Dye and pigment-free structural colors and angle-insensitive spectrum filters
Optical spectrum filtering devices displaying minimal angle dependence or angle insensitivity are provided. The filter comprises a localized plasmonic nanoresonator assembly having a metal material layer defining at least one nanogroove and a dielectric material disposed adjacent to the metal material layer. The dielectric material is disposed within the nanogroove(s). The localized plasmonic nanoresonator assembly is configured to funnel and absorb a portion of an electromagnetic spectrum in the at least one nanogroove via localized plasmonic resonance to generate a filtered output having a predetermined range of wavelengths that displays angle insensitivity. Thus, flexible, high efficiency angle independent color filters having very small diffraction limits are provided that are particularly suitable for use as pixels for various display devices or for use in anti-counterfeiting and cryptography applications. The structures can also be used for colored print applications and the elements can be rendered as pigment-like particles.
1. A transmission-type angle insensitive optical spectrum filtering device comprising:
a localized plasmonic nanoresonator assembly comprising a multi-layered metal material layer comprising a metal layer sandwiched between two highly reflective metal layers, wherein the metal layer defines at least one nanogroove and a dielectric material disposed within the at least one nanogroove and disposed adjacent to one of the two highly reflective metal layers, wherein the localized plasmonic nanoresonator assembly is configured to funnel and absorb a portion of an electromagnetic spectrum in the at least one nanogroove via localized plasmonic resonance to transmit a filtered output having a predetermined range of wavelengths that displays angle insensitivity so that the predetermined range of wavelengths varies less than or equal to about 20 nm from an incidence angle of 0° to an incidence angle of 90° with respect to the filtering device.
2. The transmission-type angle insensitive optical spectrum filtering device of claim 1 , wherein the metal material layer comprises a metal selected from the group consisting of: silver, aluminum, and combinations thereof.
3. The transmission-type angle insensitive optical spectrum filtering device of claim 1 , wherein the dielectric material has a refractive index of greater than or equal to about 1.0.
4. The transmission-type angle insensitive optical spectrum filtering device of claim 1 , wherein the dielectric material comprises silicon dioxide (SiO 2 ) and the metal material layer comprises silver.
5. The transmission-type angle insensitive optical spectrum filtering device of claim 4 , wherein the predetermined range of wavelengths of the filtered output that exits the filtering device is in a visible light range and the metal material layer defines a plurality of distinct nanogrooves disposed parallel to one another that defines a periodicity of greater than or equal to about 160 nm to less than or equal to about 200 nm, wherein the at least one nanogroove has a width of greater than or equal to about 40 nm to less than or equal to about 90 nm and a depth of greater than or equal to about 110 nm to less than or equal to about 170 nm.
6. The transmission-type angle insensitive optical spectrum filtering device of claim 1 , wherein the predetermined range of wavelengths of the filtered output that exits the filtering device is in a visible light range and has a color selected from the group consisting of: red, green, blue, and combinations thereof.
7. The transmission-type angle insensitive optical spectrum filtering device of claim 1 , wherein the localized plasmonic nanoresonator assembly comprises two adjacent nanogrooves oriented in an opposite direction from one another to form a coupled cavity that can transmit the filtered output having the predetermined range of wavelengths.
8. A pixel for a display device comprising:
a color filtering device comprising a localized plasmonic nanoresonator assembly that comprises a multi-layered metal material layer comprising a metal layer sandwiched between two highly reflective metal layers, wherein the metal layer defines at least one nanogroove and a dielectric material disposed adjacent to one of the two highly reflective metal layers and disposed within the at least one nanogroove, wherein the localized plasmonic nanoresonator assembly is configured to funnel and absorb a portion of a visible light spectrum in the at least one nanogroove via localized plasmonic resonance to generate a filtered output having a predetermined range of wavelengths in a visible light range that displays angle insensitivity, so that the predetermined range of wavelengths varies by less than or equal to 20 nm at incidence angles ranging from 0° to 90° with respect to the color filtering device.
9. The pixel for the display device of claim 8 , wherein the color filtering device has a plurality of distinct nanogrooves, so that the predetermined range of wavelengths of the filtered output that exits the color filtering device generates a color selected from the group consisting of: red, green, blue, and combinations thereof.
10. The pixel for the display device of claim 8 , wherein the pixel is a multicolored pixel and the color filtering device has a plurality of nanogrooves comprising a first nanogroove and a second distinct nanogroove having at least one distinct dimension, wherein the first nanogroove is sized to funnel and absorb a first wavelength of the visible light spectrum via localized plasmonic resonance to generate a first filtered output and the second distinct nanogroove is sized to funnel and absorb a second wavelength of the visible light spectrum via localized plasmonic resonance to generate a second filtered output, wherein the first wavelength and the second wavelength are distinct from one another.