Surface-emitting second harmonic generation from short laser pulses

Abstract

We review our recent results on ultrafast surface-emitting second-harmonic generation from mode-locked laser pulses with arbitrary pulse shapes. The spatial dependence of the SH energy density per pulse is almost the same as the temporal profile of the SH power emitted from the entire surface per waveguide width for a long waveguide. For a sinc fundamental pulse, we have obtained, rich and unique, temporal, spatial, and spectral behavior of the second harmonic. We have found that both the temporal and spectral profiles of the emitted second harmonic depend on the location at the surface. These effects can be observed with lasers currently available, and used for auto-correlation, in optical signal processing, optical communications, and practical frequency doubling of ultrafast optical pulses with an advantage of no broadening of the SH pulse. We have compared these results with those for Gaussian, Lorentzian, and hyperbolic secant fundamental pulses. After introducing saturation intensity to quantify the saturation regime, we have obtained quantitative expression for the second-harmonic intensity in terms of the pump and saturation intensities.