Abstract: A nonstandard spherical resonator which produces laser radiation having spherical modes of oscillation is formed entirely within a sphere of laser gain material. The resonator is pumped to produce the spherical modes. By pumping an isotropically coated sphere at normal incidence the entire sphere forms the resonator, and the laser radiates uniformly in all directions as from a point source. By pumping obliquely to totally internally reflect the laser radiation at the surface of the sphere, or by applying an equatorial coating on the sphere to internally reflect the laser radiation, toroidal region within the sphere forms the resonator. The pumping volume can be controlled so that the laser radiation is single longitudinal mode and single frequency by limiting the active mode volume. Prisms can be used for input and output coupling to the toroidal resonator; and optical fiber can also be used for output coupling. A compact laser design uses a Nd:YAG sphere pumped by a laser diode.

Abstract: A laser is disclosed which uses a curved spatial grating in either its reflective or output regions, or both, or distributed throughout the laser resonator, to produce an unstable optical reflection pattern which fills the resonating cavity more efficiently than in prior devices. Various combinations of different grating curvatures are disclosed. The invention is particularly adapted to semiconductor lasers.

Abstract: An unstable optical resonator having a gain region that has an elliptic or other non-circular cross section still has the benefits of a total collimated cavity Fresnel number that is azimuthally symmetric by the combination of several cavity regions of azimuthally non-uniform Fresnel number of appropriate size.

Abstract: The invention relates to a laser utilizing a negative branch unstable cavity resonator, comprising two opposed and aligned reflecting mirrors and a baffle aligned with the optic axis of the cavity and located in close proximity to the effective focal point of at least one of the mirrors as determined by the influence of the cavity's remaining optical components. The baffle is provided with an aperture of size such as to stop down the focal spot at its first minimum level of luminous intensity from center. The laser beam, which is out-coupled by conventional techniques, possesses optimum intensity-distribution spatial characteristics in space, and can be focused almost to the diffraction limits.

Abstract: An optical resonator comprising a substantially annular reflector disposed about and generally facing a central axis and comprising at least one annular reflecting surface, a central rotationally symmetric reflector positioned along said central axis and comprising at least one central reflecting surface, and a rotationally symmetric power extraction cavity located between the annular reflector and the central reflector.

Abstract: An improved unstable optical cavity for optical amplifiers or laser oscillators is made effectively single mode by altering the central Fresnel zone of the back mirror in order to provide constructive interference at the plane of the output aperture.

Abstract: A low diffraction-feedback high-energy laser system includes an injection laser, a master oscillator power amplifier (MOPA), and means for aligning the injection laser to the MOPA. The alignment means includes a relay mirror and sensor array cooperative to center the injection laser externally of the cavity, and the alignment means further includes a relay mirror and cooperative optics and sensor to center the injection laser interiorly of the cavity. The master oscillator power amplifier preferably includes a convex and a concave cavity. reflector. In one embodiment, an intracavity laser separator is disclosed for providing alignment of the injection laser, and in a further embodiment an extracavity laser separator is disclosed for providing injection laser alignment.

Abstract: A standing-wave annular laser resonator providing high energy extraction efficiency and good beam quality without the need for polarization coatings. The resonator includes an axicon, a scraper mirror, and a rear mirror system. A critical feature of the configuration is that the axicon has an inner conical mirror of which the apex is offset from the usual position, such that a radial beam reflected from an outer conical mirror has one portion that bypasses the inner mirror without impinging on it. This portion of the radial beam is reflected back along an annular path and makes two more passes through an annular gain region before becoming available for outcoupling around the scraper mirror. The rear mirror system retroreflects and annular beam back on itself in inverted form, without introducing any polarization mixing.

Abstract: A gas laser has (1) a reflecting body with a reflecting surface, (2) excitation space structure cooperative with the reflecting body for defining an excitation space which is open opposite the reflecting surface of the reflecting body, (3) devices for lasingly exciting a gas in the excitation space and (4) a mirror assembly. The mirror assembly has a mirror having a reflecting surface facing the opening in the excitation space. A radial flange is about the mirror with the reflecting surface of the mirror on one axial side of the radial flange. At least one spacer and, preferably three, circumferentially-spaced bars project from the excitation space structure and engage the radial flange substantially axially for supporting it at least one of axially slidably and tiltably. Bellows sealingly connect the one axial side of the radial flange to the opening of the excitation space structure and its other axial side to a backplate immovably connected to the spacer bar on the other axial side of the radial flange.

