Nonlinear control of tunneling through an epsilon-near-zero channel

The epsilon-near-zero (ENZ) tunneling phenomenon allows full transmission of waves through a narrow channel even in the presence of a strong geometric mismatch. Here we experimentally demonstrate nonlinear control of the ENZ tunneling by an external field, as well as self-modulation of the transmission resonance due to the incident wave. Using a waveguide section near cut-off frequency as the ENZ system, we introduce a diode with tunable and nonlinear capacitance to demonstrate both these effects. Our results confirm earlier theoretical ideas on using an ENZ channel for dielectric sensing and their potential applications for tunable slow-light structures.

Figure 1

(a) Structure of the ENZ channel and (b) equivalent-circuit model.

Figure 2

(a) The ENZ channel with a lumped tunable inclusion and (b) the corresponding equivalent-circuit model.

Figure 3

(Color online) The equivalent-circuit transmission response of an ENZ channel loaded with a lumped capacitance.

Figure 4

(Color online) Tuning of ENZ transmission with varactor diode for channel height of 3.18 mm: (a) experimental and (b) numerical results with corresponding capacitance.

Figure 5

(Color online) Tuning of ENZ transmission with varactor diode for channel height of 5.56 mm: (a) experimental and (b) numerical results with corresponding capacitance.

Figure 6

(Color online) Experimental tuning of group index for channel height of (a) 3.18 mm and (b) 5.56 mm.

Figure 7

(Color online) Experimental self-modulation of ENZ transmission by the input wave for diode-loaded channels of height of (a) 3.18 mm and (b) 5.56 mm.