Photoluminescence and lasing from deoxyribonucleic acid (DNA) thin films doped with sulforhodamine

Thin solid films of salmon deoxyribonucleic acid (DNA) have been fabricated by treatment with a surfactant and used as host for the laser dye sulforhodamine (SRh). The DNA films have an absorption peak at similar to 260 nm owing to absorption by the nitrogenous aromatic bases. The SRh molecules in the DNA films have absorption and emission peaks at 578 and 602 nm, respectively. The maximum emission was obtained at similar to 1 wt. % SRh in DNA, equivalent to similar to 100 DNA base pairs per SRh molecule. A distributed feedback grating structure was fabricated on a SiO2-Si substrate using interference lithography. The grating period of 437 nm was selected, corresponding to second-order emission at the amplified spontaneous emission wavelength of 650 nm. Lasing was obtained by pumping with a doubled Nd:YAG laser at 532 nm. The lasing threshold was 3 mu J, corresponding to similar to 30 mu J/cm(2) or 4 kW/cm(2). The emission linewidth decreased from similar to 30 nm in the amplified spontaneous emission mode to < 0.4 nm (instrument limited) in the lasing mode. The slope efficiency of the lasing was similar to 1.2%. (c) 2007 Optical Society of America.