Further Measurements of Absolute Signs of Second-Harmonic-Generation Coefficients of Piezoelectric Crystals

The signs of the second-harmonic-generation (SHG) coefficients have been determined for $\mathrm{SiC}(d_{31}+,d_{33}-)$, $\mathrm{AgGa}{\mathrm{S}}_2(d_{36}+)$, $\mathrm{ZnGe}{\mathrm{P}}_2(d_{36}+)$, $\mathrm{PbTi}{\mathrm{O}}_3(d_{31}-,d_{33}+)$, ${\mathrm{Ba}}_{0.5}{\mathrm{Sr}}_{0.5}{\mathrm{Nb}}_2{\mathrm{O}}_6(d_{31}-,d_{33}-)$, and $\mathrm{Pb}{\mathrm{Nb}}_4{\mathrm{O}}_{11}(d_{32}-,d_{33}-)$. Where comparisons between theory and experiment can be made, the agreement is good except for PbTi${\mathrm{O}}_3$. In addition, the phases of the SHG coefficients for CdTe, CdSe, and ZnTe have been redetermined in a spectral region where the crystals are transparent and the phases were found to agree with expectations-all $d\text{'}\mathrm{s}$ positive except $d_{31}$ for CdSe.