Hybrid polymer devices for improved thermal control and performance

Single-mode waveguides based on planar silica have found increasing application in passive optical components such as arrayed waveguide gratings (AWG), couplers, and splitters. Key aspects of these devices are their low insertion losses and relative insensitivity to temperature. Planar polymer waveguides present a complementary technology that is finding deployment in thermally activated components such as thermo-optic switches, variable attenuators and tunable filters. This results from the large thermo-optic effects and low thermal conductivities in polymers that lead to low power, compact and rapid thermal activation. There are a number of advantages to moving toward a hybridization of the two technologies. In some cases, the opposite signs of the thermo-optic effect in silica and polymers can be used to achieve virtually a thermal performance for highly phase sensitive devices such as AWGs. Polymer overcladdings of appropriate refractive index and optical loss can also be used to reduce stresses in thick silica waveguides. A further advantage of combining these two materials technologies is to realize waveguide chips of higher functionality and performance that combine both passive and thermally activated functions. In this way the low propagation loss of silica waveguides can be used for transmission operations, while selectively placed polymer waveguide can be used for switching and attenuation, for example. We present several examples, consider fundamental materials issues, and identify potential routes to further exploitation of hybrid polymer/silica devices in next generation optical modules.