PT SYMMETRY

Exceptionally slow light

Phys. Rev. Lett. 120, 013901 (2018)

The concept of stopping light in its tracks is one that has long captured the imagination of scientists. Now, Tamar Goldzak and co-workers from Brazil and Israel have theoretically demonstrated that the group velocity of light can tend to zero in parity–time (PT)-symmetric systems. They show that zero group velocity may be achieved if a waveguide system is prepared at an exceptional point — a point where two optical modes coalesce with degenerate eigenfrequencies and eigenvectors. In their theory, they set up a system of a small waveguide array, coupling between a waveguide with gain and another with loss, to achieve a PT-symmetric system. The waveguide widths and distance between the waveguides are ~1 μm. In principle, the effect and structural parameters can be adjusted for optical pulses in a wide range of frequencies and bandwidths. The approach can potentially be extended to acoustic and other types of wave.

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Correspondence to David F. P. Pile.

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Pile, D.F.P. Exceptionally slow light. Nature Photon 12, 123 (2018). https://doi.org/10.1038/s41566-018-0128-1

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