<title>Electro-optic polymer modulators for externally modulated fiber optic transmitters</title>

Abstract

Electro-optic modulators have been used widely in high power, large link budget fiber-optic transmitters for both analog and digital signal transmission applications. The traditional electro-optic modulators are made of lithium niobate single crystals or III-V semiconductors. The recent development of high performance electro-optic polymers has demonstrated a promising future for these materials in the fabrication of a new generation of electro-optic modulators and modulator arrays for externally modulated, wavelength division multiplexed fiber-optic transmission systems. The low dielectric constant, flexibility in device processing, compatibility with semiconductor technology, and potentially very large electro-optic coefficient are very attractive features for wide-band, high efficiency waveguide modulators. To investigate the feasibility of using the new class of materials in electro-optic modulator application, we have fabricated both Mach-Zehnder and straight channel electro-optic modulators using a representative crosslinked electro-optic polymer--polyurethane with Disperse Red 19 side groups. The polymer layers are thermally crosslinked to improve device stability. Electric field poling is used to induce a stable noncentrosymmetric structure in the amorphous polymer films. The optical waveguides are defined by reactive ion etching. The final polymer modulators are packaged in a fiber-ready configuration and can be easily inserted into fiber-optic networks. Modulator parameters related to the device performance are tested for analog transmission system applications. The fabrication techniques and experimental data will be presented along with applications to high capacity wavelength division multiplexed communications systems.