Pump light assembly for a disc laser

Abstract

A pump light assembly (1) for a disc laser comprises a focusing device including a concave mirror (2) configured to focus a pump light beam (5) onto an active medium (3) in the form of a laser disc arranged in a focus of the concave mirror (2). A deflecting device (4) disposed about a central axis (21) of the concave mirror (2) guides the pump light beam (5) along a multi-pass path by directing the pump light beam (5) between reflecting regions and deflecting regions (.1–.50). The deflecting device (4) comprises a plurality of planar mirror prisms (41) arranged on an outer circular line (42) and on at least one further circular line (43, 44) closer to the central axis (21). The reflecting regions direct the pump light beam (5) toward the concave mirror (2) via the active medium (3) to provide successive pump passes, and the deflecting regions redirect the pump light beam (5) to a subsequent region to maintain a predefined reflection sequence. The regions (.1–.50) are formed on the planar mirror prisms (41) and / or are realized by angled mirrors (45) configured for reflection and / or deflection, wherein the angled mirrors (45) are separate from each other and not part of the planar mirror prisms (41). The multi-line arrangement provides controlled optical path lengths and supports maintaining a desired pump beam focus distribution over multiple passes.

Description

Pump light assembly for a disc laserTechnical field

[0001] The present invention relates to optical pump systems for solid-state lasers, in particular thin- disc lasers and thin-disc amplifiers, more particularly multi-pass pump optics. It concerns a pump light assembly configured to focus pump radiation onto a laser-active disc and to guide the pump light in multiple passes by means of reflective and deflecting elements.Background art

[0002] It is known to provide pump light assemblies for disc lasers in which a focusing device, in particular a concave mirror, focuses a pump light beam onto a laser-active medium in the form of a laser disc. Such assemblies typically include a deflecting device comprising a plurality of reflective elements arranged around a central axis and configured to redirect the pump light beam such that the pump light beam is focused onto the laser disc in multiple successive pump passes.

[0003] Disc lasers are characterized by having a laser-active medium (amplifier medium) of low thickness, typically in the form of a laser disc, which can be efficiently cooled. This design is suitable for achieving high laser powers in the multi-kilowatt range. However, due to the low thickness of the amplifier medium, only a small amount of pump radiation is absorbed during a single pass through the laser-active medium. Without appropriate measures to ensure multiple passes of the pump radiation through the laser-active medium, the efficiency of the laser system would be low. To achieve the minimum energy or laser power required to sustain lasing in the laser-active medium, multiple passes of the pump light beam are generally necessary.

[0004] The technical problem addressed by the present invention is to reduce beam expansion caused by optical aberrations during multi-pass guidance of pump radiation between mirrors and an active medium. In particular, the invention aims to maintain a consistent pump spot size on the disc, focus, and intensity distribution on the laser-active medium over repeated passes.Summary of the Invention

[0005] In an embodiment, the present invention relates to a pump light assembly for a disc laser, preferably in particularforthin-disc laser oscillators and thin-disc amplifiers, as defined in claim 1. A pump beam is guided in a controlled multi-pass geometry to increase the pumping contribution delivered to a laserdisc while maintaining a compact optical layout. The assembly according to the present invention combines a focusing device for imaging pump light onto the laser disc with a deflecting device that guides the pump light beam through a defined sequence of reflections about a central axis.

[0006] The invention provides a pump light assembly for a disc laser comprising a focusing device with a concave mirror configured to focus a pump light beam onto a laser disc arranged in the focus, and a deflecting device that deflects the pump light beam between reflecting regions disposed about the central axis. The deflecting device includes planar mirror prisms arranged on an outer circular line and at least one further circular line closer to the central axis, whereineach prism includes reflecting regions that direct the pump light beam toward the concave mirror via the laser disc and deflecting regions that redirect the pump light beam so that it is guided along a sequence of reflections between the reflecting regions. The regions are formed on the prisms and / or by angled mirrors; the prisms on the outer circular line each provide three regions, while prisms on the further circular line each provide two regions in a two-line configuration or one region in a three-line configuration; and the angled mirrors providing reflection and / or deflection are separate from one another and not part of the planar mirror prisms.

[0007] The arrangement enables a compact multi-pass pump layout with reduced numbers of individually mounted mirror elements and reduced alignment degrees of freedom. The use of planar mirror prisms and separately positionable angled mirrors facilitates assembly and alignment while maintaining a defined beam routing sequence across the circular lines.

[0008] The focusing device comprises a concave mirror with a reflecting surface configured to focus pump radiation onto the laser disc. In an embodiment, the concave mirror may be a parabolic mirror, as commonly used in thin-disc laser and thin-disc amplifier pump optics, to provide well- defined imaging of the pump light into the disc region and to support repeated passes through the active medium with controlled beam geometry.

[0009] The active medium is provided in the form of a laser disc arranged at or near a focus of the concave mirror. The disc may comprise, by way of example, ytterbium-doped gain media such as Yb:YAG, Yb:LuAG, Yb:KGW, or Yb:KYW, and may also be with other rare-earth doped crystalline or ceramic materials suitable for thin-disc operation, depending on desired wavelength, thermal handling, and gain characteristics.

[0010] A pump light beam is directed such that it is focused by the concave mirror onto the laser disc and is repeatedly guided back through the disc along a sequence of reflections produced by the deflecting device. The repeated guidance causes multiple pump passes through the active medium, thereby increasing the total absorbed pump energy and the resulting population inversion. In this manner, the effective pumping contribution is increased over multiple passes, which correspondingly increases the achievable laser gain and amplification performance of the disc laser system, while distributing pump deposition in a controlled manner.

