Solid body laser enhancement system and solid body laser

Description

[0001] The present invention relates to a disk- or cuboid-shaped solid body containing at least one laser-active material for a laser amplification system.

[0002] Furthermore, the present invention relates to a laser amplification system comprising at least one disk- or cuboid-shaped solid body.

[0003] Furthermore, the present invention relates to a solid-state laser comprising a laser amplification system.

[0004] Solids of the type described above, which can be classified as flat and are used particularly in disk lasers and disk amplifiers, offer several technical advantages over the use of a three-dimensional medium. Thermal management is particularly noteworthy here.

[0005] However, the length or thickness of such a flat laser-active medium, formed by the disk- or cuboid-shaped solid, is not sufficient to ensure the full conversion of the energy stored in the solid into a laser beam in a single beam pass through the solid, which is partially optically transparent to the laser beam. This also applies to a pump laser beam or a pump laser radiation field used to excite the laser-active material in the solid. To provide a practical, efficient system, it is therefore necessary to extend an optical path in the laser-active medium using additional tools.

[0006] One possibility is to achieve a high number of passes of a radiation field in the solid state of a disk laser via the Q factor of the laser's resonator. In this case, the pump laser radiation field is reflected back onto the solid state multiple times using a mirror arrangement to ensure sufficiently high absorption.

[0007] In laser amplification systems that operate with a disk- or cuboid-shaped solid containing at least one laser-active material, the described principle, by which the pump radiation field is repeatedly reflected back onto the solid, is transferred to the already amplified laser beam or laser radiation field in order to achieve sufficiently high amplification. In turn, a mirror arrangement images the laser radiation field multiple times onto the disk- or cuboid-shaped solid in order to achieve further amplification with each subsequent imaging and each subsequent pass through the solid. Here, too, considerable effort is required in connection with the construction of the mirror arrangement. This also requires a significant amount of space and is also significantly lightweight, which is particularly disadvantageous for applications in space.

[0008] Laser amplification systems comprising at least one disk-shaped or cuboid-shaped solid body are known, for example, from DE 43 44 227 A1 and DE 198 35 107 A1.

[0009] To increase the interaction length for the radiation field passing through the solid, so-called slab lasers or slab amplifiers are known. In these, the radiation field is coupled into the solid through a narrow edge running perpendicular to the top or bottom surface, particularly perpendicular to one of these, to excite the laser-active material. However, with such a lateral coupling, the radiation field must be relatively tightly focused.

[0010] US 2002 / 0057725 A1 describes a laser with a gain medium configured to provide an integrated optical pump cavity. In the described gain medium, optical coupling openings are formed in regions where no reflective coating is present, at which the radiation coupled into the gain medium is reflected back and forth within the interior of the medium. Diode-pumped laser amplifiers are described in US 2006 / 0114961 A1. In this laser amplifier, too, in the described gain medium, optical coupling openings are formed in regions where no reflective coating is present, at which the radiation coupled into the gain medium is reflected back and forth. US 2006 / 0193362 A1 discloses a device for guiding beams in a laser. Laser amplification modules are known from US 8,514,906 B1.Laser amplification systems are described in US 5,553,088.

[0011] It is therefore an object of the present invention to improve a solid-state laser, a laser amplification system and a solid-state laser of the type described above in such a way that an optical structure is simplified.

[0012] This object is achieved according to the invention by a solid body having the features of claim 1.

