Two Dimensional Photonic Filters With A Circular Resonant Cavity

Optical filter is the key device in WDM optical communication system to deal with the signal of multiple channels or specific channel. It can selecte the specific wavelength from a large number of wavelengths, while the other wavelength of light will be refused. It can be used for wavelength selection, optical amplifier noise filtering and gain equalization, optical multiplexing and demultiplexing. As a periodic electrolyte structure with the characteristics of photonic band gap, photonic crystal has its own advantages in the transmission rate, bandwith and loss, etc over semiconductor materials. The defects modes can be introduced into the photonic band gap by fabricating carefully designed defects in perfect photonic crystal, and these defects modes are of more plentiful applications. By using the photonic crystal, high-performance optical filters can be obtioned, which have profound impact on the optoelectronics, optical communications, and information science. The optical filter design of base on photonic crystal structure has become an important research.In resent years, though many researchers have been produced lots of types optical filters using photonic crystals, it needs deeply study to design highly effective and multi-channel optical crystal filters, and it is primary objective of this thesis.Based on the research of the compsed elements of photonic crystal including the lattice structure, fill rate and dielectric constant, the photonic crystal band-pass filter and the multi-channel filter are designed in the two dimension square lattice circle rods PC in this thesis. By using Finite Difference Time Domain (FDTD) method, compared with the transmission characteristics of a micro-cavity, our numerical results show that such a filter can transmit multiple narrowband signals simultaneously due to the multimode characteristic of the circle cavity, but the output efficiency of each signals are different, and the biggest output efficiency can reach100%. According to the analysis of the problems in the design of the circle resonant cavity size, the effects of circle cavity size, the dielectric constant of the inner rods and the overall rods on the transmission characteristics of the PCBPF were also discussed, and this provides a reliable basis to improve and adjust the filtering performance of the filter. On the other hand, each output port normalized transmission spectra of the multi-channel filter is obtained by simulation. Forward and backward dropping of the photonic crystal filters can be achieved in the multi-channel filter in the condition of the output efficiency is high enough. The merits of this design method of PC filter are manufacture convenient, filter efficiency high, structure simple, and medium material simple. The method provides a very good reference for design and manufacture highly efficient multi-channel photonic crystal filter.