Nanoscale optical-regime metamaterial absorber for enhanced photon absorption in thermal emitters

This article introduces a nanoscale metamaterial absorber (MMA) with significant photon absorption characteristics for incorporating in thermal emitters intended for solar energy harvesting from the visible spectrum in the optical frequency regime. The proposed MMA unit cell has an electrical dimension of 0.13 λ × 0.13 λ × 0.07 λ , where λ represents the maximum wavelength of the visible spectrum. It comprises a quartz (fused) substrate, a tungsten resonator layer, and a gold backplane. The computational model of the absorber is created utilizing CST Microwave Studio. The proposed MMA can produce an average absorption of 91.27% within the visible wavelength spectrum (375–750 nm), featuring dual absorption maxima of 94.37% and 99.81% at 428.81 nm and 657.89 nm, respectively. The performance of the MMA is further verified through high-frequency simulation software (HFSS) that provides an average absorption of 93.04%, indicating the accuracy of the design. The comprehensive parametric studies are accomplished, and absorption phenomena are analyzed through the current and field distribution. The absorber exhibits an almost zero polarization conversion ratio (PCR) with a maximum of 5.6 × 10 −5 . Moreover, the absorption spectra are stable for variation in polarization and incident angle up to 90° for transverse electric (TE) and transverse magnetic (TM) modes. The design attains a maximum solar irradiance efficiency of 92.18% facilitating effective photon conversion and reflection reduction. Additionally, a comparison of the presented MMA is made with some recent works, revealing that some other works provide higher absorption bandwidth but expose limited angular stability (≤70°), lower solar irradiance efficiency, and higher dimensions. But the proposed absorber overcomes these constraints by optimizing structural parameters and ensuring wide-band absorption, high incident and polarization angle stability, improved photon conversion efficiency within a compact dimension. Due to its compact dimension, stable absorption performance, and high solar irradiance efficiency, this new MMA can be utilized in thermal emitters for solar energy harvesting applications.