TY - JOUR

T1 - Population difference gratings created on vibrational transitions by nonoverlapping subcycle THz pulses

AU - Arkhipov, Rostislav

AU - Pakhomov, Anton

AU - Arkhipov, Mikhail

AU - Babushkin, Ihar

AU - Demircan, Ayhan

AU - Morgner, Uwe

AU - Rosanov, Nikolay

N1 - Arkhipov, R., Pakhomov, A., Arkhipov, M. et al. Population difference gratings created on vibrational transitions by nonoverlapping subcycle THz pulses. Sci Rep 11, 1961 (2021). https://doi.org/10.1038/s41598-021-81275-8

PY - 2021/1/21

Y1 - 2021/1/21

N2 - We study theoretically a possibility of creation and ultrafast control (erasing, spatial frequency multiplication) of population density gratings in a multi-level resonant medium having a resonance transition frequency in the THz range. These gratings are produced by subcycle THz pulses coherently interacting with a nonlinear medium, without any need for pulses to overlap, thereby utilizing an indirect pulse interaction via an induced coherent polarization grating. High values of dipole moments of the transitions in the THz range facilitate low field strength of the needed THz excitation. Our results clearly show this possibility in multi-level resonant media. Our theoretical approach is based on an approximate analytical solution of time-dependent Schrödinger equation (TDSE) using perturbation theory. Remarkably, as we show here, quasi-unipolar subcycle pulses allow more efficient excitation of higher quantum levels, leading to gratings with a stronger modulation depth. Numerical simulations, performed for THz resonances of the H20 molecule using Bloch equations for density matrix elements, are in agreement with analytical results in the perturbative regime. In the strong-field non-perturbative regime, the spatial shape of the gratings becomes non-harmonic. A possibility of THz radiation control using such gratings is discussed. The predicted phenomena open novel avenues in THz spectroscopy of molecules with unipolar and quasi-unipolar THz light bursts and allow for better control of ultra-short THz pulses.

AB - We study theoretically a possibility of creation and ultrafast control (erasing, spatial frequency multiplication) of population density gratings in a multi-level resonant medium having a resonance transition frequency in the THz range. These gratings are produced by subcycle THz pulses coherently interacting with a nonlinear medium, without any need for pulses to overlap, thereby utilizing an indirect pulse interaction via an induced coherent polarization grating. High values of dipole moments of the transitions in the THz range facilitate low field strength of the needed THz excitation. Our results clearly show this possibility in multi-level resonant media. Our theoretical approach is based on an approximate analytical solution of time-dependent Schrödinger equation (TDSE) using perturbation theory. Remarkably, as we show here, quasi-unipolar subcycle pulses allow more efficient excitation of higher quantum levels, leading to gratings with a stronger modulation depth. Numerical simulations, performed for THz resonances of the H20 molecule using Bloch equations for density matrix elements, are in agreement with analytical results in the perturbative regime. In the strong-field non-perturbative regime, the spatial shape of the gratings becomes non-harmonic. A possibility of THz radiation control using such gratings is discussed. The predicted phenomena open novel avenues in THz spectroscopy of molecules with unipolar and quasi-unipolar THz light bursts and allow for better control of ultra-short THz pulses.

KW - Optical physics

KW - Optics and photonics

KW - Physics

KW - Terahertz optics

KW - EXCITATION

KW - TERAHERTZ TIME-DOMAIN

KW - RESONANT MEDIUM

KW - SPECTROSCOPY

KW - GENERATION

KW - DENSITY GRATINGS

KW - PROPAGATION

KW - WATER

KW - PAIR

UR - http://www.scopus.com/inward/record.url?scp=85099941553&partnerID=8YFLogxK

UR - https://www.mendeley.com/catalogue/af073265-0459-3e51-9aa5-455276606036/

U2 - 10.1038/s41598-021-81275-8

DO - 10.1038/s41598-021-81275-8

M3 - Article

AN - SCOPUS:85099941553

VL - 11

JO - Scientific Reports

JF - Scientific Reports

SN - 2045-2322

IS - 1

M1 - 1961

ER -