[Landau ITP Seminars] Friday 17.03.2023

[Serge Krashakov]

Уважаемые коллеги!

На заседании Ученого совета в пятницу  17 марта в 11:30 будут заслушаны 
2 доклада:

1) С.И. Матвеенко
*Ротоны в Бозе-конденсате дипольных атомов.*

Найдены аналитические и численные решения для спектров возбуждений 
ротонного типа в квазиодномерном Бозе-конденсате магнитных дипольных 
атомов. Вычислен коэффициент затухания возбуждений при конечной 
температуре. Результаты могут быть применимы к конденсату атомов 
диспрозия, для которого показано, что ротонные возбуждения достаточно 
долгоживущие и могут быть наблюдаемы.


2) Н.А. Иногамов
*Структурирование поверхности кремния с помощью фемтосекундного импульса 
и дифракции на микропузырьке*. (короткий доклад)

Laser-assisted nanostructuring of silicon interfaces provides a unique 
procedure for leading-edge technologies. We report on a new embossing 
technique with tightly focused Gaussian-shaped ultrashort laser pulses 
near the ablation threshold in liquid. We take advantage of a primary 
microbubble for controllable spatial-modulation of light intensity of 
succeeding pulses. Such a bubble, generated in liquid near the molten 
silicon surface by the first pulse, serves as an obstacle for the second 
pulse following with a sub-millisecond time delay, to produce a 
diffraction ring pattern. Variation of laser intensity can be utilized 
to guide the diffraction patterns. Thus the various annular patterns 
deeply embossed up to hundreds nanometers on the surface are produced 
with high reproducibility. Morphology of modified surface layer is 
investigated in detail using atomic-force microscopy, as well as 
scanning and transmission electron microscopies. Full-wave EM modeling 
of laser beam diffraction by the bubbles with various radii and shapes 
shows that the peak intensity in silicon is up to 1.7 times higher than 
in bubble-free liquid. Atomistic simulation of ultrafast heating with 
such a diffraction peak reveals that an annular microdimple surrounded 
by rims is formed by high-gradient pressure in molten silicon to be 
frozen after several nanoseconds.
S.A. Romashevskiy, A.I. Ignatov, V.V. Zhakhovsky, E.M. Eganova, E.A. 
Pershina, N.A. Inogamov, S.I. Ashitkov, Embossing of silicon with an 
ultrashort laser pulse diffracted by a bubble in liquid, Applied Surface 
Science, 615, 156212 (2023)


ID и пароль онлайн-трансляций в Zoom те же, что и для предыдущих 
трансляций докладов на Ученом совете:
https://zoom.us/j/96899364518?pwd=MzBsR2lYT0lYL2x2b1oyNU9LeWlWUT09
Meeting ID: 968 9936 4518
Пароль: 250319

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