Abstract: Apparatus and a related method for generating a second harmonic frequency optical output from a fundamental frequency input beam, without significant birefringence. The apparatus includes two Type II doubler crystals of equal length arranged with their corresponding axes parallel to each other, and a polarization rotator positioned between the doubler crystals, to rotate the polarization angle of a residual fundamental frequency component of an output beam from one of the crystals by 90.degree. or an odd multiple of 90.degree.. Random birefringence introduced into one of the doubler crystals is virtually canceled in the other, and the assembly of the two crystals and the polarization rotator may be angularly adjusted as needed for phase matching or tuning, without detracting from the birefringence compensation capability. The invention is also disclosed in the context of a phase conjugated master oscillator power amplifier (PC MOPA) system.

Abstract: A semiconductor laser array with features providing good beam quality at high powers, first by employing a laterally unguided diffraction region in which light from a set of waveguides is re-imaged in accordance with the Talbot effect and two arrays of waveguides may be used to provide a spatial filtering effect to select a desired array mode. This provides a laser array with increased power per unit solid angle, and with additional advantages of ability to scale the device up to larger arrays, ability to control the electrical excitation of the device for better optimization, and improved modal discrimination. A second aspect of the invention is the use of a resonance condition in an antiguide array, to produce a uniform near-field intensity pattern and improved coupling and device coherence.

Abstract: An ion milling method is disclosed that provides a manufacturing technique for mass producing microscopic surface features using a wide variety of media that includes semiconductors, metals, and glasses. In the preferred embodiment, vertical and 45 degree mirrors are formed simultaneously in semiconductor laser diodes in order to produce monolithic two dimensional arrays of surface emitting lasers. Standard double heterostructure semiconductor laser diodes are first grown on a wafer using metalorganic chemical vapor deposition techniques. An ion milling gun is oriented at a particular angle from the longitudinal axis of the active layer of the laser and emits a stream of atomic particles toward the lasers producing a generally two sided cut or notch that extends downward from the top surface of the semiconductor laser and traverses the active layer.

Abstract: An array of semiconductor lasers formed in a single substrate and having parallel waveguides that terminate in a wide diffraction region fabricated with the array structure. The diffraction region has a curved reflective surface selected to achieve a desired degree of coupling among the elements of the array, and to enhance and stabilize a preferred lateral mode of oscillation.

Abstract: A diffraction-coupled semiconductor laser array, and a related method for its operation, the array structure having a diffraction section that is electrically controllable independently of a waveguide section having multiple laser channels. Above a critical level of injected gain in the diffraction region, and with appropriate selection of channel and diffraction region dimensions, stable operation in the in-phase supermode results, with adjacent lasers operating in phase and a single-lobed far-field distribution pattern being produced. Below the critical level of injected gain, the out-of-phase supermode or multimode operation is favored and the narrow single peak of the far-field pattern is no longer present. This mode switching can be used to rapidly modulate operation of the array without directly switching it on and off.

Abstract: An electrical voting machine is disclosed which uses digital circuits to allow each of a number of voters to (1) select one of a number of alternative answers to a question and (2) express a selected degree of confidence in the selected answer, and then combines digitally the voter selections, and displays indications reflecting both the answer distribution and the degree of confidence of the voter group in the selected answers. Additionally, the machine calculates and displays: the total number of voters, a downcount of the number of voters as their votes are tallied, a weighted mean of the answer curve, an error signal if the number of votes exceeds the number of voters or if there is a circuit failure, and an error condition if an attempt is made to tally the votes before all voters have voted.