Abstract
Nanophotonics and metamaterials have revolutionized the way we think about optical space (ɛ,μ), enabling us to engineer the refractive index almost at will, to confine light to the smallest of the volumes, and to manipulate optical signals with extremely small footprints and energy requirements. Significant efforts are now devoted to finding suitable materials and strategies for the dynamic control of the optical properties. Transparent conductive oxides exhibit large ultrafast nonlinearities under both interband and intraband excitations. Here we show that combining these two effects in aluminium-doped zinc oxide via a two-colour laser field discloses new material functionalities. Owing to the independence of the two nonlinearities, the ultrafast temporal dynamics of the material permittivity can be designed by acting on the amplitude and delay of the two fields. We demonstrate the potential applications of this novel degree of freedom by dynamically addressing the modulation bandwidth and optical spectral tuning of a probe optical pulse.
Highlights
Nanophotonics and metamaterials have revolutionized the way we think about optical space (e,m), enabling us to engineer the refractive index almost at will, to confine light to the smallest of the volumes, and to manipulate optical signals with extremely small footprints and energy requirements
They can support extremely large doping levels (C1021 cm À 3) with low effective electron masses (C0.3me; me 1⁄4 free-electron-mass), enabling a metallic response in the near-infrared (NIR) region and high transmission in the visible region[8,9,10,11,12]. Such materials have been employed as transparent electrodes in various applications[13,14], but are recently receiving attention in nanophotonics, owing to their highly tunable static properties and potential for both electrical and optical control of the refractive index[15,16,17,18,19,20,21]. This versatility is extremely attractive as transparent conductive oxides (TCOs) can serve multiple roles, for example as dynamic, plasmonic and dielectric layers, which enable extreme flexibility to optimize structures for differing conditions, all with a single material
Aluminium-doped zinc oxide (AZO)[12] is one such material which combines all of these properties with reduced optical losses compared to other TCOs8 and a low manufacturing cost due to its widely available elemental compounds
Summary
Nanophotonics and metamaterials have revolutionized the way we think about optical space (e,m), enabling us to engineer the refractive index almost at will, to confine light to the smallest of the volumes, and to manipulate optical signals with extremely small footprints and energy requirements. They can support extremely large doping levels (C1021 cm À 3) with low effective electron masses (C0.3me; me 1⁄4 free-electron-mass), enabling a metallic response in the near-infrared (NIR) region and high transmission in the visible region[8,9,10,11,12] Such materials have been employed as transparent electrodes in various applications[13,14], but are recently receiving attention in nanophotonics, owing to their highly tunable static properties and potential for both electrical and optical control of the refractive index[15,16,17,18,19,20,21]. We tune the delay between the two pumps to demonstrate the dynamic control of the probe modulation bandwidth, between 0.8 and 2 THz, and optical spectrum with a wavelength shift of ±4 nm
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