Unusual optical 'crack resistance' of doped epsilon-near-zero metamaterial

In this work, we demonstrate the connectivity-dependent optical 'crack resistance' of a doped epsilon-near-zero metamaterial (ENZ), which is distinct from conventional media. The optical transmission performance of the doped ENZ is robust against one or more subwavelength cracks as long as the connectivity of the doped ENZ is not broken by these cracks. As the doped ENZ is cut off by a crack, its transmittance decreases sharply and becomes sensitive to the location of the crack, especially the width of the crack. This unusual optical 'crack resistance' exhibits potential applications in designing ultrasensitive optical devices such as optical switches and displacement sensors.