Multi-band optical bandpass filter with picometer bandwidth in visible spectrum formed by prism pair coupled planar...

An optical bandpass filter structure of multiple bands in the visible spectrum with bandwidths in picometer scale (full width at half maximum, FWHM) is theoretically analyzed. The filter is in a form of prism pair coupled planar optical waveguide. For each individual guided mode, multiple pass-bands are obtainable in violet, green, and red regions of the visible spectrum, respectively. High efficiencies and symmetric band shape with flat null sideband can be obtained with practical material dispersion and loss taken into account. The central wavelength of each band can also be angularly tuned within a certain range with little influence on the efficiency or bandwidth. This kind of ultra-narrow bandpass optical filter can be used in high resolution spectroscopies, laser technologies, optical communications, and optical sensing.