Abstract: A laser rod is provided having a tailored gain profile such that the quality of the output beam is enhanced. The laser rod has a concentration of active substitutional ions that is relatively high at the center of the rod and decreases to the surface of the rod. The laser rod further has a concentration of pre-active laser ions that is relatively high at the surface of the rod and decreases to the center of the rod. Methods are disclosed for creating a layer of inactive laser species in the near surface region of a laser rod using substitutional dopant ions and for creating a laser rod with a tailored gain profile such that the quality of the output beam is enhanced.

Abstract: A glaze soldered solid-state laser active medium. The novel laser active medium includes a first section of a first material, a second section of a second material, and a layer of ceramic glaze joining the two sections. The first and second materials may be identical, similar, or dissimilar, and may include crystals or ceramics. The glaze is a multi-oxide eutectic ceramic glaze having a refractivity, light absorption, thermal expansion, and fusion temperature that are compatible with the first material. The sections are joined using a novel glaze soldering process that includes the steps of positioning the sections, applying the ceramic glaze between the sections, and firing the glaze to solder the sections together.

Abstract: Provided is a fiber laser system including fiber containing dysprosium. The fiber laser system uses 1.7-?m pump light. A resonator of the fiber laser system includes a dichroic mirror, a partial reflection mirror, and/or an FBG. Therefore, the fiber laser system can provide 3-?m laser light and have high light pumping efficiency and high output power. The fiber laser system includes: fiber including dysprosium, a pump light source disposed at a side of the fiber and emitting pump light having a wavelength exciting electrons of the dysprosium from a ground energy level 6H15/2 to an energy level 6H11/2; a first reflection member, disposed between the fiber and the pump light source, transmitting the pump light, and reflecting first lasing light having a first wavelength; and a second reflection member, disposed at a side opposite to the pump light source with respect to the fiber, transmitting a portion of the first lasing light.

Abstract: A composite optic fibre for laser includes a core surrounded with a pump guiding sheath in contact with the core, sheath being a photonic structure formed by a substantially regular matrix assembly of coaxial capillaries, spaced apart and arranged parallel to the core, the core being a material with doping elements which may be brought into at least one excited electronic state by absorbing the energy from a pump optical signal of a first determined wavelength running through the core and capable of giving-back the former by de-energization in the form of an optical signal of a second determined wavelength, the core having a determined diameter and the sheath having a determined diameter. The diameter of the guiding sheath is greater than the core diameter and smaller than or equal to four times the core diameter, the core diameter being greater than or equal to 35 micrometers.

Abstract: Single mode oscillation at a wavelength of about 1064.4 nm is enabled with no use of an etalon installed in an optical resonator by providing one of two ends of a Nd:YAG element, which acts as one end of the optical resonator, with an HR coating arranged for the wavelength of about 1064.4 nm and determining the thickness along the direction of transmission of light of the Nd:YAG element so that the peak of reflection appears at the wavelength of about 1064.4 nm but not at a wavelength of about 1062.8 nm.

Abstract: It is an object of the present invention to provide a method that can provide regions having different thicknesses of a laminated body containing an organic compound with a light-emitting property in the same element and also can apply an electric field uniformly in all the regions of the element without depending on the thickness of the laminated body containing an organic compound with a light-emitting property. One laser element of the present invention has a laminated body containing an organic compound with a light-emitting property between two electrodes, and the laminated body includes a mixed layer of a metal oxide and an organic compound, which has a thickness distribution. The laser element emits light having different wavelengths in regions having different thicknesses of the mixed layer of a metal oxide and an organic compound, by applying voltage between two electrodes to feeding a current.

Abstract: In a semiconductor laser, a n-type AlGaInP clad layer is formed on a n-type GaAs substrate and an active layer having an emission wavelength of 600 to 850 nm is formed on the n-type AlGaInP clad layer. A p-type AlGaInP clad layer is formed on the active layer and a p-type AlGaAs contact layer in which the Al composition is controlled so that the p-type AlGaAs contact layer has an optical bandgap larger than that of the active layer is formed on the p-type AlGaInP clad layer. A p-type GaAs cap layer is formed on the p-type AlGaAs contact layer.

