基于硅基光子器件的Fano共振研究进展

Progress of silicon photonic devices-based Fano resonance

硅基光子技术的发展为新型微纳光学功能器件和片上系统提供了高可靠、高精度的实现手段.采用硅基光子技术构建的具有连续(准连续)模式微腔与离散模式的微腔耦合产生的Fano共振现象得到了广泛关注.Fano共振光谱在共振波长附近具有不对称且尖锐的谐振峰,传输光的强度在共振波长附近从0突变为1,该机制可显著提高硅基光开关、探测器、传感器,以及光非互易性全光信号处理的性能.本综述分析了Fano共振的一般数学表述,总结了当前硅基光子微腔耦合产生Fano共振的理论模型研究现状,讨论了不同类型硅光器件实现Fano共振的方法,比较各种方案优劣及适用场合,梳理了Fano共振在全光信号处理方面的应用研究情况.最后探讨存在的一些问题及未来可能的相关研究方向.

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 selfcoupling 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.