GRADIENT EFFECTIVE INDEX WAVE-GUIDE SENSORS

Experimental results are reported which demonstrate the suitability of using optical waveguides with a spatially varying measurand-dependent effective refractive-index distribution for sensing applications. In this novel approach, the effect of the measurand on guided wave propagation is analysed within the waveguide itself. Therefore, this sensing principle avoids the problems and adjustment efforts related with external optics and other auxiliary equipment, while the high sensitivity of waveguide sensing is maintained. Results of computer simulations are shown to agree well with experiments performed for a humidity sensor based on a porous-type Ta2O5 waveguide. Schemes are presented for revealing the potential of this approach for realizing small, compact and versatile sensor modules with built-in stability.