NSF-BSF:Fluid-fluid interfaces with diminished surface tension and giant thermal and quantum fluctuations as novel materials for ultrasoft photonics

材料在极端条件下的行为往往是新的基础发现和新的应用开发的地方。该项目的作者研究了两种不同液体之间的界面在极端柔软度极限下的行为，使得材料即使稍微柔软一点也会导致热振荡破坏界面。本项目将利用界面两侧的折射率差异，研究限制在球面界面内部的光。这种新颖的限制使研究人员能够使用受限光的模式以前所未有的分辨率和精度研究超软界面的热波动的细节。除了提供有关分子热运动的信息外，界面限制的光学激发允许研究人员光学影响其机械振荡，这反过来又会影响光学激发。这种所谓的光机相互作用预计将显着增强超软材料，并将允许研究新的光机现象。这一国际合作项目还将促进两个参与机构（纽约皇后学院和以色列特拉维夫大学）的教育活动，围绕项目主题开发新课程，并让学生，特别是代表性不足群体的学生参与项目工作。特别是，该项目将资助一名学生在皇后学院的硕士研究实习机会。在光子学计划，旨在帮助学生从代表性不足的群体进入劳动力市场在光子学相关的industries.Technical abstractionThis项目涉及的光学机械性能的流体中流体的球形液滴作为whispering-gallery-mode谐振器驱动。液滴形成界面的弹性由表面活性剂控制，并且可以降低到最终柔软度的极限，使得任何额外的表面活性剂将通过布朗波动破坏液滴。微滴的机械柔软度不会影响其作为光学谐振器的性能，这是由微滴材料与周围介质之间的折射率对比决定的。机械柔软性和由于形成回音壁模式而引起的共振增强灵敏度的组合使得能够以超过现有瑞利极限成像技术的分辨率的分辨率对表面的布朗波动进行光学询问。液滴的极端柔软性导致对共振增强的光学力的巨大机械响应，使研究人员能够实现远超过任何其他可用的光机系统的光机耦合强度。极强的光机耦合的制度，使研究的光机现象，以及通常可用的参数范围之外。例如，在这些系统中，可以实现有效的腔介导的表面振荡的冷却到最小的声子种群数量，尽管较低的声子频率施加的惩罚。该项目的高价值目标是将软化液滴的毛细振荡冷却到量子力学基态，同时保持浴在室温下。通过在不同温度、压力和表面活性剂吸附浓度下测试各种气-液界面和液-液界面，可以降低此类项目的高风险。实验工作将伴随着理论研究，将开发一种基于广义Mie散射理论的新的微扰方法来计算形状偏离球形的谐振腔的光谱。一个边带冷却的理论也将被开发，以最大限度地减少声子数在未解决的边带limit.This奖项反映了NSF的法定使命，并已被认为是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的支持。

Nontechnical abstractThe behavior of materials under extreme conditions is often where new fundamental discoveries are made and new applications are developed. The authors of this project study the behavior of interfaces between two different liquids in the limit of extreme softness such that by making the material even a little bit softer will result in the destruction of the interface by thermal oscillations. This project will study light confined in the interior part of the spherical interface by using the difference in refraction indexes on the opposite sides of the interface. This novel confinement enables the researchers to study the details of the thermal fluctuations of the ultrasoft interface with an unprecedent resolution and accuracy using the modes of the confined light. In addition to providing information about thermal motion of the molecules, optical excitations confined by the interface allow researchers to optically affect its mechanical oscillations, which will, in their turn affect the optical excitations. Such so-called optomechanical interaction is expected to be significantly enhanced in the ultrasoft materials and will allow studying novel optomechanical phenomena. This international collaborative project will also contribute to educational activities of both participating institutions (Queens College, New York and Tel-Aviv University, Israel) by developing new courses around the themes of the project and involving students, especially those from underrepresented groups, in work on the project. In particular, this project will fund a research internship opportunity for a student at Queens College’s M.S. in Photonics program, designed to help students from underrepresented groups to enter the labor market in photonics related industries.Technical abstractThis project deals with optomechanical properties of fluid-in-fluid spherical droplets actuated as whispering-gallery-mode resonators. The elasticity of the droplet-forming interface is controlled by surfactants and can be reduced to the limit of ultimate softness such that any additional surfactant would destruct the droplet by Brownian fluctuations. The mechanical softness of the droplets does not affect their performance as optical resonators, which is determined by the refractive index contrast between the material of the droplet and the surrounding medium. The combination of mechanical softness and the resonance enhanced sensitivity due to the formation of whispering gallery modes enables the optical interrogation of Brownian fluctuations of the surface with resolution exceeding that of existing Rayleigh- limited imaging techniques. The extreme softness of the droplets results in the giant mechanical response to resonantly enhanced optical forces allowing researchers to achieve a strength of optomechanical coupling far exceeding that in any other available optomechanical system. The regime of the extremely strong optomechanical coupling enables the study of optomechanical phenomena well outside of typically available range of parameters. For instance, in these systems one can achieve efficient cavity-mediated cooling of the surface oscillations to the smallest phonon population numbers despite the penalty imposed by the lower phonon frequencies. The high-value goal of the project is to cool the capillary oscillations of the softened droplets toward the quantum mechanical ground-state while maintaining the bath at room temperature. The high risks of such a project will be mitigated by testing various gas-liquid and liquid-liquid interfaces at different temperatures, pressures, and surfactant adsorption-concentration. The experimental efforts will be accompanied by theoretical research, with a novel perturbation approach based on generalized theory of Mie scattering to computing optical spectra of resonators with shapes deviating from spherical will be developed. A theory will also be developed of sideband cooling to minimize the phonon number at the non-resolved sideband limit.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.