Ewald’s spheres for the selected geometry, using ${\lambda }_r=532$ nm for the recording process and ${\lambda }_c=473$ nm as the designed wavelength for the reconstruction stage. The recording structure (green) is built upon the recording angles in the material: $19.4^{\circ }$ and $35.1^{\circ }$. The equivalent assembly for the reconstruction step (blue) yields angles of $1.0^{\circ }$ and $55.5^{\circ }$. The average refractive index is $n_0=1.505$, so the critical angle is ${\theta }_c=41.6^{\circ }$.