Asymmetrical interleaver filters based on one-dimensional photonic crystal theory

Based on the theory of one-dimensional photonic crystal, an asymmetrical interleaver filter is proposed. It is composed of cascaded thin-film glass cavities. Each thin-film glass cavity is formed by evaporating several layers of reflecting films on two surfaces of glass medium. Compared with other proposed structures, the proposed interleaver structure is not only very simple but also easy to accomplish. Moreover, flat passband and stopband can be obtained by the interleaver. A design example of a 50 GHz interleaver filter with duty cycle of 1∶5 is presented. The influence of each structural parameter on spectral performance, especially for the duty cycles is discussed. On this basis, design results of interleaver filters with duty cycle of 1∶3 and 1∶4 are shown and analyzed. A design example of an interleaver filter with five cascaded cavities is given at last.