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We performed simulations and experiments of wavefront distortions induced by propagating through diode-pumped square-section amplifying laser rods of Nd-doped phosphate glass and 0.5

We performed simulations and experiments of wavefront distortions induced by propagating through diode-pumped square-section amplifying laser rods of Nd-doped phosphate glass and 0.5 % N d : 5 % L u : C a F 2 . We observed that depending on the material, wavefront distortions’ profile can vary from a circular lens-like distortion to a complex astigmatic distortion. We showed that this difference comes from the relative sign of piezo-optic tensor coefficients.

In this work, we propose a method to discriminate between upper and lower side material removal during double side polishing of fused silica parts. It consists in engraving cone-shaped craters on the two sides, then measuring the profile of each crater before/after a polishing run. The comparison of the profiles leads to the thickness removed on each side during the run. The craters have been engraved using a CO2 laser and their profiles measured thanks to a nano-scratcher. We have evaluated that this method can determine material removal with an accuracy of about 1μm, is insensitive to a part repositioning error under the tip of about 35μm, and has a repeatability of 0.5μm. Finally, we have been able to measure effective removal differences of 2μm between the two sides.

International audience; Two centuries ago, Fresnel, Poisson, and Arago showed how the wave nature of light induces a bright spot behind an opaque disk. We develop an analytical model based on the Fresnel diffraction theory to show how small perturbations such as digs or scratches can yield intense light enhancements on the downstream axis. The impact of defects with complex morphology on light diffraction is shown to be accurately modeled by the Fresnel theory applied to a set of opaque disks characterized by phase shift and trans-mittance. This model can be used either to define the geometry of the defects that optimizes the light enhancement or to improve the defect specification on the surface of the optical components. We explain why partial information of the defect morphology can suffice to specify a safety distance beyond which light intensifications are not dangerous. The validity of this analytical approach is studied by measuring the intensifications created by three different microdefects.

New capabilities including laser micro-shaping and chemical treatment have been developed in an optics recycle loop to bring Megajoule laser (LMJ) damaged large optics (40×40 cm2) back to an operational condition.

The Laser MegaJoule (LMJ) is a French high power laser that requires thousands of large optical components. For all those optics, scratches, digs and other defects are severely specified. Indeed, diffraction of the laser beam by such defects can lead to dangerous “hot spots” on downstream optics. With the help of a near-field measurement setup, we make quantitative comparison between simulated and measured near-fields of reference objects (such as circular phase steps). This leads to a better understanding which parameters impact the diffracted field. In this paper, we proposed to study two types of reference objects: phase disks and phase rings. We actually made these objects by CO2 laser ablation. The experimental setup to observe the diffracted intensity by these objects will be described and calibrated. Comparisons between simulations and measurements of the light propagation through these objects show that we are able to predict the light behavior based on complete phase measurement of these objects.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.