ABSTRACT
Intensity, polarization and wavelength are intrinsic characteristics of light. Characterizing light with arbitrarily mixed information on polarization and spectrum is in high demand1-4. Despite the extensive efforts in the design of polarimeters5-18 and spectrometers19-27, concurrently yielding high-dimensional signatures of intensity, polarization and spectrum of the light fields is challenging and typically requires complicated integration of polarization- and/or wavelength-sensitive elements in the space or time domains. Here we demonstrate that simple thin-film interfaces with spatial and frequency dispersion can project and tailor polarization and spectrum responses in the wavevector domain. By this means, high-dimensional light information can be encoded into single-shot imaging and deciphered with the assistance of a deep residual network. To the best of our knowledge, our work not only enables full characterization of light with arbitrarily mixed full-Stokes polarization states across a broadband spectrum with a single device and a single measurement but also presents comparable, if not better, performance than state-of-the-art single-purpose miniaturized polarimeters or spectrometers. Our approach can be readily used as an alignment-free retrofit for the existing imaging platforms, opening up new paths to ultra-compact and high-dimensional photodetection and imaging.
ABSTRACT
It is a grand challenge for an imaging system to simultaneously obtain multi-dimensional light field information, such as depth and polarization, of a scene for the accurate perception of the physical world. However, such a task would conventionally require bulky optical components, time-domain multiplexing, and active laser illumination. Here, we experimentally demonstrate a compact monocular camera equipped with a single-layer metalens that can capture a 4D image, including 2D all-in-focus intensity, depth, and polarization of a target scene in a single shot under ambient illumination conditions. The metalens is optimized to have a conjugate pair of polarization-decoupled rotating single-helix point-spread functions that are strongly dependent on the depth of the target object. Combined with a straightforward, physically interpretable image retrieval algorithm, the camera can simultaneously perform high-accuracy depth sensing and high-fidelity polarization imaging over an extended depth of field for both static and dynamic scenes in both indoor and outdoor environments. Such a compact multi-dimensional imaging system could enable new applications in diverse areas ranging from machine vision to microscopy.
ABSTRACT
Daytime radiative cooling with high solar reflection and mid-infrared emission offers a sustainable way for cooling without energy consumption. However, so far sub-ambient daytime radiative coolers typically possess white/silver color with limited aesthetics and applications. Although various colored radiative cooling designs have been pursued previously, multi-colored daytime radiative cooling to a temperature below ambient has not been realized as the solar thermal effect in the visible range lead to significant thermal load. Here, we demonstrate that photoluminescence (PL) based colored radiative coolers (PCRCs) with high internal quantum efficiency enable sub-ambient full-color cooling. As an example of experimental demonstration, we develop a scalable electrostatic-spinning/inkjet printing approach to realize the sub-ambient multi-colored radiative coolers based on quantum-dot photoluminescence. The unique features of obtained PCRCs are that the quantum dots atop convert the ultraviolet-visible sunlight into emitted light to minimize the solar-heat generation, and cellulose acetate based nanofibers as the underlayer that strongly reflect sunlight and radiate thermal load. As a result, the green, yellow and red colors of PCRCs achieve temperatures of 5.4-2.2 °C below ambient under sunlight (peak solar irradiance >740 W m-2), respectively. With the excellent cooling performance and scalable process, our designed PCRC opens a promising pathway towards colorful applications and scenarios of radiative cooling.
