A Multi-Channel Tunable Periodic Narrowband Filter Chip Composed of Cascaded Silicon Nitride Microring Resonators

A multi-channel tunable periodic narrowband filter chip composed of cascaded silicon nitride (Si
3
N
4
) microring resonators (MRR) is proposed and implemented in this paper. We have assembled eight MRRs with the same structure on a silicon based chip with a size of 9mm*1.8mm. The waveguide material is silicon nitride with low transmission loss, and its transmission loss is about 0.2dB/cm. The central wavelength of the MRR can be tuned by thermal-optical effect. The experimental results show that the FSR is about 260GHz, the channel's 3dB bandwidth range is 0.7B-1.33GHz, the thermal modulation coefficient is about 0.33GHz/mW, and the central frequency tuning range is about 60GHz. The chip has the following features, including multi-channel, narrow bandwidth and wide tuning range, which can be used in microwave photonic system instead of traditional optical filters.