Abstract: Apparatus and a related method for controlling the characteristics of a high-power laser beam to provide a desired beam divergence, spectral content, and phase. A high-power beam, as from a free-electron laser, is directed into a conical Raman amplifier, together with a Stokes seed beam having the desired characteristics. The amplified output from the amplifier is divergent and its intensity falls of rapidly enough to allow the use of solid material optics without damage or destruction of the optical elements. The Raman amplifier is contained in part by two moving-gas windows, which seal the amplifier from the vacuum environment of the laser without the use of solid material optics. In one embodiment of the apparatus, the resulting output beam is precorrected for phase aberrations caused by optical elements and the transmission medium through which the beam is directed.

Abstract: A diode laser having an acitve layer bounded by confinement layers and two end facets that include etched mirrors selected to form an unstable resonator with good transverse mode quality. Energy from the unstable resonator is coupled out of the device through a transmissive window in one of the facets, the window providing a relatively large flux area and permitting higher output powers without loss of mode quality. Since stripe geometry is not used to control mode quality, a large current-carrying area is available, which reduces the current density and also permits higher output powers and longer operating lives.

Abstract: A carbon dioxide slab laser includes a pair of cooled metal electrodes disposed to form a gap of less than about 3 millimeters. The electrode surfaces on either side of the gap are polished and highly reflectant. A radio frequency discharge is provided between the electrodes to pass through gas disposed in the gap which is suitable for laser action. Cooling of the gases between the electrodes is achieved by conduction to the metal surfaces of the electrodes. Contrary to conventional flowing gas lasers, the two electrodes both reflect and guide the laser light and serve to cool the gas by conduction.

Abstract: A device utilizing lasers wherein efficient wavelength shifting of the generated laser radiation is provided using stimulated Raman scattering both in atomic vapor and molecular media. A coupled pair of confocal unstable resonators in conjuction with an integral injection laser is utilized in a novel optical arrangement for providing the efficient conversion of laser power into Stokes radiation without beam obscurations. The wavelength, spectral bandwidth, polarization and beam divergence are controlled by the spatial evolution of the main laser output which is locked to the seed radiation provided along the optical axis by the injection laser. Mode matching of the wavefront is automatically achieved by the use of common optical surfaces which couple the injection laser, main laser and the Raman converter. The resulting Stokes output through a partially reflecting/transmitting mirror is an unobscured beam whose intensity profile is determined by the laser medium power distribution.

Abstract: A method of operating and apparatus for an optical bistable device is disclosed in which an active laser medium is placed between two mirrors within an optical resonator and bistable switching is achieved by operating the active resonator across the transition borderline between the stable and unstable resonator regions. Several different embodiments are disclosed.

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: An improvement for an off-axis, unstable, ring-resonator laser wherein the feedback beam 16 is rotated 90.degree. by a 90.degree. rotator 18 and is then magnified by magnification means 22 so that the dimensions of the rotated, magnified beam 24 will correspond to the dimensions of the gain medium 12 of the laser.

Abstract: A laser comprises a laser medium and multiple resonators, together with means for switching coherent radiation from one resonator to another. If one of the resonators includes appropriate loss means, the laser can be self injection-locked and provide high-power, single-longitudinal mode radiation. Another embodiment of the laser provides successive laser pulses, separated by a short time interval and having different characteristics. A phase conjugate laser and an improved ring laser are also provided.

Abstract: A high-power laser, especially one with a gaseous excitation medium, having an unstable optical resonator is disclosed. Fully reflecting mirrors, whose planes of curvature are parallel to one another, form the ends of the unstable optical resonator. A third mirror is concavely curved in a plane perpendicular with respect to the other two mirrors. The mirrors have a rectangular cross section and are preferably metallic. The mirrors constituting the ends of the unstable optical resonator form a confocal resonator.

