All-optical polymer waveguide devices

We fabricated all-optical polymer devices such as Mach-Zehnder modulator and 1×2 switch using a polymer doped with photoresponsive dyes. The refractive index change of the photoresponsive dyes by irradiation of light was utilized to fabricate switching and modulation devices. All-optical Mach-Zehnder modulator and switch are demonstrated which are composed of a polymer waveguide doped with the dyes in the core and a thick light blocking metal layer on the waveguide. The metal layer was opened on one arm of the Mach-Zehnder modulator and 1×2 Y-branch switch, so that only one arm could be irradiated by control light, thus allowing a changing of refractive index. The optical modulator and switch exhibited an extinction ratio of about -12 dB and a crosstalk of -14 dB at a wavelength of 1.55 μm, respectively. A simple kinetic model developed to delineate the refractive index change in the dye doped polymer film was applied to predict the evolution of the modulation characteristics. We have also fabricated polymeric wavelength filters with Bragg grating. The surface relief grating was formed using an azobenzene polymer film and used as an etch mask to transfer the pattern to polymer waveguides by reactive ion etching (RIE). The grating period was ∼500 nm and the depth was ∼30 nm with 10-mm-long grating length. A crosstalk of -20 dB at the Bragg wavelength and the 3-dB transmission bandwidth of 0.2 nm were obtained from the device.