Abstract: A YAG ceramic bonded body in which a YAG ceramic and a YAG ceramic or optical glass are bonded, wherein the YAG ceramic bonded body comprises glass as a bonding layer, and has a rate of change of transmittance that is within 7%. An object of this invention is to provide a bonded body in which a YAG ceramic and a YAG ceramic are bonded, or a bonded body in which a YAG ceramic and optical glass are bonded, and which is capable of suppressing the reflection of light at the bonded interface, as well as the production method thereof.

Abstract: A system for correcting the wavefront of a laser beam includes a beamsplitter for splitting off a fraction of the laser beam to be used as a diagnostic beam, a focusing element for bringing the diagnostic beam to a focus, a measurement subsystem for measuring sizes of the diagnostic beam at upstream and/or downstream locations with respect to a nominal location of the focus, and at least one adaptive optic, located upstream from the beamsplitter, for correcting the wavefront of the laser beam at least partly based on the measured sizes of the diagnostic beam at the upstream and/or downstream locations. The upstream and downstream locations correspond to mid-field locations in the laser beam as imaged by the focusing element. The system takes advantage of the sensitivity of the laser beam size to a waist location shift being greatest at one Rayleigh length from the nominal waist location.

Abstract: Devices and associated methods for measuring orientation using an optical gyroscope are disclosed. One example optical gyroscope includes a spherical component configured to allow propagation of light in one or more confined modes inside the spherical component. The spherical component includes a gain medium for enhancing a sustained confinement of light within the spherical component. The optical gyroscope also includes one or more detectors positioned outside of the spherical component to detect at least one characteristic of the light, or a change thereto, in response to a rotation of the optical gyroscope.

Abstract: The present disclosure relates to a system and apparatus having an optic and a cooling system for cooling the optic. In one example an optically addressed light valve forms the optic. The cooling system includes first and second windows on opposing surfaces of the optically addressed light valve which constrain a cooling fluid to flow over the opposing surfaces. The fluid pressure outside the optically addressed light valve is low enough that it does not compress a liquid crystal gap of the optically addressed light valve. The cooling fluid is also transparent to a high powered light beam which is projected through the first and second windows, and also through the optically addressed light valve, during an additive manufacturing operation.

Abstract: Optical signal receivers, systems, and methods of operating the same include a non-line of sight optical signal receiver configured to receive and detect a complex modulated optical signal through a non-line of site propagation path from an optical transmitter, comprising an optical resonator configured to receive the complex modulated optical signal through the non-line of sight propagation path, and to convert the complex modulated optical signal to an intensity modulated signal, and a detector configured to convert the intensity modulated signal into an electrical signal, the electrical signal having an amplitude indicative of an intensity of the intensity modulated signal from the optical resonator, and to provide a detected signal.

Abstract: A laser system having a multi-pass amplifier system which includes at least one seed source configured to output at least one seed signal having a seed signal wavelength, at least one pump source configured to output at least one pump signal, at least one multi-pass amplifier system in communication with the seed source and having at least one gain media, a first mirror, and at least a second mirror therein, the gain media device positioned between the first mirror and second mirror and configured to output at least one amplifier output signal having an output wavelength range, the first mirror and second mirror may be configured to reflect the amplifier output signal within the output wavelength range, and at least one optical system may be in communication with the amplifier system and configured to receive the amplifier output signal and output an output signal within the output wavelength range.

Abstract: An apparatus includes a base that includes a raised surface and a first opening through the raised surface. The apparatus also includes a cover configured to be coupled to the base in order to form a cavity, where the cover includes a second opening through the cover. The raised surface is configured to allow passage of a first portion of optical energy through the first opening and to reflect a second portion of the optical energy. Portions of the cover and the base surrounding the cavity are configured to absorb the reflected second portion of the optical energy. The base may further include one or more baffles positioned around the raised surface, and/or the cover may further include one or more baffles positioned around the second opening.

Abstract: A semiconductor device includes a substrate, a plurality of solders, and a semiconductor chip. The plurality of solders are located adjacent to each other. At least one of composition and concentration of the plurality of solders is different from each other. The semiconductor chip includes a joining surface to be joined to the substrate with the plurality of solders. The joining surface of the semiconductor chip includes a plurality of joining areas in which heat generation of the semiconductor chip or a stress on an object to be joined is different from each other. The plurality of solders are disposed to correspond to the plurality of joining areas, respectively.

