Coherent acoustic phonon generation and development of terahertz cryogenic acoustic microscope

威尔逊0622060这项研究的目的是研究一种通过脉冲毫米波激光辐射产生高频(太赫兹)声波的新技术。该方法将首先证明声波产生技术的可行性，然后测试可使相干太赫兹声波诱导电磁辐射脉冲的反向过程，为开发能够以纳米级分辨率进行亚表面成像的声学显微镜做准备。智力价值拟议中的研究涉及一套具有挑战性的实验测量，该系统由太赫兹激光脉冲激发的掺杂半导体超晶格组成。这项研究肯定会加强关于高频声子产生和探测的知识库。设想的声学显微镜可以具有非常高的空间分辨率，接近纳米级范围。更广泛的影响拟议研究的主要应用是开发一种低温声学显微镜，该显微镜使用超流氦作为声子源/探测器和待成像样品之间的传输流体。这种显微镜如果具有纳米级的精度，可以为半导体纳米结构中的界面、衬底表面和掺杂分布的非侵入性成像提供新的方法，在生物材料和传感器方面具有潜在的应用前景。此外，通过在位于传统经济贫困地区的西弗吉尼亚州(主要是本科生)大学提供现代研究机会，更多的阿巴拉契亚本科生可能会决定攻读物理科学和工程方面的高级学位和职业。

Wilson 0622060 The objective of this research is to investigate a new technique for the generation of high-frequency (terahertz) acoustic waves by pulsed millimeter-wave laser radiation. The approach will be to first demonstrate the feasibility of the acoustic wave generation technique, followed by testing the reverse process whereby coherent terahertz acoustic waves can be made to induce pulses of electromagnetic radiation, in preparation for the development of an acoustic microscope capable of subsurface imaging with nanometer-scale resolution. Intellectual MeritThe proposed research involves a challenging set of experimental measurements in a novel phonon generating system that consists of a doping semiconductor superlattice excited by terahertz laser pulses. The research would certainly enhance the knowledge base concerning the generation and detection of high-frequency phonons. The envisioned acoustic microscope could have a very high spatial resolution approaching the nanometer-scale range. Broader Impacts The primary application of the proposed research is towards the development of a cryogenic acoustic microscope that uses superfluid helium as the transmitting fluid between phonon source/detector and sample to be imaged. Such a microscope, if it possessed nanometer scale accuracy, could provide new methods for non-invasive imaging of interfaces, substrate surfaces, and doping profiles in semiconductor nanostructures, with potential applications in biological materials and sensors. Furthermore, by providing modern research opportunities at a West Virginia state (primarily undergraduate) university, located in a traditionally economically disadvantaged area, larger numbers of Appalachian undergraduates may decide to pursue advanced degrees and careers in the physical sciences and engineering.