Ultracompact add-drop filters based on single nanobeam cavity

Ultracompact silicon-on-insulator add-drop filters using single nanobeam photonic crystal cavity are proposed, designed and experimentally demonstrated in this work. Transversely antisymmetric multimode nanobeam photonic crystal cavities are employed in the design to implement mode-selective waveguide-cavity coupling and achieve complete channel drop filtering function. Experimental results show the insertion loss of through port, drop port and the crosstalk of add port are -0.1 dB, -0.2 dB and -12.5 dB, respectively. The footprint of the involved nanobeam photonic crystal cavity is only 12 μm ² and indicating huge potentials in future VLSI photonics applications.