Guided-wave acousto-optic Bragg diffraction and surface
acoustic-wave propagation in epitaxially matched
SrTiO3/BaTiO3(001)/SrTiO3
thin-film heterostructures have been theoretically studied. The
optimum electromechanical coupling and Bragg diffraction efficiency
have been determined at several acoustic frequencies by means of
varying the thickness of the SrTiO3 overlayer and the
BaTiO3 waveguiding layer. A strain-controlling
nonpiezoelectric SrTiO3 overlayer upon the
BaTiO3/SrTiO3 structure is found to enhance
the coupling coefficient (k2) and the
diffraction efficiency significantly. A comparison of asymmetric
and symmetric structures shows an increase in the diffraction
efficiency from 10.5% to 43.0% and a decrease in the
untuned-transducer conversion efficiency from 36 to 23 dB at an
operating frequency of 1 GHz with an interaction length of 1 mm and an
acoustic power of 1 mW.

Enhanced acousto-optic diffraction efficiency in a symmetric SrTiO 3 /BaTiO 3 /SrTiO 3 thin-film heterostructure

Propagation characteristics of surface waves on Ba(Ti095Zr005)O3 ceramics have been studied under various conditions The Ba(Ti095Zr005)O3 ceramic has two second‐phase transition temperatures, around 0 and 54 °C, and has a Curie temperature of 96 °C The attenuation constant for surface wave propagation has a peak value in the vicinity of the phase transition temperature The logarithmic decrement is nearly independent of frequency over the range 08–18 MHz Also, the attenuation is nearly constant for the range of input voltage below 40 V, but increases rapidly beyond 40 V It is concluded that for the input voltage with small amplitude, the attenuation due to the dielectric loss is predominant, but the attenuation due to the hysteresis mechanism increases for an input voltage above 40 V Furthermore, it is found that at the second‐phase transition temperature, the conversion efficiency of the transducer attains the peak value, while the propagation velocity takes a minimum value

Propagation Characteristics of Surface Elastic Waves on Ba (Ti0.95Zr0.05)O3 Ceramic Plates

Up to the beginning of the sixties, the shortest measurable time duration was of the order of one nanosecond (10−9 s). Short pulses were produced through the generation of short electrical discharges. After the laser was invented in 1960, the situation quite rapidly changed. In 1965, the picosecond (10−12 s) regime was reached by placing a saturable absorber inside a laser cavity. Twenty years of continuous progress led to the production of light pulses of less than 10 femtoseconds. In the race towards ever shorter pulses, recent developments in the generation of tabletop X-ray lasers have opened the way to dynamical studies in the attosecond (10−18 s)regime [4.1-2]. In the meantime, progress was made on the tunability of the pulsed-laser sources. Today’s tunability extends from the near ultraviolet to the near infrared [4.2-6].

Further Methods for the Generation of Ultrashort Optical Pulses

It is shown that impurities introduced by thermal diffusion can improve propagation properties of surface waves excited on unpolarized ceramic plates using an interdigital arrangement of electrodes. In BaTiO3 ceramics, CO2O3 reduces the attenuation constant of surface waves to one‐half the values obtained with specimens with no added impurities. In the most favorable case, the output voltage due to the surface waves increased by a factor of 3.

K. Okazaki

Papers

Effects of thermally diffused impurities on propagation of elastic surface waves on the ferroelectric ceramics