# Amplification of light in sol-gel based Nd-glass waveguides

Natarajan, SR and Ramamurthi, Anand V and Selvarajan, Ananth and Muthuraman, M and Patil, KC (1998) Amplification of light in sol-gel based Nd-glass waveguides. In: SPIE:Rare-Earth-Doped Devices II, 26 January, San Jose, CA, USA, Vol.3280, 125-129.

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## Abstract

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 $\lambda=633 nm$.

Item Type: Conference Paper http://dx.doi.org/10.1117/12.305397 Division of Electrical Sciences > Electrical Communication Engineering 29 Mar 2007 27 Aug 2008 12:39 http://eprints.iisc.ernet.in/id/eprint/9979