Number 186 (Story #1), July 5, 1994 by Phillip F. Schewe and Ben Stein NEAR-FIELD OPTICAL MICROSCOPES can achieve a spatial resolution of a fraction of a light wavelength by positioning the optical source only tens of nm from the sample. By working in this "near field," scientists can greatly reduce the resolution-limiting effects of diffraction. Physicists at AT&T Bell Labs were able to image dye molecules with a resolution of less than 100 nm using laser light with a wavelength of 600 nm brought to the sample in an optical fiber tapered at the tip to only 20 nm. (Physics Today, May 1994.) Using the incident light to excite photoluminescence in a sample, the microscope becomes a spectrometer with potentially high spatial and energy resolution. In this way, the Bell Labs researchers are beginning to resolve individual centers of luminescence in quantum wells, structures in which electrons are confined to an essentially 2-dimensional GaAs region sandwiched between AlGaAs layers. The study of quantum wells in such fine (spatial) detail is important since they play a key role in certain high- tech lasers and transistors. (H.F. Hess et al., Science, 17 June 1994.)