Passive compensation of laser-induced higher-order aberrations in high-power NIR optics

We report a method for passive compensation of thermally induced focal shifts and higher-order aberrations of NIR laser processing optics. Theoretical considerations are made on the elimination of aberrations including polarization effects using a multi-stage compensation element with optical flats of both positive and negative dn/dT. A compensation layout is designed and optimized utilizing numerical simulations of thermo-optic effects. Based on these findings, optical elements for compensation of an F-Theta objective are manufactured. By means of wavefront measurements and beam caustic measurements the feasibility of simultaneous passive compensation of focal shifts and higher-order aberrations is demonstrated.