MRF applications: on the road to making large-aperture ultraviolet laser resistant continuous phase plates for high-power lasers

Abstract

Over the past two years we have developed MRF tools and procedures to manufacture large-aperture (430 X 430 mm) continuous phase plates (CPPs) that are capable of operating in the infrared portion (1053 nm) of high-power laser systems. This is accomplished by polishing prescribed patterns of continuously varying topographical features onto finished plano optics using MRF imprinting techniques. We have been successful in making, testing, and using large-aperture CPPs whose topography possesses spatial periods as low as 4 mm and surface peak-to-valleys as high as 8.6 µm. Combining this application of MRF technology with advanced MRF finishing techniques that focus on ultraviolet laser damage resistance makes it potentially feasible to manufacture large-aperture CPPs that can operate in the ultraviolet (351 nm) without sustaining laser-induced damage. In this paper, we will discuss the CPP manufacturing process and the results of 351-nm/3-nsec equivalent laser performance experiments conducted on large-aperture CPPs manufactured using advanced MRF protocols.

Developing magnetorheological finishing (MRF) technology for the manufacture of large-aperture optics in megajoule class laser systems

“…A major portion of this work centers upon developing and engaging state-of-the-art technology to set the stage for creating nuclear fusion in a laboratory setting. Continuous phase plates (CPPs) form the vital and enabling portion of the optics chain used in these kilojoule-and megajoule-class laser systems because they make it possible to manipulate and control laser beam-shapes, energy distributions, and wavefront profiles 1,2,3,4,5,6,7 . This prescribed beam characteristic control is made possible via manipulation of the incoming wavefront by the CPPs.…”

“…These laser systems also require large-aperture optics such as lenses and windows that need to perform with enhanced laser damage resistance, particularly in the UV. In many cases, these optics are subjected to an environment where temporal UV laser pulses of about 3-nsec with average fluences of 8 J/cm 2 and peak fluences between 12 and 15 J/cm 2 are used. To operate effectively and reliably, the optics not only have to be manufactured with precise optical figure and finish, they also have to be free of bulk and surface artifacts to reduce the risk of laser-induced damage in this hostile environment.…”

A novel Deal–Grove‐inspired model for fluorine‐based plasma jet etching of borosilicate crown optical glass

“…[ 13 ] With increasing miniaturization and ongoing downscaling of optical systems, more complex freeform surface designs with a higher degree of precision are gaining increasing importance. [ 14–16 ] Manufacturability and fabrication efficiency are often a limiting factor when specialized individual optical elements or low lot sizes are to be produced by mechanical abrasive techniques such as grinding and subaperture polishing. [ 17 ] Here, a processing chain [ 12 ] including PJM steps comes into play, as it has been shown to be able to efficiently fabricate precise freeform surfaces.…”

Development of a model for ultra‐precise surface machining of N‐BK7® using microwave‐driven reactive plasma jet machining

“…Thus, new approaches are necessary to overcome the limitations of classical‐mechanical treatments with respect to geometric flexibility and achievable surface shape accuracy as well as production costs and time. Therefore, different types of deterministic surface machining methods such as freeform grinding, computer‐controlled polishing, magnetorheological polishing, ion beam figuring, or elastic emission machining have been developed to generate optical components with complex surface shapes …”