Optical quality micromachining of glass with focused laser-produced metal plasma etching in the atmosphere

Recent results are reported about the optical quality surface finish obtained on glass substrates with focused laser beam produced metal plasma etching in the atmosphere. The bombardment of high-speed, high-temperature electrons from an underdense plasma on the surface of glass substrates appears to play a dominant role in this process. The effective laser fluence window for this high-quality glass machining on common microscope slides is relatively narrow. With a Corning microslide 2947, and by use of carbon steel as the plasma source, we obtained parameters between 3.5 and 4.5 J /cm^2 . Above the upper limit, laser-induced optical breakdown occurs in the glass material and leads to the formation of microcracks. Below the lower limit, the process was found to be ineffective. In these experiments highly defined, clean, sharp-edged, 50 x 50 micropit arrays of 15.0- (mu)m diameter with a depth of 3.2 (mu)m and a center-to-center separation of 18.0 (mu)m were fabricated on Corning microslide 2947 glass substrates.