Enhancing the Purity of Reflective Structural Colors with Ultrathin Bilayer Media as Effective Ideal Absorbers

Abstract

Structural colors of high purity and brightness are desired in various applications. This study presents a general strategy of selecting the appropriate material and thickness of each layer to create high‐purity reflective colors in a classic asymmetric Fabry–Pérot cavity structure based on a dielectric–absorber–dielectric–metal multilayered configuration. Guided by the derived complex refractive index of the ideal absorber layer, an effective absorbing bilayer medium consisting of two ultrathin lossy films is used to improve the color purity of reflective colors by suppressing the reflection of its complementary colors with the enhanced optical absorption. Highly pure red, green, and blue reflective colors are designed and experimentally demonstrated employing different effective bilayer absorbers. Due to the high refractive index of the dielectric material, the colored structures exhibit great angle‐robust appearance (blue and red colors are up to ±60°, and green color is up to ±45°). The generalized design principles and the proposed method of using effective bilayer absorbers open up new avenues for realizing high‐purity thin‐film structural colors with more materials selections.

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

“…Their spectral transmission, reflection, and absorption can be aptly tailored owing to their outstanding merits, which include a simple structure, high efficiency, good scalability, a lithography-free fabrication process [1][2][3][4][5][6] , and easy fabrication on exotic flexible substrates [7][8][9] . As representative examples, a suite of color-filtering devices, drawing upon a thin-film nano-resonator, has been constructed to adaptively manipulate transmission and reflection in the visible band [9][10][11][12][13][14][15] .…”

Accurate inverse design of Fabry–Perot-cavity-based color filters far beyond sRGB via a bidirectional artificial neural network

“…The high-index materials of phase compensation overlayers can also achieve great angle insensitivity for both transverse-magnetic (TM) and transverse-electric (TE) polarizations [17]. There are several works published on the aspect of improving the performance of F-P cavity-based structural color in both transmissive and reflective modes [18][19][20]. In addition, the F-P-cavity-based color filter also demonstrates high lateral resolution.…”

High-purity reflective color filters based on thin film cavities embedded with an ultrathin Ge2Sb2Te5 absorption layer

“…A Fabry-Perot (F-P) cavity comprising metalinsulator-metal (MIM) continuous layers is of signicant interest as a lithography-free planar structure for controlling the transmission, reection, and absorption of light. [19][20][21][22][23][24][25][26][27] In transmission mode where both metal layers are sufficiently thin (i.e., semitransparent), the cavity can selectively transmit a narrow frequency range of incident light, thus producing fairly vivid transmissive colors. The colors are tunable by varying the thickness of the insulator layer (i.e., the dielectric spacer).…”

“…An alternative structure consisting of dielectric-absorber-dielectric-metal layers was also proposed, in which the absorber layer was made of two ultrathin lossy lms. 20 Highly pure R/G/B colors (bandwidth $ 100 nm) were demonstrated from the structure, but they required different bilayer absorbers: W/Ge, Au/Ni, and Ni/W bilayer absorbers for red, green, and blue, respectively. This makes color tuning troublesome because different materials need to be deposited for different colors.…”