Results of EFP with a hybrid mask on -z. Top views of the patterns, revealed after
the poling by a wet-etch in an HF:H2O solution: (a) top (patterned) surface, originally
-z and (b) bottom (upatterned) surface, originally + z. For details, see Manzo et
al., Opt. Mater. Express 1, 365 (2011). .