Random lasing with scatterers of diameters 20 nm in an active medium

In this letter we reported random lasing achieved in MEH-PPV/glass waveguide with the 20-nm TiO2 scatterers in diameter significantly reduced in size compared to submicrometer of TiO2 scatterers in films or suspensions previously reported on random lasing. The spectral lines were dramatically narrowed by almost two orders of magnitude compared with those excited by Xenon lamp. The amplified spontaneous emission (ASE) was identified as the dominant mechanism in our system. Thouless number [H. Cao, Wave Random Media 13 (2003) R1] should be δ ≡ δν/(dν/dN) = 1.6 × 106 ≫ 1. It indicates again that there is no coherent amplification with coherent feedback due to Anderson localization of light in our case.