**2. Fabrication of a surface-relief structure with optical polymers**

Before hybrimers were considered UV-curable materials for surface-relief structures, commercially available optical prepolymers such as J-91, SK-9 (Summers Optical), and NOA-73 (Norland Products Inc.) were applied in soft lithography. Table 1 shows the main properties of these materials (Summers) (Norland).


Table 1. The properties of three commercial optical prepolymers
