基于纳米机械振子耦合系统的全光质谱仪的研究

The mass of molecule is traditionally measured using mass.spectrometry, in which the molecules have to be ionized in the first instance and the charge on the ionized molecule needs to be known before their mass can be extracted . But not all molecules are easy to ionize, and uncertainty about the charge of the molecules lead to uncertainty in the mass values reported. In recent years, the mass spectrometries based on NEMS have been studied by many research groups. These mass spectrometries rely on a resonant frequency-shift due to an accreted mass and do not need the process of molecules' ionization.In conventional electrical detection, the nanomechanical resonators should be suspended between two electrodes above a conducting plate, while a voltage applies through them. However, most of these electrical approaches requires the device to be operated at high magnetic fields and at low temperatures. As motivated by optical pump-probe technique researches, we shall propose a novel optical mass sensing method based on some coupled nanomechanical resonator systems. This mass sensor proposed here is so far the first all-optical measurement without any electrical parameters. In the presence of a strong pump field, the accreted mass landing on the resonator can be weighed easily and precisely due to the frequency-shift in the probe absorption spectrum. Taking advantage of long vibrational lifetime of nanomechanical resonator and two-laser excitations, our optical method has much more sensitivity and accuracy in measuring individual molecular mass than conventional electric method which just applies to the relative low-frequency (less than 1 GHz) of nanomechanical resonator.This all-optical mass sensing has the potential to break through the limitation of frequency restriction and will enhance the sensitivity of mass sensing. Also this mass sensor may lead to a novel ultrasensitive measurement technique in nanoscience.

微观粒子(如生物分子、中性原子等)质量的测量一直是国际上关注的课题。当这些粒子落到具有特殊结构并通有电流的纳米介质上(如纳米机械振子)时，这些纳米介质的固有振动频率就会发生变化，通过测量频率的变化量，人们可以测得落入的粒子质量。但是，由于电路引起的热效应、能量损失、频率受限等因素，电学的测量方法往往存在很大的误差，严重影响微观粒子质量测量的精确度。本项目将提出一种新的全光学的量子测量方法，基于纳米机械振子耦合系统或纳米腔光机械系统，在双光控制的条件下，利用光学方法精确测出振子频率的变化量从而得到微观粒子质量。此方法不涉及任何电学的参量，使得测量灵敏度比电学方法高出几个数量级。本项目拟深入系统地研究基于这类纳米机械振子耦合系统的全光质谱仪，并进一步推广到其它灵敏度更高且更有应用前景的纳米机械振子系统如纳米碳管和石墨烯，为今后的实验研究提供有力的理论指导和可靠的物理基础。

本项目已系统全面地研究了基于纳米机械振子耦合系统的全光学质谱仪，并进一步推广到其它灵敏度更高且更有应用前景的纳米机械振子系统如纳米碳管和石墨烯以及更为实用的室温光学质谱仪，为今后的实验研究提供有力的理论指导和可靠的物理基础。我们已完成本项目的所有计划要点、并达到或超越了预期研究结果，同时根据国内外研究发展状况，我们还系统研究了在半导体/超导异质结和铁磁原子链中探测马约拉纳费米子全新的光学方案以及其他量子非线性光学效应等。在国际重要学术期刊共发表SCI论文31篇，其中发表在Physics Reports （影响因子为22.929）和Critical Reviews in Solid State and Materials Science（影响因子为6.450）为长篇综述文章（封面文章）。撰写《量子光学研究前沿》书的其中一章“微腔光机械系统及其拓展应用”（上海交通大学出版社，总主编 张杰，2014）。特别地，发表在Physics Reports 525, 223 (2013)的关于本项目的纳米光学质谱仪（即光秤）的长篇综述文章引起国内媒体广泛报道，这是自1971年创刊以来，该期刊一共只发表了以中国大陆科研机构为唯一单位的综述性论文9篇，其中2000年以来仅4篇，这也是上海交通大学首次以唯一单位在该期刊上发表论文。论文被国际文献他人引用总数为200余次（与本项目相关的），其中包括专门发表综述文章的 Rev. Mod. Phys.（影响因子为44.982）和Physics Reports （影响因子为22.929）以及影响因子为19.352的Nature Physics, 影响因子为13.025的Nano Letters和影响因子为7.943的 Phys. Rev. Lett.的重点和多次引用。