Laser etching of LiNbO3 in a Cl2 atmosphere

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Abstract
Single‐crystal LiNbO3 is etched in an atmosphere of 500‐Torr Cl2 by focusing a 257‐nm, frequency‐doubled CW argon‐ion laser beam onto the surface. The observed laser intensity threshold for etching is consistent with a process involving surface melting of the crystal. A single laser scan forms a shallow depression with marked ripples transverse to the direction of laser polarization, while repeated scans give a groove with a nearly triangular cross section. During laser etching, reacted material is redeposited on the crystal surface. This material is subsequently analyzed for chemical composition. The LiNbO3 surface is partially depleted of Li and O both at the etched grooves and at significant distances away from the grooves. Studies at low light intensities suggest that photochemical generation of gas‐phase Cl radicals is responsible for the O depletion and part of the Li depletion. In addition, a dark reaction between Cl2 and LiNbO3 depletes only Li.