In collaboration with their colleagues from MIPT’s Center for Photonics and 2D Materials, scientists from ITMO University have devised the world's smallest laser that emits light in the blue spectrum. With a volume 13 times smaller than the wavelength of the produced light, it paves the way for the creation of a new generation of ultra-high-resolution displays and compact biomedical devices. The research is supported by grants from the Russian Science Foundation.

^{Credit: OlgaSalt / photogenica.ru}

In collaboration with their colleagues from MIPT’s Center for Photonics and 2D Materials, scientists from ITMO University have devised the world's smallest laser that emits light in the blue spectrum. With a volume 13 times smaller than the wavelength of the produced light, it paves the way for the creation of a new generation of ultra-high-resolution displays and compact biomedical devices. The research is supported by grants from the Russian Science Foundation.

The key problem that the scientists managed to solve was overcoming the diffraction limit – a fundamental physical barrier that prevents conventional lasers from shrinking to nanoscale dimensions, especially in the blue part of the spectrum, which is critically important for full-color displays.

The nanolaser has a volume of just 0.005 cubic microns, which is roughly 13 times smaller than the wavelength cube of the emitted light. This is a record for the blue spectrum (400-500 nm). The active element of the laser is a microscopic perovskite cube (CsPbCl3) grown by chemical synthesis in solution. Its dimensions are approximately 195 x 190 x 145 nanometers. The particle is placed on a silver substrate which serves as a mirror to confine and enhance the light within the nanoparticle.

The record-breaking small size and its operation in the blue spectrum make this technology highly promising for a number of high-tech fields. Such nanolasers could become the basis for pixels in next-generation displays, including augmented reality devices. In addition, these light sources are a key component in the creation of optical and quantum processors. Miniature laser sources can also be used in compact sensors and imaging systems.

“For more than seven years, our laboratory has been developing nano- and microlasers, but the technology we have now created for producing such compact nanolasers in the blue spectrum is unique. We have succeeded in synthesizing these nanolasers as a colloidal solution of nanoparticles in liquid, which allows them to be deposited on any surface. This will make it possible to integrate them with active matrices for displays and photonic integrated circuits, and even using them for bioimaging applications,” adds Sergey Makarov, a professor at ITMO’s Faculty of Physics and the head of the Hybrid Nanophotonics and Optoelectronics Laboratory.

The laser employs a unique mechanism based on polaritons, a kind of hybrid between light and matter. Unlike conventional lasers, it does not need to overcome a high “threshold” barrier to start generating light.

“The operating mechanism of the device is based on the advanced concept of polariton lasers. It involves a strong connection between excitons (quasiparticles in the perovskite) and light localized inside the nanoparticle. This allows for generation without a population inversion threshold, which reduces energy consumption and simplifies the design. The combination of perovskite's strong exciton response, its high crystalline quality, and the optimized resonant properties makes our nanolaser design the best among all current solutions,” notes Denis Baranov, a leading researcher and the head of the laboratory at the Center for Photonics and 2D Materials at MIPT. 

Currently, the laser's operation has been demonstrated at low temperature (around 80 K or -193 °C). The scientists’ next goal is to achieve room-temperature generation, which is essential for the commercial application of this technology.