Design and Fabrication of All-Polymer Photonic Devices
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Design and Fabrication of All-Polymer Photonic Devices Claire L. Callender1, Jia Jiang1, Chantal Blanchetière1, Julian P. Noad1, Robert B. Walker1, Stephen J. Mihailov1, Jianfu Ding2 and Michael Day2 1 Communications Research Centre, P.O. Box 11490, Station H, Ottawa, ON, Canada K2H 8S2 2 Institute for Chemical Process and Environmental Technology, National Research Council of Canada, Ottawa, ON, Canada K1A 0R6 ABSTRACT High quality optical waveguides have been fabricated from fluorinated poly(arylene ether ketone) materials using a standard photolithographic process. Fabrication of waveguide devices on a polymer substrate is described, including a method of end-facet preparation using excimer laser micromachining. Material issues affecting waveguide birefringence and device performance are discussed. INTRODUCTION The material properties required for the fabrication of high performance polymer photonic devices are well known – low optical loss, easy processability, tailorable refractive index, high thermal stability and low birefringence. In the past few years, the required properties have been engineered in several classes of polymer and many photonic devices have been fabricated for demonstration or commercial applications [1,2]. Polymers are particularly attractive for photonic components in metro- and local area networks, where low cost is a key issue and performance specifications are less stringent than those in long-haul WDM networks. However, even with the large (20 nm) channel spacings used in current coarse (C)WDM systems, a birefringence of 10-4 or less is desirable for polarization independent operation of wavelength- or phase-control devices. Birefringence in polymer films for photonic applications has been reported from 8 x 10-3 for highly thermally stable polymers such as polyimides [3], to as low as 10-5 in fluorinated acrylates [4]. This property is often difficult to optimize, as decreasing birefringence through molecular engineering often results in a concomitant degradation in the thermal stability of the material. Some birefringence compensation can be achieved through waveguide cross-section and device design, but ultimately, the realization of high performance, thermally stable polymer devices requires a good understanding of the material and process parameters that can be adjusted to minimize birefringence. Birefringence in polymer films depends on the chemical structure of the polymer chains, and on the stresses built up during the processing into thin film on a substrate. Previous work has investigated several factors influencing birefringence in polymer films for waveguide applications. At the molecular level, designing the polymeric structure with a minimum aromatic content in the polymer network can lower film birefringence by reducing the rigidity of the polymer backbone and minimizing stress-producing orientation effects [5]. In addition, previous studies have demonstrated that careful control of solvent evaporation and polymer cross-linking during film heating and cooling proc
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