Preparation and thermo-optic switch properties based on chiral azobenzene-containing polyurethane

A chiral azo chromophore compound 4-(4′-nitro-phenyl-diazenyl)-phenyl-1,2-propanediol ether (NPDPPE) was prepared with p-nitroaniline, phenol and R(−)-3-chloro-1,2-propanediol by the diazo-coupling reaction. Then, the chromophore molecule NPDPPE was polymerized with isophorone diisocyanate (IPDI) to obtain novel chiral azobenzene-containing polyurethane (CACPU). The chemical structures of chromophore molecule and CACPU were characterized by the FT-IR and UV–visible spectroscopy. The physical properties (thermal conductivity, thermal diffusion coefficient, and specific heat capacity) and mechanical properties (tensile strength, elongation at break and hardness) of CACPU thin films were measured. The refractive index and thermo-optic (TO) coefficient (dn/dT) of CACPU thin film was investigated for TE (transversal electric) polarizations by using an attenuated total reflection (ATR) configuration at the wavelengths of 532, 650 and 850 nm. The transmission loss of film was measured using the charge coupled device (CCD) digital imaging devices. A Y-branch switch and Mach–Zehnder interferometer (MZI) thermo-optic switches based on thermo-optic effect were proposed and the performances of switches were simulated. The results showed that the power consumption of the Y-branch thermo-optic switch was only 3.28 mW. The rising and falling times of Y-branch and MZI switches were 12.0 ms and 2.0 ms, respectively. The conclusion has potential significance to improve and develop new Y-branch digital optical switch (DOS), MZI thermo-optic switch, directional coupler (DC) switch and optical modulators.

► Preparation and characterization of chiral azobenzene-containing polyurethane(CACPU). ► The physical properties and measurements of dn/dT and transmission loss. ► Simulations of Y-branch and MZI thermo-optic switch based on CACPU. ► Analysis of switching power consumption and response time.