CONTACTLESS TRANSMISSION METHOD FOR DETERMINING THE ENERGY CHARACTERISTICS OF LASER-RADIATION

A contactless method is proposed for determining the energy of large-diameter laser beams propagating in air. The energy distribution is found from an analysis of interference fringes, and the compact expressions needed in this analysis are given. A crossed Mach- Zehnder interferometer is one of the most sensitive interferometers for laser pulses propagating in air when the absorption at certain wavelengths is minimal. The error of the proposed transmission method (25%) can be reduced by a single calorimetric calibration. The upper limit of the method is set by breakdown in air and by the self-induced transparency. The physical basis of the method is considered and main expressions for the defocussing of a beam in air are given. These expressions can be used to determine the energy distribution and total energy of a beam.