Light amplification in dye doped DNA-surfactant complex films

We observed amplified spontaneous emission (laser action without cavities) from several kinds of dyes doped in films of salmon DNA (deoxyribonucleic acid) derivatives. We employed laser dye Rhodamine-6G, Pyrromethene 556, and nonlinear optical dye DMASDPB for dopants. Most of sample films with several mum thickness were prepared as follows: 1) DNA aqueous solution was mixed with hexadecyltrimethylammonium chroride aqueous solution. 2) Precipitated DNA-lipid complex and dyes were dissolved in ethanol or chloroform. 3) Films were formed on substrates by casting from the solution. The amplified spontaneous emission was observed when the films were pumped with a nanosecond laser of 532 nm at the intensity above a threshold value. Spectral narrowing occurred at the threshold energy, and it was accompanied with superlinear dependence of the emission intensity on the pumping intensity. Dye molecules in DNA films can be intercalated in the double helix structure. Because molecules are separated from one another, it is possible to increase chromophore concentration without fluorescence quenching due to aggregation. Furthermore, it is known that DNA shows a good conducting property. We will discuss the possibility of optical and electronic devices utilizing these characteristics.