[0013] With the proposed enhanced solid, it is possible to achieve multiple passes of a radiation field, in particular a seed laser radiation field and / or a pump laser radiation field, in a simple manner, namely through multiple reflections at the first reflective coating and the second reflective coating. The radiation field thus remains in the solid between its top and bottom surfaces for the multiple passes, namely more than one round trip through the solid. The radiation field is thus essentially trapped between the reflective-coated top surface and the reflective-coated bottom surface and reflected back and forth multiple times.Depending on the selected angle of inclination, it is particularly possible, in the case of a very thin solid, to laterally displace a radiation field with a diameter of several millimeters by only a fraction of its own diameter with each pass, so that after each pass, almost the same volume of the solid is traversed. A coupling opening is understood here in particular to be any opening that allows the radiation field to pass through, i.e. allows it to enter the solid. In particular, this does not just mean a spatial opening, but also an optical opening that allows the radiation field to penetrate the solid under certain conditions, for example for a specific wavelength or a specific wavelength range, at a specific angle of incidence or range of angles of incidence and / or depending on a polarization of the radiation field.In particular, the latter optional dependencies make it possible to selectively define an opening for a radiation field for the entire top side and / or the entire bottom side, thus eliminating the need for optimal focusing of the radiation field on a specific area of ​​the solid body, for example, a coupling opening formed by an uncoated surface area of ​​the top side or bottom side of the solid body, which is therefore free of a reflective coating. The proposed refinement of the solid body thus fundamentally avoids the extensive optical arrangements known from the prior art, particularly mirrors. On the one hand, this simplifies the construction of laser amplification systems, since mirrors can be dispensed with, and they then also do not need to be adjusted.On the other hand, significant costs are saved and the weight of the laser amplification system, which is particularly relevant for space applications of laser systems, is reduced because components that were previously considered essential can be dispensed with. The solid body can in particular be formed in one piece or in several parts. In particular, in the case of a two- or multi-part design of the solid body, a disk-shaped or cuboid-shaped design is to be understood as meaning that the parts forming the solid body are each disk-shaped or cuboid-shaped. Furthermore, the at least one optical coupling opening is designed in the form of a wavelength-dependent and angle-of-incidence-dependent coupling opening for a pump laser radiation field and / or a seed laser radiation field. Such a coupling opening can in particular extend over an entire surface of the solid body, which is defined by its top side or its bottom side.In particular, radiation fields with a large radiation field diameter can be easily coupled into the solid body and captured therein. According to the invention, the first reflective coating and / or the second reflective coating define / define the at least one wavelength-dependent and angle-of-incidence-dependent coupling opening. The coupling opening can therefore be defined by the respective coating. The coupling opening also forms, in particular, the coupling-out opening in order to enable the radiation field to emerge from the solid body under appropriate conditions, i.e. depending on the wavelength and the angle of incidence on the coating inside the solid body. According to the invention, the first reflective coating is designed in the form of a highly reflective coating or in the form of a wavelength- and / or angle-of-incidence-dependent reflective coating.If a reflection of the coating is wavelength- and angle-of-incidence dependent, in particular the entire top side and / or the entire bottom side of the solid body can be used to couple in a radiation field. This has advantages in that essentially the entire area defined by the top side or the bottom side can be used to couple in the radiation field, so that essentially the entire solid body is permeated by the respective radiation field. Furthermore, according to the invention, the second reflective coating is designed in the form of a highly reflective coating or in the form of a wavelength- and / or angle-of-incidence dependent reflective coating. What was stated above regarding the different forms of the first reflective coating applies accordingly here.In particular, any combination of highly reflective coatings and wavelength- and / or angle-of-incidence-dependent reflective coatings on the top and bottom sides is possible, for example, a wavelength- and angle-of-incidence-dependent reflective coating on the top side and a highly reflective coating on the bottom side. A reverse arrangement is also conceivable. Furthermore, both coatings can be designed to be reflective depending on the wavelength and / or angle of incidence.

[0014] It is advantageous if the solid body is formed in one piece. This allows for a particularly high-performance arrangement, for example, for the construction of a laser amplification system. Furthermore, a solid body formed in one piece can also exhibit greater thermal stability and be less susceptible to vibrations than a solid body formed in two or more parts.

[0015] It is advantageous if the solid body is constructed in two or more parts. In this sense, two-part or multi-part means in particular that the solid body is constructed from two separate or separable parts, thus not formed as a single piece, hereinafter also referred to as solid body elements. In this way, the two reflective coatings can each be arranged or formed on two separate parts of the solid body. These coatings can therefore be arranged at any desired distance from one another. In particular, the two solid body elements do not have to be made of the same material. However, together they form the solid body, also referred to as a solid body element arrangement. By constructing the solid body in two or more parts, the geometric complexity of its components, i.e. of the solid body elements, can be reduced.

[0016] Advantageously, the solid body comprises at least a first solid body element and at least a second solid body element. In particular, a first and a second solid body element can be provided. For example, these can be designed in the form of plane-parallel discs or plates that are arranged or formed at an angle relative to one another by the angle of inclination.

[0017] Preferably, at least one of the at least two solid-state elements contains the laser-active material. In particular, the at least one second solid-state element can contain the laser-active material. For example, the at least one first solid-state element can serve exclusively as a substrate for the first or second reflective coating.

[0018] Furthermore, it may be advantageous if at least one of the at least two solid-state elements is formed from a material that is translucent for the seed laser radiation field and / or the pump laser radiation field, in particular from glass.

[0019] It is advantageous if the at least one first solid element and the at least one second solid element are plane-parallel. This allows the angle of inclination between the top and bottom of the solid element to be easily adjusted as desired. Plane-parallel solid elements are also particularly easy to manufacture.

[0020] According to a further preferred embodiment of the invention, it can be provided that the at least one first solid-state element has a first upper side and a first lower side, that the at least one second solid-state element has a second upper side and a second lower side, that the first lower side and the second upper side are arranged or formed facing each other, and that the first lower side forms the upper side defining the upper side plane, and that the second lower side forms the lower side defining the lower side plane. Alternatively, the first upper side can also form the upper side defining the upper side plane. With two solid-state elements, for example, four side surfaces can be formed, which can be coated as desired, i.e., in particular, one side surface of each of the two solid-state elements

[0021] Advantageously, the second upper side of the at least one second solid-state element is provided with an anti-reflection layer. This effectively prevents unwanted reflection of the seed laser radiation field and / or the pump laser radiation field at the second upper side, or facilitates the penetration of the seed laser radiation field and / or the pump laser radiation field into the at least one second solid-state element.

