Thermal stability and transmission losses of the poled polyimide side-chain thin films

Abstract

The new side-chain polyimide thin films have been prepared. Through in situ second-harmonic generation (SHG) measurement, the corona poling temperature has been optimized by measuring the temperature dependence of in situ SHG signal intensity under the poling electric field. The second-order NLO coefficient χ 33 (2)=5.6 pm/V at λ=1064 nm was determined by using Maker fringe method after poling the films at optimal poling condition. The depoling knee temperature of the poled polyimide films can reach up to 200°C. Their lower-order optical waveguide-propagation losses were measured at 632.8 nm. The measurements have shown that the optical loss of the fundamental mode is less than 1.0 dB cm −1 for TE polarization.