D. V. Roshchupkin

X-ray Bragg diffraction from langasite crystal modulated by surface acoustic wave

X-ray diffraction on the X cut of a langasite crystal (La3Ga5SiO14) modulated by a Λ=12 μm Rayleigh surface acoustic wave (SAW) has been studied at the ESRF synchrotron radiation source. Due to the sinusoidal modulation of the crystal lattice involved by the SAW diffraction satellites appear on the rocking curve, with their number, angular positions, and intensities depending on the amplitude and wavelength of the ultrasonic superlattice. Full extinction of a specific satellite could be performed by adjusting the acoustic amplitude. It is shown that x-ray diffraction can be used to study surface acoustic wave field distributions in crystals.

X-ray diffraction from perfect silicon crystals distorted by surface acoustic waves

High-resolution X-ray diffraction measurements were carried out on ZnO/Si devices under surface acoustic wave excitation and revealed some very clear satellite diffraction peaks that are obtained from the sinusoidal modulation of the near-surface region. This experiment shows that the propagation of a Rayleigh surface acoustic wave in a perfect crystal acts as a dynamical diffraction grating. The variation of the acoustic velocity has been followed across the crystal surface from the acoustic source region (beneath the ZnO film) to the far field region (not covered by the ZnO film).

X-ray topography analysis of acoustic wave fields in the SAW-resonator structures

The formation of fields of standing surface acoustic waves (SAW) in LiNbO/sub 3/ and La/sub 3/Ga/sub 5/SiO/sub 14/ (LGS) crystals was studied by high-resolution topography method on a laboratory X-ray source. The fields of standing SAW were formed using SAW-resonator structures consisting of interdigital transducer (IDT) and reflecting gratings. The SAW amplitudes and power flow angles were measured by X-ray topography, diffraction in acoustic beam was visualized, and the SAW interaction with the crystal structure defects was studied.

Surface acoustic wave amplification by direct current-voltage supplied to graphene film

Using a high-resolution X-Ray diffraction measurement method, the surface acoustic wave (SAW) propagation in a graphene film on the surface of a Ca3TaGa3Si2O14 (CTGS) piezoelectric crystal was investigated, where an external current was driven across the graphene film. Here, we show that the application of the DC field leads to a significant enhancement of the SAW magnitude and, as a result, to amplification of the diffraction satellites. Amplification of 33.2 dB/cm for the satellite +1, and of 13.8 dB/cm for the satellite +2, at 471 MHz has been observed where the external DC voltage of +10 V was applied. Amplification of SAW occurs above a DC field much smaller than that of a system using bulk semiconductor. Theoretical estimates are in reasonable agreement with our measurements and analysis of experimental data for other materials.

Coherent and diffuse X-ray scattering in crystals modulated by a surface acoustic wave

Equations describing the coherent and diffuse scattering in a crystal modulated by a surface acoustic wave (SAW) are derived using the dynamical X-ray diffraction theory. The effect of depth attenuation of the Rayleigh surface wave amplitude on the crystal rocking curve profiles is investigated. Results of the numerical simulation of the dynamical diffraction in a mosaic crystal modulated by a SAW, taking into account a block size distribution, are presented. It is shown that the diffuse scattering is distributed in the reciprocal space not only in the vicinity of the main diffraction peak but also about the satellite diffraction peaks, and this distribution depends on the size fluctuations of the crystal defects. Theoretical reciprocal space maps and rocking curves are compared with the corresponding experimental results.

Diffraction of surface acoustic waves on the zigzag domain wall in a Gd2(MoO4)3 crystal

This letter reports a scanning electron microscopy investigation of surface acoustic wave diffraction on the zigzag domain wall in a Gd2(MoO4)3 crystal. The zigzag domain wall with ∼80 μm period was formed in a Gd2(MoO4)3 crystal by applying the external mechanical stress. It is shown that the surface acoustic wave diffracts on the zigzag domain wall in a ferroelastic Gd2(MoO4)3 crystal.

Phase-matching directions, refined Sellmeier equations, and second-order nonlinear coefficient of the infrared Langatate crystal La 3 Ga 5.5 Ta 0.5 O 14

We directly measured phase-matching directions of second harmonic, sum, and difference frequency generations in the Langatate La₃Ga(5.5)Ta(0.5)O₁₄ (LGT) uniaxial crystal. The simultaneous fit of the data enabled us to refine the Sellmeier equations of the ordinary and extraordinary principal refractive indices over the entire transparency range of the crystal, and to calculate the phase-matching curves and efficiencies of LGT for infrared optical parametric generation.

High-Frequency X-ray Beam Chopper Based on Diffraction by Surface Acoustic Waves

The diffraction of an X-ray beam on an ultrasonic wave propagating at the surface of a crystal gives rise to diffraction satellites whose temporal structure is correlated to that of the ultrasonic wave. By matching the temporal structure of the surface acoustic wave with the filling mode of the storage ring, it is possible to select or reject the incident X-ray pulses. A few examples of the performance of this MHz-range chopper for various filling modes are presented.

Diffraction of a focused X-ray beam by surface acoustic waves

Abstract This paper reports the first attempt to carry out a focusing followed by a space-time scanning of a synchrotron X-ray beam. The focusing is performed through an elliptical multilayer Bragg-Fresnel lens while the space-time scanning is due to the grazing incidence diffraction on the YZ -cut of a LiNbO 3 crystal modulated by pulsed surface acoustic waves. It opens the field of a new generation of X-ray beam control devices which should be of interest for X-ray scanning microscopy or time resolved spectroscopy. These experiments were carried out at LURE (Orsay, France).

Grazing incidence phase Fresnel zone plate for X-ray focusing

Abstract A grazing incidence phase Fresnel zone plate (GIPFZP) allowing a considerable broadening of the usable spectral range in comparison with a Bragg-Fresnel zone plate is being proposed as a new type of Fresnel zone plate for X-ray focusing. A 2 μm wide image of the X-ray source was obtained by the GIPFZP.