|dc.description.abstract||Due to the increasing demand for the development of light modulator with larger bandwidth and higher efficiency in the optical communication, in this thesis we present a novel ultrahigh efficiency and high dynamic response light modulator based on an external applied voltage to modulate the excitation degree of incident waveguide light in surface plasmons (SPs), known as the attenuation total reflection method (ATR method). This waveguide-coupled surface plasmon light modulator is fabricated by spin coating an organic electro-optic (E-O) polymer film onto the metal layer with suitable thickness of 30~40 nm, and then deposited a bottom metal electrode under the polymer. The molecular orientation of E-O polymer is aligned into noncentro-symmetry structure by applying contact poling process. When an external applied electric field created a linear variation of refractive index of poled E-O polymer according to the Pockels effect, the excitation degree of incident waveguide light in surface plasmons is changed and then the reflected light is modulated.
Besides, we present in the thesis an optimizing design principle for efficient light modulator through the concentration of engery by waveguide coupled, surface plasmons, electro-optic effect, simulation, and theory analysis. To accurately determine the reflective index, attenuation coefficient, and the thickness of the metal layer, we analyzed the ATR spectra by techniques including Lorentzian equation analysis, Fresnel’s equation data-fitting and optimal linear data analysis. Alternatively, by using least square data-fitting techniques which employ two waveguide mode, we could calculate the refractive index and thickness of electro-optic polymer. We also estimated the attenuation coefficient of the polymer by anaylzing the reflection minimum of ATR spectrum. Finally, we calculated its actual electro-optic coefficient of this modulator by analyzing both E-O pockels effect and ATR spectrum. However, because the modulator fabricated in our experiment is not on optimum condition, the results so far show only 1% modulation in the intensity of the reflected light with dri
ving voltage 30V.
Finally, we present a novel and high efficiency electro-optic light modulators based on long range surface plasmon wave coupled with classical surface plasmon wave. Due to the excitation of surface plasmon wave, the energy is concentrated in the waveguide, so the efficiency could be improved. By simulation, it could effectively reduce driving voltage and increase the modulation index of 70 % with driving voltage 10 V.||en_US|