Multiplex CO2 drilling with diffractive optics

Abstract

Adding a linear diffraction grating to a CO2 focusing lens causes it to produce multiple focal spots from a single incoming beam. This arrangement is useful in converting applications such as perforation of cigarette paper, where multiple rows of holes are often desired.The implementation of this configuration can be hampered by the tendency of CO2 lasers to operate on several wavelengths. The location of the diffracted focal points is directly related to the laser wavelength, so a wavelength shift translates to a position shift and a change in the spacing of the rows.This effect may be suppressed by controlling the output wavelength of the laser. We have compared drilling results from a laser with an unstable resonator and one with a stable resonator operating on a single emission line. Better process uniformity and hole quality result from narrowing the laser bandwidth.Adding a linear diffraction grating to a CO2 focusing lens causes it to produce multiple focal spots from a single incoming beam. This arrangement is useful in converting applications such as perforation of cigarette paper, where multiple rows of holes are often desired.The implementation of this configuration can be hampered by the tendency of CO2 lasers to operate on several wavelengths. The location of the diffracted focal points is directly related to the laser wavelength, so a wavelength shift translates to a position shift and a change in the spacing of the rows.This effect may be suppressed by controlling the output wavelength of the laser. We have compared drilling results from a laser with an unstable resonator and one with a stable resonator operating on a single emission line. Better process uniformity and hole quality result from narrowing the laser bandwidth.