Bandwidth-tunable optical filter based on microring resonator and MZI with Fano resonance
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RESEARCH ARTICLE
Bandwidth-tunable optical filter based on microring resonator and MZI with Fano resonance Xia Li1 • Chen Shen1 • Xiaohan Yu1 • Yanqiong Zhang1 • Chao Chen1 Xiaoxu Zhang1
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Received: 12 January 2018 / Accepted: 1 August 2020 Ó The Author(s) 2020
Abstract A bandwidth-tunable optical filter is fabricated by combining Mach–Zehnder interferometer (MZI) and microring resonator. Both bandwidth red-shift and blueshift are observed in the experiment. The bandwidth can be tuned from 0.46 to 3.09 nm by controlling two phase shifters. The device also shows an extinction ratio higher than 25 dB. Potential applications are integrated optical signal processing such as reconfigurable filtering and channel selecting in wavelength division multiplexer. Keywords Filter Bandwidth tunable Silicon Ring resonator Wavelength division multiplexer
Introduction Wavelength division multiplexing systems play a more and more important role in the next generation telecom networks [1]. In this scenario, the bandwidth-tunable optical filters are one of the basic components. They can be used in the implementation of the gridless paradigm in wavelength division multiplexing systems. To obtain such bandwidth tunability, many solutions have been researched. The recent development of optical ring becomes more and more attractive due to a variety of functionalities such as compact structure, high Q-factor and compatible with mature silicon microelectronics [2–4]. Taking the huge advantages of microring resonators, lots of devices have been used in high
& Xia Li [email protected] 1
Department of Information Science and Electronics Engineering, Zhejiang Gongshang University, Hangzhou 310018, China
sensitive sensors, all optical switching and reconfigurable add–drop filters [5–7]. In previous works, many bandwidthtunable devices have been fabricated utilizing the characteristic of symmetric resonance in microring resonators (MRRs) [8–12]. For example, one is the filter based on a single microring resonator. Its coupling coefficient of the resonator is tuned by micro-electronic-mechanical-system. However, a high actuation voltage of nearly 40 V should be applied to realize the MEMS tunability [5]. Another one is also a filter based on a single microring resonator [13]. Its coupling coefficient of the resonator is tuned by the thermooptic phase shifters. The disadvantage of this filter is that it offers limited bandwidth variation range and poor off-band rejection. There is also a filter combining a MZI and ring resonator, the ring resonators are embedded in the MZI arms, and its bandwidth tuning is limited due to in-band ripples and insertion loss [14]. In this letter, we demonstrate a bandwidth-tunable optical filter based on the ring resonators and MZI with Fano resonance. It consists of two single MRRs and a MZI structure constituted by two 1 9 2 multi-mode interferences (MMI). The coupling coefficients of the two single MRRs are both tuned by the thermo-optic phase shifters. In this new design, the two MRRs, controlled
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