[0011] The deflecting device comprises a plurality of planar mirror prisms arranged about the central axis on an outer circular line and on at least one further circular line closer to the central axis. The planar mirror prisms provide planar reflective functionality in a compact arrangement and define discrete interaction locations for the pump light beam as it progresses circumferentially and radially through the reflection sequence. The planar mirror prism can be an optomechanical component providing one or more planar reflective surface portions, for example on different facets and / or coated areas, for reflection / deflection of the pump beam. Each planar mirror prism includes reflecting regions and deflecting regions, which are to be understood as functional regions that correspond to optical behavior imparted to the pump light beam at particular surface portions. The reflecting regions are configured to direct the pump light beam toward the concave mirror such that, on the path to and from the concave mirror, the beampasses via the laser disc. The deflecting regions are configured to redirect the pump light beam laterally so that it progresses to the next intended interaction location, thereby enforcing a predefined sequence of reflections between reflecting regions and enabling controlled multipass pumping. The functional regions may be formed on the planar mirror prisms, for example by providing different reflective surface portions, coatings, or segmented mirror facets that implement either the reflecting behavior or the deflecting behavior. Additionally or alternatively, one or more regions may be by angled mirrors that provide the required reflection and / or deflection at specified positions, thereby allowing the optical sequence to be implemented with a combination of prism surfaces and separate mirror elements.

[0012] The angled mirrors are separate from each other and are not part of the planar mirror prisms. This separation is structural and not merely conceptual: the angled mirrors are distinct optical components that can be positioned independently and set at respective angles selected to provide the correct reflection and / or deflection required by the intended pump-beam routing, including transitions between circular lines or between successive circumferential positions.

[0013] The outer circular line and the further circular line or lines closer to the central axis are geometric descriptors used to define where the planar mirror prisms and the functional regions are positioned in the deflecting device. These circular lines are therefore to be understood as abstract, coordinate-like loci around the central axis used to organize the optical routing and to define distinct radial “levels” of the reflection sequence, rather than as physical rings that must be present as separate parts.

[0014] In a preferred embodiment, the deflecting device comprises eight planar mirror prisms, providing a compact and highly segmented circumferential arrangement that supports a multipass reflection sequence around the central axis.

[0015] In a preferred embodiment, the deflecting device comprises six planar mirror prisms, enabling a reduced-component configuration while still maintaining a defined multi-pass pump routing about the central axis.

[0016] In a preferred embodiment, the deflecting device comprises four planar mirror prisms, enabling a further simplified configuration that remains capable of implementing a controlled reflection sequence across multiple circular lines.

[0017] In a preferred embodiment, the planar mirror prisms are arranged on two concentric circular lines, wherein the outer circular line of each planar mirror prism comprises three regions configured for reflection and / or deflection and the inner circular line of each planar mirror prism comprises two regions configured for reflection and / or deflection, thereby supporting both circumferential progression and controlled transitions within a two-line routing architecture.

[0018] In a preferred embodiment, the planar mirror prisms are arranged on three concentric circular lines, wherein the outer circular line of each planar mirror prism comprises three regions configured for reflection and / or deflection, a middle circular line comprises two regions configured for reflection and / or deflection, and an inner circular line comprises one region configured for reflection and / or deflection, thereby defining a three-level radial routing scheme.

[0019] In a preferred embodiment, the deflecting device guides the pump light beam such that the beam undergoes at least ten reflections at regions associated with the outer circular line and at least ten reflections at regions associated with the inner circular line or lines, thereby providing at least ten pump passes and corresponding pumping contributions in each of the outer and inner circular lines.

[0020] In a preferred embodiment, the deflecting device guides the pump light beam such that the beam undergoes at least twelve reflections at regions associated with the outer circular line and at least nine reflections at regions associated with the inner circular line or lines, thereby providing at least twelve pump passes and corresponding pumping contributions via the outer circular line and at least nine pump passes and corresponding pumping contributions via the inner circular line or lines.

[0021] In a preferred embodiment, the deflecting device guides the pump light beam in a reflection sequence in which the pump light beam is reflected three times at regions of a respective one of the circular lines and is then redirected to a next circular line, such that the pump light beam is reflected three times at regions of the outer circular line, redirected to the middle circular line for three reflections, redirected to the inner circular line for three reflections, redirected back to the middle circular line for three reflections, and then deflected to the outer circular line, thereby implementing a structured, repeating multi-line routing pattern.

[0022] In a preferred embodiment, the eight planar mirror prisms are arranged as neighboring planar mirror prisms along a circumferential direction such that adjacent planar mirror prisms are disposed next to each other without an intervening planar mirror prism, and mirror sections formed by the angled mirrors are likewise arranged as neighboring mirror sections along the circumferential direction, thereby supporting a dense and orderly circumferential routing layout.

[0023] In a preferred embodiment, the six planar mirror prisms are arranged non-symmetrically about the central axis such that the arrangement lacks axial symmetry by circumferentially shifting at least one planar mirror prism with respect to an axially symmetric arrangement, and the angled mirrors are likewise circumferentially shifted with respect to corresponding axially symmetric positions by one circumferential position, thereby enabling a deliberately asymmetric routing pattern where beneficial for packaging, beam separation, or routing constraints.

[0024] In a preferred embodiment, the four planar mirror prisms are arranged as neighboring planar mirror prisms along the circumferential direction such that adjacent planar mirror prisms are disposed next to each other without an intervening planar mirror prism, thereby providing a compact four-prism circumferential configuration.Brief description of drawingsFig. 1A represents a schematic view of embodiment of first embodiment of the present invention, in particular distribution on reflecting and deflection regions in the assembly according to the present invention.Fig. 1 B represents a model of segmented assembly according to the first embodiment of the present invention.Fig. 2A represents a schematic view of embodiment of second embodiment of the present invention, in particular distribution on reflecting and deflection regions in the assembly according to the present invention.Fig. 2B represents a model of segmented assembly according to the second embodiment of the present invention.Fig. 3A represents a schematic view of embodiment of third embodiment of the present invention, in particular distribution on reflecting and deflection regions in the assembly according to the present invention.Fig. 3B represents a model of segmented assembly according to the third embodiment of the present invention.Fig. 4A, 4B, 4C schematically illustrates the assembly according to the present invention with isometric, top and cross-section view.Detailed description

[0025] In an embodiment, a pump light assembly 1 for a disc laser is provided. The pump light assembly 1 is configured to couple pump radiation into an active medium 3 in the form of a laser disc and to guide a pump light beam 5 in a controlled multi-pass reflection sequence, thereby increasing the number of pump passes through the active medium 3 and improving pumping efficiency and gain generation in thin-disc laser or thin-disc amplifier systems.

