Large Transient Optical Modulation\nof Epsilon-Near-Zero\nColloidal Nanocrystals

Abstract

Epsilon-near-zero\nmaterials may be synthesized as colloidal nanocrystals\nwhich display large magnitude subpicosecond switching of infrared\nlocalized surface plasmon resonances. Such nanocrystals offer a solution-processable,\nscalable source of tunable metamaterials compatible with arbitrary\nsubstrates. Under intraband excitation, these nanocrystals display\na red-shift of the plasmon feature arising from the low electron heat\ncapacities and conduction band nonparabolicity of the oxide. Under\ninterband pumping, they show in an ultrafast blueshift of the plasmon\nresonance due to transient increases in the carrier density. Combined\nwith their high-quality factor, large changes in relative transmittance\n(+86%) and index of refraction (+85%) at modest control fluences (<5\nmJ/cm²) suggest that these materials offer great promise\nfor all-optical switching, wavefront engineering, and beam steering\noperating at terahertz switching frequencies.