[0022] It is advantageous if an imaging device is arranged or formed between the at least one first solid-state element and the at least one second solid-state element. The imaging device can, in particular, bridge a distance between the at least two solid-state elements from which the solid-state element is formed, thus effectively creating a free light path.

[0023] Preferably, the imaging device comprises at least two lenses. Such an imaging device can be provided cost-effectively and with high precision.

[0024] Furthermore, it may be advantageous if the imaging device is designed in the form of a 4f imaging device or a relay optics system. This makes it possible, in particular, to image the at least one first solid-state element into the at least one second solid-state element containing the laser-active material. In this way, the distance between the two interfaces of the solid-state, each of which is arranged or formed on a side surface of one of the at least two solid-state elements, can be virtually and significantly reduced. A 4f imaging device makes it possible, in particular, to increase the usable area of ​​the solid-state.

[0025] It is advantageous if the first and / or second coating are in the form of an angle-of-incidence-dependent edge filter or a single or double bandpass filter. Such coatings make it possible, in particular, to couple a radiation field into the solid body as a function of the angle of incidence. For example, for an edge filter above or below a specific wavelength range for a specific angle of incidence, a radiation field can be coupled into the solid body. Due to the mutually inclined top and bottom surfaces of the solid body, the radiation field is slightly tilted after entering the solid body, always by twice the angle of inclination between successive reflections. As a result, the angle at which the radiation field strikes the coatings changes after each reflection inside the solid body.If an entry condition for the radiation field into the solid is met at the external angle of incidence, the radiation field remains trapped in the solid if the entry or exit condition for the radiation field is no longer met after the first internal back reflection in the solid. Ideally, the exit condition for the radiation field is no longer met after an internal reflection in the solid, so that passage of the radiation field at the coating that defines the coupling opening at the external angle of incidence is no longer possible. Instead, the radiation field is now predominantly reflected back, in particular completely. In other words, the optical density of the coating for the radiation field changes depending on the angle at which the radiation field hits the coating. In this way, a radiation field can be selectively coupled into the solid and trapped there.

[0026] It is advantageous if the edge filter or the single or double bandpass filter has a slope of at least 1 OD / 3 nm. The slope is preferably in a range from approximately 1 OD / 3 nm to approximately 3 OD / 3 nm. In particular, the slope is approximately 2 OD / 3 nm. An optical density corresponds in particular to 10 dB. With a minimum slope as specified, a radiation field can be coupled into the solid at a specific angle of incidence and captured therein in the manner described. The greater the slope, the lower the losses when coupling the radiation field, for example due to reflection on an outer surface of the top or bottom or due to partial transmission of the radiation field through the first or second coating out of the solid. In principle, it is desirable to provide as large a slope as possible.

[0027] The solid-state filter can be used particularly efficiently if the edge filter or the single or double bandpass filter has a high extinction ratio. In particular, the optical density of the filter is at least 3. More preferably, the optical density of the filter is at least 6.

[0028] Advantageously, the first and / or second coating are formed in the form of a dichroic coating. Dichroic layers have the particular property that their reflectivity depends, in particular, on the angle of incidence, wavelength, and polarization of the light. In particular, dichroic layers can also be designed to exhibit a bandpass property and a transmission behavior that can be adjusted with the angle of incidence, almost independently of polarization.

[0029] Advantageously, the first and / or second coating are polarization-independent. This has the particular advantage that the reflectivity of the first and / or second coating depends only on the angle of incidence and the wavelength of the radiation field.

[0030] In order to achieve the highest possible number of multiple reflections in the solid, it is advantageous if the angle of inclination lies in a range from approximately 0° to approximately 3°. More preferably, the angle of inclination lies in a range from approximately 0.5° to approximately 1.5°. In particular, it can be approximately 1°. The smaller the angle of inclination, the greater the number of possible multiple reflections in the solid. However, depending on the properties of the first and / or second coating, in particular their flank steepness, a larger angle of inclination can be advantageous in order to couple the highest possible proportion of the radiation field into the solid and capture it therein.

[0031] It is advantageous if the solid body has a thickness corresponding to a distance between the top and bottom sides, in a range from approximately 100 µm to approximately 1000 µm. In particular, the thickness can be in a range from approximately 200 µm to approximately 500 µm. Due to the inclination between the top and bottom sides, the thickness of the solid body is not constant. In particular, a minimum thickness of the solid body and a maximum thickness of the solid body can be within the specified ranges or can be defined by them.

[0032] A laser-active material can be easily introduced into a solid if the solid is in the form of a crystal or glass. The solid can therefore, in particular, form a matrix for the laser-active material.

[0033] It is advantageous if the crystal is made of yttrium aluminum garnet, sapphire, or a semiconductor. Such crystals can be doped with a laser-active material in a particularly simple and defined manner.

[0034] In order to arrange laser-active material in the desired quantity and in a defined manner in the solid, it is advantageous if the solid is doped with the laser-active material.

