06 Sep 2002
DNA, the building block of life itself, may also be the key to expanding the range of materials used in solid-state dye lasers.
Researchers in Japan claim to have fabricated a thin-film laser containing DNA doped with dye molecules. When optically pumped, the film exhibits amplified spontaneous emission and spectral narrowing suggesting that DNA complexes might be a practical candidate for making solid-state-dye lasers. (Applied Physics Letters 81 1372)
It is well known that placing too many dye molecules close together can lead to quenching of fluorescence when pumped. But the team from Chitose Institute of Science and Technology say using DNA overcomes this problem. The DNA essentially acts as scaffolds that isolate the dye molecules and reduces fluorescence quenching caused by aggregation.
"If DNA makes other kinds of dye lase, the range of materials used in solid-state dye lasers will also be greatly expanded," say the authors.
The scientists fabricate their films from a hemicyanine dye, a lipid and DNA. The ratio of DNA base pairs to dye molecules can be varied from 10:1 to 40:1 resulting in films with thicknesses between a few microns and a few millimeters.
A frequency-doubled Nd:YAG laser emitting nanosecond pulses optically pumps the film. The incident energy is varied up to a maximum of 1000 µJ.
An intensified CCD camera gathers the emission from the edge of the film and feeds it into a spectrometer. The authors observe spectral narrowing at threshold energies above 25 µJ and conclude that amplification has occurred.
Having tested their approach on a film that does not contain DNA, the researchers believe that DNA plays an essential role for laser action.
The performance of the laser only decreased by several percent in two hours, which the team says suggest the possibility for practical use.
Further studies of structural and spectroscopic properties are now being carried out.
Jacqueline Hewett is news reporter on Optics.org and Opto & Laser Europe magazine.