[0026] The pump light assembly 1 comprises a focusing device and a deflecting device 4. The focusing device is centered on a concave mirror 2 having a reflecting surface, and the deflecting device 4 is arranged upstream of the concave mirror 2 (relative to the propagation direction of the pump light beam 5) such that it repeatedly directs the pump light beam 5 toward the concave mirror 2 and provides redirection steps that advance the pump light beam 5 through a predetermined sequence of reflection points. A central axis 21 is defined by the concave mirror 2 (and / or by the overall rotational symmetry of the optical layout). The deflecting device 4 is disposed about the central axis 21 and provides reflection and deflection functions at a plurality of locations arranged circumferentially around the central axis 21.

[0027] The concave mirror 2 is configured to focus the pump light beam 5 onto the active medium 3. In the described embodiment, the concave mirror 2 comprises a reflective surface shaped to image the pump light beam 5 to a focus region in which the laser disc forming the active medium 3 is arranged. The concave mirror 2 may be realized as a parabolic mirror or another suitable concave imaging element used in thin-disc laser pumping optics. The concave mirror 2 is selected and positioned such that, for each incidence of the pump light beam 5 directed toward the concave mirror 2, the pump light beam 5 is focused into the region of the active medium 3, passes the active medium 3, and then returns toward the deflecting device 4 in a manner consistent with the intended multi-pass routing.

[0028] The active medium 3 is configured as a laser disc. The laser disc is arranged in the focus of the concave mirror 2, i.e., at a location where the pump light beam 5 reaches a desired spotsize and intensity distribution for efficient pumping. The active medium 3 may be a thin-disc gain element, for example a rare-earth doped crystalline or ceramic disc, such as an ytterbium- doped medium. The disc may be mounted on a heat sink (not shown) and may be oriented perpendicular or substantially perpendicular to the central axis 21 , depending on the optical path configuration. In the described embodiment, the pump light beam 5 is arranged to be incident on the active medium 3 in a manner that enables repeated pump passes, with each pass contributing to absorption in the active medium 3 and to the generation of population inversion.

[0029] The deflecting device 4 is configured to deflect the pump light beam 5 between reflecting regions disposed about the central axis 21. To this end, the deflecting device 4 comprises a plurality of planar mirror prisms 41 arranged about the central axis 21 .

[0030] The planar mirror prisms 41 are arranged on an outer circular line 42 and on at least one further circular line 43, 44 closer to the central axis 21. The outer circular line 42 defines a radially outer ring-like locus of interaction positions, whereas the at least one further circular line 43, 44 defines one or more radially inner loci. In the embodiment of claim 1 , the planar mirror prisms 41 are distributed circumferentially along these circular lines such that the pump light beam 5 can be guided successively from one prism location to the next while remaining within an overall compact footprint around the central axis 21.

[0031] The term “circular line” is used to designate the placement locus of optical interaction regions rather than necessarily indicating a physical ring component. Accordingly, the outer circular line 42 and the further circular line(s) 43, 44 may be implemented by positioning the planar mirror prisms 41 and / or regions thereof at radii corresponding to these lines.

[0032] Each planar mirror prism 41 comprises reflecting regions and deflecting regions .1 to .50. These regions correspond to surface portions that are configured to impart distinct optical functions to the pump light beam 5.

[0033] Reflecting regions are configured to direct the pump light beam 5 toward the concave mirror 2 such that the beam propagates to the concave mirror 2 and, on that path, is routed via the active medium 3. In otherwords, upon interaction with a reflecting region, the pump light beam 5 is launched into a “pump pass” direction toward the concave mirror 2, with the active medium 3 positioned such that the pump light beam 5 impinges on and passes through the active medium 3 before and / or after being reflected by the concave mirror 2, depending on the optical folding geometry. Deflecting regions are configured to redirect the pump light beam 5 laterally or angularly such that the beam advances to a next designated region in the sequence. Thus, the deflecting regions provide the “handoff’ of the pump light beam 5 between successive reflection points, for example from one region to another region on the same circular line or from a region on one circular line to a region on another circular line. The deflecting device 4 is configured such that, by alternating between interactions with reflecting regions and deflecting regions, the pump light beam 5 is guided along a sequence of reflections between said reflecting regions. In a practical routing scheme, the pump light beam 5 is repeatedly: (i) directed by a reflecting region toward the concave mirror 2, (ii) focused by the concave mirror2 onto the active medium 3, and (iii) returned from the concave mirror 2 to the deflecting device 4, where it is redirected by a deflecting region to a subsequent reflecting region. This controlled sequence results in multiple pump passes through the active medium 3.

[0034] The regions .1 to .50 are formed on the planar mirror prisms 41 and / or realized by angled mirrors 45. In a first implementation variant, the planar mirror prisms 41 may comprise segmented mirror surfaces, different coating sections, or physically distinct planar facets forming the reflecting regions and the deflecting regions. In such a configuration, the planar mirror prism 41 itself provides both the reflecting functionality (directing the pump light beam 5 toward the concave mirror 2) and the deflecting functionality (redirecting the pump light beam 5 to the next region). In an alternative or additional implementation variant, at least part of the deflection and / or reflection is realized by angled mirrors 45 positioned adjacent to the planar mirror prisms 41. The angled mirrors 45 provide defined mirror angles that implement the required change in propagation direction of the pump light beam 5 for either (i) handing the beam off circumferentially to a neighboring region or (ii) transitioning the beam between the outer circular line 42 and the further circular line(s) 43, 44.

