Ultrafast all-optical switch has been demonstrated by inserting Fe-doped multiple quantum wells (MQWs) in asymmetric Fabry-Perot microcavities. Heavy Fe doping during the InGaAs∕InP MQW epitaxial growth is a well-controlled technique to reach subpicosecond optical time constants. An asymmetric Fabry-Perot microcavity using gold metal as a back mirror and air/InP interface as a front mirror is realized. Pump-probe experiments using a conventional scheme on such switching devices are investigated. The device reveals an ultrafast response time, as low as 290fs, for an iron concentration of 2×1019cm−3, a contrast ratio of 8dB, a threshold switching fluence of 3.5μJ∕cm−2, and a 37-nm 3-dB bandwidth in the 1.55-μm telecommunication spectral range.

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We present the ability of bundled carbon nanotubes to replace classical III‐V semiconductor quantum‐wells in nanomaterials‐based devices, such as efficient saturable absorbers. Preliminary study of bundled carbon nanotubes films is presented using scanning electronic microscopy and Raman spectroscopy. Then, performing time‐resolved pump‐probe experiments, we show that excitonic nonlinear optical properties of bundled carbon nanotubes are simultaneously marked by ultrafast subpicosecond absorption recovery time, relative great contrast ratio and total recovery of absorption, in direct comparison with quantum‐wells nanostructures. This first direct comparison attributes strong potential to bundled carbon nanotubes for all‐optical switching devices, as lower‐cost nanomaterials solution. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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