Conical emission

Fig. 5.4. Transverse view of (a) a single filament obtained upon irradiation of a 15 mm crystal of BaF2 by incident energy of 5 pJ, (b) two filaments obtained at 8 pJ, and (c) the corresponding image of the conical emission and white light obtained in the far field...

Conical emission, 85, 89, 93 Constructive interference, 66 Continuous wavelet transforms, 145 Contrast ratio, 142-144, 191 Conversion efficiency, 96 Corona discharges, 110 Counter-propagating laser pulses, 171 CPA, 187 Critical power, 83 Cross section, 125... 

Fig. 14.5. a Conical emission observed on a screen b Multifilament pattern on a screen... 

E. T. J. Nibbering, P. F. Curley, G. Grillon, B. S. Prade, M. A. Franco, F. Salin, A. Mysyrowicz, Conical emission from self-guided femtosecond pulses in air, Optics Letters 21, 62 (1996). 

O. G. Kosareva, V. P. Kandidov, A. Brodeur, C. Y. Chen, S. L. Chin, Conical emission from laser-plasma interactions in the filamentation of powerful ultrashort laser pulses in air, Optics Letters 22, 1332 (1997). 

Induced Moving Polarisation in Sodiun, Journ. of Physics B, to be published On the Optical Characteristics of the Conical Emission, Optics Comm., to be published. 

The forward spectrum of sodium at density of 1.8 10 cm irradiated by laser with frequency loi to the blue of the D2 transition is shown in figure 1. This spectrum contains, in addition to the laser radiation, a spectrally broad off-axis conical emission attributed by us to a Cherenkov-type emission, and a narrow coherent peak to the blue of the Di transition - the "blue peak". This spectrally narrow emission is on-axis and has a threshold on the laser intensity. Thus, this emission is a stimulated one. Within the resolution of our spectrometer, its frequency does not depend on the laser detuning from the D2 transition. 

Y. H. Meyer, Multiple Conical Emissions from Near Resonant Laser... 

Our results indicate that many of the "conical emission" features previously observed in a number of systemsC3-8) have their physical origin in the scattering mechanisms identified in our experiments. The identification is based on the measurement of the frequency spectrum of the stimulated radiation. We do not as yet have a quantitative explanation for the angular dependence of the emission although we believe it to be caused by propagation effects in the highly nonlinear Na vapor. 

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