Abstract: The disclosed alignment system for a reciprocal path confocal unstable laser resonator of the present invention makes possible extremely precise cavity boresight alignment in a manner neither requiring a separate alignment laser or other alignment reference source, nor requiring physically large optical components that heretofore have placed severe constraints on system integrability, among other advantages. In accordance with the present invention, means are disclosed operative during the interpulse interval of the confocal unstable laser resonator for extracting at least two received energy beams of selected magnification factor and correspondingly reduced beam size out of the optical cavity of the confocal unstable laser resonator, and means are disclosed operative in response to the at least two received optical energy beams of selected magnification factor and beam size for determining the relative mis-alignment therebetween to provide an extremely precise signal indication of cavity boresight alignment.

Abstract: An improvement for a decentered annular ring resonator (DARR) 10 for a laser whereby misalignment sensitivity to odd-periodicity azimuthal phase errors is reduced. A front and a rear waxicon reflector 18 and 20 are employed, the front waxicon 18 having four reflecting surfaces 60,62,64 and 66 and the rear two 70 and 72. The laser beam is cycled between the waxicons twice, the front waxicon 18 separating the paths of the first and second cycle beams. The rear waxicon 20 provides a 180.degree. azimuthal shift in the orientation of an incoming beam 36 so that the beam traversing the second cycle 48,50, 52 is shifted 180.degree. in azimuth relative to the beam of the first cycle 40, 42,44. Odd-periodicity azimuthal phase errors are automatically cancelled by this 180.degree. azimuthal change in orientation of the second-cycle beam 46 before it starts on the second traversal of the internal path of the DARR.

Abstract: An annular ring resonator for a high-energy laser, including a waxicon/reflaxicon pair and a conical rear mirror, which combine to provide high energy extraction efficiency, reduced sensitivity to alignment errors, and no polarization state mixing. A cylindrical beam returned from a scraper mirror is first expanded by the waxicon to an annular beam that makes a first pass through a gain region of the laser. The annular beam impinges on the conical mirror and is reflected as an annular beam, to make a second pass of the gain region before encountering the reflaxicon, which compacts the beam for transmission to the scraper mirror. One embodiment employs a double-cone rear mirror, and another employs a single conical surface. The structure may also employ feedback decentering.

Abstract: The present invention is an improved gas laser which includes an elongated cylindrical chamber of cross-sectional dimension which has an internal cylindrical wall and which is suitable for confining a laser gas discharge. The internal cylindrical wall has a plurality of grooves extruded on its internal wall surface. A laser gas is disposed in the elongated cylindrical chamber. A pair of reflectors reflect light energy from the laser gas discharge within the elongated cylindrical chamber so that the light energy travels longitudinally the length of the elongated cylindrical chamber and is optically independent of the internal walls of the elongated cylindrical chamber. The improved gas laser also includes a pair of electrode plates which excite the laser gas and an rf generator which applies a voltage between the pair of electrode plates in order to establish a laser gas discharge in said laser gas. The plurality of grooves provide optical mode control.

Abstract: A high-energy laser system having gyroscopically stabilized optical elements includes an unstable confocal laser resonator having first and second spinning cavity feedback mirrors that resist mechanical wave energy induced spatial dislocations by gyroscopic inertia. One or both of the spinning cavity mirrors are preferably mounted for rotation with the rotor of a gyroscope. The gyroscope is operative as an actuator for selectively tilting the spinning mirror, and as a direction indicator for controlling the pointing direction of other elements with respect to inertial space. The angular rotation of the cavity feedback mirrors generates aerodynamic flows that cool the spinning mirrors by convective heat transport. Every material particle thereof describes an annular path once per revolution that prevents hot-spot formation and extends the useful lifetime.

Abstract: A laser oscillator apparatus is disclosed having a laser medium flowing in one direction in a chamber, an unstable resonator including a concave mirror and a convex mirror that face each other in order to generate a laser beam transmitted in a direction perpendicular to the direction of flow of the laser medium, an output window provided in the chamber and rotation means for rotating the laser beam provided between the unstable resonator and the output window.

Abstract: The invention deals with a face pumped slab laser in which the slab is of a rectangular configuration, favoring use of an optical resonator cavity capable of producing a rectangular beam of good quality within the cavity. The novel optical resonator cavity, which produces this rectangular beam, is stable on one axis corresponding to the smaller beam dimension and unstable on an axis orthogonal to the first axis corresponding to the larger beam dimension. The result is both high efficiency, excellent power and a good quality output beam is produced.

