In sufficiently strong scattering media, light transport is suppressed and modes are exponentially localized. Anderson-like localized states have long been recognized as potential candidates for high-${Q}$ optical modes for low-threshold, cost-effective random lasers. Operating in this regime remains, however, a challenge since Anderson localization is difficult to achieve in optics, and nonlinear mode interaction compromises its observation. Here, we exhibit individually each lasing mode of a low-dimension solid-state random laser by applying a non-uniform optical gain. By undoing gain competition and cross-saturation, we demonstrate that all lasing modes are spatially localized. We find that selective excitation significantly reduces the lasing threshold, while lasing efficiency is greatly improved. We show further how their spatial locations are critical to boost laser power efficiency. By efficiently suppressing the spatial hole burning effect, we can turn on the optimally outcoupled random lasing modes. Our demonstration opens the road to the exploration of linear and nonlinear mode interactions in the presence of gain, as well as disorder-engineering for laser applications.

中文翻译：

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随机激光器中揭示的局部模式

在足够强的散射介质中，光传输受到抑制，模式呈指数局部化。长期以来，类似安德森的局部状态一直被认为是高${Q}$ 的潜在候选者用于低阈值、具有成本效益的随机激光器的光学模式。然而，在这种情况下操作仍然是一个挑战，因为在光学中难以实现安德森定位，并且非线性模式相互作用会影响其观察。在这里，我们通过应用非均匀光学增益来单独展示低维固态随机激光器的每种激光模式。通过消除增益竞争和交叉饱和，我们证明所有激光模式都是空间局部化的。我们发现选择性激发显着降低了激光阈值，同时大大提高了激光效率。我们进一步展示了它们的空间位置如何对提高激光功率效率至关重要。通过有效抑制空间烧孔效应，我们可以打开最佳外耦合随机激光模式。