Abstract
We provide the first demonstration of exceptional light-with-light optical switching performance of a carbon nanotube metamaterial - a hybrid nanostructure of a plasmonic metamaterial with semiconducting single-walled carbon nanotubes. A modulation depth of 10% in the near-IR with sub-500 fs response time is achieved with a pump fluence of just 10 μJ/cm², which is an order of magnitude lower than in previously reported artificial nanostructures. The improved switching characteristics of the carbon nanotube metamaterial are defined by an excitonic nonlinearity of carbon nanotubes resonantly enhanced by a concentration of local fields in the metamaterial. Since the spectral position of the excitonic response and metamaterial plasmonic resonance can be adjusted by using carbon nanotubes of different diameter and scaling of the metamaterial design, the giant nonlinear response of the hybrid metamaterial - in principle - can be engineered to cover the entire second and third telecom windows, from O- to U-band.
Highlights
Nanoscale sized ultrafast optical modulators are key elements for the development of integrated all-optical signal processing circuits
To further investigate the transient behavior of the nonlinear optical response of the carbon nanotubes (CNTs) metamaterial we have compared the nonlinear dynamics of the CNT metamaterial with the dynamics of the bare CNT layer
We have found that each of the pump-probe traces measured on the CNT metamaterial in the spectral range of 1600-2200 nm can be fitted with a bi-exponential decay function where the fast component typically has decay times in the sub-500 fs range while the decay time of the slow component is in the few ps range
Summary
Nanoscale sized ultrafast optical modulators are key elements for the development of integrated all-optical signal processing circuits. In these studies enhanced switching performance is achieved in metamaterial structures hybridized with active nonlinear media In such hybrid structures, small changes in the refractive index of the active medium induced by nonresonant photoexcitation tune the metamaterial plasmonic resonance which results in significant modulation of the metamaterial transmission near the resonance. Small changes in the refractive index of the active medium induced by nonresonant photoexcitation tune the metamaterial plasmonic resonance which results in significant modulation of the metamaterial transmission near the resonance Another powerful opportunity for enhancement of the nonlinear optical response of metamaterial-based structures, not widely implemented so far, is in exploiting effects of resonant concentration of local fields in the vicinity of a metamaterial [8, 9]
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