[0035] The angled mirrors 45 are separate from each other and are not part of the planar mirror prisms 41. This feature provides a structural separation that allows the angled mirrors 45 to be positioned and aligned independently of the planar mirror prisms 41 . As a result, the angular orientation of each angled mirror 45 can be selected to provide a specific reflection or deflection angle required by the routing design, independently of the geometry of the planar mirror prisms 41. This separation is particularly advantageous where the desired routing requires deflection angles that are not conveniently achieved solely by segmenting a prism surface, or where additional degrees of freedom in alignment are needed to compensate manufacturing tolerances, to optimize beam overlap on the active medium 3, or to enforce spatial separation between successive beam segments.

[0036] In the embodiment of claim 1 , the planar mirror prisms 41 arranged on the outer circular line 42 each comprise three regions configured for reflection and / or deflection of the pump light beam 5. This means that each such prism provides three functional surface portions (selected among the regions .1 to .50) that are used by the pump light beam 5 in the reflection sequence. For example, two of the regions may serve as reflecting regions that launch the pump light beam 5 toward the concave mirror 2, while one region may serve as a deflecting region that advances the beam to a subsequent interaction location, or other allocations may be used depending on the desired sequence. The planar mirror prisms 41 arranged on the further circular line(s) 43, 44 closer to the central axis 21 each comprise two regions configured for reflection and / or deflection in a configuration with two concentric circular lines, or one region configured for reflection and / or deflection in a configuration with three concentric circular lines. Accordingly, for a two-line architecture the inner prism positions provide two functional regions to support both reflecting and deflecting actions at the inner radius, whereas for a three-line architecture the innermost prism positions may provide a single functional region because therouting can be structured such that only one interaction per prism is required at that radius before the beam is transitioned outward again.

[0037] In operation, the pump light beam 5 is introduced into the pump light assembly 1 and is incident on a first region of a planar mirror prism 41 located on the outer circular line 42. This region may be a reflecting region that directs the pump light beam 5 toward the concave mirror 2. The concave mirror 2 then focuses the pump light beam 5 onto the active medium 3, where at least a portion of the pump radiation is absorbed. After interaction with the concave mirror 2 and passage via the active medium 3, the pump light beam 5 returns to the deflecting device 4 and impinges on a deflecting region, which redirects the pump light beam 5 toward a subsequent reflecting region on a next planar mirror prism 41 arranged circumferentially about the central axis 21 . By repeating this process, the pump light beam 5 is guided around the central axis 21 through successive interaction points associated with regions .1 to .50, and is repeatedly directed via the concave mirror 2 and the active medium 3. The number of effective pump passes is thereby increased, which increases the total pumping contribution delivered to the active medium 3 for a given pump source.

[0038] The described embodiment provides a compact and scalable approach for implementing multipass pumping for a disc laser. Arranging planar mirror prisms 41 along the outer circular line 42 and at least one further circular line 43, 44 enables a dense packing of interaction locations, while the option to realize regions either on the prisms 41 or via separate angled mirrors 45 provides design flexibility in achieving desired beam routing, angular constraints, and manufacturing tolerances. The separation of angled mirrors 45 from the planar mirror prisms 41 further permits independent alignment and facilitates accurate setting of the reflection and deflection angles, which supports stable multi-pass guidance of the pump light beam 5 and reproducible focusing onto the active medium 3.

[0039] An example relates to a pump light assembly 1 for a disc laser, schematically illustrated in Figure 1A. The pump light assembly 1 comprises a focusing device having a concave mirror 2 with a reflecting surface configured to focus a pump light beam 5 onto an active medium 3 in the form of a laser disc. The active medium 3 is arranged in the focal region of the concave mirror 2, such that pump radiation directed toward the concave mirror 2 is focused onto the active medium 3 to provide a pump pass. A deflecting device 4 is disposed about a central axis 21 of the concave mirror 2 and is configured to guide the pump light beam 5 between a plurality of regions .1- 50 arranged circumferentially around the central axis 21.

[0040] In the embodiment of Figure 1A, the regions .1- 50 are positioned on two concentric circular lines, namely an outer circular line 42 and an inner circular line 43 located closer to the central axis 21. The regions .1- 50 represent functional areas of the deflecting device 4 at which the pump light beam 5 is either (i) directed toward the concave mirror 2 such that it propagates via the active medium 3 (reflecting function) or (ii) redirected to another region .1- 50 (deflecting function). In this way, the deflecting device 4 establishes a defined sequence of beam directions that repeatedly returns the pump light beam 5 to the concave mirror 2 and the activemedium 3 while advancing the beam circumferentially and / or radially between successive regions.

[0041] The deflecting device 4 may be configured to provide different optical path lengths between successive pump passes, for example by alternating interactions on the outer circular line 42 and the inner circular line 43 and / or by selecting different circumferential “jump” distances between regions .1- 50. Such variation of the optical path and imaging conditions can be used to compensate, at least in part, for beam expansion or spot-size changes arising from aberrations of the focusing device, thereby supporting repeatable focusing of the pump light beam 5 onto the active medium 3 over a large number of pump passes.

[0042] In the illustrated example, the pump light beam 5 is guided along a predetermined region sequence that includes a first series of interactions on the outer circular line 42, a second series of interactions on the inner circular line 43, and a final series of interactions again on the outer circular line 42. By way of example, the pump light beam 5 is first guided through regions .1- 10 on the outer circular line 42. At selected ones of these regions, the pump light beam 5 is directed toward the concave mirror 2 and focused onto the active medium 3, thereby providing successive pump passes; between such pump-pass directions, the pump light beam 5 is redirected to a next region on the deflecting device 4.

