Abstract: The invention relates to electromagnetic wave guiding devices or waveguides (f<10 THz) and to processes for manufacturing these waveguides, which comprise at least one body (30) supporting at least one active wall (40). The body (30) of the waveguide is made from a volume of a ceramic selected from the following: silicon carbides, aluminum nitride, boron nitrides, and especially 3C cubic and 2H hexagonal varieties of boron nitride, diamond, beryllium oxide or assemblies of said materials. Applications: waveguides, filter cavities, reflectors and antennas for radiofrequency waves and microwaves, atomic clocks and particle accelerators.

Abstract: The invention relates to electromagnetic wave guiding devices or waveguides (f<10 THz) and to processes for manufacturing these waveguides, which comprise at least one body (30) supporting at least one active wall (40). The body (30) of the waveguide is made from a volume of a ceramic selected from the following: silicon carbides, aluminum nitride, boron nitrides, and especially 3C cubic and 2H hexagonal varieties of boron nitride, diamond, beryllium oxide or assemblies of said materials. Applications: waveguides, filter cavities, reflectors and antennas for radiofrequency waves and microwaves, atomic clocks and particle accelerators.

Abstract: A highly oxygen-sensitive silicon layer (2) is formed on a substrate (4) of, for example, SiC. The layer (2) has a 4×3 surface structure. The silicon layer (2) is deposited on a surface of the substrate (4) in a substantially uniform manner. The highly oxygen-sensitive silicon layer of the present invention may be used, for example in microelectronics.

Abstract: A microwave modulable field-effect cathode which includes at least one array of emissive tips. A microwave modulation signal is produced by a device including a microwave-controllable semiconductor modulation element which is close to the tip array, and a short microline for conveying the modulation signal to the tip array. The microline provides impedance matching between the tip array and the semiconductor modulation element. Such a device can find application as a compact field-effect cathode, as one example.

Abstract: A bipolar transistor in which the emitter possesses a double "mesa" structure so as to achieve the maximum avoidance of the phenomena of electron/hole recombinations that have a deleterious effect on the current gain. The double mesa emitter can be made out of an alternation of materials M.sub.I /M.sub.II having different types of behavior with respect to a pair of etching methods. These materials may be GaInP and GaAs.