Tunable Perfect Narrow-Band Absorber Based on a Metal-Dielectric-Metal Structure

Abstract

In this paper, a metal-dielectric-metal structure based on a Fabry–Perot cavity was proposed, which can provide near 100% perfect narrow-band absorption. The lossy ultrathin silver film was used as the top layer spaced by a lossless silicon oxide layer from the bottom silver mirror. We demonstrated a narrow bandwidth of 20 nm with 99.37% maximum absorption and the absorption peaks can be tuned by altering the thickness of the middle SiO2 layer. In addition, we established a deep understanding of the physics mechanism, which provides a new perspective in designing such a narrow-band perfect absorber. The proposed absorber can be easily fabricated by the mature thin film technology independent of any nano structure, which make it an appropriate candidate for photodetectors, sensing, and spectroscopy.

Narrowband and flexible perfect absorber based on a thin-film nano-resonator incorporating a dielectric overlay

“…Figure 3a shows the calculated absorption spectra with respect to the metal thickness t for d c = 100 nm and h = 200 nm. As addressed in previous approaches 1,30 , a strong resonance combined with enhanced absorption was secured for t = ~ 30 nm with the MDM configuration involving an Ag mirror. Significant absorption beyond 99.9% was theoretically attained at λ = 694 nm with a full width at half maximum (FWHM) of 28 nm.…”

“…Perfect absorbers, which absorb a specific spectral band and do not permit reflection or transmission, have recently gained considerable interest by virtue of their wide range of applications spanning photovoltaic cells 16 , photodetectors 17,18 , thermal imaging 19 , and sensors [20][21][22][23][24][25][26][27][28] . Perfect absorbers engaging various nanostructures (e.g., plasmonic and metasurface schemes) [18][19][20][21][22][23][24][25][26][27]29 and multilayered structures [1][2][3][4]28,[30][31][32][33][34][35][36][37] are being extensively studied. Although narrowband absorbers are known to be suitable for sensing and absorption filtering 2,[25][26][27] , conventional approaches have mostly focused on multiband 21,25 or broadband absorption [31][32][33]…”

“…Nevertheless, MDM absorbers that are comprised of lossy metals including chromium (Cr), titanium (Ti), nickel (Ni), tungsten (W), and manganese (Mn), may feature a broadband absorption leading to a low Q-factor [2][3][4][32][33][34] . A viable approach to achieve higher Q-factor is using noble metals such as gold (Au) or silver (Ag) 1,12,30,50 . Metal such as Ag was chiefly utilized to realize high reflectivity and low extinction across the whole visible band [9][10][11][12][13][14]44 .…”

“…For practical application of the proposed absorber, we tried various absorbers with varying cavity thicknesses. According to the aforementioned equation, an MDM nano-resonator can flexibly tune the wavelength by tailoring the thickness of the dielectric cavity 1,30 . Figure 6 portrays a suite of device samples with different thicknesses of dielectric layers, where the metal thicknesses (t and h) were fixed.…”

Special Issue: “Thin Films for Energy Harvesting, Conversion, and Storage”

“…Enhanced electrochemical performance was obtained by optimizing the thickness of the Al 2 O 3 layer. In their brief report, Li et al [12] propose a metal-dielectric metal structure based on a Fabry-Pérot cavity, and the as-prepared narrow-band absorber can be easily fabricated by the mature thin film technology independent of any nanostructure, which makes it an appropriate candidate for photodetectors, sensing, and spectroscopy. Chen et al [13] performed an in situ investigation of the early-stage CH 3 NH 3 PbI 3 (MAPbI 3 ) and CH(NH 2 ) 2 PbI 3 (FAPbI 3 ) degradation under high water vapor pressure.…”