Fine tunable multi-cavity Si photonic crystal filters

In this work, a technique for precise position control of individual transmission channels in a triple-cavity resonator device is proposed. The resonator design is based on Si photonic crystal (PhC) and liquid crystal technologies. By filling of the particular air grooves in one-dimensional, Si-Air PhC with nematic liquid crystal, an efficient coupled Fabry- Pérot resonator can be realized in which a wide stop band is used for broad frequency channel separation and high out-of- band reflection. By random tuning of the refractive index in all coupled cavities, a continuous individual tuning of the central channel (or edge channels) up to 25% of the total channel spacing is demonstrated. Additionally, an approach for precise controllable improvement of transmission up to 100% is demonstrated for the edge channels with decrease of the channel spacing 1%. Based on the proposed design, a prototype triple-channel filter was fabricated on Silicon-On-Insulator platform and optimized to the desired operational mode.

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