ITMO Scientists Develop a Device to Control Light and Matter Quasiparticles

The transition from electronic to photonic devices is one of the most promising and hotly debated technological scenarios in science today. Photonic devices are analogs of everyday devices, such as computers, that use the energy of light particles rather than electricity. Although photonic technology-based devices are more energy-efficient and eco-friendly, as well as faster at transferring and processing information, they are, on the other hand, fairly large when compared to their electronic counterparts. Furthermore, the complete shift would be an expensive and time-consuming process.

Therefore, a team of scientists from ITMO University have found the middle ground between photonic and electronic devices. The developed system is controlled by both light and electricity and is powered by interconnected particles of light and excitons, which are bound electron-hole states that form upon the excitation of electrons. Such quasiparticles are known as exciton-polaritons. They are also called “liquid light” because they, on one hand, act as light particles and on the other – possess properties of matter, and can be controlled without much effort. Additionally, the connections between exciton-polaritons are greater than those between photons, making it easier to work with them. 

The team developed a thin plate made of several layers. A photonic crystal – a tantalum oxide lattice covered with a three-atom-thick film of molybdenum diselenide – is placed on a silicon oxide substrate. The plate is activated by a laser beam. When light lands on the device, the lattice is pumped with photons, while electrons in molybdenum diselenide start to transition into an excited state and generate excitons. Then, the photons combine with the excitons and thus produce the said exciton-polaritons. 

“Our technology makes it possible to not only turn the device on and off, but also regulate two states of exciton-polaritons that correspond to various light wavelengths. The states can be activated simultaneously or independently with varying power. This can be achieved either via a laser beam or by altering the plate’s voltage. We’re also investigating how the states are triggered by voltage and laser power. Knowing that, we can understand when exciton-polaritons transition from one state to another. This is a step towards high-precision particle control,” explains Vasily Kravtsov, a senior researcher at ITMO’s Faculty of Physics and an employee at the Frontier Laboratory “Functional Materials for Polaritonic Quantum Logic.”

The invention may be integrated into complex devices to decrease power consumption and enhance their operational efficiency. Among such devices are optical computers that are based on neural networks and can maximize the potential of AI. The technology can also serve as an interface for internet infrastructures. Additionally, it may become a part of optical regulators and modulators used to transmit and process data, as well as network switches, which transfer energy and direct it to a system’s components. 

The study was carried out within the Priority 2030 national program at the Frontier Laboratory “Functional Materials for Polaritonic Quantum Logic”