CC BY
5The 30th International Conference on Advanced Laser Technologies
ALT'23
LM-P-9
Bulk domains growth created by femtosecond laser in magnesium doped lithium niobate
B. Lisjikh1, M. Kosobokov1, A. Efimov1, D. Kuznetsov1, V. Shur1
1-Institute of Natural Sciences and Mathematics, Ural Federal University 620002, Ekaterinburg, Russia
One of the most important reasons for application of the ferroelectric crystals in nonlinear optics is related to creation of precise stable periodical domain structure for efficient frequency conversions based on quasiphase matching. The irradiation by femtosecond laser is the only method which allows to create the periodical domain patterns both, at the surfaces and in the bulk [1,2].
The crystals of lithium niobate LiNbO3 family are the most popular objects of the domain engineering due to their outstanding electro-optical and nonlinear optical properties. The MgO-doped lithium niobate (MgO:LN) is the most attractive due to higher optical damage threshold and lower value of the threshold field for polarization reversal as compare to usual congruent LN.
Here we used Yb-doped fiber laser system TETA-10 (Avesta, Russia) emitting pulses in TEM00 mode at the 1030 nm wavelength with energies from 0.7 to 6.7 ^J in filamentation regime, duration 240 fs, repetition frequency 100 kHz. The 1-mm thick plates of single-domain MgO:LN cut perpendicular to the polar axis were mounted at the motorized table to carry out point-by-point irradiation focused at depths of 200-800 ^m below Z- polar surface.
Three methods have been used for imaging of the microtracks and domains: (1) optical microscopy (Olympus BX-61, Olympus, Japan), (2) confocal Cherenkov-type second harmonic generation microscopy (CSHG) (Ntegra Spectra, NT-MDT, Russia) and (3) scanning electron microscopy (EVO LS 10, Carl Zeiss, Germany) after selective chemical etching.
It was shown that the irradiation led to formation of ferroelectric domains localized at the microtracks represented the modified crystal areas in the crystal bulk (Fig. 1a). In proper range of the pulse energy the domains grew from the microtracks to the polar surface towards the irradiation source (Fig. 1b, c). The typical for LN hexagonal shape was obtained for domains which reached the polar surface. The domain growth is attributed to polarization reversal under the action of pyroelectric field during the sample cooling after termination of pulsed irradiation [3,4].
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Fig. 1. 3D reconstructions by CSHG of ferroelectric domains in the bulk: (a) depth 400 ^m, pulse energy 2.7 J (b) depth 200 ^m,
pulse energy 4 J (c) depth 800 ^m, pulse energy 6.7 J
The obtained results can be used for development of the domain engineering methods without application of the electric field in various ferroelectric crystals.
This research was funded by the Ministry of Science and Higher Education of the Russian Federation (Ural Federal University Program of
Development within the Priority-2030 Program).
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[3] V. Ya. Shur, M. S. Kosobokov, A. V. Makaev, D. K. Kuznetsov, M. S. Nebogatikov, D. S. Chezganov, and E. A. Mingaliev, Dimensionality increase of ferroelectric domain shape by pulse laser irradiation, Acta Materialia, vol.219, p.117270 (2021).
[4] B. I. Lisjikh, M. S. Kosobokov, A. V. Efimov, D. K. Kuznetsov, V. Ya. Shur, Thermally assisted growth of bulk domains created by femtosecond laser in magnesium doped lithium niobate, Ferroelectrics, vol.604, pp.47-52 (2023).
