ABSTRACT
One of the most important drawback of organic dyes is their low photo-stability which reduces possibility of their commercial utilization. In this article we employ the strategy of dye re-crystallization from oversaturated matrix in order to enhance material's durability. One of the main advantages of perylene derivative is ability to form emissive j-aggregates, good miscibility and incorporation into liquid crystalline matrix. Investigation of perylene-based dye and LC matrix brought as the result very efficient light amplification modulation by applied external electric field. In our article we show that Stimulated Emission (STE) is possible to achieve from perylene-derivative based system, at typical fluence thresholds for laser dyes: 3.9 mJ/cm2. Moreover, presented system proves ultra-high photostability, showing lack of STE reduction even after 12 000 excitation laser pulses. Furthermore, we proved the possibility of light emission intensity control using external electric field.
ABSTRACT
We study absorption and emission spectra of optically nonlinear single crystals of 3-(1,1-dicyanoethenyl)-1-phenyl-4,5-dihydro-1H-pyrazole (DCNP) at 5 K. We argue that fluorescence has a complex origin, it is emitted from the excitonic band, with the bottom at â¼18,115 cm(-1), and from trap states, and the two main traps have depths of â¼875 and â¼2465 cm(-1). The excitonic origin of the emission is confirmed by the vibrational structure of fluorescence, closely resembling vibrations observed in the Raman scattering spectrum (recorded for DCNP crystals at 295 K) and by very short decay time of the excitonic emission, as a consequence of exciton migration and trapping at deep traps.
