Single-aperture cavities are a key component of lasers, instrumental for the amplification and emission of a single light mode. However, the appearance of high-order transverse modes as cavities size increases has frustrated efforts to scale up cavities whilst preserving single-mode operation since the invention of the laser six decades ago^1-8. A suitable physical mechanism that allows single-mode lasing irrespective of the cavity size – a “scale-invariant” cavity or laser – has not been identified yet. Here, we propose and demonstrate experimentally that open-Dirac electromagnetic cavities with linear dispersion – which in our devices are realized by a truncated photonic crystal arranged in a hexagonal pattern – exhibit unconventional scaling of losses in reciprocal space, leading to single-mode lasing that is maintained as the cavity is scaled up in size. The physical origin of this phenomenon lies in the convergence of the complex part of the free spectral range in open-Dirac cavities towards a constant governed by the loss rate of distinct Bloch band, while for common cavities it converges to zero as the size grows, leading to inevitable multi-mode emission. An unconventional flat envelope fundamental mode locks all unit-cells in the cavity in phase, leading to single-mode lasing. We name such sources Berkeley Surface Emitting Lasers (BerkSELs) and demonstrate that their far-field corresponds to a topological singularity of charge two, in agreement with our theory. Open-Dirac cavities unlock new avenues for light-matter interaction and cavity quantum electrodynamics.

单孔径腔是激光器的关键组件，有助于放大和发射单光模式。然而，自六十年前激光器发明以来，随着腔体尺寸的增加，高阶横向模式的出现阻碍了扩大腔体同时保持单模操作的努力^1-8. 尚未确定一种合适的物理机制，该机制允许单模激光发射而与腔体尺寸无关——“尺度不变”腔体或激光器。在这里，我们提出并通过实验证明了具有线性色散的开放狄拉克电磁腔——在我们的设备中是通过以六边形图案排列的截短光子晶体实现的——在倒易空间中表现出非常规的损耗比例，从而导致单模激光随着腔体尺寸的扩大，保持不变。这种现象的物理起源在于开放狄拉克腔中自由光谱范围的复杂部分向由不同布洛赫带的损耗率控制的常数收敛，而对于普通腔，它随着尺寸的增长而收敛到零，导致不可避免的多模发射。非常规的扁平包络基模将腔内的所有晶胞同相锁定，从而产生单模激光。我们将这些源命名为伯克利表面发射激光器 (BerkSEL)，并证明它们的远场对应于电荷 2 的拓扑奇点，这与我们的理论一致。Open-Dirac 腔为光物质相互作用和腔量子电动力学开辟了新途径。