Nonlinear optical materials based on fluorinated polyurethane-imides and their application in waveguide devices

Two monomers, a second-order nonlinear optical azo chromophore C containing a tricyanofuran electron acceptor and a dihydroxyethyl nitrogen electron donor, and a bisphenol AF-type diether dianhydride (BPAFDA), were designed and synthesized. Fluorinated polyurethaneimide (PUI) electro-optic (EO) waveguide materials were prepared using the synthesized monomers polymerized with 4,4′-diphenylmethane diisocyanate (MDI). The structures of the synthesized chromophore C, BPAFDA, and polymers of PUI were characterized by 1 HNMR and FTIR, and the thermal properties of the polymers were characterized by DSC and TGA. The prepared PUI exhibited good film-forming properties with glass transition temperatures (T g ) between 160–169°C and over 300°C at 5% thermal weight loss in a nitrogen atmosphere. The experimental results showed that the fluorinated PUIs possessed an EO coefficient of 56–60 p.m./V at 1550 nm and the optical propagation loss of the polymer waveguide was between 1.3–1.4 dB/cm at 1550 nm. Using PUI as the core material of the waveguides, EO modulators with Mach-Zehnder (MZ) structure were designed and prepared, showing good EO modulation performance at 1550 nm.