Whispering gallery mode microcavities for photonic sensing applications

光与它所接触的一切相互作用。当光穿过物质或从表面反射时，其性质会受到影响，从而提供有关环境的重要信息。光子传感器使用光来“感知”周围的环境，其长度尺度非常微小。小是重要的;它可以降低成本，增加“现场”操作的便携性，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。光子传感器可用于相当广泛的应用，并且正在由世界各地的研究小组和公司开发。应用范围从手持式有毒气体传感器到检测高危人群的疾病。然而，制造用于特定应用的光子传感器可能是困难的。许多相互竞争的效应可能会“重叠”，使得难以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），并且很难仅对一个特定目标进行选择性。此外，通常必须检测非常微弱的信号。我们开发了一种传感器，其基于在特别制备的微毛细管内发射的光。通道可以小到10微米宽;当流体被泵入时，设备发射波长由分析物的化学成分控制。我们的目标是将这项技术推向超低检测限，以便能够可靠快速地测量不到百万分之一的变化。该项目还旨在应用专门的方法来检测与设备结合的单个目标分子的存在，从而实现非凡的化学灵敏度和选择性。我们将寻找方法，使生物相容的激光器中的光学“增益介质”是目标分析物本身。由于激光信号是明亮的，这种方法可以将微小的变化转化为大信号，非常适合传感应用。这项工作旨在克服选择性和信号强度的关键问题，并有助于打开光子传感器技术的一系列应用。具体目标包括测量维生素D3和探测爆炸物。

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.**