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Semiconductor Materials for Ultrafast Photoswitches

100%

Coutaz J.

issue 4-5

495-512

This paper gives a review of semiconductor materials that are used to fabricate ultrafast photoswitches. The optoelectrical response of the switches is first described with simple models, from which the material requirements are deduced. The basic principles of the required material properties - ultrashort free carrier lifetime and high mobility, high dark resistivity, and high field breakdown - are explained. Then, the most popular ultrafast semiconductors are listed, together with their characteristics. A special emphasis is put on low-temperature grown GaAs. Finally, two applications of these ultrafast materials are presented, namely antennae for terahertz radiation and all-optical nonlinear devices.

Grating Diffraction Effects in the THz Domain

39%

Coutaz J., Garet F., Bonnet E., Tishchenko A., Parriaux O., Nazarov M.

We study the far infrared electromagnetic response of grating devices by THz time-domain spectroscopy. We first show that THz waves are efficiently injected into silicon waveguides using grating couplers. Moreover, changing the waveguide material parameters by white-light illumination allows us to strongly modify the coupling efficiency. Then we demonstrate resonant effects in segmented grating structures that act as perfect mirrors at selected wavelengths even for focused beams. About 10 periods of the grating participate in the phenomenon, nevertheless the resonance frequency width of the device remains narrow. This collection of experiments shows that millimeter-size mock-ups and THz waves can be effectively used to extrapolate the optical response of micron-size actual devices.

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2 Acta Physica Polonica A

1 2005

1 2002

2 Coutaz J.

1 Bonnet E.

1 Garet F.

1 Nazarov M.

1 Parriaux O.

1 Tishchenko A.

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Semiconductor Materials for Ultrafast Photoswitches

Grating Diffraction Effects in the THz Domain