Hole drilling of glass substrates with a slab waveguide CO2 laser

Using 30 - 1000 mus pulses and 9.3 mum wavelength fiom a CO2 slab waveguide laser, focused to a spot size of 130 mum, we have produced holes in synthetic quartz, soda-lime glass, and Pyrex glass substrates. In the three types of substrates, the mass removal per pulse increases almost linearly with the pulse energy used to vary the pulse interval. The removal rates of the three substrates are almost the same. We examine the effect of the pulse interval on the hole structure and the pile-up around the hole in single and multiple-pulse hole drilling. The deformation in the pile-up region can be accounted by the melting walls of the hole. Moreover, we examine the effect of pulse energy on the inclination of the hole walls. A multiple-pulse hole shaping technique is effective in decreasing the height coefficient of the pile-up region and the angle of inclination.