Abstract: A solid state laser system having at least one gas injector is disclosed. The gas injector may be configured to so as cause gas flow in a path of the laser beam in order to mitigate distortion of the laser beam due to optical path difference. Each gas injector may be configured so as to cause gas flow proximate at least one optical surface of a solid state gain element of the laser beam system. In this manner gain uniformity may be enhanced so as to facilitate use of the laser system in a variety of military and commercial applications.

Abstract: A nitride-based semiconductor laser device, includes: a first cladding layer of a first conductivity type; an active layer formed above the first cladding layer; an overflow-preventing layer of a second conductivity type formed on the active layer; and a second cladding layer of the second conductivity type formed above the overflow-preventing layer. The active layer includes three barrier layers and two well layers so that each well layer can be inserted between the corresponding ones of the three barrier layers and two of the three barrier layers are located on the outer sides of both well layers, thereby constituting a double-layered quantum well layer. The thickness of each well layer is set within a range of 2 to 5 nm.

Abstract: A laser oscillator is disclosed by means of current excitation by using a light-emitting element containing an organic matter. The present invention is a semiconductor device oscillating laser by current excitation comprising a light-emitting element having a laminated body which is formed by stacking sequentially a first layer made from an organic matter, a second layer containing an organic matter and a metal compound, and a third layer made from an organic matter interposed; and a first electrode and a second electrode formed over a substrate, the electrodes interposing the laminated body therebetween; wherein the organic matter contained in the second layer includes at least a light-emitting material.

Abstract: A rare earth ion ultrashort laser source includes a resonant cavity having a first output face partially reflecting and a second reflecting face. The source also includes a first active material, which receives a pump luminous flux transmitted via a first solid laser pump source. The resonant cavity exhibits a length of optical path travelled by the pulses greater than 7.5 m so that the pulsed energy EL is greater than 100 nJ, the optical path including at least one passage in the active material and the ultrashort laser source includes elements for lengthening the resonant cavity thereby enabling to extend the length of the optical path travelled by the luminous pulses in the resonant cavity, the ABCD propagation matrix of the resonant cavity being close to the unit matrix so that the features of the luminous beam going back and forth in the resonant cavity remain unchanged.

Abstract: A slab laser amplifier with parasitic oscillation suppression has a plurality of angled pump faces related to one another in order to decrease likelihood of parasitic oscillations, with internal beam incidence angles at total internal reflection that alleviate need for reflective coatings. No polished surfaces of gain material comprising the amplifier are parallel to one another. A beam path within the gain material is such that all incident angles of the beam path upon the two main faces and the common end face are greater than a critical angle required for total internal reflection, thereby alleviating need for reflective coatings. Based on an index of refraction of the gain material, and based on a diameter of the laser beam, dimensions of the gain material are selected to maximize beam overlap in a pumped volume of the gain material.

Abstract: A system and method for collecting radiation, which may be used in a lithography illumination system. The system comprises a first surface shaped to reflect radiation in a first hemisphere of a source to illuminate in a second hemisphere of the source; and a second surface shaped to reflect radiation in the second hemisphere of the source to an output plane.

Abstract: A nitride semiconductor laser device has an improved stability of the lateral mode under high output power and a longer lifetime, so that the device can be applied to write and read light sources for recording media with high capacity. The nitride semiconductor laser device includes an active layer, a p-side cladding layer, and a p-side contact layer laminated in turn. The device further includes a waveguide region of a stripe structure formed by etching from the p-side contact layer. The stripe width provided by etching is within the stripe range of 1 to 3 ?m and the etching depth is below the thickness of the p-side cladding layer of 0.1 ?m and above the active layer. Particularly, when a p-side optical waveguide layer includes a projection part of the stripe structure and a p-type nitride semiconductor layer on the projection part and the projection part of the p-side optical waveguide layer has a thickness of not more than 1 ?m, an aspect ratio is improved in far field image.

Abstract: As a composite laser rod capable of satisfying the positional stability and output stability of a laser beam, a laser rod in which a laser active element is doped is intimately inserted into a hollow portion of a non-doped ceramic pipe that has a crystal structure the same as the laser rod followed by baking so as to remove a gap and strain at an interface between the laser rod and the ceramic pipe after the baking further followed by polishing a surface of the ceramic pipe to form a ceramic skin layer, and thereby a composite laser rod is formed. In the composite laser rod, an influence due to fluctuation in the cooling capacity of cooling water or a heat sink is averaged by a non-doped skin layer, temperature fluctuation of the laser rod is suppressed, and an influence of vibration from the cooling water or a cooling fan can be suppressed.

