Optical frequency combs have revo­lutionized metrology, spectro­scopy, atomic clocks, and other appli­cations. Yet challenges with developing frequency comb generators at a microchip scale have limited their use in everyday technologies such as handheld electronics. Now, researchers at the University of Rochester describe new microcomb lasers they have developed that overcome previous limita­tions and feature a simple design that could open the door to a broad range of uses.

Optical frequency combs generate a spectrum of light consisting of multiple coherent beams, each tuned to a different frequency or color, in evenly spaced distances. The resulting shape resembles the teeth on a hair comb. In recent years, scientists have been working to create minia­turized versions of this techno­logy, or microcombs, that can fit on small chips. But while scientists have made progress in prototyping microcombs, they have had limited success producing viable versions that can be applied in practical devices. Obstacles include low power efficiency, limited controlla­bility, slow mechanical responses, and the need for sophis­ticated system pre-configuration.

A team of researchers led by Qiang Lin created a unique approach to solve these challenges in a single device. According to PhD student Jingwei Ling, previous approaches usually rely on a single-wavelength laser injected into a nonlinear converter that can transfer the single wavelength into multiple wavelengths, forming the optical comb. “We eliminated the single wavelength because that’s going to degrade the system’s efficiency,” says Ling. “We instead have all the comb itself being amplified in a feedback loop inside the system, so all the wavelengths get reflected and enhanced inside a single element.”

The simplicity of the “all in one” microcomb laser results in lower power demands, lower costs, high tunability, and a turnkey operation. “It is easy to operate,” says PhD student Zhengdong Gao. “The previous methods make it hard to excite the comb, but with this method we only need to switch on the power source, and we can control the comb directly.” Hurdles remain for imple­menting these microcomb lasers, particularly with developing fabri­cation techniques to create such tiny components within the tolerances necessary for manu­facturing. But the researchers are hopeful that their devices can be used for appli­cations such as telecommuni­cations systems and light detection and ranging for autonomous vehicles. (Source: U. Rochester)

Reference: J. Ling et al.: Electrically empowered microcomb laser, Nat. Commun. 15, 4192 (2024); DOI: 10.1038/s41467-024-48544-2

Link: Laboratory for Nanophotonics, Institute of Optics, University of Rochester, Rochester, USA