A Zero-Index Waveguide
A zero-index waveguide stretches a wave of light infinitely long, creating a constant phase throughout the wire.
(Image courtesy of Second Bay Studios/Harvard SEAS).*
In 2015, researchers at the lab of Prof. Eric Mazur developed the first on-chip metamaterial with a refractive index of zero, meaning that the phase of light could be stretched infinitely long. The metamaterial represented a new method to manipulate light and was an important step forward for integrated photonic circuits, which use light rather than electrons to perform a wide variety of functions.
Now, the researchers have pushed that technology further – developing a zero-index waveguide compatible with current silicon photonic technologies. In doing so, the team observed a physical phenomenon that is usually unobservable — a standing wave of light.
When a wavelength of light moves through a material, its crests and troughs get condensed or stretched, depending on the properties of the material. How much the crests of a light wave are condensed is expressed as a ratio called the refractive index — the higher the index, the more squished the wavelength.
When the refractive index is reduced to zero the light no longer behaves as a moving wave, traveling through space in a series of crests and troughs, otherwise known as phases. Instead, the wave is stretched infinitely long, creating a constant phase. The phase oscillates only as a variable of time, not space...
*Continue reading "A Zero-Iindex Waveguide: Researchers Directly Observe Infinitely Long Wavelengths for the First Yime" by Leah Burrows, October 9, 2017. https://www.seas.harvard.edu/news/2017/10/zero-index-waveguide.
**O. Reshef, P. Camayd-Muñoz, D.I. Vulis, Y. Li, M. Lonc̆ar, and E. Mazur, "Direct Observation of Phase-Free Propagation in a Silicon Waveguide," ACS Photonics (Oct 9, 2017) DOI: 10.1021/acsphotonics.7b00760.