Ultraprecision grinding of potassium dihydrogen phosphate crystals for getting optical surfaces (Abstract Only)

In the NIF research program, potassium dihydrogen phosphate (KDP) crystals have been studied on rapid growth methods and single point diamond turning for getting optical surface. KDP has several weak points such as soft, brittle and deliquescent from the machining point of view. This paper shows a new possibility to get optical surfaces on KDP crystals by ultraprecision grinding. The KDP crystal was ground with a SD5000-75-B diamond wheel under the conditions of wheel peripheral speed vs equals 160m/min, feed per wheel revolution f equals 0.5 micrometers /rev and depth of cut a equals 1 micrometers in a mixture of 10cSt silicon oil and 5 wt percent heptanol as a grinding fluid after grinding of LHG-8 laser glass. The surface roughness of 0.553 nm rms, 0.441 nm Ra or 3.40 nm p-v was obtained by the ultraprecision surface grinding without polishing process. This surface is smoother than single point diamond turned surfaces or optically polished ones ever obtained.