DESIGN OF A TUNABLE OPTICAL FILTER BY USING A ONE-DIMENSIONAL TERNARY PHOTONIC BAND GAP MATERIAL

A band pass filter with a linearly periodic refractive index profile is discussed in analogy with Kroning Penney model in band theory of solids. The suggested filter is a one-dimensional ternary periodic structure and provides better control in dispersion relation as compared to a binary structure because it has two more controlling parameters relative to those of the binary one. Since three layers are involved in the formation of band gaps a much broader range of dispersion control is obtained. Both refractive index modulation and optical thickness modulation are considered. A mathematical analysis is presented to predict allowed and forbidden bands of wavelength with variation of angle of incidence. It is also possible to get desired ranges of the electromagnetic spectrum filtered with this structure by manipulating the value of the lattice parameters.