Abstract: Diode lasers type of devices with good coupling between field distribution and gain are disclosed. A single element has a flat field distribution that couples with the uniform current injection in a contact region. A multi element array having almost flat field distribution in each element and almost equal amplitude for the field intensity in all elements is provided. Injection by multiple contacts couples well with the overall field distribution. Also, the lasers are stable against filament formation and mode switching.

Abstract: An apparatus and method is disclosed which may comprise a laser produced plasma EUV system which may comprise a drive laser producing a drive laser beam; a drive laser beam first path having a first axis; a drive laser redirecting mechanism transferring the drive laser beam from the first path to a second path, the second path having a second axis; an EUV collector optical element having a centrally located aperture; and a focusing mirror in the second path and positioned within the aperture and focusing the drive laser beam onto a plasma initiation site located along the second axis. The apparatus and method may comprise the drive laser beam is produced by a drive laser having a wavelength such that focusing on an EUV target droplet of less than about 100 ?m at an effective plasma producing energy if not practical in the constraints of the geometries involved utilizing a focusing lens. The drive laser may comprise a CO2 laser. The drive laser redirecting mechanism may comprise a mirror.

Abstract: A structure including a grating and a semiconductor nanocrystal layer on the grating, can be a laser. The semiconductor nanocrystal layer can include a plurality of semiconductor nanocrystals including a Group II-VI compound, the nanocrystals being distributed in a metal oxide matrix. The grating can have a periodicity from 200 nm to 500 nm.

Abstract: Highly compact quantum well based laser systems with external cavity configurations are tightly integrated in a very small mounting system having high thermal and vibrational stability. The mounting systems may include adjustability and alignment features specifically designed to account for the particular nature of the micro components used. The laser systems may provide for wavelength selection, including dynamic wavelength selection. The laser systems may also provide special output couplers.

Abstract: A novel method and apparatus for suppressing ASE and parasitic oscillation modes in a high average power laser is introduced. By roughening one or more peripheral edges of a solid-state crystal or ceramic laser gain media and by bonding such edges using a substantially high index bonding elastomer or epoxy to a predetermined electromagnetic absorbing arranged adjacent to the entire outer surface of the peripheral edges of the roughened laser gain media, ASE and parasitic oscillation modes can be effectively suppressed.

Abstract: Highly compact quantum well based laser systems with external cavity configurations are tightly integrated in a very small mounting system having high thermal and vibrational stability. The mounting systems may include adjustability and alignment features specifically designed to account for the particular nature of the micro components used. The laser systems may provide for wavelength selection, including dynamic wavelength selection. The laser systems may also provide special output couplers.

Abstract: A laser medium includes a single crystal of chromium-doped LiScl-xInxGe1-ySiyO4, where 0?x?1 and 0?y?1. Preferably, x and y are not both 0. A laser, such as a tunable near infrared laser, can contain the laser medium.

Abstract: A sensor and method for surface plasmon resonance sensing, wherein a small variation of the refractive index of an ambient medium results in a large variation of loss of a sensing mode. The surface plasmon resonance sensor comprises an antiguiding waveguide including a core characterized by a refractive index and a reflector surrounding the core. The reflector has an external surface and is characterized by a band gap and a refractive index higher than the refractive index of the core. A coating is deposited on the external surface of the core, the coating defining with the ambient medium a coating/ambient medium interface. In operation, the coating is in contact with the ambient medium, and the antiguiding waveguide is supplied with an electromagnetic radiation to (a) propagate a mode for sensing having an effective refractive index lower than the refractive index of the core and higher than a refractive index of an ambient medium and (b) produce surface plasmons at the coating/ambient medium interface.

Abstract: An apparatus and method is disclosed which may comprise a laser produced plasma EUV system which may comprise a drive laser producing a drive laser beam; a drive laser beam first path having a first axis; a drive laser redirecting mechanism transferring the drive laser beam from the first path to a second path, the second path having a second axis; an EUV collector optical element having a centrally located aperture; and a focusing mirror in the second path and positioned within the aperture and focusing the drive laser beam onto a plasma initiation site located along the second axis. The apparatus and method may comprise the drive laser beam is produced by a drive laser having a wavelength such that focusing on an EUV target droplet of less than about 100 ?m at an effective plasma producing energy if not practical in the constraints of the geometries involved utilizing a focusing lens. The drive laser may comprise a CO2 laser. The drive laser redirecting mechanism may comprise a mirror.

