Characterization of infrared laser systems

Laser beam measurement instruments have long been available for visible laser beams, but there is a growing need for such instruments in the near IR. This is especially true far the 1-1.7 mu m region that is used for communication lasers. While a few cameras have been developed for this region, there are currently no instruments for measuring laser beam phase that operate in this regime. We have begun the development of an infrared wavefront sensor based on the Shack-Hartmann principle using an InGaAs IR camera. With this method, the laser beam is dissected into a number of focal spots, which are projected onto a detector. The focal spot position is related to the local wavefront slope. Through appropriate analysis, the laser beam intensity and phase distribution can be obtained.