Efficient Mach-Zehnder interferometer design based on low-symmetric photonic crystals

Abstract

In this study, a Mach-Zehnder interferometer (MZI) design is presented based on low-symmetric photonic crystal (PC) waveguides. As is known, breaking the translational or rotational symmetries of PC unit-cell may provide enhanced optical characteristics; for example, rotating the low-symmetric PC unit-cell around its axis, may support different phase indices (np) at certain wavelengths without changing dielectric filling amount. Moreover, this phenomenon could be implemented to create the arms of MZI to obtain required phase difference at each section. However, purely symmetric PCs cannot satisfy that phase difference characteristic so that it is essential to change the optical path of the arms to obtain a required phase difference. Dependence of the interference effect on the incident wavelengths is also demonstrated for the proposed low-symmetric PCs, whereas the interference in high-symmetric PC-based MZIs is not directly depend on the incident wavelengths. A three-channel interferometer is also designed and its transmission behavior is analyzed depending on the intentional modifications of the PC waveguide channels. Phase indices' change with respect to the PC unit-cell orientations may enable to design compact and efficient PC-based MZIs, which is not possible using high-symmetric PCs.