Compact WDM demultiplexer for seven channels in photonic crystal

Abstract

We demonstrate a new device concept for wavelength division demultiplexing based on planar photonic crystal waveguides. The filtering of wavelength channels is realized by shifting the cutoff frequency of the fundamental photonic bandgap mode in consecutive sections of the waveguide. The shift is realized by modifying the size of the border holes.The proposed demultiplexer has an area equal to (16.5μm×6.5μm) and thus it is verified that this structure is very small and can be integrated easily into optical integrated circuits with nanophotonic technologies. The output wavelengths of designed structure can be tuned for communication applications, around 1550nm. The wavelengths of demultiplexer channels are λ1=1.590μm, λ2=1.566μm, λ3=1.525μm, λ4=1.510μm, λ5=1.484μm, λ6=1.450μm, λ7=1.400μm respectively. Designs offering improvement of number of the separate wavelengths (seven), miniaturization of the structure (107.25μm2) is our aim in this work.In our structure, we consider that the 2D triangular lattice photonic crystal is composed of air holes surrounded by dielectric. Its parameters are: radius of holes (r=0.130μm), lattice constant (a=0.380μm), and index of membrane (n=3.181:InP). The numerical model used to simulate the structure of the demultiplexer is based on the finite difference time domain (FDTD).