1. Flash heating plastic yields Hydrogen and Graphene;
"Synthesis of Clean Hydrogen Gas from Waste Plastic at Zero Net Cost" (2023) https://onlinelibrary.wiley.com/doi/10.1002/adma.202306763 https://news.ycombinator.com/item?id=378869822. This produces microwave (and THz) with Copper as the dielectric; though I don't think they were trying to make a microwave oven; "Pulsed THz radiation under ultrafast optical discharge of vacuum photodiode" https://news.ycombinator.com/item?id=40858955
3. Metasurface arrays could probably also waste less energy on microwaving clothing and textiles in order to recycle.
4. Are SPPs distinct from Cherenkov radiation, and photon-electron-phonon vorticity?
From "Electrons turn piece of wire into laser-like light source"
https://news.ycombinator.com/item?id=33493885 :
Surface plasmon polaritons : https://en.wikipedia.org/wiki/Surface_plasmon_polaritons :
> [...] SPPs enable subwavelength optics in microscopy and photolithography beyond the diffraction limit. SPPs also enable the first steady-state micro-mechanical measurement of a fundamental property of light itself: the momentum of a photon in a dielectric medium. Other applications are photonic data storage, light generation, and bio-photonics.
But that's IR and visible light EM, not microwave EM.