Characterization of Domain-Inverted Layers in LiTaO 3 by Line-Focus-Beam Acoustic Microscopy

Abstract

A characterization procedure of domain-inverted layers employed in LiTaO3 optoelectronic devices by line-focus-beam acoustic microscopy is explored. A special specimen of -Z-cut LiTaO3 with a domain-inverted layer of about 1.8 µm thickness, processed under the fabrication conditions for quasi-phase-matching second-harmonic-generation devices, was prepared for measurements of the leaky surface acoustic wave (LSAW) velocities in the frequency range 100 to 300 MHz. Intrinsic decreases in LSAW velocity were obtained with the rate of 0.127 m/s/MHz, which were in excellent agreement with the theoretical results. These resulted from formation of a domain-inverted layer on the -Z surface. Slight variations in domain-inverted depth on the specimen, caused by variation in process temperature, were also detected, with the measurement resolution of 0.01 µm at 225 MHz.