Properties Study On Photonic Crystal Add-drop Filters Based On Ring Resonator In Square Lattice

The most striking characteristics of photonic crystal is the photonic band gap which isproduced by its periodic structure, then the incident electromagnetic wave can’t transmission andall be reflected off in the frequency range so as to control the movement of light. As the photonicband gap have a constraint effect on the distribution of photon states, photonic crystals also beused to make integrated optical waveguides and resonant cavities, filters and other optical passivecomponents. Optical filter is the key device in signal processing in WDM optical communicationsystems, and ring resonator based on photonic crystal structure have inspired great interestsrecently because of their potential ability for controlling light wave propagation and theadvantages of its high integrations.In this paper, first we analysised the coupling process between photonic crystal waveguidesand ring resonances by finite element method on the base of the Coupled-Mode Theory, based onthis we present an optical add-drop filter designed structure which can achieve filteringnarrow-band consists of two coupled waveguides and a ring cavity. And we deeply researched thecurve of law changing of the transmitted optical outflow power in various ports of the ringresonator filter structure varies with the wavelength. In order to effectively improve the quality ofthe structure of the filter factor, we also put forward an improved model of photonic crystal filterbased on before and analyzed the transmitted light outflow power spectrum of each port changeswith the refractive index of the dielectric-rod in ring resonator. Research found that: the couplingwavelength between waveguides and circular cavity resonance changes with the cavity column’srefractive index, then we can by accommodating the boundary scattering medium columns’arrangement and the refractive index of the dielectric-rod in the ring resonator to realize the sizeof the different wavelengths of the resonance effect. The results provides effective references forreducing the scattering loss between the waveguide and cavity to achieve the best ideal filteringeffect to design of the two-dimensional photonic crystal filter.