Laser microcutting is used to machine precise holes and grooves by vaporizing portions of the material with a laser beam. The vaporization rate is related to the absorption coefficient and was measured as a function of the laser wavelength for various materials. The cutting process can be controlled by adjusting laser power, focal spot size, scanning speed, pulse repetition rate, and pulse length. We have developed photovaporization spectroscopy as an ultraprecise diagnostic technique in laser micromachining. With suitably chosen feedback the cavity enhanced signal could be used to adjust the cutting speed through the rate of vaporization of flat polymer, metallic, and other materials. A pulsed tunable dye laser beam is focused onto the sample placed on a motorized microposition stage inside a confocal etalon. The cutting laser beam produces a minute ablation plume by vaporizing material from the sample surface. This plume then causes optical scattering losses in the fixed frequency probe beam. At cavity resonance the transmitted probe beam intensity is a sensitive means to detect minute vaporization rates and cutting speeds. Scattering losses of <1 part in 103 can be detected. The measurement of even lower rates is possible when the accompanying photothermal effects1,2 are taken into consideration.
© 1990 Optical Society of AmericaPDF Article