[0035] According to a further preferred embodiment of the invention, the laser-active material can comprise at least one chemical element from the group of lanthanides or a transition metal. In particular, this can be ytterbium, neodymium, or erbium, which are preferably doped into yttrium aluminum garnet crystals. Optionally, transition metals in the form of titanium or zirconium can also be used as the laser-active material. Depending on the laser-active material, a laser wavelength can be specified.

[0036] It is advantageous if the cuboid solid body has a first and a second side surface, and if the first and second side surfaces extend transversely, in particular perpendicularly or substantially perpendicularly, to the top surface plane and / or the bottom surface plane. For example, the first and / or second side surfaces can define a coupling opening for a seed laser radiation field. A pump radiation field can then optionally be coupled into the solid body through an optical coupling opening on the top or bottom surface. The first and / or second reflective coating of the top or bottom surface can therefore also be used in a solid body that serves to form a slab laser or a slab laser amplifier.

[0037] It is advantageous if the first and / or second reflective coatings are in the form of a VersaChrome®< TBP01-900 / 11-26×36 coating or an LP02-1064RE coating. Such coatings are available, for example, from Semrock Inc.

[0038] The object underlying the invention is further achieved according to the invention by a laser amplification system of the type described above, which comprises at least one of the disc-shaped or cuboid-shaped solid bodies according to the invention described above.

[0039] A laser amplification system with such a solid body then also has the advantages described above in connection with preferred embodiments of solid bodies.

[0040] Advantageously, the laser amplification system comprises at least one pump laser for generating a pump laser radiation field. The pump laser radiation field can be used, in particular, to excite the laser-active material in the solid state into a laser-active state.

[0041] It is advantageous if the wavelength of the pump laser radiation field generated by the pump laser lies in a wavelength range from approximately 300 nm to approximately 1200 nm. In particular, it can lie in a range from approximately 480 nm to approximately 580 nm, or in a range from approximately 750 nm to approximately 850 nm, or in a range from approximately 900 nm to approximately 1000 nm. It is advantageous if the wavelength of the pump laser is approximately 808 nm, or approximately 532 nm, or approximately 950 nm. Pump lasers with pump laser wavelengths in the specified ranges are ideally suited for pumping high-power disk lasers.

[0042] Furthermore, it is advantageous if the laser amplification system comprises a seed laser for generating a seed laser radiation field. This can, in particular, improve wavelength stability, beam quality, and power stability or pulsability of a laser.

[0043] Particularly for solids doped with chemical elements from the lanthanide group, it is advantageous if the wavelength of the seed laser radiation field generated by the seed laser lies in a wavelength range from approximately 500 nm to approximately 3000 nm. In particular, the seed laser wavelength can be in a range from approximately 1000 nm to approximately 1100 nm. The wavelength of the seed laser is preferably approximately 1030 nm. With this wavelength, an ytterbium-doped yttrium aluminum garnet crystal can be used as a solid for a solid-state laser.

[0044] According to a further preferred embodiment of the invention, it can be provided that the pump laser radiation field is aligned with the solid at a pump laser radiation field angle relative to a surface normal of the top side or the bottom side, that the seed laser radiation field is aligned with the solid at a seed laser radiation field angle relative to a surface normal of the top side and the bottom side, and that the pump laser radiation field angle and the seed laser radiation field angle differ. In this way, a pump laser radiation field and a seed laser radiation field can be coupled into the solid independently of one another in a simple manner. Furthermore, the angle of incidence can also, in particular, also specify a number of multiple reflections, taking into account the angle of inclination between the top side and the bottom side.

[0045] Advantageously, the pump laser radiation field angle is larger than the seed laser radiation field angle. This allows for a higher number of multiple reflections between the first coating and the second coating with the pump laser radiation field.

[0046] To further increase the number of revolutions of the pump laser radiation field in the solid, it is advantageous if the laser amplification system comprises at least one first deflection mirror arrangement for deflecting the pump laser radiation field emerging from the solid back onto the solid. The pump laser radiation field can be captured in the solid as described above. In particular, it can be imaged back onto the solid by the at least one first deflection mirror arrangement and, when it strikes the solid again at a suitable angle of incidence, captured again in the solid, allowing it to traverse the solid as a result of a plurality of multiple reflections. In this way, the efficiency of the laser amplification system can be further improved.

[0047] Preferably, the at least one first deflecting mirror arrangement comprises at least one first deflecting mirror. It can also comprise two, three, or more deflecting mirrors, with which the pump laser radiation field can be deflected back onto the solid after passing through it multiple times. The first deflecting mirror arrangement can, in particular, be designed such that the pump laser radiation field can be trapped multiple times in the solid, thus absorbing as much of the energy contained in the pump laser radiation field as possible in the solid.

[0048] It is advantageous if the laser amplification system includes at least a second deflection mirror arrangement for deflecting the seed laser radiation field emerging from the solid back onto the solid. Similar to the pump laser radiation field with the first mirror arrangement, the second mirror arrangement allows the seed laser radiation field to be used even more efficiently. Thus, it can be captured not just once, but possibly multiple times in the solid to further increase the power of the laser beam.

