Comparison of CW and pulsed UV laser etching of LiNBO3

The results of CW frequency-doubled argon-ion laser etching and pulsed excimer laser etching of lithium niobate (LiNbO3) are compared. Argon-ion laser etching occurs in the presence of Cl2 at laser intensities of 1.1 MW/cm2 or higher. The 257 nm laser beam with up to 25 mW power is focused to a 1.5 μm diameter spot and scanned at speeds of 10 μm/s or less. Excimer laser etching is done at 248 nm (KrF) with the laser beam focused onto the sample with cylindrical optics. Trenches >20 μm wide and several millimeters long are produced by ablating the target and without scanning the beam. Excimer laser etching of lithium niobate has been attempted in the presence of Cl2, O2, N2, H2 or air. Excellent results are obtained with air as the etching medium