Non-linear optical device with long grating persistency

A non-linear optical device comprising a polymer configured to provide a grating holding ratio of 20% or higher after about four minutes, wherein the polymer comprises a first repeating unit comprising a first moiety having formula (M-1) and a second repeating unit comprising a second moiety having formula (M-2):

• wherein each Q in (M-1) and (M-2) independently represents an unsubstituted or substituted alkylene group;
• and wherein Ra1-Ra8 and Rb1-Rb27 in (M-1) and (M-2) are each independently selected from the group consisting of hydrogen, C1-C10 alkyl, C4-C10 aryl and C4-C10 heteroaryl wherein the ratio of the first to second repeating units is in the range of about 1:10 to about 5:1.