The conversion efficiency of the new mid-infrared laser diode exceeds 50%

Researchers at Northwestern University in the United States have developed a small mid-infrared laser diode with a conversion efficiency of more than 50%. Relevant reports claim that this achievement is a major breakthrough in the research of quantum cascade lasers (QCL), making quantum cascade lasers practical applications in many fields, including remote detection of hazardous chemicals, an important step forward. Relevant research results were published in the recent online edition of "Nature Photonics" magazine.

The quantum cascade laser is a new type of diode laser with a light-emitting mechanism that is different from traditional semiconductor lasers. It is designed according to the principles of quantum mechanics and its light-emitting wavelength can cover the mid-infrared region. Different from traditional diode lasers, quantum cascade lasers are unipolar devices that only need electrons to operate, and use electrons to switch between the conduction bands of one-dimensional quantization to achieve light emission. After years of research and industrial development, the conversion efficiency of modern near-infrared (wavelengths of about 1 micron) laser diodes is close to the extreme value, while mid-infrared (wavelength greater than 3 micron) laser diodes are difficult to reach the extreme efficiency. Previous reports believed that the conversion efficiency of high-efficiency quantum cascade lasers would not be higher than 40% even when cooled to a low temperature state.

Researchers at Northwestern University’s Center for Quantum Device Research (CQD) have made breakthrough progress in quantum cascade laser efficiency by optimizing the material quality of laser equipment. They eliminated non-essential design elements in laser operation under low temperature conditions, and developed a new type of laser when the temperature was cooled to 40 Kelvin, the conversion efficiency of 4.85 micron wavelength light reached 53%.

The leader of the research team and the professor of electrical engineering and computer science at Northwestern University’s McCormick School of Engineering and Applied Sciences, Manije Razerji believes that the advent of this high-efficiency laser is a major breakthrough, and this is the first time for scientists. The light energy emitted by the laser exceeds the thermal energy. She emphasized that the conversion efficiency of the laser broke the 50% threshold, which is a milestone achievement.

According to reports, improving conversion efficiency is still the primary goal of laser research. The high efficiency demonstrated by the new device can greatly expand the power calibration range of the quantum cascade laser. Recent studies have shown that with the extensive development of quantum cascade lasers, the output power of single-pulse lasers has reached 120 watts, compared to 34 watts a year ago.

The research was jointly funded by the High Efficiency Mid-Infrared Laser (EMIL) project of the US Department of Defense Advanced Research Projects Agency and the US Naval Research Institute.