DEPTH PROFILING OF PROTON-EXCHANGED LINBO3 WAVE-GUIDES BY MICRO-RAMANSPECTROSCOPY

Z-cut LiNbO3 wafers were proton exchanged (PE) with pyrophosphoric aci d. The polished edges provided a side view of the exchanged region. Th e region was probed by micro-Raman spectroscopy by stepping a 488.0 nm laser at intervals as small as 0.2 mum across the edge face starting below the exchanged region and moving towards the wafer surface, there by traversing the PE region. Profiling revealed significant changes, i n the 125-800 cm-1 and 3200-3600 cm-1 frequency ranges. The PE region expanded after annealing at 300-degrees-C indicating proton penetratio n into the wafer. Continued annealing resulted in the progressive reco very of spectral characteristics resembling unexchanged lithium niobat e. Micro-Raman profiles provide spectroscopic information regarding wh ich vibrational modes are affected by the exchange and the annealing p rocesses as a function of depth.