Research Of Coarse Wavelength Division Demultiplexer Based On Photonic Crystal Microcavity

The photonic crystal with bandgap and localization effect has attracted much attention as it can well control the transmission of light. Photonic crystal multiplexer/demultiplexer is an important application. The resonance of certain frequencies of light is allowed in photonic crystal point defect micro-cavity and micro-ring. In this paper, two kinds of demultiplexer are designed and analyzed. The main content is as follows:1)Aiming at application requirements of coarse wavelength division multiplexing system in metro and access network, a coarse wavelength division demultiplexer based on photonic crystal micro-cavity is proposed.The bandgap of a two-dimensional square-lattice photonic crystal containing Si rods in air is calculated by plane wave expansion method,based on this, a micro cavity is constructed by introducing a five-point defect, by means of finite difference time domain, the effect of defect radius and index to resonant wavelength is analyzed, a four-channel demultiplexer in accordance with ITU G.694.2 standard is designed theoretically. The results of Rsoft simulation shows that, the resonantwavelength is nonlinear with the defect radius and linear with the defect index, the center wavelength of demultiplexer is close to objective wavelength, the four full width at half maximum are all less than 5.7nm,the crosstalk are all lower than-15.66 d B, the output spectrum intensity are all greater than 90% and the power difference among four channels is little,this is meaningful for further study of demultiplexer.2)The photonic crystal contains large radius air holes is relatively easy to process, a demultiplexer based on triangular lattice photonic crystal which contains air holes is designed in this paper. The bandgap of triangular lattice photonic crystals are calculated and analyzed, on this basis,the resonant wavelength of a photonic crystal single ring is calculated using FDTD method, and find that the micro-ring has a plurality of resonant wavelengths. The same to double loop cascade structure demultiplexer, the output spectrum still includes plurality of peaks. Finally, structure of tricyclic cascade successfully output a single spectrum. Therefore, tricyclic cascade demultiplexer has important significance to future WDM systems.