Hot spots in parametric fluorescence with a pump beam of finite cross section

The parametric fluorescence from a nonlinear crystal driven by a pump beam of finite cross section displays a hot spot in the angular and spectral distribution of the signal radiation. The hot spot in the signal radiation occurs where the pump and idler Poynting vectors are collinear. Similarly, a hot spot in the idler radiation is predicted when the pump and signal Poynting vectors are collinear. Signal photons entering the signal hotspot are generally not correlated in direction or frequency with idler photons entering the idler hot spot. We report experimental observation of the signal hot spot in a AgGaS/sub 2/ crystal pumped by a Nd:YAG laser and describe a theory developed to understand the phenomenon. Qualitative and quantitative comparisons of the theory and data show good agreement.<
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