Thursday, July 05, 2018

Harvard University Proposes Flat Lens

Photonics.com: Harvard University Prof. Federico Capasso and his group present "a single flat lens that can focus the entire visible spectrum of light in the same spot and in high resolution. Professor Federico Capasso and members of the Capasso Group explain why this breakthrough in metalenses could have major implications in the field of optics, and could replace bulky, curved lenses currently used in optical devices."

12 comments:

  1. Link to main article that has info on how the lenses are made.
    https://www.photonics.com/a63628/Capasso_Group_Develops_Flat_Lenses_with_Same

    Questions:
    What's the lens transmission efficiency? How does it vary with distance from center?
    What's the approximate distance (for mobile sensors, for large >1/2" sensors) between lens and chip that's achievable for VIS, what about NIR?
    What's the MTF like compared to a 6/7 glass lens?
    Are there process limitations to the titanium dioxide lens during sensor packaging like reflow temperatures, etc?
    Would be good to understand performance of lens as you vary the parameters of the nanofins to tailor the lens for VIS vs NIR, etc.

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    1. You asked the questions I was waiting for, except apparently you asked them before I started waiting! Lens transmission is a biggie, as I understand it. But might be ok for NIR/IR applications. It would be interesting if the technology catches on.

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  2. There is a key question to ask here. Just waiting...who will ask it?

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    1. That's easy: What's the market forecast for the next 3 years? Wait: "Exploding", as usually here at ISW. Starting from over 300 billion USD this year ;-)
      -dkf

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    2. Why is the lens non-transparent? And throws a deep shadow on the table?

      On the other hand, it's not clear what is the actual lens there. There is a small round spot in the center that is transparent. May be this spot is the lens?

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  3. 1. Stray light?
    2. Can I touch the lens?

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  4. I work in the field of metalenses. The big issues are chromatic aberration and off-axis aberration. These are essentially diffractive lenses, much like artificial dielectric or fresnel lenses. Achromatic lenses have been demonstrated by the Capasso group but only for circularly polarised light or for reflective lenses. Finally Capasso grows a 600 nm thick TiO2 film using atomic layer deposition. It probably took 2 days to grow such a film!

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  5. Diffractive optics have been looked at since the beginning of Mobile imaging. The only question to be asked is how do you get away with zero order transmission? Pierre Cambou - Yole Développement

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    1. Pierre what do you mean by "how do you get away with zero order transmission"? The metaelement unit cell is selected such that all the transmitted light occurs in the zero order. There us negligible higher order diffraction.

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    2. neglectable higher order diffraction for one wavelength seems easy but how is it possible for the whole color spectrum ? If this research solves the issue then this is great news - Pierre Cambou - Yole Développement

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  6. isn't this a typical wafer camera? maybe better image quality, not sure about the innovation part

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  7. The whole point about metalenses is lightweight and compact. The entire "phase shifting" is done in a single planar layer that is is one wavelength thick.

    It's possible to stack multiple lenses in a very small volume.

    Pierre, the unit cell of each phase shifter is subwavelength and is seelected so as there is negligible higher order diffraction.

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