Photonic crystal multi-channel drop filters with Fabry–Pérot microcavity reflection feedback

We have designed a multi-port channel-drop filter (MCDF) based on a two-dimensional photonic crystal (PhC) with a Fabry–Pérot reflector at the end of the bus waveguide. The conditions to achieve 100% drop efficiency at the resonance frequency were derived through the coupled mode theory in time and the transmission properties for such structure were calculated by finite-difference time-domain (FDTD) method. The results show that the light with different wavelengths can be successfully filtered to different ports by setting different radii of the center defect rods in the drop waveguides and high drop efficiency can be achieved by means of reflection feedback. The MCDF we designed can easily separate the light with five different wavelengths simultaneously with high drop efficiency. Among them are the wavelengths of 1.31 and 1.55 μm which are two main communication wavelengths. It is superior than the MCDFs reported before and can be used extensively in optical communication systems.