A subwavelength sized source or detector of visible light can be raster scanned in close proximity to the surface of a sample to generate images at a resolution well beyond the classical diffractional limit. Applications of the resultant technique, near-field scanning optical microscopy (NSOM), include fluorescence imaging of fixed cells, mode profiling of semiconductor lasers, and high density magnetooptic data storage. The focus of this presentation, however, will be on the more recent use of NSOM in the identification and characterization of discrete quantum emitters from within an ensemble.Two such systems will be discussed. The first involves the detection and characterization of single fluorescent molecules. The usual difficulty with single molecule detection is not the inherently weak luminescence signal from each molecule, but rather the large background from impurity luminescence and Raman scattering within the excitation volume. NSOM greatly reduces this volume and hence the resultant background, yielding sensitivity of 0.005 molecules.
Demonstrating Applications of Non-optically Regulated Tapping-Mode Near-Field Scanning Optical Microscopy to Nano-optical Metrology and Optical Characterization of Semiconductors
