A device according to claim 46, wherein the surrounding material comprises silicon, gallium arsenide, indium phosphide or other material having a refractive index in the range from about 2.5 to about 3.5, the width of the strip being in the range from about 0.1 ??m to about 2 ??m and the thickness of the strip being in the range from about 5 nm to about 30 nm. 54.