Nanostructured materials for laser science

这个研究项目包括用简单的方法开发纳米结构材料，然后将其用于固态激光器件，以增强其发射特性。这项研究建立在我们最近在纳米结构薄膜制造方面取得的进展的基础上，纳米结构的孔隙度和纳米结构可以调整其光学特性。使用一种称为掠角沉积的技术，我们能够从最初的各向同性材料中制造出具有非常高双折射和光活性的人造材料。我们还可以用椭偏法来表征这些复合材料的光学常数。我们将使用这些薄膜作为激光谐振器的内部元件，以产生有关偏振态，模式轮廓和发射光谱的原始发射特性。我们还致力于使这些解决方案具有功率可扩展性，即能够承受高输出功率的解决方案。我们将重点关注激光二极管泵浦掺Yb3+陶瓷，因为它们具有适合功率缩放和小型化的热学和机械特性。薄膜的高多孔纳米结构也使得通过使用发光溶胶-凝胶溶液的浸渍工艺来改变其“主动”光学特性成为可能。多孔薄膜将被用作支架，为各向异性发光分子施加特定的排列。在应用方面，我们将制造高度各向异性的薄膜输出耦合器反射镜，使其能够实现紧凑的高重复率脉冲激光器，其偏振状态（否则是随机的）得到很好的定义。我们还将在某些规定的共振波长上使用圆形布拉格反射来获得单一频率的激光发射。由此产生的光谱亮度增强将有助于增强非线性晶体中的波长转换或用于超高亮度激光器的相干光束组合。结合微芯片激光器设计的小型化潜力，这项研究可以生产出价格合理的高亮度激光器设计，而无需求助于大型基础设施。本研究计划将培养学生在材料科学和光学之间的理论和实验，以及基础和应用方面的接口。

This research program consists in developing nanostructured materials with simple methods and then using them in solid-state laser devices to enhance their emission characteristics. This research builds on recent progress we have made on the fabrication of nanostructured thin films, the porosity and nanostructure of which can be tailored to tune their optical properties. Using a technique known as glancing angle deposition, we were able to make artificial materials that display very high birefringence and optical activity from initially isotropic materials. We can also characterize the optical constants of these complex materials with ellipsometry. We will use these thin films as internal elements of a laser resonator to produce original emission characteristics with respect to the polarization state, mode profile, and emission spectrum. We also aim at making these solutions power-scalable, i.e., solutions that can withstand high output powers. We will focus on laser-diode-pumped Yb3+-doped ceramics because they have suitable thermal and mechanical characteristics for power scaling and miniaturization. The highly porous nanostructure of the thin films also makes it possible to modify their ''active'' optical characteristics by using a dipping process with luminescent sol-gel solutions. The porous thin film will be used as a scaffold that imposes a specific arrangement for the anisotropic luminescent molecules. As for applications, we will fabricate highly anisotropic thin-film output coupler mirrors that make it possible to realize a compact high-repetition-rate pulsed laser, of which the polarization state, otherwise random, is well defined. We will also use circular Bragg reflection at some prescribed resonance wavelength to obtain laser emission at one single frequency. The resulting enhanced spectral brightness will be useful for enhanced wavelength conversion in a nonlinear crystal or for coherent beam combining for ultra-high-brightness lasers. Combined with the miniaturization potential of microchip lasers design, this research could produce affordable high-brightness laser designs without resorting to large infrastructures. This research program will train students in theoretical and experimental, as well as fundamental and applied aspects at the interface between materials science and optics.