Nanostructured Color Filters: A Review of Recent Developments

Abstract

Color plays an important role in human life: without it life would be dull and monochromatic. Printing color with distinct characteristics, like hue, brightness and saturation, and high resolution, are the main characteristic of image sensing devices. A flexible design of color filter is also desired for angle insensitivity and independence of direction of polarization of incident light. Furthermore, it is important that the designed filter be compatible with the image sensing devices in terms of technology and size. Therefore, color filter requires special care in its design, operation and integration. In this paper, we present a comprehensive review of nanostructured color filter designs described to date and evaluate them in terms of their performance.

Keywords: color filters; liquid crystal display; mie scattering; nanoholes; photonic crystals.

Figure 1

Vector diagram for transmission and reflection in FP-cavity when light comes across (a) Single and (b) Multiple material discontinuities.

Figure 2

(A) Calculated and measured transmission and reflection spectra for the three fabricated devices shows RGB in transmission and CMY in reflection mode. The CIE 1931 further provides the coordinates of the produced results [12]. (B) Calculated and measured spectra along with the camera images of broadband visible and near-infrared absorbers implemented with planar nanolayered stacks. Reproduced with permission of [42]. Copyright American Chemical Society, 2020. (C) Demonstration of angle invariance of up to 0 to 65${}^{\circ }$ view angle for fabricated lossy medium-based optical cavity using optical images. Reproduced with permission of [43]. Copyright John Wiley & Sons, 2014.

Figure 3

Generating Plasmons. (a) Dispersion relation of surface plasmons compared to light in vacuum and in the dielectric medium. Incident light on a (b) glass prism with gold sputtered on one of its faces, SPP propagates along the glass and Au interface (c) Diffraction grating with period $\mathrm{\Lambda }$ (d) shows diffraction grating with varying refractive index and path for the incident light (e) represent a GMR-based grating (f) The reaction of single nano-particle on dielectric to the incident light (g) shows the reaction of lattice of nanoparticles to the incident angle and (h) GSP resonance, a special kind of FP-cavity with thin dielectric film and one metallic truncated film on the top.

Figure 4

(A) Schematic of plasmonic nano-cavity along with its fabricated device is illustrated. The charge distribution and Poynting vector direction is shown with the help of a simulator. The impact of dimension of nanoslits on reflection spectra is further shown theoretically and experimentally and results for CMY colors are produced [100]. (B) Scanning Electron Microscope (SEM) images of fabricated multicolor pixel and their spectral transmission. Camera image of vivid color produced shows its dependency on the grating period and angle of polarization (C) Verification of GMR for TE and TM mode transmission spectra [98].

Figure 5

(a) schematic diagram of aluminium based nanohole-nanodisk hybrid structure. (b) The impact of variation in diameter, periodicity and (spacing) diameter and periodicity on the color image due to color toning and mixing is demonstrated experimentally. Reproduced with permission of [170]. Copyright American Chemical Society, 2014. (c) Color printing resolution test pattern for LSPP based nanostructures at the scale bar of (i) 200 nm, (ii) 1 $\mathsf{\mu }$m and (iii) 500 nm [171].

Figure 6

(A) Experimental and theoretical results of vivid colors produced due to Al nanorod as a single nanorod and in hexagonal array [189]. (B) Schematic diagram of Ag nanopatch on glass substrate with different periodicities allowing angle invariant (up to ${60}^{\circ }$) additive and subtractive color filtration in transmission and reflection respectively. The plot for simulated and experimental spectra with the color image inset shows the obtained results. SEM gives a close look at the fabricated nanopatch array. Reproduced with permission of [187]. Copyright John Wiley & Sons, 2016. (C) schematic diagram of randomly distributed Ag nanodisks, the ${\lambda }_{res}$ was swept by varying the diameter of the nanodisks. The transmission spectra with color image in inset shows the color quality produced. Reproduced with permission of [190]. Copyright The Optical Society, 2013. (D) Schematic diagram of thin Al nanopatch array on a glass substrate, this design filters out white color into distinct subtractive colors by varying the pitch of array. The color quality is evident in SEM and camera image of the fabricated filters. The polarization independence is verified by plotting reflection spectra at different polarization angles. Reproduced with permission of [191]. Copyright American Chemical Society, 2014.

Figure 7

(A) Schematic diagram of a circular gap plasmonic nano microscopic images of the highly uniformed colors due to an array (B) Precise color printing on an optical microscopic image demonstrate bright colors with high contrast, and demonstrate that even single pixel details are colored and discernible. Reproduced with permission of [194]. Copyright American Chemical Society, 2014.

Figure 8

(A) Schematic diagram of TiO${}_2$ based color filter, the reflection spectra shows dependence of filter on the device dimensions (here the width of the bottom face w is varied from 200 to 250 nm). (B) Color image printing is exhibited with the top view SEM image of the logo with transmission and reflection colorful images under bright field microscope. Reproduced with permission of [220]. Copyright American Chemical Society, 2017. (C) Simulated and experimental results for additive colors of all dielectric metasurfaces based on cross-shaped resonators. Reproduced with permission of [221]. Copyright American Chemical Society, 2017. (D) Schematic diagram of 2D lattice of a-Si:H nanodisks on a glass substrate [222].

Figure 9

Phases of liquid crystals. (a) Nematic phase. (b) Smectic A phase. (c) Smectic B phase. (d) Cholestric phase.

Figure 10

Liquid crystal-based color filters. (A) Setup of electrically tunable color filter exploiting a visible dichroic resonator with subwavelength metal-dielectric resonant structure in conjunction with a LC-based polarization controller. Reproduced with permission of [19]. Copyright The Optical Society, 2013. (B) Schematic diagram of electrically tunable color filter exploiting TN-LC and rectangular lattice of nanoholes on Al film to control the polarization of incident light, and (C) Optical photographs of printed colors in TM and TE mode. Reproduced with permission of [244]. Copyright American Chemical Society, 2017.

Figure 11

Key Performance Indicator charts for nanostructure color filters.