Stanley Electric and the University of Tokyo Demonstrate for the First Time in the World that Red Laser Diodes Promote Plant Growth

Plant factories are gaining attention as a solution to increasing agricultural risks, but high energy costs remain a major barrier to wider adoption. Because artificial lighting strongly affects both productivity and operating costs, improving light-source efficiency is critical.
While LEDs are currently mainstream technology, recent advances in laser diodes prompted this study to evaluate LDs as a next-generation alternative.

Red LDs emit highly precise, narrow-band monochromatic light that closely matches the chlorophyll absorption peak (Figure 1). In experiments using tobacco plants, red LD irradiation increased photosynthetic rates by up to 19% compared with red LEDs of the same wavelength.

In a 12-day continuous lighting experiment, plants grown under red LDs showed significantly higher biomass and leaf area (Figure 2). Moreover, stress symptoms such as leaf chlorosis and photoinhibition observed under red LED lighting were not detected under red LD conditions, indicating greater tolerance to the light environment.

These results demonstrate that red laser diodes are a promising next-generation light source for plant factories, with potential to improve productivity and energy efficiency in artificial-light-based agriculture.

Stanley Electric has already commercialized aquaculture lighting systems that promote fish growth for fisheries operators. Going forward, the Company will continue to advance research and development in light source technologies, contributing not only to automotive and industrial fields but also to the realization of sustainable agriculture and fisheries.