Collaborative Research: Nanoprobes for mapping the spatiotemporal evolution of ultrafast optical vector near field

合作研究：用于绘制超快光矢量近场时空演化图的纳米探针

• 批准号: 1711036
• 负责人: Yizheng Zhu
• 金额: $ 6万
• 依托单位: Virginia Polytechnic Institute and State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-07-15 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1711036&HistoricalAwards=false
• 关键词: Collaborative; Research; Nanoprobes; mapping; spatiotemporal

Advances in optical nanotechnology have enabled a wide range of applications, such as increased sensitivity for the detection of just a few molecules with plasmonic nanoparticles. To quantify the performance of optical devices and develop new capabilities, it is essential to measure the behaviors of ultrafast optical fields with nanoscale spatial resolution and femtosecond scale temporal resolution. To address the challenge, this program engenders a novel type of nanoprobe, integrated with a custom near-field scanning microscope system, for comprehensive characterization of the ultrafast optical near field. The research program will enhance understanding by combining the expertise of three researchers in different research areas at three universities. The exciting areas in ultrafast optics and nano-optics will provide excellent education opportunities for graduate and undergraduate as well as K-12 students in the lab, in the classroom, and through outreach activities. Graduate and undergraduate students will be trained through the research activities such as nanoprobe fabrication, application of near-field scanning optical microscope system, optical measurements, and numerical simulation and retrieval in a collaborative setting across the three universities. Results will be incorporated into courses. In keeping with prior projects of the researchers, women and underrepresented groups will be encouraged and expected to participate in the program.The goal of this program is to develop a nanoprobe based characterization method that can map the spatiotemporal evolution of ultrafast optical vector near field in nanometer-femtosecond scale. A nanoprobe, which consists of a second order nonlinear nanocrystal perched on a nanowire or a near-field scanning optical microscope (NSOM) probe, will be integrated with a custom-built NSOM system to achieve sample-probe distance control and nanoscale spatial resolution. The nonlinear response of the nanocrystal (i.e., second harmonic generation -SHG) can be exploited to characterize both the amplitude and the phase profiles of the local ultrafast field as well as the spatiotemporal evolution through the collinear SHG frequency resolved optical gating (FROG) holography. Due to the presence of a strong "local oscillator" and the reliance on homodyne detection, FROG holography will also improve the measurement sensitivity. Finally, polarized SHG from the nanoprobe is utilized to probe the polarization of the local ultrafast optical field. Since the second harmonic signal has a distinct wavelength, it is insensitive to any background noise generated by the reflection or scattering of the fundamental field. Further, the second order nonlinear tensor is determined by the material properties such as the crystal structure and is largely independent of the particle morphology, leading to a more controllable nanoprobe sensor. Knowledge of the local spatiotemporal fields enhances the capability to quantify spectroscopic signals from plasmonic structures, a long-standing challenge in nanospectroscopy.

光学纳米技术的进步已经实现了广泛的应用，例如通过等离子体纳米粒子提高了检测少数分子的灵敏度。为了量化光学器件的性能并开发新功能，必须以纳米级空间分辨率和飞秒级时间分辨率测量超快光场的行为。为了应对这一挑战，该计划产生了一种新型纳米探针，与定制的近场扫描显微镜系统集成，用于超快光学近场的全面表征。该研究计划将通过结合三所大学不同研究领域的三名研究人员的专业知识来增进理解。超快光学和纳米光学领域的激动人心的领域将为研究生和本科生以及 K-12 学生在实验室、课堂和外展活动中提供极好的教育机会。研究生和本科生将在三所大学的合作环境中通过纳米探针制造、近场扫描光学显微镜系统应用、光学测量以及数值模拟和检索等研究活动接受培训。结果将纳入课程中。为了与研究人员之前的项目保持一致，将鼓励并期望女性和代表性不足的群体参与该计划。该计划的目标是开发一种基于纳米探针的表征方法，该方法可以绘制超快光矢量近场的时空演化图。纳米飞秒尺度。纳米探针由安装在纳米线上的二阶非线性纳米晶体或近场扫描光学显微镜 (NSOM) 探针组成，将与定制的 NSOM 系统集成，以实现样品探针距离控制和纳米级空间分辨率。纳米晶体的非线性响应（即二次谐波生成 -SHG）可用于表征局部超快场的振幅和相位分布，以及通过共线 SHG 频率分辨光门控 (FROG) 全息术的时空演化。由于存在强大的“本地振荡器”以及对零差检测的依赖，FROG全息术还将提高测量灵敏度。最后，利用纳米探针的偏振二次谐波来探测局部超快光场的偏振。由于二次谐波信号具有不同的波长，因此它对基波场的反射或散射产生的任何背景噪声不敏感。此外，二阶非线性张量由晶体结构等材料特性决定，并且很大程度上独立于颗粒形态，从而形成更可控的纳米探针传感器。对局部时空场的了解增强了量化等离子体结构的光谱信号的能力，这是纳米光谱学中长期存在的挑战。