Investigation and Simulation of a Two-Channel Drop Filter with Tunable Double Optical Resonators

Abstract

In this paper, a photonic crystal (PhC) two- channel drop filter based on two 2 × 2&2 × 3r ing res- onators is proposed. This structure is made of Germanium rods in an air background at a two-dimensional (2D) square lattice. Refractive index is chosen in a way in which that device can be easily fabricated. The photonic crystal two- channel drop filter is composed using a horizontal waveg- uide and two ring resonators, which are placed symmetri- cally about the horizontal axis. These ring resonators op- erate as energy coupling and capture the electromagnetic energy propagated in bus waveguide at their resonance fre- quencies. The filter characteristics are calculated using 2D finite-difference time-domain (FDTD) and plane wave ex- pansion (PWE) methods. We show a two-channel drop filter with two resonators, based on studied basic structures and achieving optimal modes for channel drop filters with one resonator. We have done this through choosing the proper radii for all rods of lattice, setting radii of coupling rods, lattice constant, and studying basic structures having differ- ent refractive indexes. Finally, we show 84 % and 100 % dropping efficiencies can be achieved at D and C ports in the communication window and 100 % in direct port. The size of this device is 14.56 μm (length) × 11.96 μm (width). This small size makes it possible to use the device in multi- plexer applications in future communication systems and in all-optical integrated circuits.