Specialty Optical Fibers Handbook

penetrate to a small extent into the metal and thereby become lossy. To reduce

this loss, dielectric layers may be placed on top of the metal layer [30–34]. By

proper choice of the dielectric layer thicknesses, the reflected waves established at

the dielectric layer interfaces will interfere destructively with the transmitted

waves, reducing the amplitude of the mode field in the vicinity of the lossy

metal and reducing the loss of the mode. This process, which is only operational

within a limited frequency range, essentially places a dielectric mirror in front of

the metal mirror. Of course, with a sufficient number of properly chosen dielec-

tric layers, a 1D photonic band-gap can be formed, which eliminates the need for

the metal layer entirely. ...