Metasurfaces Can Sense Spatial Coherence of Light

Summary form only given. We report on a discovery that homogeneous metallic non-diffracting metasurfaces of a certain type respond differently to spatially coherent and incoherent light, enabling robust speckle-free discrimination between different degrees of coherence. The effect has no direct analogue in natural optical materials and may find applications in compact metadevices enhancing imaging, vision, detection, communication and metrology. Here we describe and investigate an intriguing optical phenomenon whereby the transmission (and reflection) response of apparently trivial, non -diffracting metallic metasurfaces acquires different spectral components, depending on whether the metasurfaces are illuminated with spatially coherent or incoherent light (see Fig. 1). This effect, previously unseen in metamaterials, and metasurfaces in particular, is robust and exceptionally strong (absolute difference in transmission exceeds 50%), which makes it immediately suitable for practical applications, such as optical metrology, imaging and communication.