Box-like spectral response of a series-coupled microring resonant filter in a parallel channel

Formulas of the transfer functions are presented for a series-coupled microring resonant filter and the filtering characteristics of this device are investigated around the central wavelength of 1.55 μm. The simulation results show that when the number of the microring is 4, the amplitude coupling ratio between the channel and the microring is 0.25, that between two microrings is 0.022, and the flat box-like spectral response can be formed. The 3-dB bandwidth is about 0.2 nm, the insertion loss is about 1.5 dB, and the minimum of non-resonant light is close to −150 dB. Supported by National 863-Projec (2001AA312160) & 973-Projec (G2000036604), the Chinese Academy of Sciences (One Hundred Talent Project) and the foundation of Changchun Institute of Optics Fine Mechanics and Physics, Chinese Academy of Sciences (c03Q14z)