[0049] To create an efficient solid-state laser, it is advantageous if the solid is arranged in a resonator.

[0050] Ideally, the resonator includes an end mirror and an output mirror. This allows the laser beam to be amplified in a targeted manner and, if necessary, output from the resonator continuously or in pulsed form.

[0051] Preferably, the end mirror is highly reflective. This prevents the laser beam from leaving the resonator through the end mirror.

[0052] The laser amplification system can be designed in a particularly simple and compact manner if the end mirror comprises the first reflective coating. The first reflective coating can therefore also form the end mirror of the resonator. In particular, the solid body with the first reflective coating can be arranged on a heat sink to dissipate the heat released into the solid body by the absorbed energy from the pump laser radiation field and / or from the seed laser radiation field.

[0053] It may also be advantageous if the laser amplification system comprises at least one dispersive optical element for wavelength-dependent expansion or splitting of the pump laser radiation field generated by the pump laser and / or the seed laser radiation field generated by the seed laser. With the dispersive optical element, it is particularly possible to expand or split the pump radiation field generated by a non-monochromatic pump light source in such a way that different wavelengths can be collimated at different angles, thus, in principle, allowing a non-monochromatic pump radiation field to be coupled into the solid in a single step. This prevents only a portion of the pump light source's spectrum from being trapped in the solid for exciting the laser-active medium.The dispersive medium eliminates the need for additional mirrors to redirect portions of the pump light source's spectrum reflected by the solid, thereby optimizing the angle of incidence for the remaining spectrum upon a second incidence of the pump laser radiation field onto the solid. This can be repeated several times using multiple mirrors if necessary.

[0054] A particularly simple design of the laser amplification system can be achieved in particular by designing the dispersive optical element in the form of a prism or an optical grating.

[0055] The optical grating is preferably designed as a transmission grating. Alternatively, it can also be designed as a reflection grating.

[0056] According to a further preferred embodiment of the invention, it can be provided that the pump laser radiation field is directed at the solid body at a pump laser radiation field rotation angle deviating from 0° with respect to a plane of symmetry of the solid body that runs perpendicular to the top surface plane and the bottom surface plane, and / or that the seed laser radiation field is directed at the solid body at a seed laser radiation field rotation angle deviating from 0° with respect to the plane of symmetry. Directing the pump laser radiation field at the pump laser radiation field rotation angle and / or the seed laser radiation field at the seed laser radiation field rotation angle at the solid body has the particular advantage that the radiation fields are not directly redirected in the direction from which they impinge on the solid body. This allows for a simple spatial separation between incident and outgoing branches of a radiation field.Optionally, the pump laser radiation field can also be defined by a plurality of pump laser beams.

[0057] In order to enable a simple further separation between the pump laser radiation field and the seed laser radiation field, in particular between the radiation fields emerging from the solid, it is advantageous if the pump laser radiation field rotation angle and the seed laser radiation field rotation angle differ.

[0058] Optionally, additional optical arrangements, such as in particular the first and / or second deflection mirror arrangement, can be easily spatially positioned if the pump laser radiation field rotation angle and / or the seed laser radiation field rotation angle are in a range between 0° and approximately 10°. In particular, they can be in a range from approximately 4° to approximately 6°. Preferably, they are approximately 5°.

[0059] In order to avoid widening of the pump laser radiation field as much as possible, it is advantageous if the pump laser radiation field is collimated.

[0060] The object posed at the beginning is further achieved by a solid-state laser which comprises one of the laser amplification systems described above.

[0061] Such a solid-state laser then also has the advantages described above in connection with preferred embodiments of laser amplification systems.

[0062] Furthermore, the use of a solid-state laser according to the invention for material processing, in particular for cutting, joining, sintering and / or engraving, as well as for laser ablative propulsion and for space debris removal is proposed.

