Beam profiling quantifies light sources

Applications ranging from optical telecommunications to bar-code scanning require precise characterization of light beams. Ideally, you could characterize a beam with a single number that defined its width or diameter. Unfortunately, beams—even laser beams—don't have sharp edges, and measurements require a judgment about the portion of a beam that contains "useful" energy.

FWHM and 1/e squared  diameters characterize a light beam.

Traditionally, engineers have used phosphors, Plexiglas blocks, burn papers, or photographic film to measure beam widths, but such approaches require subjective evaluation. In contrast, beam profilers that combine scanning apertures with photodetectors or that employ CCD array cameras provide numerical outputs. So, too, do goniometric radiometers, which make measurements by rotating detectors through the divergent beams from components such as edge-emitting laser diodes and some vertical-cavity surface-emitting lasers (VCSELs).

Beam profilers such as the NanoScan from Photon (San Jose) can help automate applications such as the collimation of fiber-lens pairs in optical communications equipment. A multiaxis positioning stage in an automated collimation fixture can manipulate lens-to-fiber alignment while monitoring beam-profiler output; epoxy curing can complete the assembly process when the fixture achieves optimum alignment. To learn more about beam profiling, visit www.photon-inc.com/BeamProfiling.pdf.