Solvent detection using porous silicon optical waveguides

Since the first report on the use of porous silicon as an optical waveguide medium in 1995, significant development has been made towards the understa nding and applicability of such material. Here, the introduction of solvent s (acetone, methanol, and propan-2-ol) into the pores is shown to dramatica lly reduce the loss of the waveguides, in a reversible manner. Both the mag nitude and duration of this effect are sensitive to the solvent introduced. In some waveguides, for example, the measured loss (at 0.633 mu m) falls b y as much as 34 dB cm(-1) on the introduction of acetone. Theoretical estim ates of the effect of solvents on the interfacial scattering loss confirm t his as the origin of the observed reductions. These results, combined with the fact that a substantial portion of the guided-mode field interacts with the solvent, indicate an enhanced sensitivity for sensor applications may be achievable. (C) 1999 Elsevier Science B.V. All rights reserved.