Angular Spectrum and Evanescent Waves

/ edmundsj
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What happens when we have really high frequencies present in our angular spectrum? (Higher than the frequency of the illuminating plane wave). This video explores the propagation of evanescent waves, and what happens to very high-frequency components of the input pattern as they propagate through space. This effectively forms an upper bound on the spatial frequencies that can be 'remembered' by an optical system, and this is one explanation for the resolution of an optical system.
This is part of my graduate series on optoelectronics / photonics, and is based primarily on Coldren's book on Lasers as well as graduate-level coursework I have taken in the EECS department at UC Berkeley.
Hope you found this video helpful, please post in the comments below anything I can do to improve future videos, or suggestions you have for future videos.

[@hideakipage2993]

Beautiful explanation

[@hideakipage8151]

Thanks for a wonderful refresher course in Fourier optics. It was 30 years ago when I first learned this stuff. I've got a little rusty since. What proportion of the input energy is scattered into the evancent field?

[@abharadwaj6814]

Can you detect evanescent waves by keeping the detector very close (few nm's) away from the aperture? I suppose such an experiment could be done in labs.

[@JordanEdmundsEECS]

Yes! Yes you can! It’s called Frustrated Total internal reflection and you can do it with a laser and a couple of prisms.

[@hideakipage2993]

Yes you can. That's the near field.