- TL;DR Summary
- Could an extra layer be better than air?
I am interested in experimenting with AR lenses and one of the main technologies is a waveguide. They rely on total internal reflection, which needs light to go from a higher to lower refractive index medium. I am reading that current AR lenses use an outer layer with a lower refractive index to allow this to happen but why would this be better than having no outer layer and using the refractive index of air, which is lower than most transparent materials? Thanks.