Coherent Random Lasing from Dye Aggregates in Polydimethylsiloxane Thin Films

The coherent random laser (CRL) from dye doped polydimethylsiloxane (PDMS) has been investigated in both nanoparticle-doped (NP-doped) thin films and pure dye thin films. Compared with the literature, the pump threshold is only 1.5 mJ/cm(2) in the pure dye thin film with a low dye concentration. The spontaneously formed micro-/nanocrystals of Pyrromethene 597 (PM597) dye support both gain and random feedback in the bulk of the PDMS during the sample preparation. When the SiO2 NPs were doped, the pump threshold was reduced to 0.75 mJ/cm(2). The threshold increased after the film was peeled off from glass, which indicates that the photon localization effect of the leaky-waveguide structure plays an important role in the reduction of the CRL threshold. By a change in the pump stripe length or the thickness of the film, the peak wavelength red-shifts 6.7 or 5.93 nm, respectively. The PM597 dye molecule solubility changes, and they spontaneously aggregate in the process of toluene volatilization; the PDMS cures, which is the reason for the formation of PM597 micro-/nanocrystals. This thin film random laser with a low dye concentration can be used in integrated optoelectronics and display imaging.