Highly Efficient and Thermally Stable Electro‐optic Polymer from a Smartly Controlled Crosslinking Process

A nonlinear optical polymer , which is thermoreversibly crosslinkable (see Figure), has been developed to overcome the nonlinearity–stability trade‐off in poled polymers. High poling efficiency has been achieved after controlled, mild lattice hardening via the Diels–Alder crosslinking reaction. The resulting material exhibits a large electro‐optic coefficient ( r 33 = 76 pm V –1 at 1.3 μm) and excellent temporal stability.