A device according to claim 46, wherein the surrounding material comprises silicon dioxide, silicon oxynitride, silicon nitride or other material having a refractive index in the range from about 1.4 to about 2.0, the width of the strip is in the range from about 0.5 ??m to about 12 ??m and the thickness of the strip is in the range from about 5 nm to about 50 nm. 48.