Ultra-large actively tunable photonic band gaps via plasmon-analog of index enhancement

We present a novel method for active continuous-tuning of a band gap which has the great potential to revolutionalize current photonic technologies. We study a periodic structure of x and y-aligned nanorod dimers. Refractive index of an y-polarized probe pulse can be continuously-tuned by the intensity of an x-polarized auxiliary (pump) pulse. Order of magnitude index-tuning can be achieved with a {\it vanishing loss} using the plasmon-analog of refractive index enhancement~[PRB 100, 075427 (2019)]. Thus, a large band gap can be created from a non-existing gap via the auxiliary pulse. The new method, working for any crystal dimensions, can also be utilized as a {\it linear} photonic switch operating at tens of femtoseconds.