Abstract: A micro disk laser having a greater strength of oscillation in one direction than in another direction and unidirectionally oscillating includes a micro disk having an oval shape corresponding to a modified ellipse obtained by changing a length of a short axis of an ellipse according to a position of a long axis while lengths of first and second side portions of the long axis are fixed in the ellipse, the ellipse having the long axis and the short axis having a different length than the long axis.

Abstract: The present invention relates to a microdisk laser having characteristics of unidirectional emission and an ultra-high quality factor and also a microdisk laser composed of four circular arcs and configured to emit light in one direction in a resonance mode having the form of a whispering gallery mode formed by total reflection.

Abstract: An active element slab for a laser source is presented. The active element slab includes at least one input surface of a pump beam, a first section in the shape of an elongated bar along a longitudinal axis that includes a first doped matrix configured to absorb the beam pump to amplify a laser beam travelling longitudinally, a second section that covers at least partially the first section, the second section that includes a second doped matrix configured to absorb the laser beam and of being transparent to the pump beam.

Abstract: A solid-state optical amplifier chip is described, with improved pumping, in which pump light from one or more solid-state light sources is coupled efficiently into the doped areas of the chip, resulting in amplification of an optical signal. The optical signal is carried in the core of an optical waveguide. Rare-earth elements are used as dopants, primarily in the cladding of the optical signal's waveguide core, in order to provide amplification of the optical signal through stimulated emission. A variety of waveguide structures are described for routing and distributing the pump light to the doped areas of the chip.

Abstract: A solid-state optical amplifier is described, having an active core and doped cladding in a single chip. An active optical core runs through a doped cladding in a structure formed on a substrate. A light emitting structure, such as an LED, is formed within and/or adjacent to the optical core. The cladding is doped, for example, with erbium or other rare-earth elements or metals. Several exemplary devices and methods of their formation are given.

Abstract: A microchip laser includes a microchip laser base comprising a gain region and a passive Q-switch region. The microchip laser also includes a solid etalon coupled to the microchip laser base, and an interfacial coating disposed between the microchip laser base and the solid etalon. In some embodiments, the microchip laser further includes a dichroic coating disposed on a surface of the microchip laser base opposite the interfacial coating.

Abstract: A gyroscope having a mechanical resonator, a plurality of electrodes located around the resonator, and a thin gap being located between the resonator and the plurality of electrodes. The resonator is axi-symmetric and may be at least partially toroidal in shape or composed of concentric rings. Piezoelectric electrodes or transduction may be used to drive or detect displacements of the resonator. The resonator may be fabricated using a fused silica flowing process.

Abstract: The patent refers to one or more droplets of chiral liquid crystals used as point source(s) of laser light. The source is shaped as a droplet of chiral liquid crystals (1) and an active medium preferably dispersed in the liquid crystals. The source is spherical and with a size of preferably between a few nanometres and 100 micrometres. A droplet consists of chiral liquid crystals (1) that have selective reflection in the range of the active medium's emission and can be cholesteric liquid crystals, a mixture of nematic liquid crystals and a chiral dopant or any other chiral liquid-crystal phase, preferably the blue phase, the ferroelectric phase, the antiferroelectric phase, any of the ferrielectric phases or another chiral phase of a soft substance, that need not be chiral by itself.

Abstract: A spherical laser includes a transparent or semi-transparent outer spherical vessel having an internal cavity, an amplifying medium in the cavity, and means to excite the amplifying medium. The sphere is provided with a partially reflective coating to act as a spherical optical resonator. The spherical resonator includes a plurality of optically different regions containing alternative optical media from the cavity medium differing in bulk optical parameters utilized for mode tailoring. The optically different regions work collectively to exclude the whispering gallery modes from those supported by the spherical cavity. Excitation of the amplifying medium produces an optical gain. When the gain exceeds cavity losses and threshold conditions are met, lasing is supported. This creates a three-dimensional, spherically radiating emission, emulating a point source. The sphere is enclosed within a mirrored ellipse to image the output to a point, or within a mirrored parabola to columinate the emission.

Abstract: A solid state laser includes an optical resonator cavity and a containment vessel disposed in the optical resonator cavity. The solid state laser also includes a gas-flow system operable to pump solid state nano-structures through the containment vessel and one or more diode pumps optically coupled to the containment vessel.

