J. Kushibiki et al., QUANTITATIVE CHARACTERIZATION OF PROTON-EXCHANGED LAYERS IN LITAO3 OPTOELECTRONIC DEVICES BY LINE-FOCUS-BEAM ACOUSTIC MICROSCOPY, IEEE photonics technology letters, 8(11), 1996, pp. 1516-1518
Application of line-focus-beam (LFB) acoustic microscopy is extended t
o quantitative characterization of proton-exchanged/annealed layers em
ployed in LiTaO3 optical waveguides. Several specimens of Z-cut LiTaO3
substrates, processed under the fabrication conditions for second-har
monic generation (SHG) optoelectronic devices, were prepared for measu
rements of the leaky surface acoustic wave (LSAW) velocities. Remarkab
le decreases in LSAW velocity due to the processes of proton exchange
and annealing were observed, providing very useful information on the
proton concentration and depth in diffusion layer, and on the process
temperature distribution. It is found that measurement sensitivity is
highest in the Y-axis wave propagation direction and the resolution to
the optical waveguide parameters of diffusion depth and refractive in
dex is much greater than the conventional techniques. It is suggested
that this ultrasonic method should be adopted as a new analytical tech
nique for development and evaluation of device fabrication processes a
nd systems destined for future mass production.