Abstract: A high speed optical switching device includes a waveguide arrangement, incorporating a pn junction, with a large bondpad for the purposes of increasing the capacitance presented by the device. Data and control signals can be input at an input port of the waveguide arrangement, presence of the control signal operating to modify the optical path length of the device for the data signal. By incorporating the device in an interferometer arrangement, or by exploiting a Fabry-Perot cavity of the device, it can be used to transmit the data signal selectively, for instance so as to demultiplex a time multiplexed optical communications signal. The high capacitance provides a very short recovery times so that data rates of 10 GHz and substantially above can be accommodated.

Abstract: An avalanche photodiode having a beryllium guard ring. The beryllium is implanted at a dosage of at least 5.times.10.sup.14 per cm.sup.2 and subsequently annealed to provide a guard ring profile with a p+core and a superlinearly graded tail. The doping profile of the guard ring immediately adjacent the core is superlogarithmic.

Abstract: An opto-electronic device, comprising an optical waveguide and means for imposing an electrical field in a direction transverse to the waveguide, is designed such that the spatial spread of the electrical field is very small. The electrical field overlies the region of peak amplitude of the profile of optical radiation in the waveguide. Constructed principally out of semiconductor materials made from elements selected from the III and V groups of the Periodic Table, the device lends itself to monolithic integration in optical communications systems.