Abstract: A laser includes a Ti:sapphire gain-medium in the form of a thin-disk. The thin-disk gain-medium is optically pumped by pump-radiation pulses having a wavelength in the green region of the electromagnetic spectrum. The pump-radiation pulses have a duration less than twice the excited-state lifetime of the gain-medium.

Abstract: A method for generating high power electromagnetic radiation based on double-negative metamaterial (DNM), includes providing electrons of an electron beam moving in a vacuum close to an interface between the DNM and the vacuum at a predetermined average speed larger than a phase velocity of an electromagnetic wave propagating in the DNM so as to generate coherent high power radiation. The method can be applied but not limited to high power and compact Terahertz radiation sources and Cherenkov particle detectors and emitters.

Abstract: A semiconductor laser outputs a laser light from an output facet of a waveguide having an index waveguide structure, via a lens system. The waveguide includes, in order from a rear facet opposite to the output facet, a first narrow portion, a wide portion that is wider than the first narrow portion, a second narrow portion narrower than the wide portion, a first tapered portion formed between the first narrow portion and the wide portion, which expands toward the wide portion, and a second tapered portion formed between the wide portion and the second narrow portion, which narrows toward the second narrow portion. Each of the first narrow portion, the wide portion, and the second narrow potion has a uniform width.

Abstract: A semiconductor laser includes a ridge section on top of a semiconductor laminated section. The ridge section is a stripe-shaped projection or ridge and serves as a constriction structure for constricting current and light. A pair of terrace sections is located on top of the semiconductor laminated structure. The terrace sections are raised island portions sandwiching and spaced from the ridge section. An active region is located below the ridge section as viewed in plan. High refractive index regions are located on both sides of the active region and below the terrace sections, respectively. Cladding regions are located between the active region and the high refractive index regions. The high refractive index regions have a higher refractive index than the cladding regions.

Abstract: A compact CO2 slab-laser is contained in a fluid cooled housing having three compartments. One compartment houses discharge electrodes and a laser resonator. Another compartment houses a radio-frequency power supply (RFPS) assembled on a fluid-cooled chill plate and an impedance-matching network. The remaining compartment houses beam-conditioning optics including a spatial filter. The housing and RFPS chill-plate are on a common coolant-fluid circuit having a single input and a single output. The spatial filter is optionally fluid-coolable on the common coolant fluid circuit.

Abstract: To suppress the amplification of spontaneous emission light in a principal plane width direction to thereby suppress a gain in directions other than a beam axis direction and output a high-power laser, in a solid-state laser element of a plane waveguide type that causes a fundamental wave laser beam to oscillate in a beam axis direction in a laser medium of a flat shape and forms a waveguide structure in a thickness direction as a direction perpendicular to a principal plane of the flat shape in the laser medium, inclined sections 12 are provided on both sides of the laser medium, the inclined sections 12 inclining a predetermined angle to reflect spontaneous emission light in the laser medium to a principal plane side of the flat shape, the spontaneous emission light traveling in the beam axis direction and a principal plane width direction as a direction perpendicular to the thickness direction.

Abstract: A main amplifier system includes a first reflector operable to receive input light through a first aperture and direct the input light along an optical path. The input light is characterized by a first polarization. The main amplifier system also includes a first polarizer operable to reflect light characterized by the first polarization state. The main amplifier system further includes a first and second set of amplifier modules. Each of the first and second set of amplifier modules includes an entrance window, a quarter wave plate, a plurality of amplifier slablets arrayed substantially parallel to each other, and an exit window. The main amplifier system additionally includes a set of mirrors operable to reflect light exiting the first set of amplifier modules to enter the second set of amplifier modules and a second polarizer operable to reflect light characterized by a second polarization state.

Abstract: A laser system having a cooling apparatus is disclosed. The laser system includes a resonator, a gain medium and multiple heat-absorbing discs. The resonator is formed by a first mirror and a second mirror. The gain medium, which is contained within the resonator, is collectively formed by a group of gain medium segments. Each of the gain medium segments is preferably in the shape of a cylindrical disc. The heat-absorbing discs are interleavely disposed among the gain medium segments to provide face cooling for the gain medium segments during the operation of the laser system.

