Enhanced harmonic generation using different second-harmonic sources for the two-color pump of extended laser-produced plasmas

Studies of high-order harmonic generation using single-color and two-color pumps of the long plasmas produced on various metal surfaces are presented using different sources of second-harmonic pump. We apply the barium borate (BBO) crystals of different thickness to manipulate the pump intensity ratios and the overlapping of two pumps in the plasma area. Different relations between the delays and intensities of these pumps allowed the definition of the optimal length of BBO for the efficient generation of even and odd harmonics using targets possessing various ablation properties. The 50x enhancement of odd and even harmonics was achieved in the case of the two-color pump compared with the single-color pump of silver plasma. (C) 2014 Optical Society of America