Optical properties of CdS nanocrystallites embedded in (Si0.2Ti0.8)O2 sol–gel waveguide

Abstract We report on the implementation of a two-grating coupler technique for measurement of repopulation of deep traps in CdS nanocrystallites embedded in a (Si 0.2 Ti 0.8 )O 2 waveguiding glass layer of high refractive index. A sol–gel process is used to produce this waveguide. The low attenuation (∼1 dB/cm) of the waveguide allows to in- and out-couple light by surface relief gratings embossed on the top layer of the waveguide. The spectral region of waveguiding (≈700 nm) that was studied corresponds to the deep trap spectral position in CdS. The waveguiding beam is used as a probe beam and we used the third harmonics of a YLF:Nd laser (347 nm) as a pump. The influence of bimolecular recombination on repopulation of deep traps is demonstrated. The linear recombination time as well as bimolecular and Auger coefficients are determined.