Researchers at EPFL have developed a chip-scale blue laser that combines stable light emission with rapid frequency control, opening possibilities for underwater communication, environmental sensing and quantum technologies.

Blue light has some useful properties: it travels through water more easily than infrared light, which is widely used in today’s optical communication systems. It also scatters strongly when it encounters tiny particles in the air. These properties make blue lasers attractive for underwater communication, pollution monitoring and scientific instruments.

But these applications demand precise control over the laser’s light. For example, the frequency must remain stable enough to distinguish a useful signal from background noise, while also changing rapidly when needed to transmit information or make measurements.