Preparation of azo waveguide polyurethane and its analysis of Y-branch and Mach–Zehnder optical switches

Azo waveguide polymers are of particular interest in the design of materials for applications in optical devices. The aim of this contribution was the preparation and thermo-optic switch properties of azo waveguide polyurethanes. A series of monomers and novel azo polyurethanes (Azo PU1 and Azo PU2) were prepared and characterized by Fourier transform infrared, UV–vis spectroscopy and 1H NMR. The physical properties (thermal conductivity, thermal diffusion coefficient, specific heat capacity and thermal property) and mechanical properties (tensile strength, elongation at break and hardness) of Azo PU1 or Azo PU2 thin films were measured. The refractive index and thermo-optic (TO) coefficient (dn/dT) of Azo PU1 or Azo PU2 thin films were investigated for TE (transversal electric) polarizations by using an attenuated total reflection (ATR) configuration at different laser wavelengths of 532, 650 and 850 nm. The transmission loss of film was measured using the Charge Coupled Device (CCD) digital imaging devices. The results showed the polyurethane thin film material (Azo PU2) containing chiral azobenzene chromophore had lower transmission loss. Subsequently, a 1 × 2 Y-branch optical switch and a 2 × 2 Mach–Zehnder optical switch based on the prepared azo polyurethanes thin film materials were designed and simulated. Furthermore, comparing with 1 × 2 Y-branch optical switch, the 2 × 2 Mach–Zehnder optical switches based on the same thin film material have the faster response time, which were about only 0.5 and 1.2 ms, respectively.