Polarized doping-induced infrared absorption in highly oriented conjugatedpolymers

We present polarized, doping-induced absorption spectra obtained from conju gated polymers oriented by gel-processing in ultrahigh molecular weight pol yethylene. Upon doping with iodine vapor, both poly(2-methoxy, 5-(2'-ethyl) hexyloxy) paraphenylene vinylene), MEH-PPV, and poly (3-octyl thiophene, P3 OT, show absorption features in the mid-infrared (the infrared-active vibra tional (IRAV) modes and the low energy electronic absorption) that are stro ngly polarized parallel to the chain axis. All observed features have predo minantly parallel polarization. We suggest that carrier-induced and electro de-induced losses in electrically pumped waveguide structures could be grea tly reduced by using highly oriented films, with molecular axes orthogonal to the electric field polarization of the waveguide mode. (C) 2001 Elsevier Science B.V. All rights reserved.