Research progress on topological semiconductor lasers
Drawing inspiration from the concept of topological phases in condensed matter physics,topological photonics has undergone significant development.It offers innovative mechanisms for manipulating light fields,including unidirectional edge states,spin-orbit coupled transport,and high-dimensional light field control.Meanwhile,the identification of topological edge states,corner states,and defect states,alongside the integration of diverse semiconductor gain materials(including quantum dots,multi-quantum wells,and perovskites),has promoted the emergence and development of topological lasers.In this paper,we examine the advancements in topological laser research,analyzing the principles,structures,and physical foundations of various topological lasers.Based on topological theory,topological lasers can be broadly categorized into those originating from topological insulators and topological defects.Lasers employing the 1D Su-Schrieffer-Heeger model represent a distinct category.In a topological 1D SSH system,the zero-energy states localized at the boundaries are identified as the topological edge states.Additionally,the domain wall between topological and trivial systems can be regarded as a zero-dimensional dislocation,which hosts the topological defect state.In contrast to conventional microring arrays or photonic crystal lasers,topological lasers exhibit defect immunity and band-gap mode characteristics.These features facilitate the creation of robust single-mode lasers with high efficiency and low thresholds,providing significant advantages in practical applications where environmental stability and reliability are paramount.Meanwhile,certain lasers based on topological insulators excite topological edge states via the quantum Hall effect,quantum spin Hall effect,and valley Hall effect,whereas others induce topological corner states using the 2D Su-Schrieffer-Heeger model and Kagome lattice.The former can construct coherent laser arrays,create traveling-wave resonators with arbitrary profiles,and generate vortex light.The latter features topological nanocavities capable of producing single-mode lasers with narrow spectra,high coherence,and low thresholds.Lasers utilizing topological defects employ Dirac vortex cavities and topological disclination cavities to excite topological defect states.Compared to topological edge states and topological corner states,cavities based on topological defect states offer a large free spectral range,a small far-field divergence angle,and vector light field output.Consequently,these topological lasers exhibit higher power and robustness.Additionally,there are topological bulk lasers based on band-inversion-induced reflection and magic-angle lasers within nanostructured moiré superlattices.These topological lasers are anticipated not only to serve as light sources for photonic integrated chips but also to pave the way for new semiconductor laser development.Moreover,they lay the groundwork for exploring novel phenomena such as non-Hermitian physics,bosonic nonlinearity,and topological quantum electrodynamics,thereby advancing lidar,laser processing,and optical communication technologies.
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