Proton-Exchanged Waveguides for Surface Acoustic Wave on Z-cut LiNbO3 Using Octanoic Acid

Abstract

The properties of the surface acoustic wave (SAW) on proton-exchanged Z-cut Y-propagation LiNbO3 waveguides using octanoic acid are investigated. The distribution of hydrogen in the PE samples measured by secondary-ion mass spectrometry (SIMS) shows a step like profile with the diffusion constant D0 and the activation energy Q of about 1.18×106 µ m2/ h and 63.21 kJ/mol, respectively. The results show that the acoustic velocity (V p) of SAW on PE samples decreases monotonically with increased kd, where k is the wave number (2π/λ) and d is the waveguide depth. Furthermore, the variation of the electromechanical coupling coefficient (K2) is similar to that of V p. The SAW insertion loss (IL) becomes saturated at about kd=0.13, with a maximum increase of about 5-6 dB. The temperature coefficient of delay (TCD) calculated from the frequency change of the output of the SAW delay line for the temperature ranging from -10 to 50° C shows a clear increase in the PE layer.