Accurate second-order susceptibility measurements of visible and infrared nonlinear crystals

Using the wedge technique we have directly compared the second-order nonlinear susceptibilities of infrared and visible nonlinear crystals. The measured nonlinear coefficient ratios at 2.12 μm relative to $d_{31}\left(\mathrm{LiI}{\mathrm{O}}_3\right)$ are: for $\mathrm{LiNb}{\mathrm{O}}_3\left(d_{33}\right)$, 4.53 ± 4.3; $\mathrm{GaP} \left(d_{36}\right)$, 12.1 ± 1.7; $\mathrm{GaAs} \left(d_{36}\right)$, 26.9 ± 2.1; $\mathrm{AgGa}{\mathrm{Se}}_2 \left(d_{36}\right)$, 10.5 ± 1.2; $\mathrm{CdSe} \left(d_{33}\right)$, 10.2 ± 1.2. The measured ratios at 1.318 μm relative to $d_{31}\left(\mathrm{LiI}{\mathrm{O}}_3\right)$ are: for $\mathrm{LiI}{\mathrm{O}}_3 \left(d_{33}\right)$, 0.990 ± 0.05; $\mathrm{LiNb}{\mathrm{O}}_3 \left(d_{31}\right)$, 0.870 ± 0.07; $\mathrm{LiNb}{\mathrm{O}}_3 \left(d_{33}\right)$, 4.66 ± 0.56; $\mathrm{K}{\mathrm{H}}_2{\mathrm{PO}}_4 \left(d_{36}\right)$, 0.088 ± 0.01; $\mathrm{GaP} \left(d_{36}\right)$, 12.0 ± 1.2. We have used the parametric fluorescence method to accurately measure the absolute second-order susceptibility of $\mathrm{LiI}{\mathrm{O}}_3 \left(d_{31}\right)$ and $\mathrm{LiNb}{\mathrm{O}}_3 \left(d_{31}\right)$ at 4880 and 5145 Å. Our recommended values for $d_{31}\left(\mathrm{LiIO}{\mathrm{O}}_3\right)=(7.31\mathrm{}\pm 0.62)\times {10}^{-12\mathrm{}}$ and $d_{31}\left(\mathrm{LiNb}{\mathrm{O}}_3\right)=(5.82\mathrm{}\pm 0.70)\times {10}^{-12\mathrm{}}$ m/V agree very well with previous independent absolute measurements. By scaling the nonlinear susceptibilities through the relatively dispersionless Miller's $\Delta$ and using the wedge ratio results, we have, for the first time, established a uniform scale of nonlinear susceptibility values relative to $d_{31}\left(\mathrm{LiI}{\mathrm{O}}_3\right)$ that extends from 0.488 to 10.6 μm in the infrared.