Color is a fundamental aspect of how we perceive and understand the world around us. It informs us about the safety of food, the temperature of metal, and aids medical practitioners in diagnosing various conditions. While significant investment has been made to improve color imaging in digital systems, there’s another property of light that holds valuable information: polarization.
Polarization, which describes how the electric field oscillates as light travels, is rich in information. However, polarization imaging has primarily remained confined to laboratory settings, relying on bulky optical components like waveplates and polarizers. Now, researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have introduced a compact, single-shot polarization imaging system that can offer a comprehensive view of polarization.
Using just two thin metasurfaces, this imaging system has the potential to revolutionize various applications, including biomedical imaging, augmented reality, virtual reality, and smartphone technology. Published in Nature Photonics, this research marks a significant advancement in polarization imaging.
“This system, devoid of moving parts or bulky optics, opens up new possibilities for real-time medical imaging, material characterization, machine vision, target detection, and more,” explained Federico Capasso, the Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering at SEAS, and senior author of the study.
In their previous work, Capasso and his team developed a compact polarization camera to capture Stokes images, revealing the polarization signature of objects without controlling the incident illumination. Now, they’ve taken a step further by introducing ‘active’ polarization imaging, known as Mueller matrix imaging.
Mueller matrix imaging captures the complete polarization response of an object by controlling the incident polarization. Traditionally, this method required complex optical setups with multiple rotating components. However, the new system developed by Capasso’s team simplifies this process using just two thin metasurfaces.
One metasurface generates polarized structured light, while the other captures and analyzes the light after interacting with the object. This allows for the construction of a complete polarization image in a single shot, enabling real-time advanced imaging crucial for various applications.
Combining structured light and polarized imaging into a single system, powered by nanoengineered metasurfaces, streamlines the design and facilitates widespread adoption of advanced imaging techniques. This breakthrough opens doors for innovative applications across multiple fields, from medical diagnostics to material classification and beyond.
