Nonlinear-Optical Method for Combining High Power Laser Beams in Gases or Plasmas

摘要

The purpose is to investigate concepts for laser controlled optics via near resonance nonlinear dispersion, so that a laser induced index grating which is capable of high power laser beam combining might be produced and demonstrated. The principle of coherent addition of several input laser beams into one output beam had been demonstrated by the use of binary phase gratings. Properly shaped phase gratings had been etched onto a solid surface, establishing that multiple laser beams can be combined into a single beam with good conversion efficiency. For high power beams, the limited damage thresholds and maximum permissible thermal loading of solid state devices encouraged a search for more satisfactory working media. Gases and plasmas appeared to offer better solutions as working media. It had been predicted that two laser fields of differing wavelengths interacting with a collision-dominated atomic or molecular system with three effective energy levels could influence one another in a nonreciprocal manner; the creation of and interaction with a grating via near-resonance nonlinear dispersion thus should provide a method for low power laser beams to create a grating in which other beams combined to form a high power beam.