Abstract: Briefly, in the invention a photodetector and an optical amplifier are integrated in the same semiconductor chip. The optical amplifier and the photodetector are positioned side-by-side on the same chip. A portion of the electromagnetic energy carried in the evanescent tail of the optical mode is detected by the photodetector for monitoring the average output power of the optical amplifier. Current confinement and lateral index guiding can be provided by Fe or Ti doped semi-insulating layers of InP. The side-by-side arrangement enables the detector to monitor the output power of the optical amplifier without degrading the output power of the optical amplifier.

Abstract: The device here disclosed comprises an optical amplifier coupled to direct optical energy into a passive waveguide for transmission through the waveguide to its other end. A photodetector, positioned relative to the passive waveguide, detects the presence of optical energy in the passive waveguide. The photodetector in the structure illustrated is positioned downstream from the optical amplifier and spatially positioned with respect to the optical amplifier to receive optical energy only from the waveguide. The photodetector does not receive optical energy directly from the optical amplifier. A small fraction of the optical energy carried by the passive waveguide is received and detected by the photodetector.

Abstract: Briefly, in this invention, the output optical power of an optical amplifier is determined by detecting and measuring the electrical signal induced on the bias lead of the optical amplifier when an optical data stream with additional amplitude modulation passes through the optical amplifier. This additional amplitude modulation can consist of a base band signal, a pilot tone and/or a sub-carrier which is amplitude modulated, frequency modulated or phase modulated. The modulation depth and bandwidth of the additional amplitude modulation should be kept small enough that the data stream is not excessively affected. The induced electrical signal provides a measurement of the optical power at the output facet of the optical amplifier. Control of the output power of the optical amplifier is effected by controlling the bias current applied to the bias lead of the optical amplifier.

Abstract: This invention is an optical memory device in which data is written, stored and read out in optical form without any conversion to electronics. The functions performed such as readout, reset and the like can be via electronic means, optical means, or a combination of both. The inherent bistability/hysteresis which is required for the memory function is obtained with a laser structure which includes a saturable absorber and, as a portion of the cavity, a waveguide.