Lasing in Haloalkanes-based polymeric mixtures

We report on lasing from a new organic mixture, in which a high resolution one dimensional reflection hologram is recorded via blue laser light irradiation at λ = 457.9 nm. The mixture is made by a photo-sensitized acrylate (di-pentaerythrithol-penta/hexa-acrylate) blended with halo-alkanes (1-bromo-hexane and 1-bromo-butane).The halo-alkanes mixture is selected on the basis of its ability to originate phase-separation from the acrylate during the photo-polymerization process and for its relatively low refractive index value. This last property allows the achievement of a good dielectric contrast between polymer-rich and haloalkane-rich layers constituting a one dimensional grating. The recorded structures show a narrow reflection peak and a 40% value diffraction efficiency. The addition of a small percentage (10−3 M) of a fluorescent molecule (9-[2-(Ethoxycarbonyl)phenyl]-N-ethyl-6-(ethylamino)-2,7-dimethyl-3H-xanthen-3-iminium chloride) allows lasing when the structure is optically pumped with a pulsed laser. The reflected grating peak (λr = 563 nm) is indeeed tuned to fall inside the emission band of the fluorescent molecule. The periodic grating selects and amplifies only a very narrow band of frequencies which represent our laser radiation.