A major technological milestone in optical glass melting has been achieved by Hoya Corp. USA (Fremont, CA). The firm is using a novel continuous glass melting system (approximately 150 feet long and two stories high) to produce 20 tons of high quality laser glass per month. To date the system has produced more than 600 neodymium (Nd)-doped laser amplifier glass slabs for Lawrence Livermore National Lab's National Ignition Facility (NIF; Livermore, CA) and 125 slabs for Laser Megajoule Project (LMJ), a French government facility currently under construction in Bordeaux, France.
Each laser glass slab, which measures 790 mm x 440 mm and is 45 mm thick, is fine-annealed and tested and inspected in Hoya's new 32,000-square-foot laser glass manufacturing facility in Fremont. The glass produced by the firm�s continuous melting system meets all of the stringent glass specifications required for NIF and LMJ. For example, the glass contains essentially no microscopic platinum particles that could cause laser-induced damage. In addition, the "water" (OH) content in the glass is less than 200 ppm, which minimizes Nd fluorescence quenching. Finally, the optical homogeneity surpasses the transmitted wavefront specification by about a factor of two.
"Our goal was for Hoya to produce 500 glass slabs during their current melting campaign,� said Ed Moses, NIF project manager. �They have exceeded that by 50 percent." Hoya's current continuous glass melting campaign, which began last June, will end as planned in February. Beginning in this summer, the firm will begin to produce the remaining laser glass needed to supply their 50-percent share of the amplifier slabs required for NIF and LMJ. Schott Glass is to provide the other 50 percent. It is anticipated that between Hoya and Schott, approximately 1500 slabs will be produced annually. The combined amount needed for NIF and LMJ is about 8000 laser slabs.