Bandwidth improvement of microwave photonic components based on electro-optic polymers loaded with TiO2 nanoparticles
Résumé
Electro-optic (EO) polymers offer a veryattractive possibility of realizing low-cost microwavephotonic components with a wide bandwidth and a lowdriving voltage, thanks to a low dispersion from microwaveto optical frequency of polymeric materials on the onehand, and the progress in the synthesis of high hyperpolarizabilitychromophores on the other hand. This paperstudies the influence of titanium dioxide (TiO2) nanoparticleloading on the microwave and optical properties ofEO polymers. Thus, poly(methyl methacrylate) (PMMA)and disperse red 1 (DR1) are used as host polymer andguest EO chromophore, respectively. With 1–3% TiO2nanoparticle homogeneously incorporated in the polymer,the dielectric constant varies from 2.73 to 3.40 over the400 MHz–10 GHz range, and the refractive index increasesfrom 1.483 to 1.488 at the wavelength of 1539.6 nm. Itis shown that fine tuning of dielectric constant andrefractive index could allow improvement of themicrowave photonic component bandwidth. For example,with an EO interaction length L = 2 cm (typical length ofEO modulators), the ultimate modulator bandwidth couldbe raised to 258 GHz by loading PMMA–DR1 EO polymerwith 1% wt of TiO2 nanoparticles. It is also found thatloading polymer with nanoparticles could improve the EOresponse of poled polymers, represented by the intensity ofthe second-harmonic-generation (SHG) signal. The latterpresents more than a threefold increase by loading PMMA–DR1 EO polymer with 2% wt TiO2 nanoparticles.