[0043] After the outer-line sequence, the pump light beam 5 is redirected from the outer circular line 42 to the inner circular line 43, for example from region .10 to region .11 , and is then guided through a further sequence of regions .11- 30 on the inner circular line 43. In this inner-line sequence, the same functional alternation is implemented: reflecting functions direct the pump light beam 5 toward the concave mirror 2 via the active medium 3 to provide additional pump passes, while deflecting functions advance the pump light beam 5 to subsequent regions on the inner circular line 43.

[0044] Following completion of the inner-line sequence, the pump light beam 5 is redirected back from the inner circular line 43 to the outer circular line 42, for example to region .31 , and is guided through a further series of regions .31- 50. Accordingly, the pump light beam 5 is routed such that it repeatedly impinges on the active medium 3 as focused by the concave mirror 2, while the deflecting device 4 steps the beam through the overall sequence until a predetermined number of passes and a desired pump distribution are achieved.

[0045] In the embodiment schematically indicated by the radial dividing lines in Figure 1A, the regions .1- 50 can be viewed as grouped into ten circumferential segments, each segment containing five regions. In each segment, three regions lie on the outer circular line 42 and two regions lie on the inner circular line 43. The pump light beam 5 can be guided segment-by-segment such that, within a segment, a transition between the outer circular line 42 and the inner circular line 43 is performed when required by the routing design, while circumferential progression is implemented by redirection to a neighboring segment.

[0046] The regions .1- 50 are realized by a plurality of planar mirror prisms 41 of the deflecting device 4 and / or by angled mirrors 45. In particular, the planar mirror prisms 41 provide surface portions that implement reflecting functions (launching the pump light beam 5 toward theconcave mirror 2 via the active medium 3) and deflecting functions (redirecting the pump light beam 5 toward a next region). In addition, angled mirrors 45, which are separate components and not part of the planar mirror prisms 41 , may be positioned and angled to implement certain redirections and / or to provide transitions between the outer circular line 42 and the inner circular line 43 with the required angular precision.

[0047] The active medium 3, arranged centrally with respect to the deflecting device 4 and in the focal region of the concave mirror 2, receives the focused pump light beam 5 during each pumppass direction. The repeated guidance of the pump light beam 5 via the active medium 3 increases the number of pump passes and thus increases the total pump energy delivered to and absorbed in the active medium 3, which in turn supports efficient operation of the disc laser and, in amplifier implementations, contributes to high achievable gain.

[0048] Figure 1 A therefore illustrates an example of a compact multi-pass pump routing in which the deflecting device 4 distributes a pump light beam 5 across a plurality of circumferentially arranged regions .1- 50 on two concentric circular lines 42, 43, and repeatedly directs the pump light beam 5 toward a concave mirror 2 for focusing onto a laser disc forming the active medium 3. This configuration enables a high number of pump passes while maintaining a controlled beam routing geometry and alignment-friendly implementation using planar mirror prisms 41 and, where required, separate angled mirrors 45.

[0049] Figure 1 B shows a schematic three-dimensional representation of a first embodiment of the pump light assembly 1. The deflecting device 4 is arranged around the central axis 21 in a plurality of circumferential segments. In the illustrated example, the arrangement is divided into ten segments, of which a majority are implemented by planar mirror prisms 41 , while remaining segment positions include regions realized by separate angled mirrors 45. The model illustrates that the functional regions .1- 50 are distributed on an outer circular line 42 and on an inner circular line 43 closer to the central axis 21.

[0050] Each segment provides reflecting regions and deflecting regions for guiding the pump light beam 5. The planar mirror prisms 41 are oriented at defined angles relative to one another so that selected surface portions provide reflection of the pump light beam 5 toward the concave mirror 2 (and thus via the active medium 3) and other surface portions provide deflection of the pump light beam 5 to a subsequent region in the routing sequence. The angled mirrors 45, where present, are separate components and are positioned and angled to provide additional reflection and / or deflection functions, in particular for controlled transitions between neighboring regions and / or between the circular lines 42, 43.

[0051] In Figure 1 B, one initial reflecting element is intentionally omitted. This omission serves to make the entry path of the pump light beam 5 visually accessible, namely the approach of the pump light beam 5 into the deflecting device 4 before the beam reaches the first region of the defined reflection / deflection sequence.

[0052] Figure 2A illustrates a further embodiment of a pump light assembly 1 for a disc laser. The pump light assembly 1 comprises a focusing device with a concave mirror 2 having a reflecting surface configured to focus a pump light beam 5 onto an active medium 3 formed as a laserdisc. The active medium 3 is arranged in the focal region of the concave mirror 2. A deflecting device 4 is disposed about a central axis 21 of the concave mirror 2 and is configured to guide the pump light beam 5 along a predetermined multi-pass routing.

[0053] In the embodiment of Figure 2A, the deflecting device 4 provides a plurality of regions .1- 40 arranged circumferentially about the central axis 21 on two concentric circular lines, namely an outer circular line 42 and an inner circular line 43 located closer to the central axis 21 . The regions .1- 40 are realized on planar mirror prisms 41 and / or by angled mirrors 45 (not shown in Figure 2A), and are configured such that, depending on the respective region, the pump light beam 5 is either (i) directed toward the concave mirror 2 such that it is focused onto the active medium 3 (pump pass), or (ii) redirected to a subsequent region .1- 40 to advance the beam along the routing sequence.

