In a zero-index material, there is no phase advance, meaning light no longer behaves as a moving wave, traveling through space in a series of crests and troughs. Instead, the zero-index material creates a constant phase -- all crests or all troughs -- stretching out in infinitely long wavelengths. The crests and troughs oscillate only as a variable of time, not space.
This uniform phase allows the light to be stretched or squished, twisted or turned, without losing energy. A zero-index material that fits on a chip could have exciting applications, especially in the world of quantum computing.
"Integrated photonic circuits are hampered by weak and inefficient optical energy confinement in standard silicon waveguides," said Yang Li, a postdoctoral fellow in the Mazur Group and first author on the paper. "This zero-index metamaterial offers a solution for the confinement of electromagnetic energy in different waveguide configurations because its high internal phase velocity produces full transmission, regardless of how the material is configured."