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Impact of incorporation of TiO2 and Al2O3•nH2O metal oxide nanoparticles on bulk properties of KDP crystals

Igor M. Prytula 1Marina I. Kolybaeva 1Anna Kosinova 1Olga N. Bezkrovnaya 1Viacheslav M. Puzikov 1Valentin Tkachenko 1Maksim Kopylovsky 2Mykhaylo Brodyn 2Vladimir Gayvoronsky 2

1. Institute for Single Crystals NAS of Ukraine (ISC), 60 Lenin Ave., Kharkov 61001, Ukraine
2. Institute of Physics NAS of Ukraine, pr. Nauki 46, Kiev 03680, Ukraine

Ferroelectric single crystals (SCs) of the KDP family are characterized by a unique set of properties, such as a wide range of optical transparency, nonlinear, electrooptical and piezoelectric effects. However, one of the main shortcomings of KDP SCs is its relatively low quadratic susceptibility. A possible way to increase this susceptibility and, subsequently, the efficiency of the three-wave processes is by altering its structure through a formation of nanocomposite medium. Nanoparticles (NPs) incorporation into the KDP matrix was realized in order to design novel lasing media.
In the present work, the impact of titanium dioxide (anatase, TiO2) and aluminium oxyhydroxide (Al2O3•nH2O, NOA) metal oxide NPs on growth process, optical and structural properties of KDP single crystal was was determined by several complementary methods: transmission and scanning electron microscopy, Uv-vis-IR spectroscopy, EDAX, FTIR, measurements of nonlinear optical (NLO) response.
It is found that the incorporation of TiO2 NPs (C = 10-5 –10-3 wt.%) into the crystal matrix is accompanied with insignificant lowering of the growth rate. X-ray diffraction analysis shows that TiO2 NPs are captured preferentially by the pyramidal face. For KDP:TiO2 crystals there was found a relative change of the crystal lattice parameter caused by incorporation of TiO2  into the boundaries of the growth layers. It leads to formation of two-dimensional layered macroscopic structure KDP:TiO2:KDP with spatial period 15-20 µm. High optical quality of the KDP:TiO2 SCs was shown experimentally [1,2]. The effect of the NOA NPs on the growth kinetics of the crystal faces is investigated. The predominating interaction of the NPs with the {100} crystal faces is established. This is confirmed by an elevated NPs concentration in the {100} growth sector, the increase of the dead zone and the halfwidth of DRC exceeding the one of the {101} faces. The capture of the NPs by the {100} faces is shown to be realized through the formation of hydrogen bonds.
The presence of the metal oxide NPs in the crystal matrix caused the enhancement of the cubic NLO response and the sign change of the nonlinear refraction index of the composite system at picosecond pulses excitation at 1064 nm. The effect has been explained by giant NLO response of the anatase NPs due to the resonant excitation of their surface defect states under picosecond laser pulses. The enhancement of frequency conversion efficiency (~70%) was obtained in KDP:TiO2 versus KDP SCs due to the internal self-focusing effect of the pumping beam caused by the giant cubic NLO response of the embedded NPs [3].
For the KDP:NOA SCs demonstrated the sign inversion and enhancement of the refractive nonlinear optical response relatively to nominally pure KDP matrix at the self-action of pulsed laser radiation of picosecond range (λ=1064 nm).

[1] I Pritula et al. Optical Materials 33 (2011) 623
[2] V Grachev et al. J. Appl. Phys.112 (2012) 014315I
[3] V Ya Gayvoronsky et al. Laser Phys. Lett. 10 (2013) 035401


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Presentation: Oral at 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17, Topical Session 6, by Igor M. Prytula
See On-line Journal of 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17

Submitted: 2013-03-27 17:19
Revised:   2013-03-27 17:19