Graded index waveguide elaboration by silver–sodium or silver–lithium ionic exchange for various glass compositions

The synthesis of planar optical component has a particular interest in the manufacturing of complex waveguides as multiplexer, coupling unit or optical fiber connector. Most important criteria of choice of these components are the network losses and the Δn value of the refractive index variation between the treated glass and the non treated part and the operating life. In this way ionic exchange is a very efficient method to achieve the realization of planar waveguides. Thus, it is the optical index changing between the silver doped glass and the matrix which determines the allowed trapped mode. The choice of substrate composition (glass) which will contain silver ions and the ionic exchange conditions are fundamental criteria in the manufacturing of these components. In this paper, we present three characterization methods allowing the understanding of the exchange mechanisms according to the silicate glass composition selected: Scanning Electron Microscopy measurement (SEM) allows the evaluating of the silver concentration profile and the determination of the silver diffusion coefficient after a fitting procedure, UV/Visible Absorption gives the absorption spectra after the ionic exchange and the identification of a potential Surface Plasmon Resonance (SPR) linked to silver nanoparticle formation which would entail linear losses and infrared spectroscopy gives refractive index thanks to the permittivity value obtained above 1250 cm−1 (below 8 μm) in the glass electronic transition domain. Finally, we show the effect of the alkaline rate and other glass compounds about the optical properties for obtaining waveguide.

► We detail Ag+ for Na+ or Li+ ionic exchange method to make planar waveguides.
► We obtain the silver diffusion coefficient according to the glass composition.
► We point out the role of the glass compound categories according to their rate.
► We obtain the refractive index values according to the glass composition.
► We show the lithium diffusion coefficient is higher than in the sodium case.