Proton-exchanged Z-cut LiNbO3 waveguides for surfaceacoustic waves

摘要

Proton-exchanged (PE) waveguides in Z-cut LiNbO3 havenbeen fabricated using benzoic acid. Secondary-ion mass spectrometryn(SIMS) measurements show that the distribution of hydrogen in the PEnZ-cut LiNbO3 samples exhibits a step-like profile with thendiffusion constant D0 and the activation energy Q of aboutn2.82×108 Μm2/h and 87.76 kJ/mol,nrespectively. On the other hand, the important parameters for the designnof surface acoustic wave (SAW) devices are measured and discussed. Thenresults show that the phase velocity and electromechanical couplingncoefficient decrease with the increase of kd, where k is the wavenumbernand d is the waveguide depth. The variation of insertion loss becomesnsaturated at about kd=0.068 with a maximum increase of about 4~5 dB. Thentemperature coefficient of delay calculated from the frequency change ofnthe output of SAW delay line shows an evident increase in the PE layer.nMoreover, the effects of postannealing can result in a restoration ofnthe decreased velocity and an improvement of the insertion loss