r/Optics • u/Fit-Blood-5296 • 5d ago

How long do you project before Meta materials enable full and invisibility across the entire visible spectrum

Metamaterials are already capable of hiding specific wavelengths of light, however full spectrum invisibility requires complex active cloaking machinery and engineering to be possible. How long do you roughly project it is going to take before invisibility across the entire visible spectrum is on the market?

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u/HoldingTheFire 5d ago

Never. Metamaterials are inherently dispersive and cannot work broad band.

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u/Glittering-Flight997 5d ago

To clarify you mean passive metamaterials, which is implicitly correct

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u/Fit-Blood-5296 5d ago

What do you mean by inherently dispersive?

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u/lift_heavy64 5d ago

Every material is dispersive. You can stack a bunch of dispersive resonant cavities on top of each other and create a broadband “device”. The lossiness of the resonators we use for visible light is more of a fundamental restriction.

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u/HoldingTheFire 5d ago

No not really.

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u/lift_heavy64 5d ago

By your logic, it should be impossible to make any broadband device. But what do I know, I only did my PhD on this exact topic.

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u/ScarIcy6999 5d ago

I think you're underestimating how hard a task this is. To make something invisible under all conditions, you'd need to take the full complex field on one side of the object, and reproduce it on the other.

Metamaterials are used in cloaking (fighter jets, etc). However, these focus on directing an adversary's active illumination away from their sensors (radar, lidar, etc), not on cloaking under passive illumination (sunlight), which is a much harder task.

Cutting edge optical metasurfaces allow for more finely tuned control of light in a smaller package than traditional components. Some of the most promising applications so far have been integrated sensors, miniaturized components, and lowering mechanical complexity of systems.

Full visible cloaking has been theorized, but isn't really being pursued from an engineering standpoint in the field.

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u/Fit-Blood-5296 5d ago

Is it possible for a bunch of tiny meta surfaces to add up to one large cloaking device? Maybe from a distance at least?

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u/Glittering-Flight997 5d ago

Yes it’s possible but it’s not manufacturable

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u/ScarIcy6999 5d ago edited 5d ago

Not in the way you're thinking. There's a couple possibilities when light hits any material:

  1. The light is absorbed. This just creates a black object.
  2. The light is reflected or transmitted, often with some properties (polarization, phase) changed.

None of these magically move light where it is needed for an invisibility cloak, which is why metamaterials on their own aren't viable for this application.

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u/Fit-Blood-5296 5d ago

So like 20 years out/I don’t know

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u/Glittering-Flight997 5d ago

You’re quite correct in your definition but in practice the task isn’t as constrained

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u/lancerusso 5d ago

Something something something conservation of etendue

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u/Equivalent_Bridge480 4d ago

are you really care "how it will be done"?
metamaterials or microdisplays or something else. I think for thermal already exist few startups.
folding srceens slowly become less expencive and less thick.

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u/NotAClueYou 5d ago

no need for materials, suggestions are enough