Quantum Interference Control of Photoexcited Carriers for K-Space Microscopy

非技术描述：显微镜是科学和技术中普遍存在和熟悉的工具。它通过确定正在研究的样品内对象的空间位置来提供信息。对于光学显微镜，光必须在空间上局部化，即，聚焦，以能够确定空间位置。该项目将探索固体中光学显微镜的另一种形式，其中物体的动量（这里是电子）将被确定，而不是它们的位置。为了解析电子的动量，光必须聚焦在动量上，这是通过单个光子的吸收和多个光子的吸收之间的干涉来实现的。通过这种方法获得的信息将深入了解固体的动量结构，也称为能带结构，这决定了它们的基本性质，例如它们是绝缘体，导体还是半导体。它还将表征动量的变化，这与由固体制成的设备的操作特性有关。该项目的广泛影响包括为研究生和本科生提供先进光学方法的独特培训，并为半导体行业提供新工具，以表征和完善用于电子和光电产品的材料和器件。技术描述：该提案描述了一个实验项目，以解决缺乏动力的问题-通过在涉及不同数量光子的吸收路径之间使用量子干涉来实现载流子分布的光学方法中的空间灵敏度，在k空间中。双光子和三光子吸收过程之间的干涉提供了横向动量的定位，打开了选择性探测k空间区域的大门，或者在动量空间中进行“显微镜”。这种能力最终将允许光学方法对能带结构和能带内的载流子分布敏感。除了提供有关能带结构的信息外，选择性激发k空间区域的能力还将提供有关非平衡电子激发如何热化和恢复平衡的独特信息。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

Non-technical Description:Microscopy is a ubiquitous and familiar tool in science and technology. It provides information by determining the spatial location of objects within a sample being studied. For optical microscopy, light must be spatially localized, i.e., focused, to enable the determination of spatial locations. This project will explore an alternate form of optical microscopy in solids where the momentum of an object, here electrons, will be determined, rather than their positions. To resolve the momentum of the electrons, the light must be focused in momentum, which is achieved by interference between absorption of a single photon and absorption of multiple photons. The information gained by this method will give insight into the momentum structure, also known as the band structure, of solids, which determine their fundamental properties such as whether they are insulators, conductors or semiconductors. It will also characterize changes in momentum, which are relevant for operating properties of devices made from the solids. The broader impacts of this project include unique training for graduate and undergraduate students in sophisticated optical methods and providing new tools for the semiconductor industry to characterize and perfect materials and devices used for electronics and optoelectronic products.Technical Description:This proposal describes an experimental project to address the lack of momentum-space sensitivity in optical methods by using quantum interference between absorption pathways involving different numbers of photons to achieve carrier distributions that are both asymmetric and localized in k-space. The interference between two-photon and three-photon absorption processes provides localization in the transverse momentum, opening the door to selectively probing regions of k-space, or performing “microscopy" in momentum-space. This ability would ultimately allow optical methods to be sensitive to band structure and carrier distributions within the bands. Beyond providing information about the band structure, the ability to selectively excite regions of k-space will provide unique information about how non-equilibrium electronic excitations thermalize and return to equilibrium.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.