[0054] The redirection sequence of the pump light beam 5 in Figure 2A is defined by the order of the numbered regions and proceeds as follows. The pump light beam 5 enters the deflecting device 4 and is guided to region .1 on the outer circular line 42. From region .1 , the pump light beam 5 is redirected to region .2, from region .2 to region .3, and from region .3 to region .4. The pump light beam 5 continues along the outer circular line 42 in the same manner through the consecutive regions .5, .6, .7, .8, .9, .10, .11 , .12, .13, .14, .15, and .16. During this outerline sequence, the deflecting device 4 is configured such that selected ones of the regions .1- .16 direct the pump light beam 5 toward the concave mirror 2 so that the pump light beam 5 is focused onto the active medium 3, while other ones of the regions provide lateral redirection to the next region of the sequence.

[0055] After reaching region .16 on the outer circular line 42, the pump light beam 5 is redirected from the outer circular line 42 to the inner circular line 43, namely from region .16 to region .17. The pump light beam 5 is then guided on the inner circular line 43 through the consecutive regions .17 — .18 — .19 — .20 — .21 — .22 — .23 — .24 — .25 — .26 — .27 — .28 — .29 — .30 — .31 .32. As on the outer circular line 42, the regions on the inner circular line 43 are configured such that, at selected regions, the pump light beam 5 is directed toward the concave mirror 2 and focused onto the active medium 3 to provide further pump passes, whereas at other regions the pump light beam 5 is redirected to advance to the next region on the inner circular line 43.

[0056] Upon completion of the inner-line sequence at region .32, the pump light beam 5 is redirected back to the outer circular line 42, namely from region .32 to region .33, and is then guided through the final outer-line sequence .33 .34 .35 .36 .37 .38 .39 .40. After region .40, the pump light beam 5 is output-coupled from the deflecting device 4, for example toward a beam dump or for further optical use depending on the system design.

[0057] In the embodiment shown, the regions .1-.40 can be arranged in eight circumferential segments (as indicated by the radial dividing lines), each segment including five regions, with three regions positioned on the outer circular line 42 and two regions positioned on the inner circular line 43. The transitions between the outer circular line 42 and the inner circular line 43 — in particular the redirections .16 .17 and .32 .33 — are implemented by correspondingregion geometries on the planar mirror prisms 41 and / or by separate angled mirrors 45, which provide the required deflection angles for changing the beam radius while maintaining the intended progression of the sequence.

[0058] The dashed beam indications in Figure 2A schematically illustrate that, when a region is configured as a reflecting region in the sense of claim 1 , the pump light beam 5 is directed toward the central region of the assembly (along a chord passing close to the central axis 21) toward the concave mirror 2, is focused by the concave mirror 2 onto the active medium 3, and then returns to the deflecting device 4 for subsequent redirection to the next region of the sequence.

[0059] Accordingly, the embodiment of Figure 2A implements a defined multi-pass pump routing in which the pump light beam 5 is redirected in a fixed order across regions .1- 40, including a first portion on the outer circular line 42, a second portion on the inner circular line 43, and a final portion again on the outer circular line 42, thereby repeatedly delivering pump radiation to the active medium 3 while maintaining a compact arrangement about the central axis 21 .

[0060] The use of planar mirror prisms 41 and / or separate angled mirrors 45 for forming the regions .1- 40 enables the redirection angles between successive regions to be set precisely. This supports stable guidance of the pump light beam 5 through the full sequence and repeatable focusing of the pump light beam 5 onto the active medium 3 for the intended number of pump passes.

[0061] The described routing therefore increases the cumulative pump energy incident on and absorbed in the active medium 3 compared with a single-pass pump arrangement, while permitting the redirection sequence to be implemented in a segmented, alignment-friendly geometry around the central axis 21.

[0062] Figure 2B shows a schematic three-dimensional representation of a further embodiment of the pump light assembly 1. The deflecting device 4 is arranged about the central axis 21 in eight circumferential segments. Each segment comprises optical elements providing reflecting and deflecting functions, implemented by planar mirror prisms 41 and / or by separate angled mirrors 45, so as to guide the pump light beam 5 along the predetermined routing. The arrangement illustrates the distribution of functional regions on an outer circular line 42 and an inner circular line 43 closer to the central axis 21 .

[0063] In Figure 2B, two segments are depicted with increased detail to illustrate the local structure of the deflecting device 4. In these segments, selected surfaces act as reflecting regions that direct the pump light beam 5 toward the concave mirror 2 such that it is focused onto the active medium 3, while other surfaces act as deflecting regions that redirect the pump light beam 5 to subsequent regions in the sequence. The shown geometry therefore illustrates how each segment contributes to both (i) launching the pump light beam 5 toward the focusing device for a pump pass through the active medium 3, and (ii) advancing the pump light beam 5 circumferentially and / or radially to the next segment.

[0064] One initial reflecting element is intentionally omitted in the schematic of Figure 2B. This omission is provided to make the entry path of the pump light beam 5 visible, namely thetrajectory of the pump light beam 5 as it enters the deflecting device 4 before the pump light beam 5 reaches the first region of the defined reflection / deflection sequence.

[0065] Figure 3A illustrates a further embodiment of a pump light assembly 1 for a disc laser. The pump light assembly 1 comprises a focusing device with a concave mirror 2 having a reflecting surface configured to focus a pump light beam 5 onto an active medium 3 formed as a laser disc. The active medium 3 is arranged in the focal region of the concave mirror 2. A deflecting device 4 is disposed about a central axis 21 of the concave mirror 2 and is configured to guide the pump light beam 5 between a plurality of regions .1- 36 arranged around the central axis 21.

