Researchers from Jinan University, under the direction of Professor Yanjun Bao and Baojun Li, developed a novel metasurface-based imaging method that allows for the simultaneous measurement of intensity, phase, and polarization of arbitrary light fields in a single exposure. This method overcomes the limitations of traditional optical systems, which require complex setups and multiple measurements. The study was published in the journal National Science Review.
Schematic diagram of metasurface-based single-shot imaging system for complete characterization of arbitrary light field intensity, phase, and polarization. Image Credit: Science China Press
Light fields are electromagnetic waves with fundamental characteristics including polarization, intensity, and phase. Precise imaging of these three parameters is essential for biomedical diagnostics, communication, and optical detection.
Conventional light parameter measurement techniques mostly depend on intricate optical systems that call for several bulk optical components, including beam splitters, waveplates, and polarizers.
This significantly restricts its use in dynamic light field characterization by raising system complexity and cost and necessitating numerous measurements to obtain comprehensive parameter distribution information. Metasurface-based imaging technology has emerged as a new technical solution to traditional optical systems in recent years.
However, most current metasurface imaging techniques have specific requirements for the parameter distribution of the light field being tested and can only obtain partial parameter information, which severely limits their practical application range.
Thus, there is significant scientific value and potential for application in developing new imaging technology that can measure all parameters simultaneously for arbitrary light fields.
This technology precisely designs the metasurface structural parameters using optimization algorithms, producing the necessary reference light field while achieving controllable and effective diffraction of the incident light field's orthogonal polarization components.
The system can acquire all of the light field's parameter information in a single exposure, thanks to this creative design. The application possibilities of metasurfaces in the optical field are significantly increased by this work, and the associated results were published.
An incident light field with any distribution of intensity, phase, and polarization can be diffracted into seven sub-images by the metasurface imaging system, which can then image these sub-images on a CMOS sensor.
Four of the sub-images are distinct phase interference patterns of x and y-polarized images, used for intensity and polarization information extraction; three of the sub-images are interference patterns between x-polarized images and uniform background light fields with 120° phase differences, used for phase information reconstruction.
The research team used a gradient descent algorithm to optimize the uniform background light field intensity and multiple diffraction efficiencies. The uniform background light intensity increased by about 14 times, and the multi-level diffraction efficiency improved by about 5 times when compared to the traditional forward design.
Pixel units made up of four nanorod structures can be used to realize the four degrees of freedom of the optimized metasurface Jones matrix. For verification, the research team created three distinct input light field distributions.
Complete characterization of intensity, phase, and polarization information for arbitrary light field distributions under single-exposure conditions was accomplished by successfully reconstructing all parameter information of the input light field following processing through this imaging system and image calibration.
Journal Reference:
Bao, Y. & Li, B. (2025) Single-shot simultaneous intensity, phase, and polarization imaging with metasurface. National Science Review. doi.org/10.1093/nsr/nwae418.