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

非技术抽象材料在极端条件下的行为通常是有新的基本发现和开发新应用的地方。这个项目的作者研究了两种不同液体之间在极软极限下的界面行为，使材料变得更软会导致热振荡对界面的破坏。这个项目将利用球面两侧折射率的差异来研究限制在球面内部的光。这种新的限制使研究人员能够利用限制光的模式以前所未有的分辨率和精度研究超软界面的热涨落细节。除了提供有关分子热运动的信息外，受界面限制的光学激发允许研究人员光学地影响其机械振荡，而机械振荡反过来又会影响光学激发。这种所谓的光机械相互作用有望在超软材料中得到显著增强，并将使研究新的光机械现象成为可能。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，方法是围绕该项目的主题开发新的课程，并让学生，特别是来自代表性不足群体的学生参与该项目的工作。特别是，这个项目将资助皇后学院光子学硕士项目的一名学生的研究实习机会，该项目旨在帮助代表人数不足的群体的学生进入与光子学相关的劳动力市场。技术摘要本项目研究液体中球形液滴作为耳语画廊模谐振器驱动的光力学特性。液滴形成界面的弹性由表面活性剂控制，并可以降低到极端柔软的极限，因此任何添加的表面活性剂都会通过布朗波动来破坏液滴。液滴的机械柔软性不影响其作为光学谐振器的性能，这是由液滴材料与周围介质之间的折射率对比度决定的。机械柔软性和由于耳语走廊模式的形成而产生的共振增强的灵敏度相结合，使得能够以超过现有瑞利限制成像技术的分辨率来光学询问表面的布朗起伏。液滴的极度柔软导致了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远超过任何其他可用的光学机械系统的光机耦合强度。极强的光机耦合机制使得对光机现象的研究远远超出了通常可用的参数范围。例如，在这些系统中，人们可以实现有效的腔中介冷却表面振荡到最小的声子布居数，尽管较低的声子频率施加了惩罚。该项目的高价值目标是冷却软化液滴向量子力学基态的毛细振荡，同时将浴缸保持在室温下。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，将发展一种新的基于广义Mie散射理论的微扰方法来计算形状偏离球面的谐振器的光谱。还将开发边带冷却理论，以将未解决的边带限制处的声子数量降至最低。该奖项反映了NSF的法定使命，并已通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.