Population of metastable barium associated with conical emission

Monochromatic Conical IR Emission from Decaying KrF Laser Filaments in Xenon as Coherent Stimulated Four-Wave Mixing Process

“…It was observed for the first time in borosilicate glass [1] and potassium vapor [2] fifty years ago. In most of the cases, CE has been studied in alkali and alkaline-earth vapors with ns-pulse and cw laser excitation when the laser frequency is tuned to the blue side of a resonance transition [3][4][5][6][7][8][9][10][11]. Femtosecond laserinduced CE has been observed in dense cesium [12] and rubidium [13] vapors.…”

“…Nonlinear interaction of KrF laser radiation with xenon proceeds in the regime of near-resonant two-photon 1 S 0 − 2p 5 ( 2 P 3/2 )6p[1/2] 0 transition which makes it in a definite sense analogous to the mentioned above case of sodium [19][20][21]. Previously, CE in xenon has been observed as strong coherent continua emissions in the visible and near-infrared (650-850 nm) and in the UV (185-400 nm) spectral ranges with a tightly-focused femtosecond KrF laser radiation at intensities up to 10 15 W/cm 2 [30,31].…”

Electromagnetically induced conical emission

“…Typically, experimental CE observations have been made with pulsed laser intensities greater than 10 6 W/cm 2 . But CE has also been reported in metastable barium vapor under off-resonant cw excitation with only 25 W/cm 2 [10]. Nonetheless, such relatively low intensity used in the barium experiment is about three orders of magnitude higher than the saturation intensity of the excited atomic transition at line center.…”

“…To verify that the CE patterns result from the XPM phase shift induced on the probe field by the signal field, we artificially set φ(ρ) ≡ 0, but keep the radial dependence of the absorption coefficient α(ρ) in Eq. (10). The diffraction patterns with and without the XPM phase are shown in Fig.…”