14 DAY TRIAL // A team of German investigators has recently developed a new way of using quantum-dot lasers for producing tunable wavelengths of light. This is a very important characteristic of lasers, and it is sought-after by many researchers in the international community. Usually, the light-amplification devices only accelerate (amplify) photons of a single wavelength, but some lasers can produce two or even more types of photons. Changing between the various wavelengths has now become a lot easier due to the recent innovation, AlphaGalileo reports.
The research team, which is based at the Technische Universitat Darmstadt, says that possible applications for their new scientific instruments include the fields of biomedicine and nanosurgery, where tunable-wavelength lasers could make all the difference. In order for the new quantum-dot devices to become operational, the German group had to completely “reinterpret” the physics of semiconductor lasers, essentially turning it upside down.
In regular lasers, when light amplification begins, the first photons to be emitted are those corresponding to transitions that come from the lowest energy level. Higher-energy photons, those of shorter wavelengths to be more precise, are emitted only when the current powering the instrument has been increased well beyond the lasing threshold. What the team did was basically create a laser in which the opposite happens, with high-energy photons being produce first, and longer-wavelengths ones later. The work was conducted by scientists at the TUD Institute for Applied Physics Semiconductor Optics Group, led by professor Dr Wolfgang Elsaßer.
The investigation was a part of the “FAST-DOT” project, which is a research initiative funded by the European Union. The team says that quantum-dot lasers emit in “reverse” only when particular conditions are met. “This inverted hierarchy of emission states that we are the first to discover effectively allows generating intentionally custom-tailored wavelengths covering a wavelength range of interest in many applications. Furthermore, the method not only allows switching back and forth between two wavelengths and but also exploiting beneficially effects occurring in the laser systems involved for improving pulse parameters,” the group leader explains.
He adds that, in the future, these devices will be used to produce scalpels capable of carrying out molecular surgery. This means that the laser pulses will create small changes in the structure of individual cells, or cellular organelles, without affecting the cells around their targets. This level of control in surgery will come in very handy in brain operations, as well as when surgeons will attempt to remove tumors without affecting too much of the surrounding tissue.