Behind the Cover: July 2024

Each month, Physics Today editors explore the research and design choices that inspired the latest cover of the magazine.

Imagine if you could see light’s polarization the same way you can see its color. Some animals, including many insects and crustaceans, can do just that. We humans, on the other hand, tend to associate polarization with bulky, specialized optical instruments, and we often fail to appreciate the rich information that polarization can carry in the natural world. The collagen fibers in your skin, for example, have a polarizing effect on light. So a specialized polarization-sensitive camera can distinguish a photograph of your face from your actual face. It may also be able to tell whether a mole on your face is likely to be cancerous.

Just like any color can be decomposed into some combination of red, green, and blue, any polarization state can be represented as a sum of four components. (But whereas the color breakdown is an artifact of the biology of human vision, the polarization breakdown is an inherent property of light.) The cover story of Physics Today‘s July issue describes recent efforts to use optical metamaterials to unlock the secrets of polarized vision. Not satisfied with imaging the four components of the polarization of natural light, researchers have measured how objects transform the polarization of any incident light. The result is not just 4 spatially resolved images but 16.

For the cover, Physics Today art director Freddie Pagani created a whimsical drawing that invokes the color–polarization analogy through a play on the photography exercise of using filters to cast shadows of different colors. But instead of three shadows, there are four, each with a subtle color gradient inspired by optical interference patterns.