It’s not easy making green.

Scientists have made small red and blue lasers for years, but other colors have been a challenge. Now, researchers have filled an important technology gap by creating orange, yellow, and green lasers tiny enough to fit on a chip. Low-noise, compact lasers in this wavelength range are important for quantum sensing, communications, and information processing.

Series of visible-light colors generated by a microring resonator. Credit: S. Kelley/NIST

For years, scientists have fabricated small, high-quality lasers that generate red and blue light. However, the method they typically employ—injecting electric current into semiconductors—hasn’t worked as well in building tiny lasers that emit light at yellow and green wavelengths. Researchers refer to the dearth of stable, miniature lasers in this region of the visible-light spectrum as the “green gap.” Filling this gap opens new opportunities in underwater communications, medical treatments, and more.

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