Israeli Researchers Identify Fundamental Limit on Terahertz Quantum Laser Power
A team of Israeli scientists has discovered a basic physical limitation affecting the performance of terahertz (THz) quantum lasers, which emit radiation in the terahertz frequency range. Contrary to previous assumptions that increasing the number of electrons in the laser would enhance its optical gain and output power, the researchers found that beyond a certain electron concentration, interactions between electrons cause quantum energy levels to broaden and overlap. This spectral overlap reduces the laser's ability to amplify light, meaning that adding more electrons past a threshold actually weakens the laser's performance.
The study was conducted by Dr. Asaf Albo's research group at Ariel University's Department of Electrical and Electronics Engineering, in collaboration with Bar-Ilan University, the University of Leeds in the UK, and Sandia National Laboratories in the United States. Their findings were published in the journal Nanophotonics. Terahertz lasers are considered a promising technology for future applications including ultra-fast wireless communication (such as 6G networks), advanced medical imaging, security scanning, hazardous material detection, industrial quality control, and precise spectroscopy.
To uncover the underlying mechanism, the researchers combined experimental measurements with advanced physical simulations, systematically varying electron concentrations in the devices. They identified a universal physical parameter (Γavg/Δ) that predicts the point at which increasing electron density ceases to improve laser performance and begins to degrade it. This parameter offers a new design principle not only for terahertz lasers but potentially for a broad range of photonic devices based on quantum structures.
Dr. Albo emphasized that while the research is fundamental in nature, its insights could significantly influence the design of next-generation photonic components. Understanding these physical limits will enable engineers to optimize terahertz lasers for higher power and operation at elevated temperatures, facilitating future technologies in communications, imaging, security, and industrial sensing. The research received funding from the Israel Science Foundation, the Ministry of Innovation, Science and Technology, and European and British research grants.
