Nickel dithiolene-PMMA guest-host polymers for all-optical signal switching

ABSTRACT Thenonlinear susceptibility, andnonlinear refractive index, n7, of a range of dithiolenes :-metal-sulfurligandcomplexes bearing simple H, alkyl and aryl substituents have been measured by degenerate four wave mixing(DFWM) and self focussing/defocussing (z -scan) at 1.O64m using iOOps pulses. Materials with the largestcoefficients consistent with low linear and two photon absorption, for example bis[1-ethyl-2-phenylethene-1,2-dithiolato(2-)-S,S'}nickel have been modified to be soluble as guests in PMMA host polymers. n2's as high as io- cm2/kW have been found but intermolecular interaction causes increased two photon absorption at the high loading necessary for this n2. Some simple chemical modifications which may improve figures of merit aresuggested. Power requirements for simple waveguide devices using these materials are estimated and it isconcluded that improved materials are still needed. Dithiolenes have sufficient variability in structure to suggestthat this may be achievable with new derivatives of the same family.1. IFRODUCTIONModern telecommunications systems use optical transmission for much of the trunk network. In the future opticalfibre may also be widespread in the local loop if the range of entertainment and information services requiring