Abstract: The annular energy distribution in the output beam of a laser having an unstable resonator is evenly distributed across the entire beam profile by a synthesizer comprising a pair of mirrors adjacent to the output end of the resonator and operative on the output beam to redirect part of the beam from the annular outer portion to the energy-vacant central portion. One of the pair of mirrors is partially optically transmissive and concavely shaped and is disposed to reflect and converge part of the outer beam portion toward the other mirror and to transmit the balance. The other mirror is highly reflective and convexly shaped and is disposed to redirect and collimate the reflected beam part within the central portion toward the concave mirror parallel to the outer beam portion.

Abstract: A two-mirror system for transforming an azimuthally or linearly polarized laser beam into a beam having a number of sections, the average phase and polarization of each section being substantially similar. Both mirrors are segmented into eight pie-shaped sections, each of which contains a coating that gives a .+-.90.degree. phase shift or the appropriate uniform optical path difference.

Abstract: Along an axis (2) of an optical cavity there are: a mirror (3) having a W-shaped cross section to give inner and outer conical reflecting surfaces (4, 6) which are oppositely inclined, a plane mirror (8) having an axial opening and facing the W-shaped mirror (3), a convex mirror (16) receiving the oscillating radiation from the W-shaped mirror (3) via the opening in the plane mirror (8), and a mirror (17) disposed between the plane mirror (8) and the convex mirror (16), said mirror (17) having an aperture and being inclined to the axis so as to extract laser energy from the oscillator.

Abstract: An improvement of a common-pass, decentered, annular ring resonator (CPDARR) in which the waxicon mirror-reflector component 18 is formed with five reflecting surfaces, two on the central axicon 40, 42 and three on the outer ring axicon 44,46,48. The orientation and curvature of the reflecting surfaces is designed to provide three reflections of an input laser beam impinging on the inner reflector 40 of the central axicon and two reflections of an input wave impinging on the outer reflector surface 48 of the ring axicon (or vice versa). The number of reflections in the waxicon 18 combined with the two reflections in the rear ring mirror 20 of the CPDARR allows all reflecting surfaces to be coated with conventional high-reflectance coating and still provide a uniform-polarity output laser beam from the CPDARR.

Abstract: An optical resonator having an annular cylindrical gain region for use in a chemical laser or the like in which two ring-shaped mirrors having substantially conical reflecting surfaces are spaced apart along a common axis of revolution of the respective conical surfaces. A central conical mirror reflects incident light directed along said axis radially outwardly to the reflecting surface of a first one of the ring-shaped mirrors. The radial light rays are reflected by the first ring mirror to the second ring mirror within an annular cylindrical volume concentric with said common axis and forming a gain region. Light rays impinging on the second ring mirror are reflected to diametrically opposite points on the same conical mirror surfaces and back to the first ring mirror through the same annular cylindrical volume. The return rays are then reflected by the conical mirror surface of the first ring mirror back to the central conical mirror.

Abstract: A waveguide laser having a square bore and an external modulator has its power doubled by proper relationship of a coupled cavity external to a cavity in the waveguide medium.

Abstract: A laser system with a folded beam path is disclosed. The beam path is formed by a plurality of mirrors (18-21). Mirrors (18-21) reflect light in a closed loop from one mirror to the other. Electrodes are disposed on opposite sides of the path between the mirrors and form channels through which the path extends. In addition to serving to direct the beam in a closed loop, one of the mirrors may have the characteristic of reflecting one wavelength of light with a reflectivity of 100% while reflecting other wavelengths of light with a reflectivity of only 85%, such mirror thus acting to pass the other wavelength of light while completely reflecting the one wavelength of light. In one of the disclosed embodiments, four wavelengths of light are directed in a loop comprising mirrors 85% reflective to a wavelength while otherwise 100% reflective which promotes ring laser operations with respect to other wavelengths without passing such other wavelengths.

Abstract: An apparatus and process for pumping a lasing media (preferably krypton fluoride) over a 500 nanosecond period and thereafter compressing and focusing to a target with a final 10 nanosecond compression wave is disclosed. An exciting 10 nanosecond pulse is shaped in an overall rectangular shape with the major axes vertically aligned and this shaped beam directed upwardly and to the side of a normal extending between parallel and opposed mirrors at remote ends of a chamber. The chamber includes at the top thereof a plurality of stripper mirrors aligned along axes substantially normal to the beam path and tilted upwardly to shave successive segments off the upper portion of the beam. Beam passage opposite to the direction of stripper mirror emission produces a series of emitted shaved beam segments each spaced temporally in accordance with stripper mirror separation.

