Polarization-insensitive Perfect Absorber Research Articles

Extremely broadband light absorption by bismuth-based metamaterials involving hybrid resonances.

An ultra-broadband polarization-insensitive perfect absorber for the 400-4000 nm spectral range is proposed and studied. The absorber is composed of a dielectric film and a phase change material film sandwiched between a bismuth square ring array and a continuous bismuth mirror. Greater than 94% absorptivity across the wavelength range of 400-4000 nm and an averaged absorptivity of about 97% can be achieved. The physical origin results from the mixed effect of guided mode resonance (GMR), cavity resonance (CR) and surface plasmon resonance (SPR). In addition, such a property is maintained excellent in a very large viewing angle range. Furthermore, the proposed scheme exhibits certain geometrical parameter tolerance, which is beneficial for practical fabrication with low cost. Finally, the potential application of the solar cells is investigated as an illustration. The designed metamaterial absorber will find promising applications in solar cells, thermo-photovoltaics and detection.

Ultra-broadband, lithography-free, omnidirectional, and polarization-insensitive perfect absorber

Perfect absorbers (PAs) at near infrared allow various applications such as biosensors, nonlinear optics, color filters, thermal emitters and so on. These PAs, enabled by plasmonic resonance, are typically powerful and compact, but confront inherent challenges of narrow bandwidth, polarization dependence, and limited incident angles as well as requires using expensive lithographic process, which limit their practical applications and mass production. In this work, we demonstrate a non-resonant PA that is comprised of six continuous layers of magnesium fluoride (MgF2) and chromium (Cr) in turns. Our device absorbs more than 90% of light in a broad range of 900–1900 nm. In addition, such a planar design is lithography-free, certainly independent with polarization, and presents a further advantage of wide incidence up to 70°. The measured performance of our optimized PA agrees well with analytical calculations of transfer matrix method (TMM) and numerical simulations of finite element method, and can be readily implemented for practical applications.

Wide-angle wideband polarization-insensitive perfect absorber based on uniaxial anisotropic metasurfaces

A wide-angle, wideband, and polarization-insensitive metamaterial (MM) absorber was studied based on the theoretical concept of uniaxial perfect matching layer (UPML) in the terahertz range. The MM absorber was designed as a multi-layered anisotropic array structure consisting of a conductive VIA, a bi-layered slot-FSS, and a split-ring resonator (SRR) separated by porous silica spacers. Each component is optimized to approach the required macroscopic uniaxial property for satisfying the reflection-less boundary condition. The SRRs and VIAs were found to play an important role in maintaining large absorption when the angle of oblique incidence increases under transverse electric (TE) and transverse magnetic (TM) polarization, respectively. The absorption achieves 90% in the frequency regime of 0.9 to 10.5 THz, corresponding to a bandwidth of 168% to the central frequency, and retains such high performance up to 60° oblique incidence for both TE and TM waves.

A broadband and polarization-insensitive perfect absorber based on a van der Waals material in the mid-infrared regime

A broadband and polarization-insensitive optical absorber based on van der Waals (vdW) material h-BN is proposed in the mid-infrared regime. By utilizing the finite-difference time-domain (FDTD) simulation, the broadband absorption spectrum above 95% is achieved from 6490 to 7295 nm. Moreover, the proposed structure can maintain the excellent performance and broadband absorption in a wide range of incident angles. To illustrate the physical mechanism of proposed absorber, we investigate the magnetic field distributions in the each h-BN structural unit at different wavelengths, and comprehend it with the dispersion relation. Thus, we believe that our research can find some important applications for thermal emitters and photovoltaic devices with outstanding properties working at mid-infrared regime.

Multiband and broadband polarization-insensitive perfect absorber devices based on a tunable and thin double split-ring metamaterial.

We demonstrate a polarization-insensitive perfect absorber with multiband and broadband absorption based on a tunable and thin metamaterial, which consists of a double split-ring microstructure (DSRM) on double-layer and a coating substrate. The multiband absorption at different frequencies and broadband absorption with the relative bandwidth of 90.63% from 5.69GHz to 15.12GHz, of which the absorptivity is larger than 90%, can be achieved by changing the rotary angle of the proposed DSRM perfect metamaterial absorber (DSRM-PMA). The advantages of polarized-insensitivity, wide bandwidth and multiband absorption are illuminated by the angular absorptions and the surface current distributions. The DSRM-PMA device with similar geometry in simulation is fabricated and tested to clearly validate the functionality of our design. The simulated and experimental results indicate that the DSRM-PMA performs multiband and broadband absorptions with the rotary angle of 0° and 90° respectively.

Wideband, thin, and polarization-insensitive perfect absorber based the double octagonal rings metamaterials and lumped resistances

By loading the lumped resistances into the double octagonal rings metamaterials, a wideband, thin, and polarization-insensitive perfect absorber is investigated theoretically and experimentally. The perfect absorber is constructed of double octagonal rings loading the eight lumped resistances and the substrate with height of 3 mm. The effects of the double octagonal rings and eight lumped resistances are explored by absorption and the electric field distributions. The simulated results indicate that the structure obtains 9.25 GHz-wide absorption from 7.93 to 17.18 GHz with absorptivity larger than 90% at the incident angles from 0° to 20° and achieves above 12.2 GHz-wide absorption from 5.8 to 18 GHz with a full width at half maximum at wide incident angles from 0° to 70°. The fabricated metamaterial absorber device was measured and analyzed. A good agreement is observed between the simulation and the measurement.

Wide-Angle and Polarization-Insensitive Perfect Absorber for Organic Photovoltaic Layers

In this letter, we computationally explore a wide-angle and polarization-insensitive perfect absorber based on hybrid metal-dielectric-metal structures. By introducing an organic photovoltaic layer between top metallic nanopatterns and a continuous metal bottom plate, an enhanced angle-and polarization-insensitive absorption can be obtained in the spectral range 400–700 nm, which is promising to realize improved thin-film organic photovoltaic devices. The physical mechanism of the perfect absorber is explained theoretically and numerically by the critical coupling principle.