Field-induced barrier transparency of Bloch waves in tight-binding lattices

TL;DR

This paper demonstrates that a strong ac field can make a potential barrier in a tight-binding lattice fully transparent to Bloch waves, revealing a novel form of field-induced transparency distinct from resonant tunneling.

Contribution

It introduces the phenomenon of field-induced barrier transparency for Bloch waves in tight-binding lattices, supported by numerical simulations beyond the tight-binding approximation.

Findings

Barrier becomes fully transparent under strong ac field

Transparency is not due to resonant tunneling

Numerical simulations confirm the effect in photonic waveguides

Abstract

A rectangular potential barrier for a Bloch particle in a tight-binding lattice is shown to become fully transparent by the application of a strong ac field with appropriate amplitude and frequency. Such a curious phenomenon bears some connection with the field-induced barrier transparency effect known for freely-moving particles scattered by an ac-driven rectangular barrier; however, for a Bloch particle transparency is not related to a resonant tunnneling process across the cycle-averaged oscillating potential barrier, as for the freely-moving quantum particle. The phenomenon of field-induced transparency is specifically discussed here for photonic transport in waveguide arrays and demonstrated by full numerical simulations of the paraxial (Schr\"{o}dinger) wave equation beyond the tight-binding approximation.