[0066] In the embodiment of Figure 3A, the regions .1-.36 are distributed on three concentric circular lines, namely an outer circular line 42, a middle circular line 44, and an inner circular line 43 closest to the central axis 21 . The regions .1- 36 are realized by planar mirror prisms 41 and / or by separate angled mirrors 45 (not shown in Figure 3A). Each region .1- 36 provides either a reflecting function (directing the pump light beam 5 toward the concave mirror 2 such that it is focused onto the active medium 3) or a deflecting function (redirecting the pump light beam 5 to a subsequent region of the sequence). By selecting the respective redirection angles and the radii associated with the circular lines 42, 44, 43, different optical path lengths between pump passes can be provided, which may support compensation of beam expansion and / or imaging deviations caused by aberrations of the concave mirror 2.

[0067] The redirection sequence of the pump light beam 5 in Figure 3A starts at the outer circular line 42. The pump light beam 5 is guided to region .1 and is then redirected consecutively along the outer circular line 42 according to the following order: .1 .2 .3 .4 .5 .6. During this outer-line portion, selected ones of the regions .1- 6 act as reflecting regions to direct the pump light beam 5 toward the concave mirror 2 for focusing onto the active medium 3, while the remaining ones act as deflecting regions to advance the pump light beam 5 to the next region of the sequence.

[0068] After reaching region .6 on the outer circular line 42, the pump light beam 5 is redirected radially inward to the middle circular line 44, namely from region .6 to region .7. The pump light beam 5 is then guided along the middle circular line 44 through the consecutive regions .7 .8 .9 .10 .11 .12. Also in this portion, selected regions direct the pump light beam5 toward the concave mirror 2 via the active medium 3 to provide pump passes, and intervening regions redirect the pump light beam 5 to maintain the predetermined sequence.

[0069] From region .12 on the middle circular line 44, the pump light beam 5 is redirected further radially inward to the inner circular line 43, namely to region .13. The pump light beam 5 then proceeds along the inner circular line 43 through the consecutive regions .13 .14 .15.16 .17 .18. In this inner-line portion, the deflecting device 4 likewise alternates between directing the pump light beam 5 toward the concave mirror 2 (thereby producing further pump passes through the active medium 3) and redirecting the pump light beam 5 to the next region of the inner-line sequence.

[0070] After the inner-line portion is completed at region .18, the pump light beam 5 is redirected outward from the inner circular line 43 to the middle circular line 44, namely from region .18 to region .19. The pump light beam 5 then continues along the middle circular line 44 through the consecutive regions .19 .20 .21 .22 .23 .24. After reaching region .24, the pump light beam 5 is redirected further outward to the outer circular line 42, namely from region .24 to region .25.

[0071] The pump light beam 5 subsequently completes a final outer-line portion on the outer circular line 42 by proceeding through the regions .25 .26 .27 .28 .29 .30 .31 .32.33 .34 .35 .36. After region .36, the pump light beam 5 is output-coupled from the deflecting device 4, for example to a beam dump or to further optical components, depending on the system configuration.

[0072] In the illustrated embodiment, the regions .1- 36 can be grouped into six circumferential segments (as indicated by the radial dividing lines). Each segment includes six regions, with three regions on the outer circular line 42, two regions on the middle circular line 44, and one region on the inner circular line 43. The deflecting device 4 is configured such that circumferential progression is achieved by redirection to the next region and / or next segment, while radial transitions between circular lines occur at defined transition points, specifically .6 .7 (outer-to-middle), .12 .13 (middle-to-inner), .18 .19 (inner-to-middle), and .24 .25(middle-to-outer).

[0073] The dashed beam indications in Figure 3A schematically represent that, at regions configured as reflecting regions in the sense of claim 1 , the pump light beam 5 is launched toward the concave mirror 2 along a chord passing near the central axis 21 , is focused by the concave mirror 2 onto the active medium 3, and returns to the deflecting device 4 for subsequent redirection to the next region of the sequence.

[0074] Figure 3B shows a schematic three-dimensional representation of an embodiment of the pump light assembly 1. The deflecting device 4 is arranged about the central axis 21 in six circumferential segments. Each segment comprises optical elements providing reflecting and deflecting functions, which are implemented by planar mirror prisms 41 and / or by separate angled mirrors 45. The arrangement illustrates that the functional regions are distributed on an outer circular line 42, a middle circular line 44, and an inner circular line 43 closest to the central axis 21 , thereby forming a structured three-line routing geometry around the central axis 21.

[0075] Two segments are shown in increased detail in Figure 3B to illustrate the local structure of the deflecting device 4. In these segments, selected surface portions form reflecting regions configured to direct the pump light beam 5 toward the concave mirror 2 such that the pump light beam 5 is focused onto the active medium 3 to provide a pump pass. Other surface portions form deflecting regions configured to redirect the pump light beam 5 to subsequent regions in the routing sequence, including circumferential progression to a neighboring segment and, where required, radial transitions between the circular lines 42, 44, 43.

[0076] One initial reflecting element is intentionally omitted in the schematic of Figure 3B. This omission is provided to make the entry path of the pump light beam 5 visible, namely the trajectory of the pump light beam 5 as it enters the deflecting device 4 prior to reaching the first region of the defined reflection / deflection sequence.

[0077] Figure 4A is an isometric view of the pump light assembly 1 showing the interaction of the pump light source with the focusing and deflecting components. A pump light beam 5 emitted by a pump laser source is directed toward the concave mirror 2, which in a preferred implementation is configured as a parabolic mirror. The concave mirror 2 focuses the pump light beam 5 into the central region of the assembly onto the active medium 3, and the deflecting device 4 redirects the returning pump light beam 5 between the regions on the circular lines 42, 44, 43 so as to generate the predetermined multi-pass routing described with reference to Figures 3A and 3B.

[0078] Figure 4B shows a three-dimensional top view of the pump light assembly 1 , illustrating the circumferential arrangement of the segments around the central axis 21 and the relative placement of the planar mirror prisms 41 and, where provided, angled mirrors 45. This view highlights the compact geometry by which the deflecting device 4 guides the pump light beam 5 between successive regions while maintaining clear access to the central optical path toward the concave mirror 2 and the active medium 3.