[0063] The following description of preferred embodiments of the invention serves to explain it in more detail in conjunction with the drawings. They show: Figure 1: a schematic representation of a laser amplification system of a solid-state laser according to the prior art; Figure 2: a schematic representation of a laser amplification system of a solid-state laser according to the invention; Figure 3: a schematic representation of the optical density of the coating of a VersaChrome®< TBP01-900 / 11-26×36 filter for angles of incidence of 0° and 60°; Figure 4: a schematic representation of multiple reflections in a coated solid for a seed laser beam and a pump laser beam; Figure 5: a schematic representation of a main beam path from the y-direction; Figure 6: a view of the Figure 5shown, rotated by 45° around the y-axis; Figure 7: a schematic representation of a main beam path of a double-pass arrangement; Figure 8: a schematic representation of the comparison of a spherical deformation of the solid for single or multiple reflection of a radiation field in the solid; Figure 9: a grayscale representation of higher-order phase errors; Figure 10: a schematic representation of the impingement of a pump laser radiation field on the solid; Figure 11: a schematic representation of a double-pass arrangement for the amplification of the laser beam by a seed beam; Figure 12: a schematic arrangement of the solid in a laser resonator; Figure 13: a schematic sectional view of a solid with the correct angle of incidence of a radiation field with a bandpass filter as the first coating and a highly reflective coating as the second coating; Figure 14: a view similar Figure 13, but with too flat and too steep angles of incidence of the radiation field on the solid body; Figure 15: a view as in Figure 13, but with an angle of incidence that allows the radiation field to re-emerge directly from the solid body; Figure 16: a schematic sectional view of a solid body with a first coating in the form of a double bandpass filter and a lower coating in the form of a highly reflective coating with incident and exiting radiation field; Figure 17: a schematic sectional view of a solid body which has both a first and a second coating in the form of a bandpass filter, with incoming and exiting radiation field; Figure 18: a schematic representation of a solid body with a coupling opening in the form of an uncoated surface area of ​​the upper side defining a coupling region; Figure 19: a sectional view through a solid body which is provided with coatings analogous to the solid body in Figure 13wherein a seed radiation field is coupled into the solid through a narrow edge of the solid and pumped through the first coating; Figure 20: a schematic representation of a solid with a first coating in the form of a bandpass filter and a second coating in the form of a highly reflective coating, wherein a non-monochromatic pump light source is split by means of a dispersive element and the thus split pump radiation field is coupled into the solid at different angles of incidence depending on the wavelength.

[0064] In Figure 1 An embodiment of a solid-state laser, designated overall by reference numeral 10, is schematically shown, as is known in principle from the prior art.

[0065] A disk- or cuboid-shaped solid body 12 containing at least one laser-active material is arranged on a cooling arrangement 14. A rear or underside 16 of the solid body 12 is provided with a first coating 18 that is highly reflective. A pump light source in the form of a pump laser 20 is used to excite the laser-active material in the solid body 12, generating a pump radiation field in the form of a pump laser radiation field 22.

[0066] A first deflection mirror arrangement 24 comprises a plurality of deflection mirrors 26, namely a deflection mirror 26a, a deflection mirror 26b, and a deflection mirror 26c. The pump laser radiation field 22 generated by the pump laser 20 is deflected onto the solid body 12 by the deflection mirror 26a. It passes through the solid body 12 and is reflected by the first coating 18 before exiting the solid body 12 again.

[0067] The part of the pump laser radiation field 22 that was not absorbed by the solid body 12 strikes the deflection mirror 26b, which deflects the pump laser radiation field 22 onto the deflection mirror 26c, which in turn deflects the pump laser radiation field 22 back onto the solid body 12, now at a different angle than the deflection mirror 26a.

[0068] The pump laser radiation field 22 passes through the solid body 12 twice again, being reflected by the first coating 18.

[0069] Of course, the first deflection mirror arrangement 24 can comprise even more deflection mirrors 26 in order to allow the pump laser radiation field 22 to pass through the solid-state laser 12 even more often.

[0070] Multiple passes of the pump laser radiation field 22 through the solid body 12 are necessary because the solid body 12, due to its small thickness of only about 100 µm to about 1000 µm, would not absorb sufficient energy to excite the laser-active material in a single pass of the pump laser radiation field 22.

[0071] The solid-state laser 10 comprises a laser amplification system 28, to which in particular the first deflection mirror arrangement 24 and the pump laser 20 are assigned.

[0072] The laser amplification system 28 further includes a seed laser 30 for generating a seed laser radiation field 32. The seed laser radiation 32 controls the actual laser activity of the solid-state laser 12. A wavelength of the seed laser radiation field 32 specifies the wavelength for the solid-state laser 10 and the radiation emitted by it.

[0073] In order to achieve high efficiency here as well, in particular for the conversion of laser-active states in the laser-active material, a second deflection mirror arrangement 34 is provided in order to deflect the seed laser radiation field 32 multiple times onto the solid body 12, so that the seed laser radiation field 32 can also pass through the solid body 12 multiple times.

[0074] The seed laser radiation field 32 generated by the seed laser 30 first strikes the solid body 12, passes through it once, is reflected at the first coating 18 and exits the solid body 12 at an angle of reflection that corresponds to an angle of incidence of the seed laser radiation field 32 striking the solid body 12. In the Figure 1 In the schematically illustrated embodiment of the solid-state laser 10, four deflection mirrors 36a, 36b, 36c and 36d are provided as examples.

[0075] After a first double pass through the solid body 12, the seed laser radiation field 32 strikes the deflecting mirror 36a, which deflects the seed laser radiation field 32 onto the deflecting mirror 36b. From there, the seed laser radiation field 32 strikes the solid body 12 again at a different angle of incidence. After another double pass through the solid body 12, the seed laser radiation field 32 strikes the deflecting mirror 36c, which in turn deflects the seed laser radiation field 32 onto another deflecting mirror 36d, from which the seed laser radiation field 32 is deflected back onto the solid body 12 so that it can pass through the solid body 12 once more in the manner described.

[0076] As also described for the pump laser 20 and the pump laser radiation field 22 generated thereby, the second deflection mirror arrangement 34 can comprise even more deflection mirrors in order to enable even further passes of the seed laser radiation field 32 through the solid-state body 12.

