Tunable Surface Plasmon Polaritons with Monolithic Schottky Diodes

Surface plasmon polaritons (SPPs) provide subwavelength electric field confinement ranging from microwave to the visible. Several approaches have been explored to manipulate SPPs with a typical modulation capability of only a few percent. Here, active control of SPPs using monolithically fabricated Schottky diodes has been first designed and realized, achieving a continuous and significant modulation of transmission, reflection, and absorption. The SPPs propagating on a metal line are attenuated by using split ring resonators (SRRs) with an In-Ga-Zn-O Schottky diode bridging each SRR split gap. The resistance of the diodes can be tuned over a range of a few orders of magnitude with bias voltage, which continuously transforms each SRR to a metallic quasi-loop with subdued resonance. A remarkable modulation of 40% and 19% was demonstrated for the transmission and absorption, respectively, which to the best of our knowledge has not been achieved before.