多模硅基光子学的最新进展(特邀)

Latest Developments in Multimode Silicon Photonics(Invited)

近年来,多模光子学迅速发展,受到越来越多的关注。通过突破单模条件并引入多模波导,多模光子器件展现出独特的研究价值和应用潜力。特别是,硅光波导具有超大折射率差和超强模式色散等特性,为高性能多模光子器件的实现提供了关键物理基础。随着硅光波导模式特性及调控研究的不断深入,多模光子学逐渐形成一个独具特色的新体系,主要包括模式复用器件、高阶模辅助光子器件、展宽波导器件等。本文聚焦于多模硅基光子学的发展,回顾和总结了近年来该领域面向不同应用的重要进展,并对其未来发展进行了展望。

Significance Multimode photonics has become increasingly attractive globally in recent years due to its potential for achieving ultra-high-performance on-chip photonic devices and large-scale photonic integration.This potential is realized through the introduction of broadened optical waveguides and the controlled manipulation of their fundamental and higher-order modes.Without necessitating changes to the fabrication process,multimode photonics overcomes the performance bottleneck previously inherent to single-mode condition-designed photonic devices.Consequently,this field paves the way for developing high-performance photonic devices without increasing fabrication complexity.High-index-contrast multimode photonic waveguides with strong mode dispersion play a key role in multimode photonics.Successful developments in this area have shown great potential for meeting application demands.Silicon photonic waveguides are particularly advantageous due to their ultra-small cross sections,low-cost fabrication,and strong mode dispersion from their ultra-high index contrast,providing a solid fundamental for high-performance multimode photonic devices.Flexible mode manipulation has proven multimode photonics to be extremely useful,leading to three types of devices:mode-division-multiplexed photonic devices,high-order-mode-assisted photonic devices,and broadened-waveguide photonic devices.Progress Initially,multimode photonic devices for mode-multiplexing systems offer significant benefits such as low loss,minimal crosstalk,and wide bandwidth,enabling support for multiple channels.Notable among these are multi-channel mode-division(de)multiplexing(MDM)devices,multimode waveguide bends,and crossings,demonstrating exceptional channel expansibility.Integrating MDM with wavelength-division multiplexing(WDM)and polarization-division-multiplexing establishes multi-dimensional multiplexing systems,offering promising solutions for high-capacity data transmissions.However,efficiently coupling multi-mode optical waveguides with few-mode fibers remains challenging,requiring further research to minimize coupling loss and inter-mode crosstalk.In photonic engineering,a shift towards multimode photonic waveguides beyond the conventional single-mode regime has revealed unparalleled potential.This approach has led to propagation losses and random phase errors at remarkably low levels,surpassing the limitations of traditional single-mode waveguides.Notably,this opens possibilities for key photonic components like ultra-low-loss optical delay lines,ultrahigh-Q microcavities,arrayed-waveguide gratings(AWGs)with significantly low crosstalk,and Mach-Zehnder interferometers(MZIs)with near-zero random phase errors.These advancements break existing performance ceilings,offering a promising direction for large-scale photonic integration.The advent of silicon photonic devices utilizing higher-order modes marks a new era of substantial development potential.By harnessing the transition from using only the fundamental mode to incorporating both fundamental and higher-order modes,these devices employ unique properties of higher-order modes to achieve previously unattainable feats.This includes special functional elements capable of precise polarization manipulation,adaptive dispersion control,and bandpass filtering,evidenced by efficient polarization beam splitters and rotators,dynamically tunable dispersion compensating chips,and sophisticated multi-channel photonic filters with box-like responses,underscoring the significant impact of higher-order-mode-assisted silicon photonics.As multimode photonic technologies advance,a sophisticated range of high-performance devices is emerging,playing an increasingly critical role within optical systems spanning transceivers,routing,and quantum optics.The introduction of MDM highlights the need for reconfigurable optical add-drop multiplexer(ROADM)chips capable of agile mode channel manipulation.Research in multimode photonics also ventures into quantum optic chips,transcending classical integrated photonics.Conclusions and Prospects In essence,breaking free from the constraints imposed by the single-mode condition unveils a plethora of innovative opportunities and intricate challenges in integrated photonics.This paradigm shifts purred the emergence of multimode photonics,already celebrated for pioneering functional implementation and performance enhancement.Breakthroughs in multimode photonics lay a cornerstone in the ongoing quest for superior photonic devices and serve as essential scaffolding for large-scale photonic integration,playing a pivotal role in advancing the field towards a new era of photonics technological advancements.