Porosity of pyrolysed sol–gel waveguides

Abstract

The pyrolysis of a sol–gel film dip-coated on a substrate is a convenient and inexpensive way of preparing optical waveguides with a wide range of refractive indices. Such waveguides are, however, microporous. For many uses, in particular sensing applications such as the chemical analysis of solutions, the porosity is one of the key parameters determining the response of the waveguide to its environment. In this paper, the porosity of a planar waveguide is accurately determined by measuring the mode indices for two modes with the pores filled alternately with liquid H₂O and D₂O.