Abstract: A pulsed or CW laser is rapidly switched to operate at one or more selectable wavelengths by means of intracavity insertion of beam dispersion and focussing elements and an apertured focal plane mask and shutter assembly. The laser beam has an axis and is dispersed into components or sub-beams having different axes and representing different wavelengths, the sub-beams being focussed to substantially reduced diameters on the focal plane mask at points, respectively, at which apertures are formed. Movable shutters adjacent to the respective apertures control alternate opening of and closing of the apertures and selectively permit the laser to resonate at at least one of a plurality of wavelengths corresponding to that of the sub-beam passing through an open aperture. Mask apertures having very small diameters (<50 microns) and separations are achieved enabling switching between different operating wavelengths in milliseconds.

Abstract: An unstable laser resonator having two spherical mirrors for producing a collimated output beam with rotationally unsymmetrical magnification characterized by the inclusion between the two spherical mirrors of at least two other optical elements with cylindrical surfaces and wherein the cylindrical axes of said cylindrical surfaces are essentially perpendicular to each other. These other two optical elements may be mirrors or lenses.

Abstract: A laser system for producing a laser beam in an unstable resonator whose spatial and temporal characteristics conform with those of a laser beam from a stable resonator. The laser system includes three reflectors, an optical switch and a laser gain medium positioned within an optical propagation path extending between the optical switch and the third reflector. The optical switch selectably exposes either the first or the second reflector to the aforesaid propagation path, the first and second reflectors being designed to form, in combination with the third reflector, a stable and an unstable resonator, respectively. In operation, the optical switch initially is set so as to include the first reflector in the laser resonator, thereby forming a stable resonator which produces a beam of laser light. A short time thereafter, the optical switch changes states so as to substitute the second reflector for the first, thereby forming an unstable resonator.

Abstract: A structural improvement to the feedback (i.e., output) mirror of an unstable optical resonator. The improvement may comprise either a step-like projection (either convex or concave) on the internal surface of the feedback mirror, or a change in curvature of the internal surface of the mirror. Each of these improvements actually constitutes a discontinuity in the internal surface of the mirror, with the curvature of the mirror on either side (i.e., around) the improvement remaining the same. The improvement cancels the interfering edge waves at the geometric source point of the resonator, thereby minimizing the effect of edge diffraction, and results in yielding more "geometric" modes having relatively uniform intensity profiles and large differences in feedback ratios between the dominant and higher-order modes.

Abstract: The extent of diffraction in a laser resonator is controlled to provide the desired oscillation sustaining feedback. Specifically, a laser system has an annular gain medium disposed about an optical axis. The gain medium has first and second opposite annular ends. A first reflector is disposed on the optical axis closely adjacent to the first end of the gain medium. A second reflector is disposed on the optical axis closely adjacent to the second end of the gain medium. The first and second reflectors are shaped to magnify electromagnetic waves impinging thereon beyond the periphery of one of the reflectors. A sufficiently large portion of the energy incident on an interior region of one of the reflectors to sustain electromagnetic oscillations in the gain medium is diffracted back on itself. In the preferred embodiment, a contoured circular zone plate having a focal point on the optical axis is employed as a diffracting device.

Abstract: Disclosed is a coherently optically pumped laser system wherein a pump laser beam (30) propagates through a laser medium contained in a degenerate cavity resonator (10) in a controlled multiple round trip fashion in such a way that the unused pump beam (30') emerges from an injection aperture (24) at a different angle (.beta.) from which it enters (.alpha.) the resonator. The pump beam (30) is angularly injected off of the central axis (22) of the resonator body (10) whereupon the pump beam alternately undergoes spreading and focusing (b.sub.1 . . . b.sub.8) while pumping the laser medium by a process of resonant absorption pumping. Means (32) are employed externally of the cavity resonator to sense the emergent output beam (30') which is used not only for alignment of the system but also to monitor the power of the emergent pump beam. The power in the emergent pump beam (30') provides a measure of the performance of the laser systems.

