Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, Calle Sor Juana Ines de la Cruz 3, 28049 Madrid, Spain.
Sci Rep. 2017 Jan 10;7:40141. doi: 10.1038/srep40141.
Two major elements are required in a laser device: light confinement and light amplification. Light confinement is obtained in optical cavities by employing a pair of mirrors or by periodic spatial modulation of the refractive index as in photonic crystals and Bragg gratings. In random lasers, randomly placed nanoparticles embedded in the active material provide distributed optical feedback for lasing action. Recently, we demonstrated a novel architecture in which scattering nanoparticles and active element are spatially separated and random lasing is observed. Here we show that this approach can be extended to scattering media with macroscopic size, namely, a pair of sand grains, which act as feedback elements and output couplers, resulting in lasing emission. We demonstrate that the number of lasing modes depends on the surface roughness of the sand grains in use which affect the coherent feedback and thus the emission spectrum. Our findings offer a new perspective of material science and photonic structures, facilitating a novel and simple approach for the realization of new photonics devices based on natural scattering materials.
光限制和光放大。光学腔中的光限制通过使用一对镜子或通过折射率的周期性空间调制来实现，如在光子晶体和布拉格光栅中。在随机激光器中，随机放置在活性材料中的纳米粒子为激光作用提供分布式光学反馈。最近，我们展示了一种新的架构，其中散射纳米粒子和活性元件在空间上分离，并观察到随机激光。在这里，我们表明这种方法可以扩展到具有宏观尺寸的散射介质，即一对沙粒，它们充当反馈元件和输出耦合器，从而产生激光发射。我们证明，激光模式的数量取决于所用沙粒的表面粗糙度，这会影响相干反馈，从而影响发射光谱。我们的发现为材料科学和光子结构提供了新的视角，为基于自然散射材料的新型光子器件的实现提供了一种新颖而简单的方法。
