Photonic crystal-based optical filter: a brief investigation

Ring resonator-based channel drop filters are investigated conceptually and analytically with different ring (square and hexagonal) structures. In the proposed architecture, silicon rods (\(n=3.4641\)) are contrived over an air substrate of refractive index \(n=1\) in the equilateral triangular lattice which has the lattice constant \(a=900\,\hbox {nm}\). The characteristics of the design are examined for various types of pillars (circular and elliptical) and are reported in the analysis. The band gap for each structure is calculated and observed by plane-wave expansion method. The normalized transmission spectra and resonance wavelengths for different photonic crystal ring resonators are obtained using 2D finite-difference time-domain method. From the investigation, the resonance of circular pillar falls over the region of the third window at C-band (1530–1565 nm) which has the lowest attenuation losses and most widely used. Full width at half maximum and quality factor of the desired layout are also being calculated. The size of the device is about \(20 \times 14\,{\upmu }\hbox {m}\) which is highly compact and useful for the integration of photonic circuits.