Measurement and compensation of laser-induced wavefront deformations and focal shifts in near IR optics.
We demonstrate the feasibility of passive compensation of the thermal lens effect in fused silica optics, placing suitable optical materials with negative dn/dT in the beam path of a high power near IR fiber laser. Following a brief overview of the involved mechanisms, photo-thermal absorption measurements with a Hartmann-Shack sensor are described, from which coefficients for surface/coating and bulk absorption in various materials are determined. Based on comprehensive knowledge of the 2D wavefront deformations resulting from absorption, passive compensation of thermally induced aberrations in complex optical systems is possible, as illustrated for an F-Theta objective. By means of caustic measurements during high-power operation we are able to demonstrate a 60% reduction of the focal shift in F-Theta lenses through passive compensation.
Martin
M
Stubenvoll
Bernd
B
Schäfer
Klaus
K
Mann
D065638:Absorption, Radiation; D003198:Computer Simulation; D007834:Lasers; D007909:Lenses; D009716:Numerical Analysis, Computer-Assisted; D055095:Optics and Photonics; D012822:Silicon Dioxide; D019265:Spectroscopy, Near-Infrared; D013696:Temperature; D058067:Wavelet Analysis
D012822:Silicon Dioxide