SH Power Research Articles

Dependence of Second Harmonic Generation on Crystal Inhomogeneity

Effect of the nonuniformity of the natural birefringence in a nonlinear crystal on second harmonic generation (SHG) is theoretically and experimentally studied. The second harmonic power at the phase-matching temperature, the second harmonic power vs temperature, and the temperature bandwidth are calculated in terms of the gradient of the natural birefringence and compared with those from the SHG experiment using a cw Nd:YAG laser and Ba2NaNb5O15 single crystal. It is found that the second harmonic peak power is much depressed by the nonuniformity of the natural birefringence in a crystal. The oscillations in the second harmonic power vs temperature curve become broad and the temperature bandwidth increases with decreasing crystal homogeneity. Satisfactory agreement was obtained between theory and experiment. By analytical calculation the dependence of SH power on crystal length l, is expressed in terms of the inhomogeneity length li, which is defined as a measure of the length beyond which SHG is limited by the crystal inhomogeneity. It is found that in an inhomogeneous crystal the SH power does not vary with length as l2 but decreases by the factor (1−l2/6li2).

Optical second‐harmonic generation in SbSI

AbstractThe optical second‐harmonic generation in antimonysulfoiodide (SbSI) was studied with a Q‐switched CO2‐laser. The temperature dependence for various crystals was observed in the range −140 to +40 °C which includes the ferroelectric phase transition at about 20 °C. The nonlinear susceptibility χ33 is about one order of magnitude smaller than χ11 in tellurium. The coherence length lc is estimated to be 165 μm. The SH signal in plane‐parallel samples shows strong temperature dependent modulation produced by interference of fundamental waves. Two further modulations with smaller periods are observed but not explained. Applied electric fields influence the SH power by the electro‐optic effect and by an unidentified mechanism, which causes striking enhancement.

EFFICIENT CW SECOND HARMONIC GENERATION TO 2573 Å

Efficient cw second harmonic conversion to 2573 Å has been achieved in an argon laser cavity by means of the nonlinear materials ADP and KDP. Peak SH power was 415 mW which represented 50% efficiency. Trace impurities in the crystals prevented the realization of theoretical efficiency. An increase in cavity loss was observed during the simultaneous presence of fundamental and SH beams.