Below Threshold Harmonics Dependence with Phase-Matching Parameters in Argon

This work reports the generation of Below Threshold Harmonics generated in Argon by ultrashort laser pulses. The 3^rd, 5^th, 7^th and 9^th harmonics of the laser were generated in the UV and VUV regions, and the frequency conversion occurred in flowing gas in a glass nozzle into a vacuum chamber. The harmonics generated show a blue-shift and an efficiency that depend on the laser pulses intensity and also on the gas pressure. These parameters determine the phase-matching condition, which governs the energy conversion from the laser into the harmonics, and this study shows that is possible to tune the harmonics intensity and wavelength, providing a versatile light source.