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 1HNMR 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 (Tg) 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.