ИСТИНА

Bright squeezed vacuum (BSV), the radiation at the output of a strongly pumped unseeded parametric amplifier, is known to have strong and fast intensity fluctuations. For this reason, it provides an efficiency increase in multiphoton effects. Recently we have demonstrated this enhancement for the case of 2nd-4th harmonic generation. It turns out that the output radiation has even stronger intensity fluctuations, which can be characterized by increased values of the bunching parameter g(2). For instance, for the radiation of the fourth harmonic g(2) values of up to 100 have been observed. Moreover, if BSV pumps a nonlinear effect with exponential dependence on the pump, such as supercontinuum generation, the output radiation has so high intensity fluctuations that it manifests ‘rogue-wave’ behaviour, featuring a probability distribution of Pareto type, . For such statistics, the description in terms of moments is not applicable. Figure 1 shows the photon-number distribution of supercontinuum generated at 770 nm in a 5 m single-mode fused silica fiber pumped by 240 of BSV with the central wavelength 800 nm and the bandwidth 10 nm. A straight line in a double logarithmic scale clearly shows the Pareto scaling, and the inset demonstrates the appearance of extreme events (high pulses) with amplitudes exceeding the mean value by two orders of magnitude. As to the bunching parameter, we have observed a value of , but this should be only a lower boundary because the distribution shown in Fig.1 has to be truncated in order to even calculate the mean value. This type of extremely fluctuating light can be used for further pumping nonlinear effects and for high-contrast ghost imaging. Another interesting feature is that subtraction of a photon from such radiation increases the mean photon number by a factor of g(2), i.e., at least 170 in our case.