CC BY
0Laser pump - X-ray probe diagnostics of nanosecond dynamics
in LiNbOs
E.I. Mareev1*, A.G. Kulikov12, F.S. Pilyak12, N.M. Asharchuk1, N.N. Obydennov13, Y.V. Pisarevsky12 A.E. Blagov1, F.V. Potemkin3
1- Kurchatov Complex for Crystallography and Photonics ofNRC "Kurchatov institute", Leninskiy pr-kt 59, Moscow, Russia 2- Kurchatov Complex for Synchrotron and Neutron Investigations of NRC "Kurchatov institute", Pl. akademika Kurchatova 1, Moscow, Russia 3- Faculty of Physics, M.V. Lomonosov Moscow State University, Leninskie Gory bld. 1/2,
119991 Moscow, Russia
* mareev.evgeniy@physics.msu.ru
Synchronization of laser and X-ray sources plays a critical role in conducting time-resolved measurements to explore ultrafast processes, including phenomena like photo-induced piezoelectric effect, phase transitions, and lattice dynamics in semiconductors and dielectrics such as LiNbO3. By combining optical diagnostics and optical pump - X-ray probe diagnostics using a universal approach that leverages a field-programmable gate array (FPGA), we achieved precise synchronization between nanosecond laser and synchrotron X-ray sources in KISI-Kurchatov. This synchronization method offers exceptional advantages, including high flexibility, rapid response times, and minimal jitter, enabling the synchronization of systems with varying repetition rates. We demonstrated the successful synchronization of MHz systems with a time resolution of 250 ps. Using this approach we demonstrated an unusual time-delayed variations in X-ray diffraction parameters in LiNbO3 and LiNbO3:Fe crystals after nanosecond laser impact, see Fig.1. The crystals' response to optical impact led to a reversible shift in center of mass and a decrease in integral intensity of the diffraction rocking curve (DRC), recovering in ~35 nanoseconds after the impact. The dynamics of lattice deformation suggest the formation and subsequent decay of an electrically charged layer near the surface due to directed migration of photoelectrons caused by the bulk photovoltaic effect. The decrease in the integral intensity of the DRCs seems to stem from a propagating strain wave generated by a piezoelectric deformation. In the case of the nominally undoped crystal, time-delayed processes occur within a similar timeframe but with notably smaller amplitudes.
Fig.1. Dynamics of diffraction rocking curve (DRC) of a LiNbO3:Fe (a) and pure crystal exposed to a laser pulse (ip = 4 ns, Ep = 2.0 mJ) over a time range of 150 ns, obtained for the 0012 reflection. The dotted lines indicate the dynamics of the DRC integral.
This work is supported by Russian Science Foundation, grant № 23-73-00039
[1] M.V. Kovalchuk, E.I. Mareev, A.G. Kulikov, F.S. Pilyak, N.N. Obydennov, F.V. Potemkin, Yu.V. Pisarevsky, N.V. Marchenkov, A.E. Blagov, Subnanosecond x-ray diffraction technique for the study of photoinduced polarization-dependent processes on the KISI-Kurchatov, Crystallography Reports, 69, 165-172 (2024).
[2] N. Marchenkov, E. Mareev, A. Kulikov, F. Pilyak, E. Ibragimov, Y. Pisarevskii, F. Potemkin, Hybrid approach for multiscale and multimodal time-resolved diagnosis of ultrafast processes in materials via tailored synchronization of laser and x-ray sources at MHz repetition rates, Optics, 5(1), 1-10 (2024).