Abstract: A semiconductor optical amplifier includes an input-side optical amplifier waveguide section that has a first active core layer. An output-side optical amplifier waveguide section connects to the input-side optical amplifier waveguide section and has a second active core layer that is wider than the first active core layer. The width of the first active core layer and relative refractive index difference between the first active core layer and adjacent clad section in the width direction of the first active core layer, and the width of the second active core layer and relative refractive index difference between the second active core layer and adjacent clad section in the width direction of the second active core layer are set such that the carrier density and optical confinement factor in the first active core layer are higher than the carrier density and optical confinement factor in the second active core layer.

Abstract: A laser diode is configured with a substrate delimited by opposite AR and HR reflectors and a gain region. The gain region bridges the portions of the respective AR and HR reflectors and is configured with a main resonant cavity and at least one side resonant cavity. The main resonant cavity spans between the portions of the respective reflectors, and at least one additional resonant cavity extends adjacent to the main resonator cavity. The gain region is configured so that stimulated emission is generated only in the main resonant cavity. Accordingly, the laser diode is operative to radiate a high-power output beam emitted through the portion of the AR reflector which is dimensioned to shape the output beam with the desired near-field.

Abstract: Slab lasers and method for producing high power coherent laser radiation of good quality. In one embodiment, a slab laser comprises a slab laser medium, an energy source configured to deliver energy to the laser medium, and first and second optical elements. The first optical element has a first reflective surface at a first boundary of the laser medium, and the second optical element has a second reflective surface at a second boundary of the laser medium. The first and second reflective surfaces face each other across the length of the laser medium, and at least one of the first and second optical elements includes a plurality of reflective regions configured to modify the phase distribution of the incident laser radiation propagating from the reflective regions. The first and second reflective surfaces are also positioned at an angle relative to each other to form a laser resonator.

Abstract: A high power source of electro-magnetic radiation having a multi-purpose housing is disclosed. The multi-purpose housing includes an interior filled with a material forming at least a light source and further comprising a reflector which can envelope a laser rod surrounded by light sources for providing light excitation to the laser rod. A material defining outer surfaces of the light sources extends out to and defines outer surfaces of the reflector. A high-reflectivity coating is disposed over an outer surface of the reflector, as is a protective coating. Also disposed over an outer surface of the reflector can be an optional heat sink, with cooling being performed by an optional arrangement of forced-air traveling over the heat sink. The light sources may be light source pumps, and the high-reflectivity coating may be formed to envelop the reflector.

Abstract: A high power laser source comprises a bar of laser diodes having a first coefficient of thermal expansion CTEbar on a submount having a second coefficient CTEsub and a cooler having a third coefficient CTEcool. The submount/cooler assembly shows an effective fourth coefficient CTEeff differing from CTEbar. This difference leads to a deformation of the crystal lattice of the lasers' active regions by mechanical stress. CTEeff is selected to be either lower than both CTEbar and CTEcool or is selected to be between CTEbar and CTEcool. The submount may either comprise layers of materials having different CTEs, e.g., a Cu layer of 10-40 ?m thickness and a Mo layer of 100-400 ?m thickness, or a single material with a varying CTEsub. Both result in a CTEsub varying across the submount's thickness.

Abstract: The invention relates to a method for the production of a photon pair source, which generates entangled photon pairs, having at least one quantum dot, wherein in the method the operational behaviour of the photon pair source is determined by adjusting the fine structure splitting of the excitonic energy level of the at least one quantum dot. It is provided according to the invention for the fine structure splitting of the excitonic energy level to be adjusted by depositing the at least one quantum dot on a {111} crystal surface of a semiconductor substrate.

Abstract: An optical system (31) with an input optical source (33) for projecting an input beam along an optical axis and an optical element (37, 43) which creates a cone refracted beam (41) from the input beam (35) then reconstructs the input beam (49). The optical element may comprise a first cone refractive element (37) which creates a cone refracted beam and reconstructs the beam using a reconstructing optical element (43) to apply a phase shift to the cone refracted beam. The optical system may be used to form a laser or a gain medium for a laser.