Abstract: The present invention is directed to new laser-related uses for single-crystal diamonds produced by chemical vapor deposition. One such use is as a heat sink for a laser; another such use is as a frequency converter. The invention is also directed to a ?(3) nonlinear crystalline material for Raman laser converters comprising single crystal diamond.

Abstract: An end face structure of an optical fiber includes a coreless fiber fused to an emitting end face of the fiber optical fiber and a coating material disposed around at least the coreless fiber, a refractive index of the coating material being higher than a refractive index of the coreless fiber.

Abstract: A laser rod is provided having a tailored gain profile such that the quality of the output beam is enhanced. The laser rod has a concentration of dopant ions having a first valence that is relatively high at the center of the rod and decreases to the surface of the rod. The laser rod further has a concentration of interstitial ions and dopant ions having a second valence that is lower than the first valence, the concentration being relatively high at the surface of the rod and decreasing to the center of the rod. Methods are provided for creating a layer of inactive laser species in the near surface region of a laser rod using interstitial dopant ions and for reducing the near surface absorption of incident photons intended to induce lasing in a laser rod using a layer of inactive laser ions.

Abstract: A pumping method of discrete elements solid state laser systems pumped by semiconductor laser diodes, which sends a pump beam through an active medium, comprising a first face first crossed by said pump beam, and a second face met as second by the pump beam, a pumping axis being associated to the pump beam, the active medium being inserted in a cavity to which a cavity propagation axis is associated. The pumping axis coincides with the cavity propagation axis inside the active medium, and is perpendicular to an optical surface met by the pump beam after crossing the active medium, the optical surface being at least partially reflecting at the wavelength of the pump beam.

Abstract: The invention includes a process for forming a laser pixel array useful with a pump-beam, comprising: a) forming a layer containing a formamide of an amino dye compound on a support wherein the layer absorbs light outside the laser wavelength and predominantly outside the pump-beam wavelength range; and b) subjecting the layer to UV radiation in the areas of the layer where it is desired to be free of pixels for a time sufficient to shift the absorption envelope of the areas into the pump-beam wavelength range. The invention also provides for unimolecularly forming an image or an information record and a composition of matter. The invention provides methods for forming filters, images or information records having a smooth surface and in particular for forming a pixel region pattern for use with an Organic VCSEL that would ease manufacturing.

Abstract: A laser medium includes a single crystal of Cr4+:Mg2-xMxSi1-yAyO4, where, where M is a bivalent ion having an ionic radius larger than Mg2+, and A is a tetravalent ion having an ionic radius larger than Si4+. In addition, either a) 0?x<2 and 0<y<1 or b) 0<x<2 and y is 0 or 1 with the proviso that if M is Ca2+ and x=1 then y is not 0. The laser medium can be used in a laser device, such as a tunable near infrared (NIR) laser.

Abstract: An optical semiconductor device includes a semiconductor laser chip, a base for mounting the semiconductor laser chip and a solder layer sandwiched between the top surface of the base and the bottom surface of the semiconductor laser chip. The semiconductor laser chip is warped in upward convex shape.

Abstract: To compensate for undesirable thermooptical effects in optical pumping of solid-state laser rods, regions of the lateral surface are heated in such a way that reverse thermal gradients are created at these locations. This is achieved by providing said regions with a radiation-absorbing layer which is heated by pump radiation and laser radiation.

Abstract: A simple and high-reliability constitution provides a solid-state laser system that allows a high-output, long-pulse-width laser beam to be obtained. A solid-state laser system that includes a solid-state laser medium 1, a light source 2 for pumping the solid-state laser medium 1, two reflecting mirrors 3 and 4 for flanking the solid-state laser medium 1, thereby constituting a laser resonator, is constituted in such a manner that a virtual-mirror plane 5 is defined in the space between the solid-state laser medium 1 and the reflecting mirror 4; a lens 6 is provided between the virtual-mirror plane 5 and the reflecting mirror 4; and, by means of the forward and backward paths along the route from the virtual-mirror plane to the reflecting mirror by way of the lens, the virtual-mirror plane in the forward path and the virtual-mirror plane in the backward path are made in an optically conjugated relationship with each other.

