Ordered Carbon Nanotubes for Optical Power Limiting Devices

The electrospinning (ES) process was used to fabricate composite nanofibers (NFs) of poly(methyl methacrylate), PMMA, with embedded multiwalled carbon nanotubes (MWNTs) from a solution of PMMA in N,N-dimethylformamide (DMF) with homogenously dispersed MWNTs. Using both the sinklike and the elongation flows in the electrospinning process, we aligned the carbon nanotubes (CNTs) along the fiber axis. The NFs were subsequently deposited in an aligned manner on a glass surface using the electrostatic lens created by the edge of a rotating wheel collector. Semitransparent optical power limiter (OPL) films (~50% transmittance) were fabricated using an optically compatible polymeric resin infiltrated into the collected NFs. These comprised oriented NFs with different carbon nanotube loadings and film thicknesses. The OPLs exhibited high limiting abilities, with a limiting threshold of 1.5 J/cm(2) at about 50% linear transmittance. Some degree of polarization was also achieved, but significantly lower than expected because of the NF orientation.