Filamentation in Atmospheric Air with Tunable 1100–2400 nm Near-Infrared Femtosecond Laser Source

Abstract

Intense femtosecond pulse filamentation in open-air has been utilized for long distance optical communication and remote sensing, but it results in nonlinear-effect driven eye hazards which are not addressed by current eye safety standards. A systematic study of filamentation in atmospheric air was performed using a tunable 100 fs near-infrared laser (1100 nm–2400 nm). While undergoing filamentation, each source wavelength was spectrally broadened resulting in supercontinuum and third harmonic generation in the visible and near-IR spectrum. We record the spectra at the center and fringes of the supercontinuum as it is imaged onto a planar surface. In a full beam collection regime, we report the energy of the sub-1000 nm light generation for source wavelengths from 1100 nm to 1600 nm and compare the energy density to the maximum permissible exposure values under the ANSI Z136.1 laser safety standard.

Modification of Vibrational Parameters of a CO2 Molecule by a Laser Field: Impact on Tunnel Ionization

“…If, at some values of v i and v f , the quantity ∆ (vib) v f ,v i is positive, then the value (29) effectively increases, which leads to a decrease in the tunnel ionization rate. This conclusion follows from the high sensitivity of (28) to the value of κ f i in the tunneling regime. The decrease occurs due to additional energy absorption needed to populate the excited states.…”

“…The structural coefficients in the π g HOMO's asymptotic form (1) were taken from [58]: C = 1.99, C 2 = 0.980, C 4 = 0.199, C 6 = 0.020 (we present them here in dimensionless form). For the calculations, we used Formula (28), which takes into account the excitation of the internal degrees of freedom. The electron integral of the overlap between the ground states of the neutral molecule and cation was calculated by the Hartree-Fock method with the 6-311++G(3df,3pd) basis set (see also Appendix A.1):…”

“…The purpose of this work is to investigate the effect of modifying the vibrational parameters of the carbon dioxide molecule, CO 2 , on tunnel ionization, including anti-Stokes channels. Due to the significant abundance of carbon dioxide, CO 2 , in the Earth's atmosphere, it influences substantially the propagation of laser radiation and filamentation of laser plasma [28]. The stable isotope 13 C is interesting in terms of the magnetic resonance method ( 13 C NMR) [29], and its abundance is 1.06% in the natural mixture.…”

Recent Advances in Air Lasing: A Perspective from Quantum Coherence

“…Many efforts have been applied toward understanding the underlying physics from these complex systems and also pushing forward the realization of the air lasing in the atmosphere outside of the laboratory . It has also been proposed to utilize the effect of beam filamentation in open‐air to enhance the described lasing mechanisms . In addition, due to the rich atomic and molecular species contained in the ambient air, the possibility of the lasing from the substitute gas species with the lower concentration, such as carbon dioxide and water, holds alternative ways of the air lasing and hence attracts lots of interest nowadays .…”

Тепловое Пространственное Смещение Ультракоротких Лазерных Импульсов При Распространении В Атмосфере

“…Это явление, называемое филаментацией, имеет большие потенциальные возможности прикладного значения. Одно из перспективных направлений применения филаментации − это лазерно-индуцированная эмиссионная спектроскопия (laser induced breakdown spectroscopy), в которой используется излучение флуоресценции плазмы, возникающей вследствие оптического пробоя на поверхности исследуемого образца [1]. Для большинства материалов плотность энергии в оптическом филаменте на порядок больше порога возникновения абляции в исследуемых материалах.…”