Effect of Laser Beam Amplitude Profile on Second Harmonic Generation Efficiency

The efficiency of laser radiation harmonic generation in nonlinear crystals is one of the most pressing problems in applied nonlinear optics. This work theoretically studies the second harmonic generation (SHG) in a converging (focused into a crystal) laser beam. The effect of the amplitude profile (AP) of fundamental laser radiation beam (before the lens) on the SHG efficiency and on optimal focusing and wave detuning parameters is estimated for the first time. It is ascertained that the optimal values of focusing and especially wave detuning parameters vary in very wide ranges depending on the AP. A strong influence of the AP on the effective aperture length, which mainly limits the SHG efficiency, is shown. Optimization of the AP enables increasing the SHG efficiency by no more than ∼10%.