Metasurface full-Stokes polarization camera (Conference Presentation)

Polarization is an important degree of freedom of light carrying information that is usually missing in other degrees of freedom. Polarimetric imaging is the process of measuring the state of polarization of light over an extended scene. It has several applications ranging from remote sensing to biological and medical imaging because it provides various pieces of information about the light source or the objects with which the light has interacted. So far polarization cameras have been made using polarization filters, and therefore suffer from two major drawbacks. First, there is a theoretical 50% upper limit on the efficiency of devices based on polarization filters. Second, to fully determine the state of polarization, multiple layers should be integrated in order to make polarization filters for circular or elliptical polarization states. Here, we present a polarization camera made using dielectric metasurfaces that operates based on separating and focusing orthogonal polarization states instead of polarization filtering. This allows for overcoming both drawbacks of current polarization camera designs. At the core of the design lies the capability of dielectric metasurfaces to fully control the polarization and phase of light. This enables designing and fabricating superpixels that separate and focus orthogonal polarization states of light on adjacent pixels on an image sensor over a single metasurface layer. Using this technique we have demonstrated full-Stokes polarization cameras with experimental efficiencies surpassing 60%, and superpixel dimensions reaching 4.8 µm×7.2 µm. We have also used this camera to form polarization images of custom-designed polarization targets.