Abstract: A laser system having an optically unstable cavity with a unique optical center axis longitudinally offset from the center axis of the cavity toward one side of the resonator to obtain an unobscured output beam from the opposite side. The resonator also has astigmatic magnification which provides for a greater volume utilization of the gain medium than otherwise possible. In a preferred embodiment, the off-axis astigmatic resonator employs spherical mirrors at off-normal incidence to provide for different magnification in two orthogonal planes.

Abstract: A laser having an unstable optical cavity including an output mirror having an off-axis hole therein through which laser radiation can pass to maintain lasing action in an active medium situated in the laser optical cavity, wherein the output mirror is so shaped and positioned as to present an elliptical profile to laser radiation incident upon it, the major axis of the ellipse extending in the direction of offset of the hole in the output mirror.

Abstract: This external cavity laser utilizes an unstable resonator in conjunction with a high reflectivity stripe end mirror which is oriented substantially parallel to the plane of the maximum divergence of the laser diode output beam and whose axis is substantially parallel to the plane of the junction of the laser diode. This configuration operates with high efficiency to select only the fundamental mode of the laser diode with a minimal divergence in the output beam.

Abstract: A hybrid laser resonator for use with a transverse flow waveguide laser includes cylindrical optical elements for coupling together regions of a thin slab-shaped laser medium operating in the waveguide mode through a set of reflectors which define the ends of the laser cavity. Separate waveguide cylindrical optics which focus in the thin dimension of the slab are combined with a negative cylindrical lens which diverges in the thick dimension of the slab. The negative lens causes an unstable resonator condition to exist in the thick or fluid flow direction so as to prevent narrow isolated horizontal lasing bands and thus provide a nearly diffraction limited beam quality in both thick and thin dimensions.

Abstract: A laser cavity 15 is continuously flown through by a gas such as metastable iodine and other reactants, but continuous wave lasing is inhibited, except for brief periods to obtain pulsating emission of radiation; the optical energy content of the gas in the cavity 15 is, thus, depleted, and fresh gas flows into the cavity 15 during the pause following each pulse.

Abstract: An output coupler for a high power ring laser employs a wedge mirror and a corresponding inverted wedge mirror to deflect a portion of both forward and reverse traveling waves and to combine the out-coupled radiation into a single output beam.

Abstract: An adaptive optic control system employs a single intracavity deformable mirror having a separately controlled multi-pass region and single-pass region to separately control the output power and wave front, respectively.

Abstract: An unstable resonator to be used in high power, narrow line CO.sub.2 pump lasers comprises an array of four reflectors in a ring configuration wherein spherical and planar wavefronts are separated from each other along separate optical paths and only the planar wavefronts are impinged on a plane grating for line tuning. The reflector array comprises a concave mirror for reflecting incident spherical waves as plane waves along an output axis to form an output beam. A plane grating on the output axis is oriented to reflect a portion of the output beam off axis onto a planar relay mirror spaced apart from the output axis in proximity to the concave mirror. The relay mirror reflects plane waves from the grating to impinge on a convex expanding mirror spaced apart from the output axis in proximity to the grating. The expanding mirror reflects the incident planar waves as spherical waves to illuminate the concave mirror. Tuning is provided by rotating the plane grating about an axis normal to the output axis.

Abstract: In a high power laser, such as one employing a relatively high gain lasing medium such as CO.sub.2 or Nd:YAG, the optical resonator for the laser comprises a positive branch unstable resonator. The output beam is coupled from the unstable resonator by means of a partially transmissive mirror of the resonator, whereby a filled-in beam is obtained while facilitating optical alignment of the output coupling means. In a preferred embodiment, the optical resonator comprises a pair of mirrors collinearly arranged on the optical axis of the resonator to supply an output beam which is collinear with the optical axis of the resonator. The filled-in output beam is of generally uniform power density across the transverse cross sectional dimensions thereof, whereby a near diffraction limited output beam is obtained with more uniform power density.

Abstract: A modular unstable ring resonator utilizing several independent gain modules is used to obtain output of a multiple set of mutually coherent beams. Additionally, rigorous mutual coherence is maintained even when the system operates on more than one longitudinal mode or/and on more than one gain transition; specific frequency-control elements are eliminated; satisfactory operation is possible with one or more gain-medium modules disabled. Each segment of the ring resonator's optical path may contain a laser gain medium, an output mirror, and a beam expander for continuously circulating a portion of the system flux while also coupling out a portion of the flux from each output mirror. The plural outputs may be used individually or collectively.