Silica-on-silicon optical sensor based on integrated waveguides and microchannels

The operation of a novel optical device sensitive to the refractive index of a small (<1/spl times/10/sup -12/ m/sup 3/) volume of liquid is demonstrated experimentally. The structure is a silica-on-silicon three-core directional coupler with two quasi-circular microchannels, approximately three micrometers in diameter, located between the cores. The operation of the device is demonstrated by introducing liquid into the microchannels and varying the refractive index of the liquid through a temperature change.