Research ArticleAPPLIED PHYSICS

Meta-optics achieves RGB-achromatic focusing for virtual reality

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Science Advances  27 Jan 2021:
Vol. 7, no. 5, eabe4458
DOI: 10.1126/sciadv.abe4458
  • Fig. 1 Design and simulations of an RGB-achromatic metalens.

    (A) Schematic drawing of a multizone RGB-achromatic metalens showing achromatic focusing of RGB light coming from different lens locations. E(ω) represents the interferenced complex electric field at the focal spot of frequency ω. (B) One example of the phase profile, the group delay (GD) profile, and the group delay dispersion (GDD) profile designed for a multizone, RGB-achromatic metalens. The zone is defined by an area with continuously changed dispersion. Phase discontinuities at zone boundaries, zone transition locations, and initial phase at the lens centers require independent control. (C) Schematic drawing of a Fresnel lens phasor diagram and a metalens phasor diagram at a design focal spot. Phase discontinuities of a metalens can be independently engineered without changing the dispersion within each zone. (D) Simulated focusing intensity distribution of the metalens with NA = 0.7 along its optical axis at design wavelengths of 488, 532, and 658 nm. The inset is the zoomed-in view of focusing peaks. a.u., arbitrary units. (E to G) Simulation results of the intensity profiles in the focal planes at the design wavelengths.

  • Fig. 2 Fabrication and characterizations of the RGB-achromatic metalens.

    (A) A scanning electron microscopic image of the fabricated metalens with NA = 0.7. Scale bar, 1 μm. (B) Measured focal intensity distribution of the metalens in the XZ plane showing negligible focal shift (~0.1% of the focal length) at the design wavelengths. (C to E) Measured focal intensity profiles in the focal planes. (F to H) Corresponding focusing intensity line profiles of (C) to (E). FWHM, full width at half maximum.

  • Fig. 3 Imaging of the USAF resolution target by the RGB-achromatic metalenses under different illumination.

    (A to C) Imaging results of the elements no. 5 and no. 6 from the group no. 7 of a USAF resolution target by the metalens with NA = 0.7 at design wavelengths of λ = 488, 532, and 658 nm, respectively. The smallest linewidth feature size is 2.2 μm. Scale bars, 10 μm. (D to F) Imaging results of the same target by the metalens of NA = 0.7 under synthesized light illumination by mixing two and (G and H) all three of the RGB laser sources. Scale bars, 10 μm. (I to K) Imaging results of the whole group no. 7 of the USAF resolution target by the metalens with NA = 0.3 at design wavelengths of λ = 470, 548, and 647 nm, respectively. Scale bars, 30 μm unless noted. (L) Imaging result of the target by the metalens under synthesized white light illumination that is composed of the RGB wavelengths.

  • Fig. 4 VR demonstration.

    (A) Top: Schematic illustration of the VR mode. Bottom: Cross-section view illustrating its working principle. FML is the focal length of the metalens, and L (~7 cm) is the eye relief distance. (B) Schematic illustration of the near-eye fiber scanning display. (C) The VR imaging result using a passive display under the green light illumination at λ = 548 nm. Scale bar, 20 μm. (D) Zoomed-in view of (C). The dots inside the shield pattern, which mimic pixel grains, have a diameter of 1300 nm and can be clearly resolved (see fig. S21). Scale bar, 10 μm. (E to H) Four binary optical images captured in the VR mode at λ = 548 nm. The images are displayed by scanning the fiber tip in a Lissajous pattern and temporally modulating the incident light’s intensity in two levels (on/off). Scale bars, 20 μm unless noted. (I to K) Virtual objects with a three-dimensional (3D) effect, which are displayed by applying multilevel intensity modulation. (L to N) VR images of G, B, and R letters with a 3D effect in three distinct colors by using continuous-level intensity modulation of incident light. (O) An RGB-color VR imaging result. (P) A VR image showing a “H” logo shield in seven colors, which are realized by mixing the primary RGB colors in space and time.

  • Fig. 5 AR demonstration.

    (A) Schematic illustration of the AR mode. (B) An AR image showing a floating H-shield logo pattern in purple color created by using a passive display immerses in a real-world scene. (C) An AR image showing the mixture of a real-world scene with a floating image that is created by the near-eye fiber scanning display. (D) The AR imaging result using the full-color near-eye fiber scanning display, which shows an RGB-color virtual image floating in a real-world scene. Photo credit: Zhaoyi Li, Harvard University.

Supplementary Materials

  • Supplementary Materials

    Meta-optics achieves RGB-achromatic focusing for virtual reality

    Zhaoyi Li, Peng Lin, Yao-Wei Huang, Joon-Suh Park, Wei Ting Chen, Zhujun Shi, Cheng-Wei Qiu, Ji-Xin Cheng, Federico Capasso

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