Polymer-silica hybrid 1 x 2 thermooptic switch with low crosstalk

A new polymer-silica hybrid I x 2 thermooptic switch with significantly low crosstalk is demonstrated. The top cladding and the core layers are composed of polymer, while the bottom cladding layer is made of silica. Since polymer and silica have algebraic signs of their thermooptic coefficients that are opposite to each other, the refractive index of the core changes in the opposite direction to that of the bottom cladding as the temperature is increased. Thus, switching operation is initially done through adiabatic mode evolution in the Y-branch, and then a heated waveguide arm in the Y-branch can enter into the optical cut-off region if the temperature is sufficiently high. Using this phenomenon, low crosstalk performance is achieved. The proposed device has a crosstalk of -35 dB, while most integrated-optic switches with a single stage have a relatively high crosstalk in the region of -20 dB. The switching power of the proposed device is about 70 mW. (c) 2006 Elsevier B.V. All rights reserved.