Russian physicists from luminescence department of Lebedev Institute of Physics created three-component hybrid nanoparticles, which can be used for building nanolasers..

Since the moment of invention, lasers have found numerous applications in human life. Unique properties of their radiation allow using them in various fields of science and technology, as well as in ordinary life – compact disc players, laser printers, bar code scanners, laser pointers and many more. Interestingly, making very small lasers may extremely expand their possibilities and applications. Nanolaser can become key element for new class of devices – from high-resolution optical microscopes to personal photon computers, making mentioned devices much more effective and cost-efficient. Without nanolasers human society will pause on its way to further progress in different fields of science and technology.

Researchers from the United States have already built a first prototype of nanolaser, which was called “Spaser” (surface plasmon amplification by stimulated emission of radiation"). This prototype is a two-component hybrid gold nanoparticle, covered with a glasslike coating, filled with a colouring agent. For reaching necessary energy level, spaser, like an ordinary laser, needed special excitation by means of an external source of electromagnetic radiation, and this problem found a solution – hybrid nanoparticles were irradiated with laser pulses.

Russian physicists worked with a similar system – they also used hybrid gold nanoparticles, covered with a colouring agent. However, they paid attention to spontaneous radiation emission or luminescence, unlike their American colleagues, who studied stimulated emission. Russian physicists develop production techniques for such devices and study their spectral properties.

 

 

 First, Russian scientists reproduced results of Japanese researchers, who worked with only one colouring agent, and expanded their study by using various types of colouring agents. Scientists discovered that changing a colouring agent affected spectral characteristics of the system. Further experiments revealed that placing a shining brightly molecule of a dye on a metal surface has fully quenched its luminescence, and moving this molecule away from the metal has helped restoring its luminescence. The physicists needed to maintain plasmon-exciton interactions between metal nucleus and dye molecules, and they decided to check how three-component nanoparticles would have behaved in such situation.

Experiments of the Russian scientists resulted in creation of three-component nanoparticles, consisting of a 6-micron metal nucleus (Au (gold) or Ag (silver)), covered with two concentric organic shells: a monomolecular dielectric layer of TMA (trimethylaluminium) and a colouring layer. This was an implementation of an idea of metal-organic nanoparticle, in which a dye was at a distance of 1.2 micron (which is nearly length of dielectric molecule) from a nucleus. Such a construction of nanoparticle almost eliminates quenching of dye luminescence, while maintaining interactions between a nucleus and a coating. The device will be called “plasmon-exciton nano-emitter”, and researchers plant to use it for further studies – now of stimulated radiation emission on the same objects.

There still are problems to solve – diverging waves of nanoparticles emit light in all directions, while “normal” laser should emit a directed light beam. Scientists believe that spaser will be useful for creating a new generation of super-fast nanoelectronic devices.

Source: the Institute of Physics

Kizilova Anna