Abstract: An optical device, such as for example a wavelength division multiplexer/demultiplexer, a wavelength router, an optical comb filter or a planar lens, having a first coupler and a second coupler which are connected by an array of optical waveguide channels. At least one of the couplers is a multimode imaging component (MMI), which has the property that the radiation distribution at any input thereof is imaged onto each of the coupler outputs and with uniform power distribution among the outputs. Efficient power transfer in thereby achieved. Phase differences between the inputs and the outputs are compensated by appropriate differences in optical pathlength of neighboring channels in the array.

Abstract: A process and apparatus for the photothermal and/or calorimetric investigation of gaseous, liquid and solid measuring material is based on the detuning of an ultrasonic resonator (1). The latter has an ultrasonic transmitter (2) and an ultrasonic receiver (3), which face one another. The signal from the receiver is analyzed by an analyzer (5) as to its amplitude or phase position which gives, as a result of the temperature dependence of the sonic velocity, information on thermal changes in the ultrasonic resonator designed as a gas cell or calorimeter. The present apparatus makes it possible to detect gases or to calorimetrically investigate the material to be investigated, particularly light-conducting elements (5), such as light fibers.

Abstract: Described is a method of fabricating front-illuminated silicon photodiodes having high quantum efficiency, a short response time, (high gain and low excess noise in the case of avalanche diodes), low dark currents and good reliability. In the fabrication of an n.sup.+ -p-.pi.-p.sup.+ APD the method includes the steps of: (1) epitaxially growing a high resistivity .pi.-type silicon layer on a high conductivity p-type silicon substrate; (2) forming an n-type guard ring in the .pi.-layer; (3) forming a p-type channel stop around the guard ring; (4) forming in the .pi.-layer a p-layer by ion implantation and by driving in the implanted ions by heating in a suitable atmosphere; (5) masking the p-layer and introducing phosphorus into the backside to getter defects and/or impurities; (6) ramping the furnace temperature during steps (2) through (5) to reduce crystalline defects; (7) forming a thin n.sup.+ -layer in the p-layer; (8) forming an anti-reflection and passivation coating on the n.sup.