Organic solid thin films of PMMA and surfactant-treated salmon deoxyribonucleic acid (DNA) were used as
host materials to dope sulforhodamine (SRh) laser dye. Amplified Spontaneous Emission (ASE) was observed from the
dye-doped thin films pumped by frequency-doubled Nd:YAG laser, with DNA host showed a lower ASE pump
threshold. Distributed feedback (DFB) laser structures were fabricated on both dye-doped thin films for the 2nd order
emission of SRh at 650 nm. Stimulated Emission (Lasing) was obtained by pumping with a doubled Nd:YAG laser at
532 nm. The DNA DFB devices lasing threshold was 30&mgr;J/cm2 or 3.75kW/cm2. The emission linewidth decreased from
~ 30 nm in the ASE mode to < 0.4 nm in the lasing mode. The slope efficiency of the laser emission was ~ 1.2%. Similar
emission linewidth change was observed in PMMA DFB devices while the lasing threshold was 53 &mgr;J/cm2 or
6.63kW/cm2 with a slope efficiency of ~0.63%.
DNA and PPMA were doped with the laser dye sulforhodamine 640. Red emission was observed from both dye-doped DNA and PMMA upon photoexcitation. Photoluminescence (PL) emission was studied as a function of dye concentration. The maximum PL intensity of dye in DNA host material is at least 17 times higher than that in PMMA. The DNA host shows higher doping concentration without optical quenching than PMMA does.
Deoxyribonucleic acid (DNA) extracted and purified from salmon roe and milt sacs, a waste product of the fishing industry was studied for molecular binding and photoluminescence effects using bromocresol purple (BCP). Since BCP is both water and alcohol soluble it was investigated for binding efficiency in DNA/water solutions and modified DNA-CTMA/butanol solutions. Circular dichroism studies show that there is a maximum binding concentration of BCP in the DNA/water solution at ~5% by weight of BCP:DNA. In contrast, DNA-CTMA/butanol solutions showed increased binding concentrations up through 10wt% BCP:DNA-CTMA. This apparent binding affinity of DNA-CTMA for BCP also resulted in a significantly higher (6x) photoluminescence in thin film form when compared to BCP:PMMA films of the same doping concentration.