The world has a wonderful transparency to a physicist who works on optics. There is little we cannot "see" by manipulating light and its interactions with matter—from the distant reaches of the universe to the submicroscopic details of materials and processes.
Figure 1. Lasers can probe and manipulate matter at both large and small scales. An astronomer might use an intense beam of coherent light (such as the one generated by a high-powered laser inside the University of California’s Lick Observatory, left) to correct for atmospheric and telescope errors. A "laser guide star" is created by inducing sodium atoms high in the atmosphere to back-scatter pulses of light. Impressive as a 90-kilometer beam might be, however, the laser may prove more remarkable in its ability to probe the finest details of matter. The authors have built a vertical-cavity surface-emitting laser of ultra-thin semiconductor layers (right) to probe the properties of human cells. Individual cells passed through the microscopic laser cavity become part of the lasing process and reveal their properties in the spectrum of emitted light.
Photographs courtesy of Lawrence Livermore National Laboratory, left, and Sandia National Laboratories, right.
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