Amplified spontaneous emission in the cyano-substituted oligo(p-phenylenevinylene) organic crystals: Effect of excitation wavelength

We report an unusual phenomenon in amplified spontaneous emission (ASE) from cyano-substituted oligo (p-pheny lenevinylene) (CNDPASDB) single crystals, i.e., the ASE peak wavelength, exhibits varied dependence on the pumping wavelength lambda(ex). The former is basically kept a constant when lambda(ex) < 505 nm, while a rapid redshift from 560 to 572 nm occurs when lambda(ex) > 505 nm. The observation is different from stimulated Raman resonant scattering (SRRS) in two following aspects: the nonconstant Stokes shift and a much broader emission linewidth. A model describing competition between the stimulated emission and vibration relaxations has been proposed to interpret the underlying mechanism. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3359848]