A poly(3,4-alkylenedioxythiophene) electrochromic variable optical attenuator with near-infrared reflectivity tuned independently of the visible region

Disubstituted poly(3,4-propylenedioxythiophene)s (PProDOTs) exhibit large electrochromic contrasts in the near infrared (NIR) while showing essentially no color change in the visible region when incorporated into a reflective device platform. The source of this is attributed to a conductive front that propagates through the insulating polymer film, extending from the polymer/electrode interface to the top of the polymer film. A utility of the large contrasts seen in the NIR region is demonstrated with application of the device as an electrochromic variable optical attenuator modulating fiber-optic signals for optical telecommunications. With bis(ethylhexyloxy)-stibstituted PProDOT as the active electrochromic polymer in the device, an optical attenuation of 11 dB at the telecommunications wavelengths of 1.31 and 1.55 mu m is achieved with only a 0.1-0.2 dB optical loss in the bleached state. Other favorable properties include optical memory in the absorbing state, switching speeds of under 1 s, a low operating voltage of +/- 1.2 V, and an improved processability that allows spray-casting from organic solvents.