Optical channel drop filters based on 45° photonic crystal ring resonators

A new optical channel drop filter configuration was proposed based on two-dimensional (2D) square-lattice 45° photonic crystal ring resonators (PCRRs). The ring was formed by removing the line defect along ΓM direction instead of conventional ΓX direction. Its spectral information including transmission intensity, dropped efficiency and quality factor affected by different configurations like single-ring PCRR and cascaded dual-ring PCRR was numerically analyzed with 2D finite-difference time-domain technique. More than 830 spectral quality factor and 90% dropped efficiency can be achieved at 1550-nm channel for one single-ring PCRR. Two different light wavelengths can be dropped simultaneously for cascaded serial dual-ring PCRR. These findings make the 45° PCRR optical channel drop filters as an alternative to current micro-ring resonators for ultra-compact WDM components and high density photonic integration.