Recent advances in optical metasurfaces for polarization detection and engineered polarization profiles

Like amplitude, phase and frequency, polarization is one of the fundamental properties of light, which can be used to record, process and store information. Optical metasurfaces are ultrathin inhomogeneous media with planar nanostructures that can manipulate the optical properties of light at the subwavelength scale, which have become a current subject of intense research due to the desirable control of light propagation. The unprecedented capability of optical metasurfaces in the manipulation of the light’s polarization at subwavelength resolution has provided an unusual approach for polarization detection and arbitrary manipulation of polarization profiles. A compact metasurface platform has been demonstrated to detect polarization information of a light beam and to arbitrarily engineer a polarization profile that is very difficult or impossible to realize with conventional optical elements. This review will focus on the recent progress on ultrathin metasurface devices for polarization detection and realization of customized polarization profiles. Optical metasurfaces have provided new opportunities for polarization detection and manipulation, which can facilitate real-world deployment of polarization-related devices and systems in various research fields, including sensing, imaging, encryption, optical communications, quantum science, and fundamental physics

Optical metasurfaces for polarization generation, detection and imaging

Like phase and amplitude, polarization is a fundamental property of light, which can reveal hidden information and has been used in many research fields, including material science, medicine, target detection and biomedical diagnosis. Polarization generation, detection and imaging are of importance for fundamental research and practical applications. Although conventional optics can perform these tasks, it suffers from a complex system, large volume and high cost, which cannot meet the continuing trend of miniaturization and integration. Optical metasurfaces, the two-dimensional counterparts of metamaterials, are planar nanostructured interfaces, which have recently attracted tremendous interest in realizing ultrathin and lightweight planar optical devices. Optical metasurfaces can manipulate light’s amplitude, phase and polarization in a desirable manner, providing a new and compact platform to generate, detect and manipulate light’s polarization. This thesis utilises optical metasurfaces to realise and experimentally demonstrate novel optical devices for polarization generation, detection and imaging. Due to the simplicity of the design and fabrication, this thesis is mainly focused on geometric optical metasurfaces, which are superior to other types of metasurfaces. 2D and 3D polarization structures are generated based on a metalens approach. A ring focal curve, an Archimedean spiral focal curve, and seven-segment-based decimal numbers are experimentally demonstrated in 2D space, while a 3-foil knot, a 4-foil knot, and a 5-foil are realized in 3D space. The geometric metasurfaces are designed based on colour and phase multiplexing and polarization rotation, creating various 3D polarization knots. Various 3D polarization knots in the same observation region can be achieved by controlling the incident wavelengths, providing unprecedented polarization control with colour information in 3D space. Novel polarization detection is experimentally demonstrated through optical holography, light’s orbital angular momentum, and optical ring vortex beams. The measured polarization parameters such as major axis, ellipticity, and handedness are in good agreement with the theoretical prediction. A multifunctional microscope is proposed and developed to image different objects, including biological samples such as cheek cells and beef tendons. For the same sample, five images with different optical properties are obtained on the same imaging plane, which can simultaneously perform edge imaging, polarimetric imaging, and conventional microscope imaging. Benefiting from the ultrathin nature, compactness and multifunctionality of the optical metasurface devices, the integration does not excessively increase the volume of the optical system. With its promising capabilities and potential for expandability, we believe our microscope will herald an exciting new era in biomedical research. The ultrathin nature of optical metasurfaces and their unprecedented capability in light control have provided a compact platform to develop ultrathin optical devices with novel functionalities that are very difficult or impossible to achieve with conventional optics. The metasurface platform for polarization detection and manipulation is very attractive for diverse applications, including polarization sensing and imaging, optical communications, optical tweezers, quantum sciences, display technologies, and biomedical research as well as wearable and portable consumer electronics and optics where miniaturized systems are in high demand

Optical Metasurface Generated Vector Beam for Anticounterfeiting

The potential in cost and energy savings by replacing a feed forward weather compensated control (WCC) controlled radiator system with a linear MPC controller is investigated in a Modelica-Python setup. It is shown that if the MPC is optimized for minimum energy consumption it can reduce the energy consumption by up to 12 %. It is also demonstrated how variable price signal can influence the heat demand profile, and thereby shift energy consumption away from peak hours. By introducing a peak load tariff, it is also possible to reduce the rapid changes and large peaks often caused by optimization-based controller