Physical Effects And Sensing Applications In Optical Coupled Microring Resonators

In recent years,integrated microring resonators have attracted intensive research attentions because of their advantages in compact sizes,high performance,and CMOS compatibility.Integrated microring resonators are promising optical devices to realize various on-chip functional devices,such as lasers,modulators,filters,logic gates,and biological sensors.By coupling more than one microrings together,or coupling microring with other photonic components,various coupled-microring structures are constructed,promising to further enhance device performances.On the other hand,many interesting physical effects analogous with quantum field phenomena,such as electromagneticallyinduced-transparency(EIT)and Fano effects,could also be found in coupled-microring structures when parameters are properly chosen.Although coupled-microring structures have been studied preliminarily,previous works are mainly focused on the realization of a specific application with one type of coupled-microring resonators,and there is still a lack of an in-depth and general theoretical investigation.In this work,we conducted a thorough theoretical study on various coupled-microring structure types,with an emphasis on the intriguing physical effects and their practical applications.Detailed works are summarized as follows:First,we identified for the first time various phase regimes of EIT effect in optical integrated microrings and gave a fundamental physical explanation to it.The new EIT phase characteristics could be utilized to further enhance optical delay and nonlinearity properties as compared to those obtained from a traditional EIT phase regime.These phase features exist ubiquitously in coupled resonance systems.As an example,we also demonstrated their performance improvement to the quantum phase gate.Second,we demonstrated for the first time the “superfine spectrum”in MR-FP systems,which could be regarded as an “embedded”EIT effect,and its origin.This high-Q spectral feature is robust against various fabrication errors,and could be of great significance to optical filters,switches,and modulators.Third,we investigated the reverse Fano effect(reported firstly in quantum system)in embedded micoring structures.We also compared the sensing performance of embedded rings working in reversed Fano regime as to those in common Fano regime,and found reversed Fano effect is much more advantageous.Combining the theoretical analysis with low-thermal-noise and low-loss optical waveguide design,we designed an optical biochemical sensor with high sensitivity and ultra-low limit of detection(LOD).Fourth,we developed performance quantifications for optical integrated sensing systems based on intensity detection.Various noise sources are identified and classified into different mechanisms.We also analyzed the impact of noises on systematic signal-tonoise ratio(SNR)and LOD for different microcavity types,and proposed design guidelines for microcavity-based sensing system in terms of noise suppression and LOD improvement.Fifth,three coupled microring structures are compared,as an example,as gas sensors.Multiple groups of parameters are analyzed to find the best parameter region for each type of coupled rings.These results help us to gain a more generalized understanding of coupled microring structures,and provide theoretical foundations for the design of other optical functional device based on coupled-microrings structures.