Researchers have constructed a laser with a size of only 300 nanometers that can generate green light at room temperature for the first time.

Micro light source: Researchers have constructed a laser with a size of only 300 nanometers for the first time, which can generate green light at room temperature. Nanolaser is composed of semiconductor material perovskite, which serves as a gain medium to generate photons and amplify them as resonators. New nanolasers can be used for photonic chips, sensors, or other optoelectronic devices.

For a long time, laser has been an indispensable part of daily life, technology, and research, whose coherent light can serve as measurement aids, universal tools, communication means, or sensors, and for countless variants from ultrashort pulses to carrier data. However, researchers are still searching for the best nanolaser that can be directly integrated into photonic chips, especially in the field of computer technology. There are already the first prototypes made of indium arsenide lattice and silicon nanostructures.

Nanoparticles as laser
Researchers led by Yekaterina Tiguntseva of ITMO University have now developed this type of nanolasers. They reported that their micro light source is the most compact semiconductor laser, producing visible light at room temperature. The laser is composed of nanoparticles with a size of only 310 nanometers and a semiconductor material with a perovskite structure.

In order to form lasers, these nanoparticles must be stimulated by femtosecond laser pulses, that is "pumping". Then, the internal photostimulated phosphor generates cascade photons. “The generation of laser is a threshold process," explained Kirill Koshelev, a colleague of Tiguntseva. “You use a laser pulse to stimulate nanoparticles, and at a certain threshold intensity of the external pulse, the particles begin to emit the laser itself.”

Simultaneous presence of photon source and resonator
The perovskite material of the nanolaser serves as both a photon supply laser medium and a resonator, enriching photons before they are released externally. This is achieved through a special resonance effect inside the semiconductor crystal. "Our nanoparticles support third-order Mie resonance, which has never been done before." explains Tiguntseva.

It means that the light in the crystal is reflected in space, which corresponds exactly to the three wavelengths of the generated light. Researchers achieved this structure by using special synthesis techniques to form small cubes of appropriate size from perovskite materials. In testing, this design has been proven to be an efficient laser generator. "We have demonstrated that this nanolaser can operate for at least one million stimulation periods," Tiguntseva said.

The challenge of green light
One characteristic of this nanolaser is that it produces green light. “In the field of light-emitting semiconductors, there is a so-called green gap issue,"explains Sergey Makarov, a senior author at ITMO. “This means that the quantum efficiency of semiconductors commonly used for light-emitting diodes sharply decreases in the green region of the spectrum.”

Therefore, compared to longer wavelengths of infrared and red light, lasers with green light are more difficult to construct. As explained by researchers, the volume of microlasers is closely related to the wavelength of light. Due to the fact that the wavelength of green light is approximately three times that of infrared light, hence this also requires correspondingly larger miniaturization. However, the advantage is that the human eye is more sensitive to green light than other wavelengths, which is why, for example, even at the same light intensity, a green laser pen looks brighter than a red laser pen.

Working at room temperature
However, for the application of new semiconductor nanolasers, it is also crucial that they operate under normal conditions at room temperature, that is they do not require cooling, pressurization, or any other special treatment. According to researchers, their technology may therefore be particularly suitable for optical computer chips, sensors, and other photonic applications.

Source: diodelaser net