Ultracompact 2 $,\times,$ 2 Photonic Crystal Waveguide Power Splitter Based on Self-Imaging Effect Realized by Asymmetric Interference

The properties of two-fold images, based on asym metric interference in multimode interference-based photonic crystal waveguides, are numerically studied with finite-difference time-domain simulations. With these image properties, 2 × 2 power splitters (PSs) with an ultracompact size are designed. Ar bitrary splitting ratio can be achieved by modifying the sizes (the effective refractive indices) of one pair of rods in the multimode region. As an example, a 3-dB 2 × 2 PS with a size of 24 × 8 μm² is presented with an output efficiency as high as 98%. The method can be extended for the design of M × N PSs for photonic integrated circuits applications.