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

Abstract

The velocity and attenuation of surface acoustic waves (SAW) in a 128 degrees -rotated Y-cut lithium niobate crystal with a proton-exchanged optical waveguiding layer on its surface have been studied. The measurements were carried out using the acoustic-optical diffraction method in the SAW frequency range 30-600 MHz. The SAW propagation was mainly along the X axis, though some velocity measurements were carried out for the normal direction. Strong velocity decrease and attenuation increase due to the proton exchange were observed. The acoustic dispersion and losses grow with the waveguide depth and SAW frequency, and are strongly affected by the post-exchange annealing. The results are explained by the formation of a HxLi1-xNbO3 layer on the LiNbO3 with many defects.

Diffraction of Guided Optical Waves by Surface Acoustic Waves in Proton-Exchanged 128� Rotated Y-Cut LiNbO3

“…The proton exchange was performed by heating the 128 rotated Y-cut This relation has been obtained by determining from measured refractive index spectra the thicknesses of multi-mode waveguides formed at different exchange durations [10]. For our case of 20 min exchange duration, it yields d ¼ 0.7 mm.…”

“…The SAW velocity for the given orientation is 3980 m/s on a free surface of pure LiNbO 3 , corresponding to the acoustic wavelength 51 mm. As the protonated layer was very thin in comparison with the acoustic wavelength, its influence on the SAW velocity [10] could be neglected, and we used the above given velocity value in our calculations. The propagation direction of the guided optical mode was normal to that of the SAW.…”

“…Among various cuts of LiNbO 3 characterized by a large value of K 2 , the 128 rotated Y-cut possess the advantage that the proton exchange process does not lead to the drastic surface damage as it does, e.g., in the case of the Y-cut [7]. The PE process has been succesfully applied to fabricate in 128 rotated Y-cut LiNbO 3 good-quality optical waveguides with a relatively high refractive index change [8][9][10]. The Braggtype diffraction of GOWs by SAWs in PE LiNbO 3 for this orientation has been reported in Ref.…”

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].…”

Multidimensional patterning and manipulating of microparticles and cells using surface acoustic waves

“…From literature, SAW velocities on LiNbO3 128Y cut wafer along the x-axis and yaxis are 3982 m/s and 3675 m/s, respectively [149,151], which correspond to the SAW wavelengths of 299.4 µm and 297.6 µm.…”