Progress of silicon photonic devices-based Fano resonance

Abstract

The development of silicon photonics provides a method of implementing high reliability and high precision for new micro-nano optical functional devices and system-on-chips. The asymmetric Fano resonance phenomenon caused by the mutual coupling of optical resonant cavities is extensively studied. The spectrum of Fano resonance has an asymmetric and sharp slope near the resonance wavelength. The wavelength range for tuning the transmission from zero to one is much narrow in Fano lineshape, therefore improving the figure of merits of power consumption, sensing sensitivity, and extinction ratio. The mechanism can significantly improve silicon-based optical switches, detectors, sensors, and optical non-reciprocal all-optical signal processing. Therefore, the mechanism and method of generating the Fano resonance, the applications of silicon-based photonic technology, and the physical meaning of the Fano formula’s parameters are discussed in detail. It can be concluded that the primary condition for creating the Fano resonance is that the dual-cavity coupling is a weak coupling, and the detuning of resonance frequency of the two cavities partly determines Fano resonance lineshapes. Furthermore, the electromagnetically induced transparency is generated when the frequency detuning is zero. The methods of generating Fano resonance by using different types of devices in silicon photonics (besides the two-dimensional photonic crystals) and the corresponding evolutions of Fano resonance are introduced and categorized, including simple photonic crystal nanobeam, micro-ring resonator cavity without sacrificing the compact footprint, micro-ring resonator coupling with other structures (mainly double micro-ring resonators), adjustable Mach-Zehnder interferometer, and others such as slit waveguide and self-coupling waveguide. Then, we explain the all-optical signal processing based on the Fano resonance phenomenon, and also discuss the differences among the design concepts of Fano resonance in optimizing optical switches, modulators, optical sensing, and optical non-reciprocity. Finally, the future development direction is discussed from the perspective of improving Fano resonance parameters. The topology structure can improve the robustness of the Fano resonance spectrum; the bound states in continuous mode can increase the slope of Fano spectrum; the Fano resonance can expand the bandwidth of resonance spectrum by combining other material systems besides silicon photonics; the multi-mode Fano resonances can enhance the capability of the spectral multiplexing; the reverse design methods can improve the performance of the device. We believe that this review can provide an excellent reference for researchers who are studying the silicon photonic devices.

Generalized Fano resonance theory based on Fabry-Perot cavity

“…Two primary factors influence the asymmetric Fano line shape: (1) the frequency distribution of the discrete state and continuous state [29,30] and (2) the initial phase distributions of the modes [17,[31][32][33]. These factors affect the occurrence of maximum and minimum values within the Fano line shape, which are connected with the asymmetric parameter q [2,34]. While the TCOM can account for the first factor, it is unable to explain the appearance of distinct Fano line shapes associated with the differing phase distributions of the discrete state and the continuous state.…”

Design of independently tunable dual Fano devices based on asymmetric microrings

“…The transmission spectrum of the microring resonator is usually a symmetrical Lorentzian line. If the narrowband Lorentzian response is superimposed with the broadband background field, an asymmetric resonant linear spectrum will appear, and the formed spectrum is Fano resonance spectrum [3] . The microring resonator itself also has the characteristics of low insertion loss and low crosstalk.…”

Reconfigurable optical filter based on microring resonator assisted by tunable Sagnac reflector

“…) ，其余 MZI 处于可调状态 (0<∆φ<π)时，器件重构为反射式非对称 MZI 滤波器 [17] 。图 3(a)和图 3(b) [19] ，这种现 象常出现在光学耦合谐振腔中 [20,21] 。Out1 端口为类似 EIT 现象的频谱，ER 约为 波长解复用 [17] 和多参量可重构微波光子滤波器 [15] 方面具有极大的潜力。 得益于反射提供的额外相干光干涉路径，自干涉微环滤波器产生了 Fano、 EIT 和 EIA 三种不同线型。其中 Fano 共振型光谱响应能应用于节能型集成光开 关 [23] 。对比洛伦兹线型开关状态的波长调谐量(∆λ L =101.5 pm)，Fano 共振线型只 需要不到 1/2 波长调谐量(2.25 ∆λ F ≈∆λ L ) 。基于 EIT 与 EIA 现象的窄带透射峰与 吸收峰可用于窄带滤波、 精细信号处理、 密集波分复用 [24] 及光学陀螺仪 [25] 等领域。 provides a new degree of design freedoms, breaks the inherent footprint limit, and achieves a wide range of free spectral ranges. Our proposed tunable Sagnac loop reflector assisted microring resonator provides a new scheme for realizing flexible, tunable and multi-functional reconfigurable integrated photonic filters, and has broad applications in the integrated photonic analog signal processing and microwave photonics.…”