Very compact photonic crystal resonant cavity for all optical filtering

In this paper, an all-optical filter is proposed which employs a resonant cavity localized between input and output waveguides as wavelength selecting part of the filter. We study the impact of different parameters on the filtering of the structure using plane wave expansion and finite difference time domain methods. We also study the effect of the output waveguide position on the performance of the filter and results show that the proper position of the output waveguide is straight to the center of the resonant cavity. The initial form of filter is capable of selecting the optical waves at λ = 1,554.2 nm and the transmission efficiency of the filter is obtained about 100 %. The total footprint of the filter is 76 µm^2. High transmission efficiency, simplicity of design and compact size are the most significant advantages of filter.