Figure 6
(a) I2 and I4 values reported for all measured BTO nanocrystals (markers), together with simulated values (thick colored line) resulting from the model of a pure tetragonal bulk crystal oriented with a varying θ from ~0° to 90° (the data are similar for all φ and ψ values), encoded as a color scale. Open circles indicate data for BTO nanocrystals in air, taking the averaged values over the central 25 pixels of the I2 pattern. Filled diamonds are similar data taken in oil. Small open green circles indicate values obtained on BTO nanocrystals in air, averaging the 25 pixels obtained at the border of the radial I2 pattern. The black dot indicates the response for a single isolated 1D dipole (i.e. \({\chi }_{xxx}^{(2)}=1\)). BTO crystal unit cells oriented with θ = 90°, 45°, 0° are schematically represented. (b) I2 and I4 values for a simulated pure KTP crystal. (c) Illustration of a KTP crystal unit cell with the blue arrow indicating the main optical axis of the crystal. The atoms in the KTP unit cell illustration are colored red for potassium, green for titanium, blue for phosphorus and orange for oxygen.
