EFFECTS OF WAVELENGTH ON BORON-NITRIDE ABLATION BY A TRANSVERSELY EXCITED ATMOSPHERIC CO2-LASER

Laser ablation processing for a reaction sintered cubic boron nitride (cBN) by a transversely excited atmospheric CO2 laser was found to be Strongly affected by the laser wavelength. The ablation threshold of t he cBN was 3 J/cm(2) at 9.3 mu m for the 9R(10) branch but 18 J/cm(2) at 10.8 mu m for the 10P(38) branch since the 9.3 mu m laser pulse is resonantly absorbed by the transverse optical phonons. Although the re flectance of the cBN surface is very high, it was efficiently ablated by the 9.3 mu m laser irradiation. Hot pressed hexagonal BN samples we re also ablated by a 9 mu m band laser as well as a 10 mu m laser, how ever, a boron rich layer was left on the ablated surface. (C) 1996 Ame rican Institute of Physics.