Binary gratings for CO(2) laser-beam diagnostics.

Properties of binary gratings for beam diagnostics of high-power CO(2) lasers are investigated. The layout uses a modal theory that includes absorption of metallic surfaces by an impedance boundary condition. Radiation-resistant gratings were fabricated in copper with photolithography combined with galvanic technology. In this way gratings have been realized in which the first-order diffraction efficiencies are polarization independent. Use of a second grating to reduce elliptical beam distortion is demonstrated. Finally it is shown that Rayleigh anomalies for binary diagnostic gratings are accompanied by high absorption.