On June 4, according to foreign media reports, an international team of researchers announced the development of a more compact and smaller semiconductor laser in the world, which can work in the visible light range at room temperature. According to the author, the laser is a nanoparticle with a size of only 310 nanometers (3,000 times smaller than a millimeter), and can produce green coherent light at room temperature. The research article was published on ACS Nano.

Sixty years ago in mid-May, the American physicist Theodor Maiman demonstrated the working principle of the first optical quantum generator, the laser. Now, an international team of scientists (most of them from the ITMO University) reported that they have experimentally developed the world's most compact semiconductor laser, which works in the visible light range at room temperature, which means that it produces coherent The green light can be easily recorded and can even be seen with the naked eye using a standard optical microscope.

The uniqueness of perovskite nanoparticles as laser materials

Scientists have successfully developed the green part of the visible band, which is of great significance for nano lasers. Sergei Makarov, the principal researcher of this article and a professor at the School of Physics and Engineering at ITMO University, said: "In the field of modern light-emitting semiconductors, there is a'green gap' problem.'Green gap' means the tradition of light-emitting diodes The quantum efficiency of semiconductor materials drops significantly in the green part of the spectrum. This problem complicates the development of room-temperature nanolasers made of traditional semiconductor materials."

In this case, the research team chose the halide perovskite as the material for the nano laser. Traditional lasers consist of two key components: one is an active medium that allows coherent stimulated emission, and the other is an optical resonator that helps limit electromagnetic energy to the interior for a long time. Perovskite can provide these two characteristics at the same time: a specific shape of nanoparticles can be used as both an active medium and an effective resonator.

As a result, scientists succeeded in producing cube-shaped particles with a size of 310 nanometers. When excited by femtosecond laser pulses, they can generate laser radiation at room temperature.

Ekaterina Tiguntseva, a junior researcher at ITMO University and co-author of the paper, said: "We used a femtosecond laser pulse to pump the nano laser and irradiated the isolated nano particles until the laser generation threshold of a specific pump intensity was reached. After that, the nano particles Start working like a typical laser. We proved that this nano laser can work in at least one million excitation cycles."

Advantages of the smallest semiconductor laser

The uniqueness of the nano laser developed this time is not limited to its small size. The newly designed nano particles can effectively limit the stimulated emission energy, thereby providing a sufficiently high electromagnetic field magnification for generating laser light.

Kirrill Koshelev, a junior researcher at ITMO University and one of the co-authors of the article, explained: "Our idea is that laser generation is a threshold process. You use laser pulses to excite nanoparticles at a specific "threshold" intensity of an external light source. Particles start to produce laser emission. If you can’t limit the light to a good enough range, there will be no laser emission. In experiments that used other materials and systems but had similar ideas, it was shown that fourth-order or fifth-order Mie can be used. Resonance, that is, resonance at the wavelength of light, the frequency of the laser generated inside the material is suitable for four to five times the volume of the cavity. We have proved that our nanoparticles support third-order Mie resonance, which has never been done before, in other words , We can generate coherent excitation emission under the condition that the resonator size is equal to the three light wavelengths inside the material."

It is worth noting that no external pressure or very low temperature is required to make the nanoparticles act as lasers, and all the effects described in the study were generated at normal atmospheric pressure and room temperature. This makes the technology attractive for experts focused on creating optical chips, sensors, and other devices that use light to transmit and process information, including chips used in optical computers.

The benefit of lasers operating in the visible range is that they are smaller than red and infrared light sources with the same characteristics when all other characteristics are the same. The fact is that the volume of small nanoparticle lasers usually has a cubic relationship with the emitted wavelength, and because the wavelength of green light is three times smaller than the wavelength of infrared light, the limit of miniaturization is much larger for green lasers, which is The optical computer system's production of ultra-compact components is critical.

(Reprinted from the optical particle network)