Research On The Infrared Broadband Absorption Of Plasmonic Metasurface Absorbers And Their Applications

Integration,miniaturization,and multi-function are essential trends in the development of photonics devices.At present,compared with integrated circuit chips,the development of photonics devices in terms of multi-function and integration is still in its infancy,and there is a certain gap between standard integration and large-scale market applications.As an important branch of micro/nanophotonics,plasmonic metasurface absorber(PMA)has potential applications in gas sensing,infrared detection,and radiation cooling due to its excellent light field localization,electromagnetic parameter control,and photothermal conversion ability.The research on the theoretical basis,analysis and design method,numerical simulation method,device fabrication,characterization method,and practical application of PMA is of great significance.This dissertation focuses on the physical mechanism and optimization design of PMA and explores its application in uncooled infrared detection and thermal radiation control.The main content of this dissertation includes the following aspects.The first part of this dissertation is mainly about the research background of PMA.PMA has potential in the integration and multi-function of uncooled thermal detectors.The development trend of PMA and its application in infrared detection and thermal radiation control are summarized.The fundamental knowledge of plasmonics is also introduced.Then the mainstream theoretical analysis methods and numerical simulation methods for PMA are introduced in detail.Finally,the fabrication methods and characterization methods are presented.In the second part,a new physical mechanism to achieve infrared broadband absorption is proposed based on the strong coupling between optical phonon and plasmonic resonance.The rich phenomena in the optical responses and local electromagnetic fields of a phonon mediated metal-insulator-metal(MIM)absorber are numerically and experimentally explored.The physical mechanisms responsible for novelty spectral absorption,including the strong coupling between the plasmon resonances and the phonon vibrations is systematically analyzed by finitedifference time-domain method and two-coupled damped oscillator model.The incident-angle dependence and polarization dependence of the broadened absorption spectrum is evaluated.The spectral broadening mechanism can be generalized to other frequency bands by employing different spacing materials.A MIM-based infrared PMA consisting of deep subwavelength meander line nanoantennas is reported.High absorption from 11μm to 14μm is experimentally demonstrated with a pixel pitch of 1.47μm.Such a miniaturized absorber can adapt to infrared focal plane arrays with a pixel size smaller than 5μm.This approach provides an effective way to minimize the antenna footprint without undermining the absorber performances,paving the way towards its integration with small pixels of infrared focal plane arrays for enhanced performances and expanded functionalities.In the third part,the current PMA design method is improved by an inverse design method based on the particle swarm algorithm.First,starting from the inverse design background and concept,the inverse design based on the intelligent optimization algorithm is introduced.The principle and implementation of the particle swarm algorithm are also emphasized.Subsequently,because of the insufficient research of broadband polarization selective PMA,the mid-wave infrared is used as the design band and adopted inverse design method.A highly broadband and polarization selective mid-IR metal-insulator-metal absorber is designed and experimentally demonstrated,covering the 3–5 μm atmospheric transparency band.With spectrally averaged absorption exceeding 70%,a high polarization extinction ratio of 40.6 is concurrently achieved.The fourth part proposes an infrared information encoding,multiplexing,and hiding technology,using phonon-assisted PMA instead of traditional PMA.The experimental results show that this technology can more effectively control the spatial distribution,intensity,and polarization of thermal radiation compared with conventional solutions.Then,experiments and simulations verified that phonon-assisted PMA could encode and display infrared information with resolution up to the diffraction limit.An original image with up to 13 grayscale levels is successfully implemented with this PMA.Furthermore,this design can also encode single or multiplexed polarized grayscale patterns into the same region.Finally,these patterns can be concealed visually with ink while uncovered using an infrared microscope.In the fifth part,a PMA based polarization imaging architecture is proposed,unlike conventional architecture,which has the advantages of small optical crosstalk,simple fabrication,and high integration.Based on metal-insulator-metal-insulator-metal structure,a high broadband absorption(87.2%)PMA covering 8-14 μm with highly polarization selectivity is also achieved via inverse design.By setting additional constraints on the range of optimized parameters due to fabrication limitations and selecting CMOS-compatible materials,a CMOS-compatible absorber,which I-line steppers can realize,is designed.A comprehensive figure of merit for evaluating the infrared polarization detection performance of the PMA integrated microbolometer is also presented.Finally,relying on numerical simulation,the effect of pixel gap and pixel size on the absorption characteristics of PMA is explored.Then a systematic 3D photothermal simulation is carried out on the microbridge structure integrated with PMA.