Abstract: An amplifying optical fiber includes a core containing oxides of elements selected from the group consisting of silicon, germanium, phosphorus, bismuth, aluminum, gallium with a concentration of bismuth oxide of 10-4-5 mol %, a total concentration of silicon and germanium oxides of 70-99.8999 mol %, a total concentration of aluminum and gallium oxides of 0.1-20 mol % wherein both aluminum and gallium oxide are present and a ratio of aluminum oxide to gallium oxide is at least two, and a concentration of phosphorus oxide from 0 to 10 mol %, and provides a maximum optical gain at least 10 times greater than the nonresonant loss factor in the optical fiber. An outside oxide glass cladding comprises fused silica. The core has an absorption band in the 1000 nm region, pumping to which region provides an increased efficiency of power conversion of pump light into luminescence light in the 1000-1700 nm range.

Abstract: A composite optical waveguide 1 includes a first optical waveguide 9 comprising a silica-based core and a second optical waveguide 11 comprising an Si-based core. The second optical waveguide 11 is joined to the first optical waveguide 9. The length of the first optical waveguide 9 corresponds to a permissible propagation loss of the second optical waveguide 11. The second optical waveguide 11 includes a sharply curved portion 13 having a radius smaller than the minimum bend radius of the first optical waveguide 9.

Abstract: A laser amplifier arrangement includes an optical pump source and an axially arranged laser oscillator-amplifier configuration pumped by the pump radiation. The laser oscillator-amplifier configuration includes a laser oscillator excitable by a portion of the pump radiation to emit a laser beam, and a laser amplifier that amplifies the laser beam using the pump radiation. The laser oscillator and laser amplifier are arranged in a substantially coaxial or collinear manner relative to a longitudinal axis of the laser oscillator-amplifier configuration. The pump source includes a first beam source for producing a first pump radiation to pump the laser oscillator, a second beam source for producing a second pump radiation for the laser amplifier, and a pump radiation conducting device, by means of which both the first and the second pump radiation can be lead into the laser oscillator-amplifier configuration substantially in the direction of the longitudinal axis for longitudinal pumping.

Abstract: Optical resonators and optical devices based on optical resonators that implement diffractive couplers for coupling light with the optical resonators.

Abstract: A tunable laser light source having emission wavelengths in a visible or an adjoining spectral region includes a rotationally disposed laser substrate having more than one emission wavelength, a drive unit coupled to the laser substrate, a pulsed light source having a pulse transmitter, a trigger device, and a signal-delay unit. The trigger device, the signal-delay unit and the pulse transmitter are sequentially connected downstream of the drive unit.

Abstract: A high power laser source comprises a bar of laser diodes having a first coefficient of thermal expansion CTEbar on a submount having a second coefficient CTEsub and a cooler having a third coefficient CTEcool. The submount/cooler assembly shows an effective fourth coefficient CTEeff differing from CTEbar. This difference leads to a deformation of the crystal lattice of the lasers' active regions by mechanical stress. CTEeff is selected to be either lower than both CTEbar and CTEcool or is selected to be between CTEbar and CTEcool. The submount may either comprise layers of materials having different CTEs, e.g., a Cu layer of 10-40 ?m thickness and a Mo layer of 100-400 ?m thickness, or a single material with a varying CTEsub. Both result in a CTEsub varying across the submount's thickness.

Abstract: Disclosed herein are systems and methods for generating a side-pumped passively Q-switched non-planar ring oscillator. The method introduces a laser into a cavity of a crystal, the cavity having a round-trip path formed by a reflection at a dielectrically coated front surface, a first internal reflection at a first side surface of the crystal at a non-orthogonal angle with the front, a second internal reflection at a top surface of the crystal, and a third internal reflection at a second side surface of the crystal at a non-orthogonal angle with the front. The method side pumps the laser at the top or bottom surface with a side pump diode array beam and generates an output laser emanating at a location on the front surface. The design can include additional internal reflections to increase interaction with the side pump. Waste heat may be removed by mounting the crystal to a heatsink.

Abstract: A surface emitting laser includes a stepped structure having a step between a first region and a second region, the stepped structure provided in an emission area located in an upper portion of the upper mirror. The surface emitting laser includes a light shielding member provided in a third region between the first region and the second region. The light shielding member is not provided in a portion of the first region and a portion of the second region.

Abstract: A method of producing a lasing microsource of colloidal nanocrystals. The method includes the steps of preparing a nanocrystal solution in a solvent; depositing at least a drop of the nanocrystals solution with a drop volume below 1 nl on a flat substrate; and evaporating the solvent to dryness thereby to obtain at the edge of the evaporated drop a single annular stripe including a domain wherein the nanocrystals are arranged in an ordered array, wherein the ordered nanocrystals in the domain constitute an active region capable of lasing and the radially inner and outer edges of the stripe define a resonant cavity in which the active region is inserted.

