Broadband optical absorbance spectroscopy using a whispering gallery mode microsphere resonator.
Broadband optical absorbance spectroscopy using a whispering gallery mode microsphere resonator.
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使用回音壁模式微球谐振器的宽带光学吸收光谱。
DOI：
10.1063/1.2894307
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发表时间：
2008
期刊：
影响因子：
--
通讯作者：
J. Hryniewicz
中科院分区：
文献类型：
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作者：
S. L. Westcott;Jiangquan Zhang;R. Shelton;N. Bruce;Sachin Gupta;Steven L Keen;Jerry W. Tillman;L. Wald;B. N. Strecker;A. Rosenberger;R. Davidson;Wei Chen;K. Donovan;J. Hryniewicz
我们展示了同时激发和监测微球谐振器的多个回音廊模式(WGM)的能力，以便进行宽带光吸收测量。将直径340微米的微球放置在微流控通道中。半球棱镜用于将WGMS耦合到微球中和从微球中耦合出来。棱镜的平面密封微流控通道。微球中轻微的非球形性导致耦合到进动模式，其发射与反射的激发光在空间上是分开的。捕获在WGMS中的光的逝去场与周围环境相互作用。在进动模式中观察到的透射率变化被用来确定周围环境的吸光度。与我们的宽带光吸收测量不同，以前的WGM传感器只使用单一的窄模式来测量折射率等属性。用微流体池测量了染料(李萨明绿B、日落黄、橙G和亚甲蓝)、芳香族分子(苯甲胺和苯甲酸)和生物分子(色氨酸、苯丙氨酸、酪氨酸和邻磷酸-L酪氨酸)的溶液在可见光和紫外光下的吸光度。微球表面与有机硅烷分子反应，将十八个基团、氨基和氟基连接到微球表面。通过测量不同有机硅烷的有效路径长度的变化，观察到分析物和微球表面之间的静电和疏水相互作用。对于给定的分析物和涂层微球，路径长度测量的重复性在几个百分点内。亚甲基蓝染料与表面有很强的相互作用，测量了几厘米的光程长度。选择合适的表面涂层与特定分析物相互作用应可获得最高灵敏度的检测。
We demonstrate the ability to excite and monitor many whispering gallery modes (WGMs) of a microsphere resonator simultaneously in order to make broadband optical absorbance measurements. The 340 microm diameter microsphere is placed in a microfluidic channel. A hemispherical prism is used for coupling the WGMs into and out of the microsphere. The flat surface of the prism seals the microfluidic channel. The slight nonsphericity in the microsphere results in coupling to precessed modes whose emission is spatially separated from the reflected excitation light. The evanescent fields of the light trapped in WGMs interact with the surrounding environment. The change in transmission observed in the precessed modes is used to determine the absorbance of the surrounding environment. In contrast to our broadband optical absorbance measurements, previous WGM sensors have used only a single narrow mode to measure properties such as refractive index. With the microfluidic cell, we have measured the absorbance of solutions of dyes (lissamine green B, sunset yellow, orange G, and methylene blue), aromatic molecules (benzylamine and benzoic acid), and biological molecules (tryptophan, phenylalanine, tyrosine, and o-phospho-L-tyrosine) at visible and ultraviolet wavelengths. The microsphere surface was reacted with organosilane molecules to attach octadecyl groups, amino groups, and fluorogroups to the surface. Both electrostatic and hydrophobic interactions were observed between the analytes and the microsphere surface, as indicated by changes in the measured effective pathlength with different organosilanes. For a given analyte and coated microsphere, the pathlength measurement was repeatable within a few percent. Methylene blue dye had a very strong interaction with the surface and pathlengths of several centimeters were measured. Choosing an appropriate surface coating to interact with a specific analyte should result in the highest sensitivity detection.