Progress In Electromagnetics Research Symposium, Hangzhou, China, March 24-28, 2008 1097 A New Broadband L-shaped Bend Based on Photonic Crystal Ring Resonators M. Djavid, F. Monifi, A. Ghaffari, and M. S. Abrishamian Department of Electrical Engineering, K.N.Toosi University of Technology, Tehran, Iran Abstract— In this paper, we propose a new type of 2D photonic crystal L-shaped bent waveg- uide based on ring resonator with broadband acceptable bandwidth; FDTD method concludes output efficiency over 90%. 1. INTRODUCTION One of the key elements of integrated optical devices is a bent waveguide. Many papers have inves- tigated different geometries of bent waveguide in order to improve its transmission characteristics. Ring resonators are another useful element especially in add-drop filters. Because of high quality factor of the ring resonator and the ring’s intrinsic single mode nature, very high spectral selectiv- ity can be achieved [1,2]. Therefore we used this element to achieve a new type of L-shaped Bent waveguide with acceptable bandwidth about 1537 nm to 1600 nm in third communication window. 2. PHOTONIC CRYSTAL ADD-DROP FILTER BASED ON RING RESONATOR COUPLING A typical ring resonator in rectangular lattice photonic crystal of dielectric column in air host is shown in Figure 1. As shown in this figure, by adding the four scatterer rods at the corners of the ring resonator with the same properties as other rods, the performance of the ring resonator is optimized. Figure 1: Single-ring photonic crystal ring resonator (PCRR). By putting a ring resonator next to the waveguide, it can be coupled to the waveguide at its resonant frequency to trap the electromagnetic energy propagating in the waveguide and localized its energy [3]. In other word, the ring resonator drops a light from the top waveguide and sends it to the bottom waveguide, as shown in Figure 2. (a) (b) Figure 2: The electric field patterns for (a) drop (on-resonance λ = 1577 nm) and (b) through (off-resonance λ = 1500 nm) channel.