Whispering gallery mode microcavities for photonic sensing applications

光与它接触到的一切相互作用。每当光穿过物质或从表面反射时，其性质就会受到影响，从而提供有关环境的重要信息。光子传感器利用光在一个非常微小的长度尺度上“感知”周围环境。小是重要的；它可以降低成本，增加“现场”操作的可移植性，快速产生结果，并最大限度地减少对大型和昂贵实验室的需求。光子传感器的应用范围很广，世界各地的研究团体和公司都在开发光子传感器。应用范围从手持式有毒气体传感器到高危人群的疾病检测。然而，为特定的应用制造光子传感器是很困难的。许多相互竞争的效应可能会“重叠”，使得很难检测到感兴趣的特定物质的存在。许多分析物在化学上是复杂的（例如，血液），很难只对一个特定的目标进行选择。此外，通常必须检测到非常微弱的信号。

Light interacts with everything it touches. Whenever light passes through a substance or reflects from a surface, its properties are affected in ways that can give important information about the environment. Photonic sensors use light to “sense” the surroundings on a length scale that is truly tiny. Being small is important; it can reduce cost, increase portability for operation “in the field”, yield fast results, and minimize the need for large and expensive laboratories. Photonic sensors can be used in a considerable range of applications and are being developed by research groups and companies worldwide. Applications range from hand-held toxic gas sensors to the detection of disease in at-risk populations. Making a photonic sensor for a particular application can be difficult, however. Many competing effects can “overlap”, making it hard to detect the presence of the specific substance of interest. Many analytes are chemically complex (e.g., blood), and it is hard to be selective for only one specific target. Also, one must typically detect very weak signals. We developed a sensor based on light emitted inside specially prepared microcapillaries. The channel can be as small as 10 micrometers wide; when a fluid is pumped in, the device emission wavelength is controlled by the chemical composition of the analyte. We aim to push this technology to ultra-low detection limits, such that changes of less than one part in a million can be reliably and quickly measured. The project further aims toward the application of specialized methods to detect the presence of single target molecules that are made to bind onto the device, achieving extraordinary chemical sensitivity and selectivity. We will search for ways to make biocompatible lasers in which the optical “gain medium” is the target analyte itself. Since laser signals are bright, this method can turn small changes into large signals, ideal for sensing applications. This work aims to overcome the key issues of selectivity and signal strength, and could help open a whole range of applications for photonic sensor technologies. Specific targets include measurement of vitamin D3 and explosives detection.