Optimization of a 60° waveguide bend in InP-based 2D planar photonic crystals

Abstract

We present a novel design for a 𝑊��1 (one missing row of holes) waveguide 60° bend implemented in a substrate-type InP⁄InGaAsP⁄InP planar photonic crystal based on a triangular array of air holes. The bend has been designed to provide high transmission over a large bandwidth. The investigated design improvement relies only on displacing holes while avoiding changing individual holes diameter in the interest of better process control (homogenous hole depth). Two-dimensional (2D) finite-element simulations were used to increase the relative transmission bandwidth from 18% to 40% of the photonic bandgap for unoptimized and optimized 60° bends, respectively. The 2D results were verified by means of rigorous three-dimensional (3D) finite-difference time-domain (FDTD) simulations. We show that excellent agreement between 2D and 3D simulations can be obtained, provided a small effective-index shift of −0.024 (−0.74%) and an imaginary loss parameter (𝜖��″=0.014) is introduced in the 2D simulations. To demonstrate the applicability of our improved design, the bend was fabricated and measured using the endfire technique. A bending loss of 3 dB is obtained for the optimized 𝑊��1 waveguide bend compared to more than 8 dB in the unoptimized case. © 2007 Optical Society of America