Saturation Effects in Second-Harmonic Generation of Light using Unfocused Laser Beams

Abstract

The theory of second-harmonic generation of light was examined with particular emphasis on the saturation effects occurring at high laser power levels. The nonlinear coupled Maxwell's equations were solved approximately to yield solutions of simple form. The effect of beam divergence was taken into account by averaging the solution over the entire angular spread of the laser beam. The second harmonic thus generated is seen to be proportional to the32 power of the laser power independently of the length of the crystal in long crystals. Experimental data in good agreement with the theory are presented.

Optical harmonic generation and laser light frequency mixing processes in nonlinear media

“…Hence, at conditions of phase matching, the conversion of light of a given frequency to into light of double frequency 209 is a highly effective process; in practice, conversion efficiency upward of 20 ~ can be achieved, and when additionally resorting to cascade amplification the conversion yield of SHG can be raised to 30 to 35 % [45]. Some experiments have revealed conversion saturation [46] due chiefly to a limitation of the interaction length for SHG by birefringence, causing the energy of the fundamental wave and that of the second harmonic to propagate in slightly different directions [47].…”

Zur Theorie der Erzeugung der zweiten Harmonischen in einer planparallelen Kristallplatte

“…* Refraktionsvektoren dieser Wellen werden mit E, ( 2 co) bzw. g, ( 2 co) ( (14) und ihre Refraktionsvektoren konnen wegen der Gesetz-maBigkeiten der Reflexion und Brechung am optisch nicht,linearen Medium aus (15) berechnet werden [lo a]. der Grundwellen a n der hinteren Grenzflache herriihren und durch entsprechende Reflexionskoeffizienten vereinfacht werden konnen (8. Abschn.…”

“…Koharenzlange lK einzufuhren. I n unserem Fall ist Unter Verwendung von l g lautet (72) fur f l = 0 Aus (77) erhalt man als Grenzfalle die in[15] …”

“…Charakteristische Werte fur 1~ sind bei Gaslasern 1~ = 20cm und bei Festkorperlasern (Rubin, d = 4 . lO-3rad) Z g = 0 , l cm[15] 4…”