Interaction between fiber modes and surface plasmon waves: spectral properties

The interaction between a guided mode of a single-mode optical fiber and a surface plasmon wave supported by a thin metal overlayer is studied. A theoretical description is given of this phenomenon based on the mode expansion and propagation method. It is demonstrated that the interaction can take place only within a narrow wavelength range therefore is manifested by a dip in the spectrum of the transmitted optical power. One can control the wavelength position of the dip by varying the refractive index of the superstate. Experimental study of the realized structure, consisting of a single-mode optical fiber with locally removed cladding and a thin gold overlayer, shows that the 2 x 10(-3) change in the refractive index of the superstrate shifts the dip by similar to>10 nm. (C) 1997 Optical Society of America.