Interference at quantum transitions: lasing without inversion and resonant four-wave mixing in strong fields at Doppler-broadened transitions

An influence of nonlinear interference processes at quantum transitions under strong resonance electromagnetic fields on absorption, amplification and refractive indices as well as on four-wave mixing processes is investigated. Doppler broadening of the coupled transitions, incoherent excitation, relaxation processes, as well as power saturation processes associated with the coupled levels are taken into account. Both closed (ground state is involved) and open (only excited states are involved) energy level configurations are considered. Common expressions are obtained which allow one to analyze the optical characteristics (including gain without inversion and enhanced refractive index at vanishing absorption) for various V, Lambda and H configurations of interfering transitions by a simple substitution of parameters. Similar expressions for resonant four-wave mixing in Raman configurations are derived too. Crucial role of Doppler broadening is shown. The theory is applied to numerical analysis of some recent and potential experiments.Comment: 12 pages, 9 eps figures, invited paper, Proceedings of the 11th International Vavilov Conference on Nonlinear Optic

Atomic coherence and interference phenomena in resonant nonlinear optical interactions

Interference effects in quantum transitions, giving rise to amplification without inversion, optical transparency and to enhancements in nonlinear optical frequency conversions are considered. Review of the relevant early theoretical and experimental results is given. The role of relaxation processes, spontaneous cascade of polarizations, local field effects, Doppler-broadening, as well as specific features of the interference in the spectral continuum are discussed.Comment: 13 pages, 13 eps figures, review paper, Proceedings of the 15th International Conference on Nonlinear Optics - ICONO'9

Nonlinear-optical frequency-doubling meta-reflector: pulsed regime

The properties of backward-wave second harmonic meta-reflector operating in pulse regime are investigated. We show that ratio of the income pulse length to the thickness of the metaslab determines its important operational properties which are in contrast with those manifested at common second harmonic generation settings.Comment: 6 pages, 3 figure

Second harmonic generation and pulse shaping in positively and negatively spatially dispersive nanowaveguides: comparative analysis

Comparative analysis of second harmonic generation in ordinary and backward-wave settings is presented. Extraordinary properties of frequency doubling nonlinear optical reflectivity and pulse shaping through phase matching of ordinary and backward electromagnetic waves in the nanowaveguides with mixed negative/positive spatial dispersion is demonstrated with numerical simulations.Comment: 10 pages, 5 figure