Abstract: Silicon-based laser diodes, optical amplifiers, electrooptical modulators, and photodetectors in which the active region consists of a pseudomorphic GeSn multiple quantum well stack. Each quantum well is tensile-strained Ge.sub.1-x Sn.sub.x layer sandwiched between compressively strained barriers of Ge.sub.1-y Sn.sub.y with x.about.0.1, x<y and y.about.0.15. The GeSn quantum wells have a strain-induced direct gap for strongly allowed band-to-band transitions in the infrared range. The quantum well stack is grown upon a relaxed SiGeSn alloy buffer portion whose composition is graded up from a lattice match at the silicon substrate interface to a Ge or GeSn composition at buffer's top surface. Doped cladding layers are added, so that the devices have a p-i-n diode structure. The monolithic integrated Column IV devices have a rib waveguide structure, where desired, and operate typically in the 2 to 3 micron wavelength range.

Abstract: A double-injection transistor structure with an MOS gate is utilized as a guided-wave electro-optic phase modulator at infrared wavelengths in a silicon-on-insulator (SOI) waveguide. Cathode, gate and anode regions are integrated in the waveguide, longitudinally. The effective phase modulation is given by the voltage-variable overlap of the guided-mode optical field with carrier-induced local changes in the silicon refractive index. An electron-hole plasma is injected under the gate by cathode and anode. Using depletion-layer widening, the plasma channel width and mode overlap are controlled very rapidly by one or two low-power gate electrodes.