[0079] Figure 4C shows a cross-sectional view of the pump light assembly 1. The cross-section illustrates the axial arrangement of the concave mirror 2, the active medium 3 located in the focal region, and the deflecting device 4 arranged around the central axis 21 . The view further indicates how the pump light beam 5 is directed from the deflecting device 4 toward the concave mirror 2, focused onto the active medium 3, and returned for subsequent redirection, thereby implementing multiple pump passes while maintaining the intended focusing and routing geometry across the outer circular line 42, the middle circular line 44, and the inner circular line 43.

Claims

Claims1 . A pump light assembly (1) for a disc laser, comprising:• a focusing device comprising a concave mirror (2) having a reflecting surface for focusing a pump light beam onto an active medium (3) in the form of a laser disc arranged in a focus of the concave mirror (2); and• a deflecting device (4) for deflecting the pump light beam (5) between reflecting regions of the deflecting device (4) disposed about a central axis (21) ofthe concave mirror (2), wherein• the deflecting device (4) comprises a plurality of planar mirror prisms (41) arranged about the central axis on an outer circular line (42) and on at least one further circular line (43, 44) closer to the central axis (21), and wherein• each planar mirror prism (41) comprises reflecting regions and deflecting regions (.1 - .50), wherein the reflecting regions being configured to direct the pump light beam (5) towards the concave mirror (2) via the active medium (3) and the deflecting regions being configured to redirect the pump light beam (5), such that the pump light beam (5) is guided along a sequence of reflections between said reflecting regions; and wherein• the regions (.1 - .50) are formed on the planar mirror prisms (41) and / or realized by angled mirrors (45); and wherein• the planar mirror prisms (41) are arranged on the outer circular line (42) each comprise three regions configured for reflection and / or deflection of the pump light beam; and wherein• the planar mirror prisms (41) are arranged on the further circular line (43, 44) closer to the central axis (21) each comprise two regions configured for reflection and / or deflection in a configuration with two concentric circular lines, or one region configured for reflection and / or deflection in a configuration with three concentric circular lines; and• the angled mirrors (45) are configured to provide reflection and / or deflection of the pump light beam, wherein the angled mirrors (45) are separate from each other and not part of the planar mirror prisms (41).

2. The pump light assembly (1) according to claim 1 , wherein the deflecting device (4) comprises eight planar mirror prisms (41).

3. The pump light assembly (1) according to claim 1 , wherein the deflecting device (4) comprises six planar mirror prisms (41).

4. The pump light assembly (1) according to claim 1 , wherein the deflecting device (4) comprises four planar mirror prisms (41).

5. The pump light assembly (1) according to claim 2 or claim 3, wherein the planar mirror prisms (41) are arranged on two concentric circular lines (42, 43), and wherein the outer circular line (42) of each planar mirror prism (41) comprises three regions configured for reflection and / or deflection and the inner circular line (43) of each planar mirror prism (41) comprises two regions configured for reflection and / or deflection.

6. The pump light assembly (1) according to claim 4, wherein the planar mirror prisms (41) are arranged on three concentric circular lines, and wherein the outer circular line of each planar mirror prism (41) comprises three regions configured for reflection and / or deflection, a middle circular line (42) of each planar mirror prism (41) comprises two regions configured for reflection and / or deflection, and an inner circular line (43) of each planar mirror prism (41) comprises one region configured for reflection and / or deflection.

7. The pump light assembly (1) according to claim 2, wherein the deflecting device (4) is configured to guide the pump light beam (5) such that the pump light beam (5) undergoes at least ten reflections at regions of the outer circular line (42) and at least ten reflections at regions of the inner circular line (43, 44), thereby providing at least ten pump passes and pumping contributions in each of the outer and inner circular lines (42, 43, 44).

8. The pump light assembly (1) according to claim 3, wherein the deflecting device (4) is configured to guide the pump light beam (5) such that the pump light beam (5) undergoes at least twelve reflections at regions of the outer circular line (42) and at least nine reflections at regions of the inner circular line (43, 44), thereby providing at least twelve pump passes and pumping contributions via the outer circular line (42) and at least nine pump passes and pumping contributions via the inner circular line (43, 44).

9. The pump light assembly (1) according to claim 4, wherein the deflecting device (4) is configured to guide the pump light beam (5) in a reflection sequence in which the pump light beam (5) is reflected three times at regions of a respective one of the circular lines and is then redirected to a next circular line, such that the pump light beam (5) is reflected three times at regions of the outer circular line, is redirected to the middle circular line where it is reflected three times, is redirected to the inner circular line (43, 44) where it is reflected three times, is redirected back to the middle circular line where it is reflected three times, and is then deflected to the outer circular line (42).

10. The pump light assembly (1) according to claim 2, wherein the eight planar mirror prisms (41) are arranged as neighboring planar mirror prisms (41) along the circumferential direction such that adjacent planar mirror prisms (41) are disposed next to each other without an intervening planar mirror prism, and wherein mirror sections formed by the angled mirrors (45) are likewise arranged as neighboring mirror sections along the circumferential direction.11 . The pump light assembly (1) according to claim 3, wherein the six planar mirror prisms (41) are arranged non-symmetrically about the central axis such that the arrangement lacks axial symmetry, by circumferentially shifting at least one planar mirror prism with respect to an axially symmetric arrangement, and wherein the angled mirrors (45) are likewise circumferentially shifted with respect to corresponding axially symmetric positions by one circumferential position.

12. The pump light assembly (1) according to claim 4, wherein the four planar mirror prisms (41) are arranged as neighboring planar mirror prisms (41) along the circumferential direction such that adjacent planar mirror prisms (41) are disposed next to each other without an intervening planar mirror prism.

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