Colors of thin films, antiresonant phenomena in optical systems, and the limiting loss of modes in hollow optical waveguides

Wave-theory arguments often used to explain colors of thin films are applied to derive simple, physically instructive relations providing a quantitative understanding of transmission spectra of hollow optical waveguides with a complex structure of the cladding. Antiresonant phenomena in complicated optical waveguide systems are shown to weaken the coupling between certain groups of waveguide modes, suggesting ways to substantially reduce optical loss and radically improve the beam quality of radiation transmitted through hollow waveguides. It has been revealed that the presence of a single Fabry–Perot type antiresonant layer in a waveguide cladding considerably lowers the waveguide loss and enhances the suppression of high-order waveguide modes relative to standard, capillary waveguides with a solid cladding. Transmission of optical signals over large distances, however, requires waveguides with a periodically structured antiresonant cladding. The loss in such waveguides exponentially decreases, while the efficiency of high-order mode suppression exponentially increases with the growth in the number of structure periods in the waveguide cladding.