Abstract: In a first embodiment, the invention makes use of a Neodymium doped YAG (Nd: YAG) gain medium placed in an optical resonant cavity formed by two mirrors. Power extraction is maximized for a specific laser cavity. In particular the concave curvature on the rod ends contributes a negative lensing component to modify the strength of the thermal lens. In a second embodiment the present invention uses an amplifier rod medium with curved ends to act as lensing elements to collect emission from the laser gain medium and/or oscillator described in the first embodiment of the invention. The combination of thermal lens and curved rod ends produces a lensing effect which allows light to be directly coupled from a laser. In addition, variation of the input pump power allows for control of the thermal lens formed within the amplifier rod.

Abstract: A method of tuning optical components integrated on a monolithic semiconductor chip having a plurality of first optical components integrated on the chip with each fabricated to approximate an emission wavelength along a given wavelength grid and together forming a first optical component wavelength grid. A second optical component is integrated on the chip with and optically coupled to the group of first optical components. The second optical component has a second optical component wavelength grid approximating the given wavelength grid where at least one emission peak along the second optical component wavelength grid is within an acceptable wavelength tolerance range of a particular first optical component of the first optical component wavelength grid but not the same as a corresponding emission wavelength of a particular first optical component.

Abstract: A narrow linewidth fluorescent emitter can incorporate a chromophore into a microcavity that can support low-order optical modes.

Abstract: A micropost microcavity device has a maximum field intensity at the center of a high-index spacer as well as a small mode volume. The device has an approximately half-wavelength thick low-index spacer [400] sandwiched between two quarter wave stacks [410, 420]. The low-index spacer has a high-index subspacer layer [470] positioned at its center. The subspacer layer has a thickness smaller than a quarter wavelength. As a result, the electric field intensity remains a maximum at the center of the spacer where the high-index subspacer is positioned. A quantum dot or other active region [480] may be embedded within the subspacer [470]. The microcavity devices provide, for example, single photon sources, single dot lasers, low-threshold quantum dot or quantum well lasers, or devices for strong coupling between a single quantum dot and the cavity field which can be used as components of photonic integrated circuits, quantum computers, quantum networks, or quantum cryptographic systems.

Abstract: Laser equipment in which pumping every dependence of output beam diameter and beam wavefront curvature is reduced. The total pumping energy of at least one of laser active media disposed beyond terminal laser beam waists, among beam waists, is approximately one-half of the total pumping energy of laser active media disposed between two adjacent beam waists.

Abstract: The invention relates to a pump arrangement for transversally pumping an active medium, especially a laser rod, wherein two pump light sources are arranged on a plane perpendicular to the longitudinal axis of the active medium, especially pertaining to the laser rod. The value of the smallest angle between the central axes of the pump light sources is less than 180°. A pump arrangement is also provided which illuminates the active medium in a particularly uniform manner.

Abstract: A display apparatus for producing colored pixelated light includes a backlight unit for providing a pump-beam light. The apparatus also includes a microcavity light-producing array responsive to pump-beam light and having pixels wherein each pixel including a transparent substrate, a bottom dielectric stack reflective to light over a predetermined range of wavelengths, an active region responsive to pump-beam light for producing display light, and a top dielectric stack spaced from the bottom dielectric stack and reflective to light over a predetermined range of wavelengths. The apparatus further includes a light shutter for permitting selected display light from the microcavity light-producing array to pass therethrough, a polarizing layer disposed between the microcavity light-producing array and the light shutter, and a beam expander disposed over the light shutter for increasing the angular cone of view of the display light.

Abstract: A system and a method for providing more gain while minimizing the potential for parasitic oscillation and amplified spontaneous emissions in an optically pumped optical amplifier or laser system, utilizing a partitioned monolithic gain element. The monolithic gain element being partitioned into discontinuous amplifying gain regions such that parasitic modes and amplified spontaneous emissions are substantially obviated.

Abstract: Lasing at the edge of the reflection band or at a defect state within the reflection band of a thin one-dimensional feedback structure is used to create a large-area, thin-film laser source with transverse dimensions that can be much greater than the film thickness. Angular confinement of radiation propagating perpendicular to the layers leads to a spreading of the beam inside the medium which is much greater than the diffraction divergence. This enhances the spatial extent of correlation at the output surface of the thin film. When a pump source induces gain at the lasing threshold in a wide region, a spatially coherent monochromatic light beam is emitted perpendicular to the film surface from the entire gain region. Alternate embodiments of the present invention include a passive spatial filter and an active amplifier.

