A method of fabricating a high-density array of holes in glass is provided, comprising providing a glass piece having a front surface, then irradiating the front surface of the glass piece with a UV laser beam focused to a focal point within +/−100 μm of the front surface of the glass piece most desirably within +/−50 μm of the front surface. The lens focusing the laser has a numerical aperture desirably in the range of from 0.1 to 0.4, more desirably in the range of from 0.1 to 0.15 for glass thickness between 0.3 mm and 0.63 mm, even more desirably in the range of from 0.12 to 0.13, so as to produce open holes extending into the glass piece 100 from the front surface 102 of the glass piece, the holes having an diameter the in range of from 5 to 15 μm, and an aspect ratio of at least 20:1. For thinner glass, in the range of from 0.1-0.3 mm, the numerical aperture is desirably from 0.25 to 0.4, more desirably from 0.25 to 0.3, and the beam is preferably focused to within +/−30 μm of the front surface of the glass. The laser is desirable operated at a repetition rate of about 15 kHz or below. An array of holes thus produced may then be enlarged by etching. The front surface may be polished prior to etching, if desired.