Abstract: An unstable resonator system is controlled in polarization by the use of a compound resonator in which the parent resonator is coupled to a polarization control leg by an aperture that passes a small portion of the output beam into a polarization control element and returns a polarized feedback beam mode-matched to the adjoint mode of the parent resonator.

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: An unstable laser resonator is controlled in polarization by the use of a control leg coupled to the parent resonator and having a linear 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: An optically pulsed laser with an unstable resonator configuration is described with two feedback beams. The laser relies on adjoint mode feedback with a single modulator in the low power feedback beam path. The laser is characterized by a two coupled adjoint feedback beams each configured to pass through the modulator in one direction only, thereby doubling the output power potential of the laser.

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 improved ring laser system having mutual coupling between two or more ring laser resonators employs a two-step coupling process, in which coupling power is coupled into the adjoint forward mode of an adjacent resonator, from which it diffractively couples to the forward mode. A portion of forward-mode power is coupled into the adjoint reverse mode from which it diffractively couples to the reverse mode within each resonator. A portion of this reverse mode power is used to coupled into other resonators. A complementary configuration employs forward-mode radiation as the coupling radiation.