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Valentina Shumakova

Publications and source records attributed to Valentina Shumakova.

4 recordsLinked to original sources
arXiv2022

Ionization rate and plasma dynamics at 3.9 micron femtosecond photoionization of air

The introduction of mid-IR optical parametric chirped pulse amplifiers (OPCPAs) has catalyzed interest in multi-millijoule, infrared femtosecond pulse-based filamentation. As tunneling ionization is a fundamental first stage in these high-intensity laser-matter interactions, characterizing the process is critical to understand derivative topical studies on femtosecond filamentation and self-focusing. Here, we report constructive-elastic microwave scattering-based measurements of total electron count, electron number densities, and photoionization rates generated by 3.9 micron femtosecond mid-infrared tunneling ionization of atmospheric air. Consequently, we determine photoionization rates in the range of 5.0x10$^{8}$-6.1x10$^{9}$ s$^{-1}$ for radiation intensities 1.3x10$^{13}$-1.9x10$^{14}$ W/cm$^{2}$, respectively. The proposed approach paves the wave to precisely tabulate photoionization rates in mid-IR for broad range of intensities and gas types and to study plasma dynamics at mid-IR filamentation.

physics.plasm-ph↗
arXiv2021

Simple approach for extending the ambiguity-free-range of dual-comb ranging

Dual-comb (DC) ranging is an established method for high-precision and high-accuracy distance measurements. It is, however, restricted by an inherent length ambiguity and the requirement for complex control loops for comb stabilization. Here, we present a simple approach for expanding the ambiguity-free measurement length of dual-comb ranging by exploiting the intrinsic intensity modulation of a single-cavity dualcolor DC for simultaneous time-of-flight a nd D C distance measurements. This measurement approach enables the measurement of distances up to several hundred km with the precision and accuracy of a dualcomb interferometric setup while providing a high data acquisition rate (~2 kHz) and requiring only the repetition rate of one of the combs to be stabilized.

physics.ins-det↗
arXiv2018

Filamentation of Mid-IR pulses in ambient air in the vicinity of molecular resonances

Properties of filaments ignited by multi-millijoule, 90-fs mid-IR pulses centered at 3.9 μm are examined experimentally by monitoring plasma density and losses as well as spectral dynamics and beam profile evolution at different focusing strengths. By softening the focusing from strong (f=0.25 m) to loose (f=7 m) we observe a shift from plasma assisted filamentation to filaments with low plasma density. In the latter case, filamentation manifests itself by beam self-symmetrization and spatial self-channeling. Spectral dynamics in the case of loose focusing is dominated by the non-linear Raman frequency downshift, which leads to the overlap with the CO2 resonance in the vicinity of 4.2 μm. The dynamic CO2 absorption in the case of 3.9-μm filaments with their low plasma content is the main mechanism of energy losses and either alone or together with other nonlinear processes contributes to the arrest of intensity.

physics.optics↗