This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: 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. Existing blue laser systems often rely on bulky optical components to achieve this precision. Shrinking them onto photonic chips, which guide and control light through microscopic structures, has proved difficult.
At blue wavelengths, even tiny imperfections in these structures scatter light and reduce performance. Kippenberg and Simone Bianconi at EPFL has now developed a compact blue laser that addresses these challenges. Described in Nature Photonics, the device combines low-noise operation with fast electronic control of its frequency.
The researchers connected a conventional blue laser to a chip containing a microscopic ring. The ring selects a precise frequency of light and feeds some of it back into the laser, helping it produce a steadier beam. To reduce light losses, the team made the chip's light-guiding structures exceptionally thin, only 25 nanometers thick.
They also added components made from aluminum nitride, a material that changes shape when voltage is applied. This produces tiny mechanical stresses that alter how light travels through the ring, allowing the researchers to adjust the laser's frequency rapidly. The resulting laser operated at a wavelength of approximately 461 nanometers.
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