Influence of absorption-edge properties on subpicosecond intrinsic laser-damage threshold at 1053 nm in hafnia and silica monolayers.

Owing to their relatively high resistance to laser-induced damage, hafnia and silica are commonly used in multilayered optical coatings in high-power laser facilities as high- and low-refractive-index materials, respectively. Here, we quantify the laser-induced-damage threshold (LIDT) at 1053 nm in the short-pulse regime of hafnia and silica monolayers deposited by different fabrication methods, including electron-beam evaporation, plasma ion-assisted deposition and ion-assisted deposition. The results demonstrate that nominally identical coatings fabricated by different deposition techniques and/or vendors can exhibit significantly different damage thresholds. A correlation of the LIDT performance of each material with its corresponding absorption edge is investigated. Our analysis indicates a weak correlation between intrinsic LIDT and the optical gap of each material (Tauc gap) but a much better correlation when considering the spectral characteristics in the Urbach tail spectral range. Spectrophotometry and photothermal absorption were used to provide evidence of the correlation between the strength of the red-shifted absorption tail and reduced LIDT at 1053 nm.

Jones matrices of a quarter-wave plate for Gaussian beams.

The Jones matrix of a quarter-wave plate is studied theoretically and experimentally, taking into account internal reflections, the ellipsoid of the indices, geometric defects, the tilt angle, and the characteristics of the incident Gaussian beam. The influence of the different parameters is isolated, and large discrepancies are observed with respect to results obtained from the Jones matrix that are usually given in textbooks. It is shown that the effective Jones matrix of the plate does not depend on the longitudinal position of the plate on the Gaussian beam but only on the beam-waist size. This leads to a method of characterization of the defects of a quarter-wave plate that is more precise than the usual methods. Different procedures to optimize the efficiency of a given plate are discussed, taking the plate defects into account. In all cases, a good agreement between experiments and theory is obtained.