Phase relaxation of Faraday surface waves

Surface waves on a liquid air interface excited by a vertical vibration of a fluid layer (Faraday waves) are employed to investigate the phase relaxation of ideally ordered patterns. By means of a combined frequency-amplitude modulation of the excitation signal a periodic expansion and dilatation of a square wave pattern is generated, the dynamics of which is well described by a Debye relaxator. By comparison with the results of a linear theory it is shown that this practice allows a precise measurement of the phase diffusion constant.Comment: 5 figure

Delay of Disorder by Diluted Polymers

We study the effect of diluted flexible polymers on a disordered capillary wave state. The waves are generated at an interface of a dyed water sugar solution and a low viscous silicon oil. This allows for a quantitative measurement of the spatio-temporal Fourier spectrum. The primary pattern after the first bifurcation from the flat interface are squares. With increasing driving strength we observe a melting of the square pattern. It is replaced by a weak turbulent cascade. The addition of a small amount of polymers to the water layer does not affect the critical acceleration but shifts the disorder transition to higher driving strenghs and the short wave length - high frequency fluctuations are suppressed

Liquid n-hexane condensed in silica nanochannels: A combined optical birefringence and vapor sorption isotherm study

The optical birefringence of liquid n-hexane condensed in an array of parallel silica channels of 7nm diameter and 400 micrometer length is studied as a function of filling of the channels via the vapor phase. By an analysis with the generalized Bruggeman effective medium equation we demonstrate that such measurements are insensitive to the detailed geometrical (positional) arrangement of the adsorbed liquid inside the channels. However, this technique is particularly suitable to search for any optical anisotropies and thus collective orientational order as a function of channel filling. Nevertheless, no hints for such anisotropies are found in liquid n-hexane. The n-hexane molecules in the silica nanochannels are totally orientationally disordered in all condensation regimes, in particular in the film growth as well as in the the capillary condensed regime. Thus, the peculiar molecular arrangement found upon freezing of liquid n-hexane in nanochannel-confinement, where the molecules are collectively aligned perpendicularly to the channels' long axes, does not originate in any pre-alignment effects in the nanoconfined liquid due to capillary nematization.Comment: 7 pages, 5 figure

Ferroelectric AgNa(NO2)2 crystals as novel highly efficient nonlinear optical material: Phase matched second harmonic generation driven by a spontaneous and electric field induced polarizations

Paper reports the second harmonic generation(SHG) in ferroelectric AgNa ( NO 2 ) 2 crystals being driven by the spontaneous and electric field induced polarizations. Obtained results are interpreted within the phenomenological theory which considers the free energy describing the interaction between the spontaneous or electric field induced polarizations and spatially inhomogeneous electric polarizations resulted from propagating optical waves. Relatively high magnitudes of the effective second order nonlinear optical (NLO) susceptibilities in these crystals are combined with several phase matching geometries which allows to consider them as high-performance materials for potential NLO applications, such as parametric generation and amplification, frequency doubling, or other applications that require high-efficient frequency conversion. In addition, an anomalously large response of NLO susceptibilities with respect to an applied electric field has been found in the vicinity of the Curie point. This may also have a number of applications, especially in those devices where an efficient tunable control of SHG intensity is demanded

Microcrystalline Bi2ZnB2O7-polymer composites with silver nanoparticles as materials for laser operated devices

A novel type of composite for optoelectronic which is operated by second harmonic generation in the Bi2ZnB2O7 crystallites (with sizes varying within 1–30 μm) and Ag nanoparticles (NP) embedded in PMMA polymer composites is proposed. The substantial influence of the Ag NP on the bicolor induced second harmonic generation was established. The phototreatment was performed by bicolor beams of nanosecond Nd:YAG laser (1,064/532 nm) at angles between the fundamental and photoinducing beams varying within the 19°–21° range. The studies of the corresponding dependences of the SHG during illumination by the two coherent beams at 1,064/532 nm showed a maximal enhancement of the output SHG for the Ag NP average sizes equal to about 40 nm. The role of the excited plasmons may be here crucial. Additionally the time shift between the fundamental and the doubled frequency beam maxima was found, which shows strong sensitivity to illumination. The established time shift is sensitive to the pumping power

CdS Nanocrystallines: Synthesis, Structure and Nonlinear Optical Properties

We report the synthesis, structure and nonlinear optical properties of cadmium sulphide (CdS) nanocrystallines (NCs) synthesized electrochemically both with and without detergent ATLAS G3300. Relevant structural and morphological features are explored by X-ray diffraction and scanning electron microscopy (SEM) techniques. The efficiency of the second harmonic generation (SHG) appears to be strongly dependent on the energy density of the incident fundamental laser radiation and NC sizes.Comment: 2020 IEEE 15th International Conference on Advanced Trends in Radioelectronics, Telecommunications and Computer Engineering (TCSET), Conference Location: Lviv-Slavske, Ukraine, 25-29 February 2020, 5 pages, 8 figures, 3 table

beta-BaTeMo2O9 microcrystals as promising optically operated materials

Studies of optical second harmonic generation (SHG) at fundamental wavelength of 1064 nm under photoinducing treatment of monoclinic piezoelectric beta-BaTeMo2O9 (beta-BTMO) were done. Continuous wave (CW) lasers generating at 808 and 1040 nm were used as photoinducing sources. The investigations were performed for the beta-BTMO microcrystalline powder samples with grain sizes varying within the 25-300 mu m range. We showed that depending on the microcrystallites size, the photoinduced changes of the SHG were substantially different depending on number of defects which were controlled by positron annihilation. The photoinduced SHG efficiency was substantially higher for more defective crystallites. The processes are completely reversible; however, their photoinduced time kinetics is very sensitive to the wavelength of the photoinducing CW laser beam. The possible reasons for the observed differences are discussed within a framework of intrinsic defect trapping levels and their interactions with phonon subsystem