3 ms·
Nah, I bet this can be done with a 1D photonic crystal where they can get away with simply using alternating layers of uniform thin film thickness. I forget exa
by neltnerb 11y ago
Nah, I bet this can be done with a 1D photonic crystal where they can get away with simply using alternating layers of uniform thin film thickness. I forget exactly but I'd think all that's needed is alternating dielectric constant materials with a periodicity ~700nm which isn't that crazy. More expensive than glass sure, but it's not like it'll need special etching to get microlenses.
- neltnerb 11y agoFWIW, slide 21 from this presentation on the site you linked has the picture I have in mind since at that size scale the glass is effectively flat. http://ab-initio.mit.edu/photons/tutorial/L1-bloch.pdf http://ab-initio.mit.edu/photons/tutorial/L1-bloch.pdf Feel free to correct if this is oversimple, I am vaguely familiar with this stuff but it was by no means a speciality.
- Animats 11y agoThat sounds like an ordinary bandpass interference filter.[1] Those have film layers and only pass a specific wavelength of light. Unlike ordinary filters, the angle at which the light hits the filter affects the passband, because it's the spacing of the layers that makes it work. The receive side of LIDAR systems use those. But those absorb the light they reject; they don't reflect it, much. [1] http://www.edmundoptics.com/optics/optical-filters/bandpass-filters/infrared-bandpass-interference-filters/3430/ http://www.edmundoptics.com/optics/optical-filters/bandpass-...
- neltnerb 11y agoGotcha, that makes sense. I suppose most of it will come from a narrow solid angle so if it were perfectly spherical you'd be okay but that would only work for the first reflection unless it was all reflection and no emission...