Researchers from ITMO University, the Skolkovo Institute of Science and Technology, the Ioffe Physical-Technical Institute, the Moscow Center for Advanced Studies and Al Ain University in the UAE have created the world’s smallest laser operating in the blue light spectrum. This CsPbCl₃ perovskite-based nanolaser has a volume of about 0.005 μm³, which is approximately ten times smaller than comparable previous-generation devices. The compact size makes it possible to create denser photonic circuits, reduce pixel size in displays and improve precision in optical recording.
The chief problem the scientists have solved was a fundamental limitation known as the diffraction limit. Typically, a laser cannot be significantly reduced in size, since its size is related to the wavelength of light. For the blue spectrum, this is hundreds of nanometers, which is why earlier devices remained relatively large. In this study, the scientists circumvented this limitation by using a different approach involving exciton–polaritons. These are states in which light and matter interact as a single system, making it possible to compress the radiation into a much smaller volume.
In order to achieve this, the researchers created CsPbCl₃ nanocrystals ranging in size from 145 to 310 nanometers and placed them on a special silver substrate coated with a thin layer of aluminum oxide. This enhanced the interaction of light with the material. Cooling to 80 K (−193°C) changes the system’s properties: instead of a single broad signal, two peaks emerge. This means that light begins to interact strongly with matter, and polaritons form within the crystal.
With an increase in laser pump power, the system transitions to lasing. Initially, the radiation remains broad, after which it sharply narrows, followed by the emergence of narrow peaks and a rapid increase in intensity indicating laser operation. For the smallest crystal, stable emission was achieved at a wavelength of approximately 415 nm with a very narrow line, which suggests high efficiency even at this size.
The newly developed model shows that energy in the system gradually shifts to the lowest level, where ordered and coherent emission occurs. Unlike conventional lasers, this method does not require complex manipulation of energy levels, since everything is achieved through the collective behavior of the particles, which is why the laser operates at a lower energy.
While the device currently operates at very low temperatures, this limitation could be lifted in the future. If operational at room temperature, these nanolasers could form the basis for a new generation of photonic technologies.
