Meta optical device and electronic apparatus including the same
Provided is a meta optical device including a plurality of phase modulation regions respectively including a plurality of nanostructures and configured to modulate a phase of incident light, wherein a phase retardation profile of the plurality of phase modulation regions monotonically change with respect to light of a plurality of wavelength bands apart from each other, and wherein phase modulation ranges with respect to the light of the plurality of wavelength bands are different from each other.
1. A meta optical device comprising:
a plurality of phase modulation regions respectively comprising a plurality of nanostructures and configured to modulate a phase of incident light, wherein a phase retardation profile of the plurality of phase modulation regions monotonically changes with respect to light of a plurality of wavelength bands apart from each other,
wherein phase modulation ranges with respect to the light of the plurality of wavelength bands are different from each other, and
wherein, in each of the plurality of phase modulation regions, a phase retardation dispersion defined by a difference between a phase retardation profile corresponding to light of a first wavelength band among the plurality of wavelength bands and a phase retardation profile corresponding to light of a second wavelength band among the plurality of wavelength bands monotonically changes with a certain amount of change, the first wavelength band being longer than the second wavelength band.
2. The meta optical device of claim 1 , wherein the plurality of wavelength bands are included in a red wavelength band, a green wavelength band, and a blue wavelength band, and
wherein a bandwidth of each of the plurality of wavelength bands is less than or equal to 50 nm.
3. The meta optical device of claim 1 , wherein each of the plurality of phase modulation regions has a phase modulation range of 2x*k, where |k|>1, with respect to the light of the plurality of wavelength bands, and
wherein a phase modulation range corresponding to light of the first wavelength band among the plurality of wavelength bands is less than a phase modulation range corresponding to light of the second wavelength band among the plurality of wavelength bands, the first wavelength band being longer than the second wavelength band.
4. The meta optical device of claim 1 , wherein each of the plurality of phase modulation regions has a phase modulation range of 2π*L, 2π*M, and 2π*N, where |L|≥1, M|≥1, N|≥1, L ≠M≠N, with respect to the light of the plurality of wavelength bands, and
when central wavelengths of the plurality of wavelength bands are 21, 22, and 23, L*λ1=M*λ2=N*λ3 is satisfied.
5. The meta optical device of claim 1 , wherein each of the plurality of phase modulation regions comprises:
a first layer comprising a plurality of first nanostructures and a first surrounding material provided adjacent to the plurality of first nanostructures;
a second layer provided on the first layer and comprising a plurality of second nanostructures and a second surrounding material provided adjacent to the plurality of second nanostructures; and
a first zone in which sign of effective refractive index change rates corresponding to a position of the first layer is equal to the sign of the effective refractive index change rates according to the position of the second layer, and a second zone in which the sign of the effective refractive index change rates corresponding to the position of the first layer is opposite to the sign of the effective refractive index change rates according to the position of the second layer.
6. The meta optical device of claim 5 , wherein the first zone is wider than the second zone.
7. The meta optical device of claim 5 , wherein each of the first zone and the second zone is at least one, and
wherein the first zone and the second zone are alternately provided in one direction in each of the plurality of phase modulation regions.
8. The meta optical device of claim 5 , wherein a refractive index of each of the plurality of first nanostructures is higher than a refractive index of the first surrounding material, and
wherein a refractive index of each of the plurality of second nanostructures is lower than a refractive index of the second surrounding material.
9. The meta optical device of claim 8 , wherein widths of the plurality of first nanostructures monotonically change in one direction in a partial region within each of the plurality of phase modulation regions, and
wherein an increase or decrease of widths of each of the plurality of second nanostructures in the one direction changes one or more times in the partial region.
10. The meta optical device of claim 8 , wherein the plurality of first nanostructures and the plurality of second nanostructures have a pillar shape.
11. The meta optical device of claim 8 , wherein each of the plurality of second nanostructures comprises a hole provided adjacent to the second surrounding material.
12. The meta optical device of claim 8 , wherein each of the plurality of second nanostructures comprises an inner pillar and a shell pillar provided adjacent to the inner pillar.
13. The meta optical device of claim 12 , wherein the inner pillar includes a material having a refractive index lower than the refractive index of the second surrounding material, and the shell pillar includes a material having a refractive index higher than the refractive index of the inner pillar.
14. The meta optical device of claim 8 , wherein each of the plurality of first nanostructures and each of the plurality of second nanostructures have a height to width ratio greater than 2.
15. The meta optical device of claim 8 , wherein a height of each of the plurality of first nanostructures and a height of each of the plurality of second nanostructures are greater than a central wavelength of a shortest wavelength band among the plurality of wavelength bands.
16. The meta optical device of claim 1 , wherein the plurality of phase modulation regions are provided in a radial direction from a center of the meta optical device, and
wherein widths of the plurality of phase modulation regions decrease as a distance from the center increases.
17. The meta optical device of claim 1 , wherein widths of the plurality of phase modulation regions are equal to each other.
18. An electronic apparatus comprising:
a lens assembly comprising a meta optical device that comprises:
a plurality of phase modulation regions respectively comprising a plurality of nanostructures and configured to modulate a phase of incident light,
wherein a phase retardation profile of the plurality of phase modulation regions monotonically change with respect to light of a plurality of wavelength bands apart from each other,
wherein phase modulation ranges with respect to the light of the plurality of wavelength bands are different from each other,
wherein each of the plurality of phase modulation regions has a phase modulation range of 2π*L, 2π*M, and 2π*N, where L|≥1, M|≥1, N|≥1, L≠M≠N, with respect to the light of the plurality of wavelength bands, and
wherein when central wavelengths of the plurality of wavelength bands are λ1, λ2, and λ3, L*21=M*λ2=N*λ3 is satisfied; and
an image sensor configured to convert an optical image formed by the lens assembly into an electrical signal.
19. An electronic apparatus comprising:
an image projector; and
a light transmitter configured to transmit image light from the image projector to a certain position, the light transmitter comprising a meta optical device that comprises:
a plurality of phase modulation regions respectively comprising a plurality of nanostructures and configured to modulate a phase of incident light,
wherein a phase retardation profile of the plurality of phase modulation regions monotonically change with respect to light of a plurality of wavelength bands apart from each other,
wherein phase modulation ranges with respect to the light of the plurality of wavelength bands are different from each other, and
wherein each of the plurality of phase modulation regions comprises:
a first layer comprising a plurality of first nanostructures and a first surrounding material provided adjacent to the plurality of first nanostructures;
a second layer provided on the first layer and comprising a plurality of second nanostructures and a second surrounding material provided adjacent to the plurality of second nanostructures; and
a first zone in which sign of effective refractive index change rates corresponding to a position of the first layer is equal to the sign of the effective refractive index change rates according to the position of the second layer, and a second zone in which the sign of the effective refractive index change rates corresponding to the position of the first layer is opposite to the sign of the effective refractive index change rates according to the position of the second layer.