Tunable narrow-band single-channel add-drop integrated optical filter with ultrawide FSR

Abstract Free-spectral-range (FSR)-free optical filters have always been a critical challenge for photonic integrated circuits. A high-performance FSR-free filter is highly desired communication, spectroscopy, and sensing applications. Despite significant progress in filters, the with tunable narrow-band, high out-of-band rejection, large fabrication tolerance has rarely demonstrated. In this paper, we propose an exact robust design method add-drop (ADFs) operation capability, sub-nanometer bandwidth, rejection (OBR) ratio. The achieved 3-dB bandwidth of < 0.5 nm OBR ratio 21.5 dB within waveband 220 nm, which to best our knowledge, largest-FSR ADF demonstrated on silicon platform. exhibits tunability 12.3 heating efficiency 97 pm/mW maintains feature whole tuning process. addition, fabricated series ADFs different periods, all showed reliable excellent performances.