[0077] The Figure 1 The schematically illustrated design of the solid-state laser 10 is very complex, as it requires a large number of mirrors, all of which must be precisely adjusted. Furthermore, these mirrors have a significant mass. This has the particular disadvantage that, when using such a solid-state laser 10 in space, large masses must be transported into space, which is associated with high costs.

[0078] Figure 2now shows an embodiment of a solid-state laser 110 according to the invention. It comprises a laser amplification system 128 with a pump laser 120 for generating a pump laser radiation field 122 and a seed laser 130 for generating a seed laser radiation field 132.

[0079] The laser amplification system 128 further includes a solid body 112 with a top surface 138 and a bottom surface 116. The top surface 138 defines a top surface plane 140, and the bottom surface 116 defines a bottom surface plane 142. The top surface plane 140 and the bottom surface plane 142 are not parallel to each other, but rather enclose an angle of inclination 144 between them. The solid body 112 is integrally formed, i.e., molded from a single piece.

[0080] The underside 116 is provided with a first coating 118, the top side 138 with a second coating 146.

[0081] Both the first coating 118 and the second coating 146 are reflective coatings. These can be designed in different ways. For example, they can be highly reflective regardless of wavelength or highly reflective depending on wavelength and angle of incidence. Possible variants will be discussed in more detail below.

[0082] The solid body 112 is mounted on a cooling arrangement 114 to dissipate heat generated by absorbing energy from the pump laser radiation field 122 and the seed laser radiation field 132.

[0083] The solid-state laser 110 may further include a resonator 148 with an end mirror 150 and an output mirror 152.

[0084] Optionally, the laser amplification system 128 may comprise a first deflection mirror arrangement 124, for example with a deflection mirror 126a, which deflects the pump laser radiation field 122 onto the solid-state body 112. The first deflection mirror arrangement 124 may comprise further deflection mirrors in order to deflect the pump laser radiation field 122, similar to the Figure 1 shown arrangement, to be deflected back onto the solid-state laser 112 several times. In principle, however, this is not necessary with the solid-state laser 110 according to the invention, since the pump laser radiation field 122 and / or the seed laser radiation field 132 pass through the solid-state laser 112 not just once back and forth, but several times, as will be explained below.

[0085] This is achieved by the pump laser radiation field 122 and / or the seed laser radiation field 132 being virtually trapped between the coatings 118 and 146 in the solid state 112, so that they are reflected back and forth several times between the coatings 118 and 146.

[0086] For capturing or coupling the pump laser radiation field 122 and / or the seed laser radiation field 132, the top side 138 and / or the bottom side 116 have at least one optical coupling opening 154.

[0087] In the Figure 2 In the schematically illustrated embodiment, the coupling opening 154 is formed by the second coating 146. This is designed in the form of a wavelength- and angle-of-incidence-dependent reflective coating 156.

[0088] The coating 146 forms a simple bandpass filter 158. Its properties are shown schematically in Figure 3For the bandpass filter 158, a profile of the optical density of the coating 156 is schematically shown for an angle of incidence of 0° and for an angle of incidence of 60°. Accordingly, electromagnetic radiation in a transmission range 166 for wavelengths from approximately 890 nm to approximately 910 nm can penetrate the coating 156. The optical density of the coating 156 for radiation incident perpendicularly on the coating 156 is 0 in the specified wavelength range.

[0089] With decreasing wavelength, the optical density of the coating 156 increases, and with increasing wavelength above 910 nm, the optical density of the coating also increases. Both a short-wavelength flank 160 and a long-wavelength flank 162 of the coating's optical density curve exhibit a slope of approximately 2 OD / 3 nm.

[0090] If electromagnetic radiation hits the coating 156 at an angle of 60°, the result is Figure 3 The curve of the optical density as a function of wavelength is shown on the left. This results, for example, in a transmission range 164 of approximately 775 to 795 nm with an optical density of 0. Here, too, a short-wavelength flank 168 and a long-wavelength flank 170 of the optical density curve decline with a steepness of approximately 2 OD / 3 nm.

[0091] The in connection with Figure 3 The property of the coating 156 explained by way of example thus makes it possible to couple electromagnetic radiation of a specific wavelength into the solid body at a predetermined angle of incidence. This can be done, for example, at a wavelength of 780 nm at an angle of 60° for a coating 156 with the Figure 3 permeability properties shown.

[0092] If the angle at which electromagnetic radiation with a wavelength of 780 nm impinges on the coating 156 becomes smaller or larger, the optical density of the coating 156 decreases for both smaller and larger angles. Therefore, if the radiation impinges on the second coating 146 at a different angle after being reflected by the first coating, the special properties of the coating 156 may mean that the transmittance condition for the electromagnetic radiation entering the solid body 112 is no longer met for the angle of incidence at which the radiation impinges on the second coating 146 for the second time. If the optical density for the radiation at the new angle of incidence is greater than zero, the radiation is at least partially reflected by the second coating 146.

