Acoustic properties of proton-exchanged LiNbO3 studied using the acoustic microscopy V(z) technique

Abstract

We report measurements of proton-exchanged LiNbO3 using acoustic microscopy in the V(z) mode, together with optical waveguide mode observations. In the present case, samples were prepared using dilute benzoic acid containing a small mole percent of lithium benzoate. Substantial changes in surface acoustic wave (SAW) propagation velocity due to proton exchange have been observed on all three major-axis crystal cuts, with both increase and decrease in velocity occurring, depending on propagation direction. Changes in attenuation are also observed. Using the V(z) technique with a line-focus cylindrical lens has enabled complete velocity surfaces for proton-exchanged lithium niobate to be obtained with reasonable precision, based on simplified isotropic calculations of acoustic propagation in layered media and the assumption that the proton-exchange region is uniform with a depth obtainable from optical waveguide mode calculations. It is concluded that the V(z) acoustic microscopy technique can provide a powerful tool in the study of the SAW properties of proton-exchanged LiNbO3.

Temperature Coefficient of SAW Device on SiO2/Proton Exchanged LiNbO3Substrate

“…Immersion of material into molten proton sources result in the exchange by protons, and a new crystalline structure is established [1][2][3][4][5][6][7][8][9].…”

“…The PE-LiNbO 3 waveguides will change the properties of surface acoustic wave (SAW) [4][5][6], which offer new applications in the fields of acoustooptic (AO) devices. Unfortunately, it has poor temperature stability.…”

Investigation of Velocity Surface of Bulk Acoustic Waves for Proton-Exchanged LiNbO3 Crystal

“…The acoustic properties of PE LiNbO 3 used in surface acoustic waveguides were measured by using the Brillouin Scattering method [6], acoustic microscopy method [7] and the interdigital transducers (here after IDT) method [8][9][10][11][12][13]. Hinkov fabricated the first time SAW waveguides on Y-cut LiNbO 3 substractes by PE and studied the influence of the source dilution, the annealing, or the Ti pre-diffusion on the SAW velocity, by using IDT as SAW excitation source and optic probe as detector [4].…”

Velocity and attenuation of surface acoustic waves in proton-exchanged 128 degrees -rotated Y-cut LiNbO3

“…A large decrease in the SAW velocity (up to 20% at the frequency 180 MHz) has been observed for propagation in the X direction on Y -and 2-cut surfaces [2]. The changes in the SAW velocity in LiNbO3 caused by the proton exchange have been studied using Brillouin scattering at acoustic frequencies of order 10 GHz in Y-cut samples [3], with the help of the acoustic microscope at 215 MHz on X, Y and 2 cuts [4], and by the acoustooptical diffraction method at 180 and 420 MHz in Y-cut samples [5]. The detailed investigations of dispersion characteristics of the SAW in the frequency range from 100 MHz up to over 1 GHz in Y-cut PE LiNbO3 crystals and an attempt to determine the elastic stiffness constants of the H,Lil-,Nb03 layer have been reported in [6].…”