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6The 30th International Conference on Advanced Laser Technologies
ALT'23
N-I-l
Nano- and micro- size targets for generation of terahertz waves
A.V. Balakin1, N.A. Kuzechkin2, P.M. Solyankin2, A.P. Shkurinov1
1- Faculty of Physics, Lomonosov Moscow State University, Moscow 119991, Russia 2- Institute on Laser and Information Technologies of the Russian Academy of Sciences—Branch of the Federal Scientific Research Center "Crystallography and Photonics" of the Russian Academy of Sciences, Shatura, 140700,
Russia
Complex study of interaction of high intense femtosecond laser pulses with gas nanoclusters and single microdroplets aimed to providing fundamental and applied knowledge for development of effective pulsed sources of teraherz (THz) radiation is presented. High local density of the nano- and micro- targets in addition with high localization of the light wave's field near these subwavelength structures lead to appereance of strong nonlinear effects revealing, particularly, in efficient generation of new frequencies in an extremely wide spectral range: from X-ray to THz.
The nanocluster target in our experiments was formed by means of gas adiabatic expansion. In this method, the gas under high pressure expands through a special form nozzle into vacuum. Fast adiabatic cooling of the gas results in formation of nanometer scale clusters in the supersonic jet. Fig.1(a) illustrates the method and shows a distribution of the total atomic density in the cluster jet, studied in our experiments, and CCD-images of laser plasma filaments. The interaction of powerful femtosecond laser pulses with specially formed gas-cluster jet proceeds with high efficiency and is accompanied by the generation of directional beam of THz radiation [1]. Here we present and discuss the results of studies of THz generation from laser-excited nanocluster targets with various properties.
As a matter for the microdroplet targets a liquid metal eutectic alloy (48% Sn, 52% In) and dielectrics such as distilled water and isopropanol were used. The single free-falling microdroplets with a diameter of around 50 um synchronized with laser pulses were produced with special high temperature dispenser device as described in our paper [2] and illustrated in Fig.1(b). We demonstrated that double-pulse excitation significantly enhances the yield of THz signal, which is accompanied with X-ray. The study of the THz signal dependence on laser excitation parameters together with its angular distribution allowed us to make some assumptions on origin of the THz radiation and the ways of the signal optimization.
(a) (b)
Fig. 1. Formation of nano- and micro- size targets for THz generation. (a) supersonic gas-cluster jet and photos of laser focus at 1.5, 18.3 and 32.3 mm below the nozzle output. (b) free-falling droplets and photos of single droplet before and 2 us after laser excitation.
This work was funded partly by the Ministry of Science and Higher Education within the State assignment FSRC "Crystallography and Photonics" RAS and in part by the Ministry of Science and Higher Education of the Russian Federation in framework of Agreement № 075-15-2022-830 from 27 May 2022.
[1] Balakin A. V. et al. Directional terahertz beam generation under interaction of an intense femtosecond laser pulse with a cluster jet //JOSA B, vol. 38, №. 11, p.. 3515-3522 (2021)
[2] Solyankin P. M. et al. Single free-falling droplet of liquid metal as a source of directional terahertz radiation //Physical Review Applied, vol. 14, №. 3, p. 034033 (2020)
