Formation and properties of proton-exchanged and annealedLiNbO3 waveguides for surface acoustic wave

摘要

The proton-exchanged (PE) and annealed PE (APE) z-cut LiNbO3n waveguides were fabricated usingnH4P2O7. The positive strain, c-axisnlattice constant change (Δc/c), was calculated to be about +0.43%,nwhich was almost independent of the exchanged conditions. Thenpenetration depth of H measured by secondary ion mass spectrometryn(SIMS) exhibited a step-like profile, which was assumed to be equal tonthe waveguide depth (d). The surface acoustic wave (SAW) properties ofnPE and APE z-cut LiNbO3 samples were investigated. The phasenvelocity (Vp) and electromechanical coupling coefficient (Kn2) of PE samples were significantly decreased by the increasenof kd, where k was the wavenumber (2Π/Λ). The insertion lossn(IL) of PE samples was increased by the increase of kd and became nearlynconstant at kd>0.064. The temperature coefficient of frequency (TCF)nof PE samples allowed an apparent increase with kd, reaching a maximumnat kd=0.292, then slightly decreased at higher kd. The effects ofnannealing resulted in a restoration of Vp and an improvementnof IL