RIA: Near Field Photodetection Optical Microscopy and Spectroscopy

研究启动奖研究的主要目标是展示用纳米尺度空间分辨率测量倏逝光场。为了实现这一目标，人们发明了一种新的概念和方法。该方法是基于用纳米尺寸的硅光电探测器直接检测光场强度的局部变化。在靠近光学照明表面的地方对探头进行光栅扫描，并在每个点测量和记录探头的光响应。这些信息以类似于扫描隧道显微镜的方式以电子方式显示。生成的图像表示在被照射的样品表面上每个点的局部光场强度。实现这一目标将需要设计和开发一种新的硅纳米探针，并展示“近场光电检测光学显微镜”的新概念。第二个目标是探索这种新型纳米探针在纳米尺度上的局部光谱学应用。这将通过将可调谐光源聚焦到具有异质光学特性的表面来实现。纳米探针被放置在靠近特定样品特征的位置，当照明源的频率在给定的频率范围内调谐时，纳米探针的光响应被测量。测量的光响应作为频率的函数是光谱指纹，它应该允许以纳米级分辨率识别样品表面的化学或分子物种。

The primary objective of the Research Initiation Award research is to demonstrate the measurement of evanescent optical fields with nanometer scale spatial resolution. To achieve this goal, a new concept and approach has been invented. The approach is based upon the direct detection of local variations in optical field intensity by a silicon photodector probe of nanometer size. The probe is raster scanned in close proximity to an optically illuminated surface and the photoresponse of the probe is measured and recorded at each point. This information is electronically displayed in a manner similar to that of a Scanning Tunnelling Microscope. The resultant image represents the local optical field intensity at each point on the illuminated sample surface. The achievement of this goal will require the design and development of a new silicon nanoprobe and the demonstration of the novel concept of "Near Field Photodection Optical Microscopy". The second objective is to explore the use of this new nanoprobe for doing local optical spectroscopy on the nanometer scale. This will be accomplished by focusing a tunable optical source onto a surface which has heterogeneous optical properties. The nanoprobe is positioned in close proximity to a specific sample feature and the nanoprobe photoresponse is measured as the frequency of the illumination source is tuned over a given frequency range. The measured photoresponse as a function of frequency is a spectroscopic fingerprint which should allow identification of chemical or molecular species at the sample surface with nanometer scale resolution.