In previous experiments, NIST researchers have used ring microresonators to transform near-infrared laser light into a combination of longer and shorter wavelengths.
Credit: S. Kelley/NIST
In research, sometimes the bumpy path proves to be the best one. By creating tiny, periodic bumps in a miniature racetrack for light, researchers at the National Institute of Standards and Technology (NIST) and their colleagues at the Joint Quantum Institute (JQI), a research partnership between the University of Maryland and NIST, have converted near-infrared (NIR) laser light into specific desired wavelengths of visible light with high accuracy and efficiency.
The technique has potential applications in precision timekeeping and quantum information science, which require highly specific wavelengths of visible laser light that cannot always be achieved with diode lasers (devices akin to LED lights) to drive atomic or solid-state systems.
Ideally, the wavelengths should be generated in a compact device, such as a photonic chip, so that quantum sensors and optical atomic clocks can be deployed outside the laboratory, no longer tethered to bulky optical equipment.
In previous experiments, NIST researcher Kartik Srinivasan and his colleagues used perfectly smooth microresonators—ring-shaped devices with a diameter about one-quarter the thickness of a human hair—to transform a single wavelength of NIR light into two other wavelengths. The resonator, small enough to fit on a microchip, can be designed so that one of the two output wavelengths falls within the spectrum of visible light. The transformation occurs when the NIR laser light, confined to circle the ring-shaped resonator thousands of times, reaches intensities high enough to strongly interact with the resonator material.
In theory, by choosing a particular radius, width and height of the resonator—which determine the properties of the light that can re ..
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