Abstract: This invention provides a germanium electroluminescence device and a fabricating method of the same for using germanium of an indirect bandgap semiconductor without modifying a bandgap as a light-emitting layer which emits a 1550 nm-wavelength light and enabling to use not only as infrared LEDs itself but also as light sources for optical communication systems.

Abstract: SiGe quantum wells where the well material has a lowest conduction band energy minimum at k=0 (the ? point of the first Brillouin zone) are provided. Quantum well structures that satisfy this condition have “Kane-like” bands at and near k=0 which can provide physical effects useful for various device applications, especially optical modulators. In the Si1-xGex material system, this condition on the band structure is satisfied for x greater than about 0.7. The quantum well barrier composition may or may not have Kane-like bands. Optical modulators including such SiGe quantum wells can be operated at temperatures other than room temperature. Such temperature control is preferred for providing optical modulators that operate in the telecommunication C band (˜1530 nm to ˜1565 nm).

Abstract: The invention relates to an apparatus including a semiconductor grating whose optical properties can be changed electrically in order to steer a diffracted laser beam with no moving parts. Lithographically defined portions, stripes or areas formed in a semiconductor quantum well region used in association with selectable voltage supply means enable control of the optical characteristics of the grating. The optical properties of the semiconductor quantum well region vary in response to variations in voltage applied to the areas which in turn change the transmissivity or reflectivity of the areas. By selectively applying voltages, the diffraction pattern obtained in the far-field from illuminating the areas is thus controlled and beam steering results. By using a two-dimensional array of areas, or alternatively using two such one dimensional arrays, beam steering in two dimensions may be accomplished.

Abstract: A light detector comprising a photodetector disposed within an etalon or microcavity. The light detector is sensitive to light having a wavelength resonant with the etalon. Preferably, the etalon is a solid state microcavity having distributed bragg reflectors. The photodetector may be a photodiode, phototransistor or the like. The etalon has a front reflector with reflectivity Rf and a back reflector with reflectivity Rb. The photodetector has a double-pass absorption of A. In the present invention, Rf, Rb, and A are selected such that Rf=Rb(1−A). The combination of the back reflector and absorbing photodetector is indistinguishable from a single reflector of reflectivity Rf. Therefore, the light detector behaves like an etalon with matched reflectors. Preferably, Rf is greater than 0.95 and Rb is greater than 0.98. The photodetector can have a relatively thin absorption layer, thereby providing high speed capability.