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We present in this paper the mechanical analysis of tunable InP-based Fabry-Perot filters. These filters are composed by a top and a bottom InP/air Bragg mirrors with a central air microcavity. The tunability is achieved by changing electrostatically the cavity thickness. We have developed a theoretical model using finite elements analysis (FEA) calculation method, which permits to evaluate the mechanical deformation of the central cavity. This model considers the electrostatic force between the two freestanding layers delimiting the central cavity. Using this model, we have analyzed the tuning performance of two kinds of device: a bridge structure and a square membrane. We have evaluated the influence on the mechanical performances of the involuntary underetching of the clamped ends at the freestanding layers extremities. The theoretical results have been compared to experimental ones obtained by optical reflectivity measurements.

An adiabatic taper is proposed to couple light from a photonic crystal waveguide to a coupled-cavity waveguide. A Scanning Near-Field Optical Microscopy study is realized on these structures. This study permits to identify and to evaluate accurately the losses in the coupled-cavity waveguide.

The key performances of optical filters requested by optical communications for wavelength-division multiplexing (WDM) systems are: (i) a high wavelength selectivity, enabling the selection of neighboring channels 1.6 nm apart with a crosstalk ratio of 20 dB, (ii) a continuous wavelength tuning range of about 30 nm around 1.55 /spl mu/m, with no degradation of the selectivity. We demonstrate the design and the fabrication of a vertical micromachined InP-air gap based Fabry-Perot filter, continuously tunable via electrostatic micromechanical actuation of the cavity air gap, which meets the WDM system requirements.

High-quality fully strained ${\mathrm{Si}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Ge}}_{\mathit{x}}$ layers with 0%x22% grown on Si(100) by rapid thermal chemical vapor deposition have been analyzed by photoluminescence spectroscopy. We report a well-resolved near-band-gap excitonic transition observed in SiGe layers. These transitions make it possible to determine directly the fundamental band gap of such strained ${\mathrm{Si}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Ge}}_{\mathit{x}}$ alloys. The results show that high surface recombination in very thin films prevents the observation of radiative recombination, while demonstrating the striking effectiveness of a Si epitaxial capping layer in eliminating surface recombination.