Researchers at Aalto University in Finland have developed a plasma nanolaser for the first time, which can work at the frequency of visible light and use the so-called dark grid mode. The working wavelength of this laser pointer is 1,000 times smaller than the thickness of a human hair. The lifetime of light trapping on such a small size is so short that the light only rotates up and down tens or hundreds of times in this time. This research opens up new prospects for the research of chips with coherent light sources, such as miniaturization and the application of ultrafast lasers.
The laser operation in this work is based on silver nanoparticles, which are placed in a periodic array. Compared with the traditional laser whose feedback of the laser signal is through an ordinary mirror, this nano-laser utilizes the radiation coupling between silver nanoparticles. These 100 nanometer-sized particles act as tiny antennas. To produce high-intensity laser, the distance between particles is matched with the wavelength, and the radiation of all particle arrays is the same. Organic fluorescent molecules are used to provide the required laser input energy (gain).
One of the main challenges in realizing such green laser pointer is that for gain, the light may not exist long enough for such a small size. Researchers have discovered a solution to this potential problem: They generate laser light in dark mode.
“Dark mode can be intuitively understood by considering conventional antennas: For a single antenna, when a driving current is applied, the radiation will be very strong, and if the opposite current is applied and the position is very close to each other, the radiation of the two antennas will be Very small” explained the professor at the college. “The dark mode in the nanoparticle array produces a similar opposite phase current in each nanoparticle, but the frequency of visible light can now be achieved,” she continued.