Depth profiling of proton exchanged LiNbO3waveguides by microhyphen;Raman spectroscopy

摘要

Zhyphen;cut LiNbO3wafers were proton exchanged (PE) with pyrophosphoric acid. The polished edges provided a side view of the exchanged region. The region was probed by microhyphen;Raman spectroscopy by stepping a 488.0 nm laser at intervals as small as 0.2 mgr;m across the edge face starting below the exchanged region and moving towards the wafer surface, thereby traversing the PE region. Profiling revealed significant changes, in the 125ndash;800 cmminus;1and 3200ndash;3600 cmminus;1frequency ranges. The PE region expanded after annealing at 300thinsp;deg;C indicating proton penetration into the wafer. Continued annealing resulted in the progressive recovery of spectral characteristics resembling unexchanged lithium niobate. Microhyphen;Raman profiles provide spectroscopic information regarding which vibrational modes are affected by the exchange and the annealing processes as a function of depth.