Series of visible-light colors generated by a microring resonator.
Credit: S. Kelley/NIST
It’s not easy making green.
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.
Green laser pointers have existed for 25 years, but they produce light only in a narrow spectrum of green and are not integrated in chips where they could work together with other devices to perform useful tasks.
Compact laser diodes can emit infrared, red and blue wavelengths, but are highly inefficient at producing green and yellow wavelengths, a region known as the "green gap."
Credit: S. Kelley/NIST
Now scientists at the National Institute of Standards and Technology (NIST) have closed the green gap by modifying a tiny optical component: a ring-shaped microresonator, small enough to fit on a chip.
A miniature source of green laser light could improve underwater communication because water is nearly transparent to blue-green wavelengths in most aquatic environments. Other potential applications are in full-color laser projection displays and laser treatment of medical conditions, including diabetic retinopathy, a proliferation of blood vessels in the eye.
Compact lasers in this wavelength range are also important for applications in quantum computing and communication, as they could potentially store data in qubits, the fundamental unit of quantum information. Currently, these quantum applications depend on lasers that are larger in size, weight and power, limit ..
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