PHOTODECAY MECHANISMS IN SIDE-CHAIN NONLINEAR-OPTICAL POLYMETHACRYLATES

The chemical and physical properties of photobleached nonlinear optica l (NLO)-polymethacrylates were studied in order to investigate photobl eaching mechanisms. We have shown by three key measurement techniques (infrared-spectroscopy, mass spectrometry, and gel permeation chromato graphy) that the predominant bleaching process is an irreversible deco mposition of the NLO moieties accompanied by a broadening of the polym er molecular weight distribution. The quantum yield of the chromophore degradation determined by the evaluation of the bleaching kinetics fi t is in agreement with typical data from comparable chromophores. It w as found that bleaching causes an increase in surface roughness of NLO -polymer films, causing an increase in waveguide loss. Smoothing of th e film surface by an annealing step leads to a lowering of bleaching i nduced waveguide loss. (C) 1996 American Institute of Physics.