupled and it was found that they supported a single mode at λ=633 nm. The gain measurement of the $Nd^{3+}$ samples have also been carried out