Abstract: The present invention relates to an amplification device comprising an amplifying medium (2) of parallelepiped shape and pumping means comprising lamps (5) emitting first radiation in a frequency range useful for the amplification and second radiation capable of degrading the amplifying medium. It is characterized in that lamps (5) are integrated into a jacket (3) that absorbs at least some of the second radiation.

Abstract: A method of producing a lasing microsource of colloidal nanocrystals. The method includes the steps of preparing a nanocrystal solution in a solvent; depositing at least a drop of the nanocrystals solution with a drop volume below 1 nl on a flat substrate; and evaporating the solvent to dryness thereby to obtain at the edge of the evaporated drop a single annular stripe including a domain wherein the nanocrystals are arranged in an ordered array, wherein the ordered nanocrystals in the domain constitute an active region capable of lasing and the radially inner and outer edges of the stripe define a resonant cavity in which the active region is inserted.

Abstract: A laser amplifier includes a laser active slab with a source of pump power to amplify an input laser beam, the laser active slab including a block of laser active material having opposed lateral faces defining a wedge lateral dihedral angle, opposed longitudinal faces, and opposed parallel transverse faces, the wedge lateral dihedral angle specified to minimize parasitic amplified spontaneous emission. The source of pump power may be one or more laser diode bars and microlenses producing a gain sheet in the laser active slab. The lateral faces may include optical coatings highly transmitting at a wavelength of the pump power and highly reflecting at a lasing wavelength to provide a folded path for the input laser beam though the gain sheet.

Abstract: An optical system (31) with an input optical source (33) for projecting an input beam along an optical axis and an optical element (37, 43) which creates a cone refracted beam (41) from the input beam (35) then reconstructs the input beam (49). The optical element may comprise a first cone refractive element (37) which creates a cone refracted beam and reconstructs the beam using a reconstructing optical element (43) to apply a phase shift to the cone refracted beam. The optical system may be used to form a laser or a gain medium for a laser.

Abstract: A method of fabricating a color laser, comprising growing a first thin layer of ionic crystal on a substrate. The crystal can comprise many types of ionic crystals, such as sodium chloride or potassium chloride. A second thin layer of a different type of ionic crystal can be deposited above the first ionic crystal layer, such as lithium fluoride or sodium fluoride. An inert metal layer can be deposited between the first and second layers of ionic crystal and above the second layer of ionic crystal. When the first and second ionic crystal layers are radiated with gamma rays, they form color centers at the spots radiated. Because of the difference in crystalline properties of the two different ionic crystal centers, their color centers have different wavelengths. Each of the ionic crystal layers emit light at different characteristic wavelengths when illuminated at their unique absorption frequencies, and can be made to lase separately.

Abstract: A laser arrangement includes an optical resonator having a V arrangement of two resonator branches. At least one active medium includes an active volume associated with each resonator branch. The arrangement also includes folding element that is highly reflective for a fundamental wavelength of the laser arrangement and an optical pump imaging system configured to unidirectionally pump the two resonator branches. The optical pump imaging system includes a common objective lens for both resonator branches. The folding element is transparent for the pump wavelength.

Abstract: A laser amplifier includes a laser active slab with a source of pump power to amplify an input laser beam, the laser active slab including a block of laser active material having opposed lateral faces defining a wedge lateral dihedral angle specified to minimize parasitic amplified spontaneous emission. The laser amplifier may include one or more external mirrors highly reflecting at the lasing wavelength positioned and oriented to provide for zig-zag passes through the gain sheet for the input laser beam to yield a multi-pass-amplified laser beam. The source of pump power may be one or more laser diode bars and microlenses producing a gain sheet in the laser active slab.

Abstract: A solid state laser device with a lengthened pump beam path is provided herein. The laser device includes an active element having a specified geometric shape, specified optical characteristics, and further configured for lasing; and a light pumping element optically coupled to the active element, wherein the light pumping element is configured to generate a pump light beam directed at a specified angle into the active element, and wherein at least one of: the specified angle, the specified geometric shape, and the specified optical characteristics are selected such that the pump light beam is reflected one or more times within the active element resulting in an extension of an absorption path of the pump light beam within the active element.