We will present our results on fabricating transparent ceramic gain media with endcaps, planar and channel waveguides made by additive manufacturing, thin-disk structures with an undoped “face cap”, and laser rods where the doped core is surrounded by a clad. The ceramic optics are based on various garnet and sesquioxide compositions as well as for SrF2. Various gain and laser oscillation results are included as feasibility demonstrations.
Strontium fluoride ceramics have multiple prospective advantages over currently-used phosphate glass as a host for Nd ions in high-energy laser gain media, but fluoride ceramics have yet to be developed into usable gain media because of difficulties in processing. Past work on fluorides has primarily focused on processing from the liquid phase, such as fusion casting and hot forging. A powder processing route has been developed for strontium fluoride, achieving optical scatter as low as ~0.4%/cm at 1.3 μm, which is within the usable range for high-energy laser use. A series of hot-pressed samples exhibit decreasing optical scatter and increasing grain size with increasing process temperature.
Lens-coupled X-ray computed tomography (X-ray CT) using a transparent scintillator imaged on a CCD camera obtains higher spatial resolution than the more commonly employed phosphor-enhanced amorphous silicon (A-Si) panels. A-Si panels are limited to resolution typically greater than ~200 microns, have a limited working life due to degradation with dose, and provide intrinsically low efficiency with thin (few hundred microns thick) phosphor coatings. Demanding applications such as imaging the interior of complex additively manufactured components require high throughput and high resolution, best achieved with a lens-coupled system. However, for large fields-of-view, very large area but thin transparent scintillators are required – a format difficult to fabricate with high light yield single crystals – therefore, glass scintillators with both modest X-ray interaction and light yield have been used for years. We have developed a new polycrystalline transparent ceramic scintillator, Gd0.3Lu1.6Eu0.1O3, or “GLO,” that offers excellent stopping power and light yield for improved contrast in sizes up to 14” x 14” plates, with thicknesses in the 2-10 mm range, and we are implementing it in systems to increase imaging throughput for 9 MeV Bremsstrahlung X-ray CT. CT imaging performance will be described.
Transparent ceramic fabrication via solid state sintering is opening a path to a new category of laser gain media with tailor-made doping and index profiles. Techniques such as assembly of green structure pieces, direct ink writing, and Ink jet printing allow the fabrication of a wide variety of tailored optics including; slabs, rods, gradient doping, thin disks, ceramic-clad single-crystal fibers, and planar waveguides. The potential for 3D printed gain media to have a profound impact on new laser design and integrated optics is yet untapped. This work was performed under the auspices of the U.S. DOE by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-816729
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