Related papers: Enhanced Population on Ionic Excited States by Syn…
Tunneling ionization followed by strong-field excitation leads to important ultrafast phenomena such as charge migration and lasing. Recent theoretical developments suggest that the population of the ionic excited state can be greatly…
We carry out a combined theoretical and experimental investigation on the population distributions in the ground and excited states of tunnel ionized N2 molecules at various driver wavelengths in the near- and mid-infrared range. Our…
Experiments on one- and two-photon laser excitation of 232Th+ ions in a radiofrequency ion trap are reported. As the first excitation step, the strongest resonance line at 402 nm from the 6d^2 7s J=3/2 ground state to the 6d7s7p J=5/2 state…
Air-lasing from single ionized N$_2^+$ molecules induced by laser filamentation in air has been intensively investigated and the mechanisms responsible for lasing are currently highly debated. We use ultrafast nitrogen K-edge spectroscopy…
Delayed cavity-free forward lasing at the wavelengths of 391 and 428 nm was observed in recent experiments in air or pure nitrogen pumped with an intense femtosecond laser pulse at wavelength of 800~nm. The mechanism responsible for the…
Cavity-free lasing of N$_2^+$ induced by a femtosecond laser pulse at 800~nm is nearly totally suppressed by a delayed twin pump pulse. We explain this surprising effect within the V-scheme of lasing without population inversion. A fast…
An analytic study is presented of the efficient multiphoton excitation and strong harmonic generation in three-level systems specified by a pair of nearly degenerate, strongly dipole-coupled excited states. Such systems are physically…
The system of a trapped ion translationally excited by a blue-detuned near-resonant laser, sometimes described as an instance of a phonon laser, has recently received attention as interesting in its own right and for its application to…
We demonstrate low-threshold random lasing in random amplifying layered medium via photon localization. Lasing is facilitated by resonant excitation of localized modes at the pump laser wavelength, which are peaked deep within the sample…
N$_2^+$ air lasing has attracted considerable attention due to its promising applications in remote sensing and the debates surrounding its generation mechanisms. Here, we present a comprehensive theoretical investigation of the role of…
We experimentally demonstrate ultrafast dynamic of generation of a strong 337-nm nitrogen laser by injecting an external seed pulse into a femtosecond laser filament pumped by a circularly polarized laser pulse. In the pump-probe scheme, it…
Steady-state plasmonic lasing is studied theoretically for a system consisting of many dye molecules arranged regularly around a gold nano-sphere. A three-level model with realistic molecular dissipation is employed to analyze the…
Harnessing structured light is fascinating for its multi-disciplinary applications, e.g., in remote driving microrobots, sensing, communications, and ultrahigh resolution imaging. Here we experimentally demonstrated the generation of a…
A near-infrared laser generates gain on transitions between the $\text{B}^{\text{2}} \Sigma_{\text{u}}^{\text{+}}$ and $\text{X}^{\text{2}} \Sigma_{\text{g}}^{\text{+}}$ states of the nitrogen molecular cation in part by coupling the…
We have investigated photoionization of Ne$^+$ in the combined field of a short infra-red laser pulse and a delayed ultra-short pulse of the infra-red laser's 23$^r$$^d$ harmonic. We observe an ionization yield compatible with a picture in…
We report on generation of a rotational wavepacket in the ground vibronic state (v = 0) of excited electronic B2{\Sigma}u+ state of N2+ in a femtosecond laser induced plasma spark. Decoding of the rotational wavepacket is achieved with the…
We report on the lasing action of atmospheric air pumped by an 800 nm femtosecond laser pulse with peak power up to 4 TW. Lasing emission at 428 nm increases rapidly over a small range of pump laser power, followed by saturation above ~ 1.5…
Air lasing provides a promising technique to remotely produce coherent radiation in the atmosphere and attracts continuous attention. However, the polarization properties of N2+ lasing with seeding has not been understood since it was…
Simulations of ionization induced injection in a laser driven plasma wakefield show that high-quality electron injectors in the 50-200 MeV range can be achieved in a gas cell with a tailored density profile. Using the PIC code Warp with…
A two-dimensional model atom is employed to study the ionization behavior of initially excited atomic states in highly-frequent intense laser pulses beyond the dipole approximation. An additional regime of ionization suppression is found at…