With the increasing energy of high power laser devices, the laser-induced damage of optical components, especially fused quartz components, has become one of the core problems in the development of high power laser devices. Studies show that pure fused quartz glass has a high intrinsic damage threshold, but fused quartz glass will inevitably introduce a large number of subsurface damage during the process of grinding and polishing, and these subsurface damage is one of the important factors leading to the decline of laser damage resistance of optical components. It is of great significance to study the subsurface damage of solid abrasive for improving the damage resistance threshold of optical components. In this experiment, 3M's abrasive pad is used as a solid abrasive. The subsurface damage of fine grinding elements are directly observed and analyzed by combining HF pickling and optical microscopy. The results show that various subsurface damage can be detected by optical microscopy after HF pickling. Profilometer is used to measure the surface roughness of the sample, the comparative analysis of the subsurface damage of the fine grinding elements shows that the elements with solid abrasive lapping have smaller roughness when the abrasive size is the same, which has a shallower depth of subsurface damage layer correspondingly.
For the high demand of large aperture optical element, the regular trajectory errors in machining marks of double-side polishing need to be determinately controlled. The mechanism and control method of the regular trajectory errors in machining marks were deeply studied. The process was simulated and compared with the experiment. The method of active translation and pendulum motion and polishing plate correction were proposed, proved to be efficacious on eliminating the regular machining marks by the groove of the polishing pad and local surface figure errors of the polishing plate. The method of dynamic loading and motion combination was adopted, retaining the independence of the original fast convergence process on surface figure. For the optical element with 430mm×430mm×10mm, the surface figure was controlled below 1λ(PV, λ=632.8nm). Meanwhile, the regular machining marks repeatedly produced were eliminated, which provided the essential condition for the intermediate frequency index in the rear stage, small tool precision polishing, and the high efficiency and stable machining of the optical element in the index system was realized.
Conventional used ceria polishing would induce both of Ce contaminants and subsurface damages, which mainly restricts the laser induced damage resistance of fused silica optics. To control the near surface defects, nanometer sized colloidal silica are used to polish fused silica optics after the normal ceria polishing process. Then the contaminant elements and subsurface damages of the polished samples were analyzed by secondary ion mass spectrometry and Nomarski microscopy. It reveals that ceria polishing would introduce lots of subsurface damages whereas colloidal silica polishing induces much fewer subsurface damages especially no fracture induced severe subsurface damages. The laser damage tests reveal that subsequent colloidal silica polishing of the ceria pre-polished samples could gradually eliminate the ceria polishing induced subsurface damages and lower the laser induced damage density accordingly with the increased polishing time. But unlike the damage density, only the severe subsurface damages are totally eliminated could the damage threshold be substantially improved. These results incline to indicate that the subsurface damages have great influence on the laser induced damage density and the fracture related severe subsurface damages will greatly restrict the damage threshold in polished optics.
Light weighted multi-angle multi-surface mirror is made of glass-ceramic, with the structural characteristic of multicavity thin wall, high precision of surface figure and angle between surfaces, has very different processing technology with traditional solid mirror. Based on the 460mm×434mm×80mm multi-angle multi-surface mirror, glass combination manufacture method and relevant interferometry of angle measurement was designed. The process technology was studied, then the consistency of angle between surfaces and the influence on multi-cavity thin wall deformation of lateral surface and material of polishing pad on the surface figure processing were controlled. The model between the variation of angle and load was established, from which the hysteresis of angle variation was analyzed, then the prototype workpiece was finished. The difficult problem on synchronically controlling the surface angles and surface figure of the mirror, which has high center of gravity and multi-cavity thin wall, was solved. The lateral surface figure was controlled below λ/6 (PV, λ=632.8nm), and the perpendicularity of lateral surfaces were controlled below 5''.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.