Effects of Temperature on Optical Aberrations in Beam Delivery Components

The effects of temperature on aberrations in the mirrors and lenses of beam delivery systems were analyzed. Aberrations were derived using the Zernike polynomial and a Shack-Hartmann wavefront sensor. As the temperature rose, aberrations became more pronounced; in particular, orthogonal aberrations significantly increased. Computational analysis revealed that the aberrations were attributable to variations in the thermal expansion coefficients of various components of the anisotropic structure. The analytical and experimental results were similar. As the temperature rose, tilt aberrations significantly increased; the y-tilts of mirrors and lenses differed. An optical component realignment method was used to reduce aberrations as the temperature rose. We used the tilting screw to change the position of the second mirror, then used the linear slide to reduce defocusing aberration. These calibrations reduced aberrations to levels comparable with their initial values.