Propagation of transverse bulk and surface acoustic waves in LiNbO/sub 3/ variable time-delay devices

Abstract

Experimental measurements are reported on voltage-controlled acoustic time-delay lines operating at 1 GHz in the nearly pure shear-horizontal (S-H) mode in 38 degrees rotated Y-cut LiNbO(3). The high-acoustic velocity (4800 m/s) in conjunction with the large electroacoustic effect exhibited by this orientation allows high-frequency operation and optimum time-delay tuning sensitivity with a planar, single surface, device geometry. The authors demonstrate fractional time delay of 0.3x10(-6) V(-1 ) for surface electrodes that produce an in-plane E-field. However, the simultaneous excitation and propagation of both a leaky surface-acoustic wave (LSAW) and surface skimming bulk wave (SSBW), both as (nearly pure) S-H waves in these devices, seriously restricts the extent to which it is possible to maximize the time delay modulation sensitivity by reducing electrode gap spacing as done in similar SAW devices. The LSAW and surface-skimming body wave (SSBW) propagate at nearly the same velocity on a free surface, and perturbation of their velocity and relative attenuation rates by surface electrodes causes pronounced interference effects between the two modes for some device geometries.

Subsurface nanodomains with in-plane polarization in uniaxial ferroelectrics via scanning force microscopy

“…It should be emphasized that LiNbO 3 and LiTaO 3 represent important ferroelectric materials, having applications in optoelectronics, diffractive and nonlinear optics, 12 frequency conversion devices, 13 and surface acoustic wave devices. 14 In this paper, we analyze theoretically the possibility of creating domains by the application of a voltage to the SFM tip contacting the surface parallel to the polar axis of a uniaxial ferroelectric. To that end, an analytical expression is derived for the total energy of a subsurface 180…”