Lasers based on Fabry–Pérot or whispering gallery resonators generally require complex fabrication stages and sensitive alignment of cavity configurations. The structural defects on reflective surfaces result in scattering and induce optical losses that can be detrimental to laser performance. On the other hand, random lasers can be simply obtained by forming disordered gain media and scatterers, but they generally show omnidirectional emission with a low Q-factor. Here, we demonstrate directional random lasers with a high Q-factor emission (∼1.5 × 10⁴) via self-assembled microstructural cracks that are spontaneously formed upon radial strain-release of colloidal nanoparticles from the wet to dry phase. The rough sidewalls of cracks facilitate light oscillation via diffuse reflection that forms a spatially localized feedback, and they also serve as the laser out-coupler. These self-assembled cracks exhibit random lasing at optical pump powers as low as tens of μJ/mm². We demonstrate a wide variety of random lasers from nano- and biomaterials including silica nanoparticles, fluorescent proteins, and biopolymers. These findings pave the way toward self-assembled, configurable, and scalable random lasers for sensing, displays, and communication applications.

中文翻译：

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高Q，定向和自组装随机激光发射，使用通过裂纹的空间局部反馈

基于法布里-珀罗（Fabry-Pérot）或耳语回音壁谐振器的激光器通常需要复杂的制造阶段以及对腔体配置的敏感对准。反射表面上的结构缺陷会导致散射，并引起可能对激光性能有害的光学损耗。另一方面，可以通过形成无序的增益介质和散射体来简单地获得随机激光器，但是它们通常显示出具有低Q因子的全向发射。在这里，我们演示了具有高Q因子发射（〜1.5×10 ^4）的定向随机激光器）是通过自组装的微结构裂纹而形成的，这种裂纹是在胶体纳米颗粒从湿相向干相径向释放时自发形成的。裂纹的粗糙侧壁通过扩散反射促进了光的振荡，该扩散反射形成了空间局部的反馈，并且它们还用作激光输出耦合器。这些自组装的裂纹在低至数十μJ / mm ^2的光泵浦功率下表现出随机激射。我们展示了来自纳米和生物材料的各种随机激光，包括二氧化硅纳米颗粒，荧光蛋白和生物聚合物。这些发现为自组装，可配置和可扩展的随机激光器铺平了道路，可用于传感，显示和通信应用。