Y. Ren, D. Perron, F. Aurangozeb, Z. Jiang, M. Hossain and V. Van, “Silicon Photonic Vernier Cascaded Microring Filter for Broadband Tunability,” in IEEE Photonics Technology Letters, vol. 31, no. 18, pp. 1503-1506, 15 Sept.15, 2019. (web)