Whispering gallery mode microcavities for photonic sensing applications

光与它接触到的一切东西相互作用。每当光线穿过物质或从表面反射时，其性质都会受到影响，从而提供有关环境的重要信息。光子传感器使用光在一个真正微小的长度尺度上“感知”周围的环境。体积小是很重要的；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。光子传感器可以在相当广泛的应用中使用，世界各地的研究小组和公司都在开发光子传感器。应用范围从手持有毒气体传感器到检测高危人群中的疾病。然而，制造用于特定应用的光子传感器可能是困难的。许多相互竞争的影响可能会“重叠”，从而很难检测到感兴趣的特定物质的存在。许多分析物的化学成分都很复杂(例如血液)，很难只针对一个特定的目标进行选择。此外，人们通常必须检测到非常微弱的信号。*我们开发了一种基于特殊准备的微毛细管内发射的光的传感器。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极限，这样就可以可靠而快速地测量到百万分之一以下的变化。该项目还旨在应用专门的方法来检测单个目标分子的存在，这些分子被结合到设备上，实现非凡的化学灵敏度和选择性。我们将寻找制造生物兼容激光器的方法，在这种激光器中，光学“增益介质”本身就是目标分析物。由于激光信号很亮，这种方法可以将小的变化变成大的信号，非常适合于传感应用。这项工作旨在克服选择性和信号强度的关键问题，并可能有助于打开光子传感器技术的整个应用范围。具体目标包括维生素D3的测量和爆炸物检测。

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.**