Abstract: A Coupled Multiple Output Resonator (CMOR) having two symmetric modules 10,20, is created by adding self-feedback (SFB) mirrors 104,106 aligned with apertures 100,102, in output scraper mirrors 14,24, respectively, to a conventional Multiple Output Resonator (MOR). The SFB mirrors re-inject a portion of the output beams 34,42 back into the resonator cavity as adjoint beams 108,110 which alter the modes of the system such that the CMOR only lases at desired modes where all the output beams 34,42 are in-phase. The CMOR provides substantially constant acceptable mode discrimination for more than 4 modules with only one SFB mirror per module and no additional external coupling paths between modules, thereby allowing the system to be scaled to any number of lasers without reduction of target intensity. Also, the SFB mirrors are small and are easily controlled to compensate for cavity mirror variations to maintain the desired mode discrimination.

Abstract: An unstable laser resonator is controlled in polarization by the use of a control leg coupled to the parent resonator and having a polarization control element therein, so that control of a low power beam in said control leg serves to control the polarization of the parent resonator.

Abstract: A continuously pumped ring laser is pulsed by modulating a small portion of one of the circulating beams and feeding back the modulated radiation in the adjoint mode.

Abstract: A modelocked laser with an unstable resonator configuration is described. The laser relies on adjoint mode feedback with a modulator in the low power feedback beam path which is not part of the main resonator. The optical cavity length and the path length of the feedback beam are adjusted to provide a pulsed, modelocked output beam.

Abstract: An unstable resonator, dc excited, is pulsed using an adjoint coupled beam of low power as the pulsing element. The resonator feedback consists of the self-feedback and the adjoint beam feedback. The self-feedback can be sufficient for self-oscillation and pulsed operation can be achieved by controlling the repetition rate and the magnitude of the adjoint beam power. Complete control and shut-off between pulses with complete freedom of repetition rate is achieved if the self-feedback is insufficient for laser oscillation. The invention was demonstrated on a 10 kilowatt average power CO.sub.2 laser with pulse control provided by with a 100 watt adjoint feedback beam.

Abstract: An array of unstable laser resonators has a set of coupling beam paths, each of which carries coupling radiation to and from output regions of a pair of resonators in the array, so that pairs of resonators are symmetrically coupled to one other.

Abstract: A master oscillator regenerative power amplifier system is maintained in a locked state by variation of the power amplifier cavity length to minimize reverse wave radiation.

Abstract: A laser system for equalizing the cavity length of a multiline master oscillator and the resonant power amplifiers injection-locked by the master oscillator employs two selected lines from the beam spectrum for two-wavelength interferometric control.

Abstract: In accordance with the present invention, output beams from a plurality of optical amplifiers in an oscillator-amplifier optical configuration are phase matched utilizing a feedback system employing phase error signals generated by optically heterodyning a frequency shifted, two-wavelength reference beam, with a portion of the output from each of the plurality of amplifiers. Electrical signals from detectors responsive to the optical heterodyned signals are processed in control circuits to provide coarse and fine phase error signals to control elements for controlling the optical path difference of the beams of radiation passing through each of the amplifiers for phase matching the beams.

Abstract: A method for obtaining a hole in a workpiece essentially free of a recast layer and heat affected zone with laser radiation is disclosed. Pulses of laser radiation having durations comparable to the time required to vaporize workpiece material, typically less than ten nanoseconds, and power densities at the workpiece sufficient to produce vaporization, typically in excess of a billion watts per square centimeter, are interacted with a workpiece in an oxidizing environment to produce vaporization of workpiece material. The vapor reacts with the gas to produce a vapor oxide which does not adhere to the workpiece resulting in the absence of a recast laywer. A hole having a desired size and shape is obtained by interacting the pulses of radiation with the workpiece at a high rate of repetition, typically in excess of ten pulses per second, until a desired amount of material is removed. The pulse duration is less than the thermal reaction time of the material resulting in the absence of a heat affected zone.