We are just at the beginning of developing optoelectronics based on new types of semiconductors, devices, and phenomena occurring within them. There are still many fascinating problems to solve, says Prof. Tomasz Czyszanowski, who collaborates with outstanding scientists from around the world.
The paper titled "Bose-Einstein condensation of photons in a vertical-cavity surface-emitting laser" was created in collaboration with Assoc. Prof. Maciej Pieczarka, the project's originator, and Aleksandra Piasecka from Wrocław University of Technology, who conducted the experimental research described in the paper. The involvement of scientists from Lodz University of Technology was also significant. Dr. Marcin Gębski, along with Prof. James Lott from Technische Universität Berlin, built the lasers used for the research. Meanwhile, Assoc. Prof. Michał Wasiak, and Prof. Axel Pelster from Technische Universität Kaiserslautern-Landau supported the team in the theoretical analysis of experimental results, while Prof. Tomasz Czyszanowski performed computer simulations that interpreted the experimental outcomes.
What key findings have you published?
The publication in Nature Photonics shows that photons generated in a laser that is slightly different from a relatively conventional semiconductor laser—like those used in telecommunications or LIDAR systems—behave like a gas of non-interacting particles that can reach a Bose-Einstein condensation state. No one before us has proven that such a phenomenon is possible in a semiconductor laser powered by electricity and operating at room temperature, says Prof. Czyszanowski. Previous experiments allowed for observing this phenomenon only in complex optical setups built on large optical tables, not in a laser that can fit on the tip of a needle.
In their research, scientists identified key properties of photons emitted by such lasers, as explained by Prof. Czyszanowski and Prof. Wasiak:
Imagine that photons in a laser fill the rungs of a ladder, where each rung corresponds to an allowed energy level of photons. In the semiconductor lasers we study, photons distribute unevenly across these rungs; it may seem chaotic. Their numbers on individual rungs also change irregularly depending on the current powering the laser. As a result, changing the current affects changes in the beam profile emitted by the laser. Beam profile instabilities are usually obstacles in laser applications. However, when photons behave like a Bose-Einstein condensate, the vast majority occupy the lowest rung of the ladder, making the emitted beam very stable."
Where might the new principles of semiconductor lasers be applied?
Good question, responds Prof. Wasiak—reports about achieving Bose-Einstein photon condensates have emerged relatively recently, so for now, just their existence is exciting. I am convinced that applications will arise that no one is currently considering; our ability to obtain such condensates in semiconductor lasers that are essentially indistinguishable from millions of similar lasers used in telecommunications, mobile phones, and many other devices around us will greatly facilitate both idea generation and realization.
Good question, responds Prof. Wasiak—reports about achieving Bose-Einstein photon condensates have emerged relatively recently, so for now, just their existence is exciting. I am convinced that applications will arise that no one is currently considering; our ability to obtain such condensates in semiconductor lasers that are essentially indistinguishable from millions of similar lasers used in telecommunications, mobile phones, and many other devices around us will greatly facilitate both idea generation and realization.
Publication in Nature Materials
In turn, the paper "Predesigned perovskite crystal waveguides for room-temperature exciton–polariton condensation and edge lasing," published in Nature Materials, resulted from collaboration among scientists from Poland, Italy, Iceland, and Australia. The key contributors to this publication were Prof. Barbara Piętka, Mateusz Kędziora, and Dr. Andrzej Opala from the University of Warsaw.
They synthesized perovskite layers to create structures analogous to optical integrated circuits, demonstrating experimentally both simultaneous laser action and light propagation within these structures. They also provided an elegant theoretical interpretation of their experimental results—explains Prof. Czyszanowski from the Faculty of Technical Physics, Computer Science and Applied Mathematics at TUL, co-author of the publication who analyzed potential laser action through numerical simulations.
According to physicists, this new technology for obtaining perovskite crystals represents the future of integrated photonics. By developing an innovative production technology for these crystals, scientists have opened pathways to groundbreaking applications in photonics.