Topological interface states are formed when two photonic crystals with overlapping band gaps are brought into contact. In this work, we show a planar binary structure with such an interface state in the visible spectral region. Furthermore, we incorporate a thin layer of an active organic material into the structure, providing gain under optical excitation. We observe a transition from fluorescence to lasing under sufficiently strong pump energy density. These results are the first realization of a planar topological laser, based on a topological interface state instead of a cavity like most of other laser devices. We show that the topological nature of the resonance leads to a so-called “topological protection”, i.e. stability against layer thickness variations as long as inversion symmetry is preserved: even for large changes in thickness of layers next to the interface, the resonant state remains relatively stable, enabling design flexibility superior to conventional planar microcavity devices.

中文翻译：

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一维平面拓扑激光器

当两个带隙重叠的光子晶体接触时，就会形成拓扑界面态。在这项工作中，我们展示了在可见光谱区域具有这种界面态的平面二元结构。此外，我们在结构中加入了一层薄薄的活性有机材料，在光激发下提供增益。我们观察到在足够强的泵浦能量密度下从荧光到激光的转变。这些结果是平面拓扑激光器的首次实现，它基于拓扑界面态而不是像大多数其他激光设备一样的腔。我们表明，共振的拓扑性质导致所谓的“拓扑保护”，即只要保持反转对称性，就可以稳定地抵抗层厚度变化：