Righini Giancarlo C, Soria Silvia
Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi, 00184 Roma, Italy.
Istituto di Fisica Applicata Nello Carrara, CNR, 50019 Firenze, Italy.
Sensors (Basel). 2016 Jun 17;16(6):905. doi: 10.3390/s16060905.
Whispering gallery mode (WGM) microresonators, thanks to their unique properties, have allowed researchers to achieve important results in both fundamental research and engineering applications. Among the various geometries, microspheres are the simplest 3D WGM resonators; the total optical loss in such resonators can be extremely low, and the resulting extraordinarily high Q values of 10⁸-10⁸ lead to high energy density, narrow resonant-wavelength lines and a lengthy cavity ringdown. They can also be coated in order to better control their properties or to increase their functionality. Their very high sensitivity to changes in the surrounding medium has been exploited for several sensing applications: protein adsorption, trace gas detection, impurity detection in liquids, structural health monitoring of composite materials, detection of electric fields, pressure sensing, and so on. In the present paper, after a general introduction to WGM resonators, attention is focused on spherical microresonators, either in bulk or in bubble format, to their fabrication, characterization and functionalization. The state of the art in the area of biosensing is presented, and the perspectives of further developments are discussed.
回音壁模式（WGM）微谐振器凭借其独特特性，使研究人员在基础研究和工程应用两方面都取得了重要成果。在各种几何形状中，微球是最简单的三维WGM谐振器；此类谐振器中的总光损耗可能极低，由此产生的高达10⁸ - 10⁹ 的超高品质因数会带来高能量密度、窄谐振波长线以及长腔衰荡时间。它们还可以进行镀膜处理，以便更好地控制其特性或增加其功能。其对周围介质变化的极高灵敏度已被用于多种传感应用：蛋白质吸附、痕量气体检测、液体中的杂质检测、复合材料的结构健康监测、电场检测、压力传感等等。在本文中，在对WGM谐振器进行一般性介绍之后，重点关注了块状或气泡形式的球形微谐振器，涉及其制造、表征和功能化。介绍了生物传感领域的现状，并讨论了进一步发展的前景。
