Dual-microcavity design permits parallel light measurements

In fiber optic communication, optical sensing, laser processing, and other applications, scientists and engineers must be able to measure the power and wavelength of light simultaneously. However, current methods rely on separate devices to determine each, resulting in inefficiencies, difficult calibrations, and the amplification of errors, as power meters usually require wavelength be measured first.

Wang et al. developed a single device to precisely measure power and wavelength at the same time. The sensor consists of microcavities coated with magnetic nanoparticles that make them photothermal: When the microcavity absorbs light, its temperature increases. This shifts the wavelength of the microcavity’s resonance, which researchers can extract to assess properties of the light.

The microcavities demonstrated more than an order of magnitude improvement in photothermal sensitivity. To measure both power and wavelength at the same time, the device features two different-sized microcavities. Asymmetric responses in the microcavities’ resonance enabled the authors to extract power and wavelength of light in parallel.

“Our developed technique not only eradicates the dependence of optical power measurement on accurate determination of the wavelength, but also surmounts the hurdles of insufficient precision and limited efficiency that are intrinsic to existing technologies,” said author Yan Wang.

This device could monitor light in real time in a range of applications, including clinical therapeutics as well as quantum information, computing, and sensing experiments. While it measures wavelength over a wide near-infrared bandwidth, from 780 to 1064 nanometers, the authors plan to extend this range.

“Our next steps for the device include extending the measurable spectral range, improving wavelength resolution, promoting system integration and encapsulation, and enhancing long-term reliability,” Wang said.

Source: “Microcavity-based parallel measurements of optical power and wavelength,” by Yan Wang, Yu-Hao Hu, Jin-Lei Wu, Jian Tang, Ya-Feng Jiao, Ya-Chuan Liang, Hai-Yan Wang, Li-Ying Jiang, Le-Man Kuang, Ke-Yu Xia, Lei Shi, and Hui Jing, Applied Physics Reviews (2025). The article can be accessed at https://doi.org/10.1063/5.0268412 .