On-line control of laser beam quality by means of diffractive optical components

At LBOC6 meeting we presented an alternative approach for laser beam characterization, based on the decomposition of the electrical field distribution at certain cross section of the laser beam into a system of orthogonal functions. As such orthogonal function systems we selected "natural" laser eigenmodes of either GL or GH type. The looked for strength of the individual modal components then can be achieved by measuring the output signal of multi-channel correlation filters placed in a Fourier set-up, whereas the correlation filters themselves have been realized as DOEs by laser lithography. In between different systems of such GL and GH correlation filters have been designed, manufactured and experimentally tested with miscellaneous laser beams. Achieved results demonstrate a very good conformity between optical experiment and computer simulation. First attempts to compare results of our method with results of "standard" beam characterization methods (ISO11146) indicated principal conformity, but illustrated the continuing demand for a sophisticated adjustment procedure for the filter during application.