Optical frequency combs in aqueous and air environments at visible to near-IR wavelengths.
Optical frequency combs in aqueous and air environments at visible to near-IR wavelengths.
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DOI：
10.1364/oe.451631
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发表时间：
2022-01
期刊：
影响因子：
3.8
通讯作者：
Gwangho Choi;Adley Gin;Judith Su
中科院分区：
文献类型：
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作者：
Gwangho Choi;Adley Gin;Judith Su
在不使用标签或捕获剂的情况下以高灵敏度检测和识别分子的能力对于医学诊断、威胁识别、环境监测和基础科学非常重要。微环形光学谐振器与降噪技术相结合，已被证明能够进行无标记的单分子检测；然而，他们仍然需要捕获剂和目标分子的先验知识。光学频率梳有可能提供微谐振器渐逝场内分子的高精度光谱信息；然而，这尚未在空气或水生物传感中得到证实。特别是对于水溶液，障碍包括耦合和热不稳定性、Q 因子降低以及模式谱的变化。在这里，我们克服了使用光学微谐振器进行单分子光谱的一个关键挑战：当浸入空气或水溶液中时，产生可见光到近红外波长的频率梳。所需的色散是通过模间耦合实现的，我们证明这可以使用更大的微环形线圈来实现，但其形状和材料与之前被证明是超高灵敏度生物传感的理想选择相同。我们相信，该平台的不断发展将使我们将来能够在任何波长下同时检测和识别气体和液体中的单分子，而无需使用标签。
The ability to detect and identify molecules at high sensitivity without the use of labels or capture agents is important for medical diagnostics, threat identification, environmental monitoring, and basic science. Microtoroid optical resonators, when combined with noise reduction techniques, have been shown capable of label-free single molecule detection; however, they still require a capture agent and prior knowledge of the target molecule. Optical frequency combs can potentially provide high precision spectroscopic information on molecules within the evanescent field of the microresonator; however, this has not yet been demonstrated in air or aqueous biological sensing. For aqueous solutions in particular, impediments include coupling and thermal instabilities, reduced Q factor, and changes to the mode spectrum. Here we overcome a key challenge toward single-molecule spectroscopy using optical microresonators: the generation of a frequency comb at visible to near-IR wavelengths when immersed in either air or aqueous solution. The required dispersion is achieved via intermodal coupling, which we show is attainable using larger microtoroids, but with the same shape and material that has previously been shown ideal for ultra-high sensitivity biosensing. We believe that the continuous evolution of this platform will allow us in the future to simultaneously detect and identify single molecules in both gas and liquid at any wavelength without the use of labels.