Abstract: An unipolar organic injection laser in which electrically-stimulated intraband transitions result in lasing. An active region includes at least one organic injector layer and at least one organic emitter layer. Each organic emitter layer has a first energy level and a second energy level on a same side of an energy gap defined by a conduction band and a valance band. Charge carriers are injected through the organic injector layer into the first energy level of the organic emitter layer when a voltage is applied across active region. The difference in energy between the first and second energy levels produces radiative emissions when charge carriers transition from the first energy level to the second energy level. Population inversion is maintained between the first and second energy levels, producing stimulated emission and lasing.

Abstract: A narrow line width optical parametric oscillator (OPO) (10) is used a pump for a tunable optical parametric oscillator to enable it to produce a mid and long wavelength IR output over a wide 5–20 micron bandwidth. The pumping OPO (10) is then set up to be non-colinearly phase matched. To enable the pumping OPO (10) to exhibit the narrow line width, it is seeded with a narrow line width seeding source. The result is output energy having an extremely narrow 4 nanometer line width. The narrowness of the pumping OPO (10) output is derived first by using non-colinear phase matching in the pumping OPO (10) and secondly by using seeding in the pumping of the pumping OPO (10).

Abstract: Semiconductor laser diodes, particularly high power AlGaAs-based ridge-waveguide laser diodes, are often used in opto-electronics as so-called pump laser diodes for fiber amplifiers in optical communication lines. To provide the desired high power output and stability of such a laser diode and avoid degradation during use, the present invention concerns an improved design of such a device, the improvement in particular significantly minimizing or avoiding (front) end section degradation of such a laser diode and significantly increasing long-term stability compared to prior art designs. This is achieved by establishing one or two “unpumped end sections” of the laser diode. One preferred way of providing such an unpumped end section at one of the laser facets (10, 12) is to insert an isolation layer (11, 13) of predetermined position, size, and shape between the laser diode's semiconductor material and the usually existing metallization (6).

Abstract: A system and a method for providing more gain while minimizing the potential for parasitic oscillation and amplified spontaneous emissions in an electrically pumped optical amplifier or laser system, utilizing a partitioned monolithic gain element. The monolithic gain element being partitioned into discontinuous amplifying gain regions such that parasitic modes and amplified spontaneous emissions are substantially obviated.

Abstract: A laser includes an Nd:YVO4 crystal end-pumped with diode-laser light having a wavelength at which the absorption coefficient for Nd:YVO4 is less than about 0.35 (35%) of the absorption coefficient at 808 nm.

Abstract: The present invention provides a cesium-lithium-borate crystal, which can be used as a high-performance wavelength converting crystal, having a chemical composition expressed as CsLiB6O10, and substituted cesium-lithium-borate crystals expressed by the following formula: Cs1?xLi1?yMx+yB6O10 or Cs2(1?z)Li2LzB12O20 (where, M is an alkali metal element, and L is an alkali earth metal element); a method for manufacturing same by heating and melting; and an optical apparatus using such crystals.

Abstract: In order to achieve a long wavelength, 1.3 micron or above, VCSEL or other semiconductor laser, layers of strained quantum well material are supported by mechanical stabilizers which are nearly lattice matched with the GaAs substrate, or lattice mismatched in the opposite direction from the quantum well material; to allow the use of ordinary deposition materials and procedures. By interspersing thin, unstrained layers of e.g. gallium arsenide in the quantum well between the strained layers of e.g. InGaAs, the GaAs layers act as mechanical stabilizers keeping the InGaAs layers thin enough to prevent lattice relaxation of the InGaAs quantum well material. Through selection of the thickness and width of the mechanical stabilizers and strained quantum well layers in the quantum well, 1.3 micron and above wavelength lasing is achieved with use of high efficiency AlGaAs mirrors and standard gallium arsenide substrates.

Abstract: In a solid state, optically end-pumped laser, the laser gain medium has a tapered diameter to minimize the maximum path length of barrelling amplified stimulated emission (ASE), and a roughened surface region at one end to scatter barrelling ASE out of the gain medium; thereby minimizing the negative effective of barrelling ASE's, and inhibiting the trapping of rays with a large longitudinal component, but disallowing a cyclic, i.e. repeated, pass path with specular reflections.