Resonantly enhanced second harmonic generation in the charge transfer band of DAN

Abstract

Using a variety of fixed-frequency and tunable laser sources, the authors investigated optical second-harmonic generation (SHG) of wavelengths near and inside the charge transfer absorption band of the organic crystal DAN [4-(N,N-dimethylamino)-3-acetamidonitrobenzene]. The experimental procedure is described, and the results are presented and discussed. Three important results were obtained. First, a large dichroism in the strength of the charge transfer absorption band was observed. Second, room-temperature angle-tuned phase matching of SHG was found to be possible for generated wavelengths well within the absorption band. Third, a significant resonant enhancement of the nonlinearity was observed, resulting in absolute conversion efficiencies that were larger than for SHG in the transparency range of the crystal.