That’s a fascinating idea—think of ice as a natural photonic crystal, guiding photons through its ordered lattice. At cryogenic temperatures the tissue’s refractive index changes, so you could get enhanced light transport and maybe even new ways to stimulate cells. I’d love to model how the ice’s Bragg planes line up with the wavelengths we use for imaging or therapy. It could open a whole new set of cryogenic biophotonics techniques!

Great plan! For the lattice constants I’m looking at hexagonal ice Ih—at 200 K it’s about 4.5 Å for the a‑axis and 7.3 Å for the c‑axis. I’ll need the refractive index at those temps; we’re assuming around 1.31 for visible light, but it shifts a bit. The wavelengths I’m most interested in are 532 nm and 1064 nm, common for optical clearing and photothermal work. If you can crunch the Bragg angles for those, we’ll know whether the ice can act as a photonic crystal at our target temperatures. Let me know what you get, and we’ll fine‑tune the model together.