RELATIONSHIP OF THE SECOND-ORDER NONLINEAR-OPTICAL COEFFICIENT TO ENERGY-GAP IN INORGANIC NONCENTROSYMMETRIC CRYSTALS

Second order nonlinear optical coefficient and energy gap data collect ed from the literature have been classified and are organized by plott ing their respective values, The two-dimensional plots indicate that b oth large energy gap and small X-(2) and small energy gap and large X( 2) are highly correlated. It was found that a single power law express ion cannot represent the data well for energy gaps over the entire ran ge from 0 to 10 eV. Therefore a fit for narrow energy gap (0 < 1 eV) a nd for wide energy gap (E > 1 eV) materials are provided, A correspond ing trend and fitting strategy is also demonstrated for the figure of merit (FOM) which is used to rank materials for wavelength conversion efficiency. Results of the analysis are used to estimate the second or der nonlinear optical properties and conversion efficiencies of severa l less-well-known materials, is that ordered GaInP2 would be exception al as an E-O waveguide material and that the FOM of AgGaTe2 is 3.3 tim es that of AgGaSe2 and that crystals of HgGa2Se4 and TexSe(1-x) alloys should be of distinct interest as wavelength conversion materials for infrared applications. The maximum attainable X-(2) is in the range o f 3500-4000 pm/V for bound electrons. For energy gaps less than one eV , the increase in x((2)) considerably. (C) 1997 Published by Elsevier Science B.V.