A resonator for a laser includes a first resonator wall and a second resonator wall with a lasing medium disposed in a gap therebetween. The resonator further includes a first mirror disposed at a first end of the first and second resonator walls and a second mirror disposed at a second end of the first and second resonator walls. The mirrors cooperate to form an intra-cavity laser beam that travels along a plurality of paths through the lasing medium. Furthermore, the first mirror and the second mirror form a laser resonator for a parasitic laser mode. A parasitic mode suppressor is located within the superfluous region.

A device includes a first sensor configured to generate a first output signal corresponding to an energy of a portion of a forward beam transmitted by a mirror of a laser resonator system. The device further includes a second sensor configured to generate a second output signal corresponding to an energy of a portion of a return beam transmitted by the mirror. A ratio of the energy of the portion of the forward beam and the energy of the portion of the return beam corresponds to a measurement of a feedback ratio of the laser resonator system.

A semiconductor laser device includes: a semiconductor laser array in which a plurality of active layers that emit laser lights with a divergence angle .sub.S (>4) in a slow axis direction are arranged; a first optical element that reflects first partial lights by a first reflecting surface and returns the first partial lights to the active layers; and a second optical element that reflects partial mode lights of second partial lights by a second reflecting surface and returns the partial mode lights to the active layers, the first reflecting surface forms an angle equal to or greater than 2 and less than (.sub.S/2) with a plane perpendicular to an optical axis direction of the active layers, and the second reflecting surface forms an angle greater than (.sub.S/2) and equal to or less than 2 with the plane perpendicular to the optical axis direction of the active layers.

Gaseous laser systems and related techniques are disclosed. Techniques disclosed herein may be utilized, in accordance with some embodiments, in providing a gaseous laser system with a configuration that provides (A) pump illumination with distinct edge surfaces for an extended depth and (B) an output beam illumination from a resonator cavity with distinct edges in its reflectivity profile, thereby providing (C) pump beam and resonator beam illumination on a volume so that the distinct edge surfaces of its pump and resonator beam illumination are shared-edge surfaces with (D) further edge surfaces of the amplifier volume at the surfaces illuminated directly by the pump or resonator beams, as defined by optical windows and (optionally) by one or more flowing gas curtains depleted of the alkali vapor flowing along those optical windows. Techniques disclosed herein may be implemented, for example, in a diode-pumped alkali laser (DPAL) system, in accordance with some embodiments.

An optical oscillator includes a first reflection part configured to reflect light of a first wavelength, a laser medium excited by excitation light of a second wavelength different from the first wavelength and configured to emit light of the first wavelength, a second reflection part configured to form an unstable resonator together with the first reflection part, the unstable resonator being configured to output annular laser light of the first wavelength, and a saturable absorption part disposed between the laser medium and the second reflection part and of which a transmittance increases with absorption of light of the first wavelength. When a power of the excitation light is indicated by P.sub.p (kW), and an inner diameter of the annular laser light is indicated by d.sub.i, and an outer diameter is indicated by d.sub.o, and d.sub.o/d.sub.i is a magnification m, the magnification m satisfies a.sub.0+a.sub.1 Log(P.sub.p)mb.sub.0+b.sub.1P.sub.p+b.sub.2P.sub.p.sup.2.

Gaseous laser systems and related techniques are disclosed. Techniques disclosed herein may be utilized, in accordance with some embodiments, in providing a gaseous laser system with a configuration that provides (A) pump illumination with distinct edge surfaces for an extended depth and (B) an output beam illumination from a resonator cavity with distinct edges in its reflectivity profile, thereby providing (C) pump beam and resonator beam illumination on a volume so that the distinct edge surfaces of its pump and resonator beam illumination are shared-edge surfaces with (D) further edge surfaces of the amplifier volume at the surfaces illuminated directly by the pump or resonator beams, as defined by optical windows and (optionally) by one or more flowing gas curtains depleted of the alkali vapor flowing along those optical windows. Techniques disclosed herein may be implemented, for example, in a diode-pumped alkali laser (DPAL) system, in accordance with some embodiments.