[0093] This change in the angle of incidence of the radiation on the second coating 146 after a back and forth pass of the radiation through the solid body 112 results from the top side 138 and the bottom side 116 being inclined relative to one another. Due to the law of reflection, after each double pass through the solid body 112, the angle at which the radiation strikes the second coating 146 is reduced by twice the angle of inclination 144.

[0094] This results in the coating 156 forming an overall optical coupling opening 154 for the pump laser radiation field 122 and / or the seed laser radiation field 132, depending on their wavelength and an angle of incidence at which they each first impinge on the coating 156. If, after a forward and return pass through the solid body 112, during which the radiation is completely reflected back at the first coating 118, the described condition is met, namely that an optical density of the coating 156 is met for the respective wavelengths for the angle of incidence of the radiation on the coating 156 changed by twice the inclination angle 144, the radiation is reflected at the coating 156 with increasing proportions and thus passes through the solid body 112 multiple times.

[0095] The number of passes depends on both the angle of inclination and the angle of incidence of the radiation.

[0096] The coupling of a pump radiation field 122 and a seed laser radiation field 132 into the solid state 112 is shown by way of example in Figure 4 shown.

[0097] The pump laser radiation field 122 is directed onto the solid-state body 112 at a pump laser radiation field angle 172 relative to a surface normal to the top side 138. The wavelength of the pump laser radiation field 122 is 780 nm. The inclination angle 144 is 1°. The coating 156 is formed by the coating of a VersaChrome® filter from Semrock Inc., designated TBP01-900 / 11-26x36.

[0098] The tilting behavior of this coating can be calculated in a known manner according to the following formula: λ θ = λ 0 1 − sin 2 θ n eff 2

[0099] This is λ (θ) is the wavelength at a given angle of incidence, where 0° corresponds to normal incidence on the coating, and n eff is the effective refractive index of the coating. Theta is the angle of incidence relative to the surface normal 174.

[0100] The pump laser radiation field 122 enters the solid-state body 112 through the coating 156 and is completely reflected by the first coating 118. It then re-impinges on the coating 156 at an angle of 60°-2°=58° and is largely reflected back toward the first coating 118.

[0101] Taking into account the inclination angle 144 and the pump laser radiation field angle 172, 33 double reflections of the pump laser radiation field 122 result in the solid 112.

[0102] Taking into account the decreasing angle of incidence of the pump radiation field 122 after each reflection at the first coating 118 onto the second coating 146, the pump radiation field 122 travels back practically along the same path and then exits the solid body 112 again at almost the same point.

[0103] The seed laser radiation field 132 impinges on the coating 156 at a seed laser radiation field angle 176 relative to a surface normal 178 of the upper side. Figure 2 In the schematically illustrated example, the wavelength of the seed laser radiation field is 845 nm, the seed laser radiation field angle 176 is 36°.

[0104] In a manner analogous to that described for the pump radiation field 122, the seed laser radiation field 132 is trapped in the solid state 112. Here, the optical densities after the first six back reflections at the first coating 118 are schematically shown.

[0105] The first coating 118 is a highly reflective coating that is independent of the wavelength and the angle of incidence.

[0106] Taking into account the seed laser radiation field angle 176, which is smaller than the pump laser radiation field angle 172, 23 double reflections result in the solid 112.

[0107] With suitable coatings, wavelengths of approximately 951 nm for the pump laser radiation field 122 and approximately 1030 nm for the seed laser radiation field 132 can be captured in the solid state in the manner described. For these wavelengths, for example, a coating from Semrock Inc., designated LP02-1064RE, can be used for a solid state 112 formed from an yttrium aluminum garnet crystal doped with ytterbium as the laser-active material. This coating forms a long-pass filter that transmits long wavelengths. The tilt angle 144 for such a system is 0.5°. The average thickness of the wedge-shaped solid state is 200 µm. A pump wavelength of the pump laser 120 is 941 nm, a wavelength of the seed laser radiation field 132 generated by the seed laser 130 is 1030 nm. Both the pump laser radiation field 122 and the seed laser radiation field 132 are P-polarized.The pump laser radiation field angle 172 is 48°, and the seed laser radiation field angle 176 is 25°. This results in 26 revolutions of the seed laser radiation field 132 in the solid state 112 and 48 revolutions of the pump laser radiation field 122. This results in a total loss of approximately 4.5% for the seed laser radiation field 132 if no amplification is taken into account.

[0108] The LP02-1064RE coating has the advantage over the TBP01-900 / 11-26x36 coating that the transmittance of the coating is reduced by several optical densities after just one cycle, so that secondary rays do not represent any significant sources of loss or interference, and the overall gain of the system is reduced by only a few percent.

[0109] To further increase the number of rotations, the tilt angle 144 must be reduced. A prerequisite for achieving the specified gain and loss values ​​is the P-polarization of the pump laser radiation field 122 and the seed laser radiation field 132.

[0110] In order to counteract the described direct return of the radiation fields 122 and 132, it is possible to slightly rotate the solid body 112, i.e. to rotate the radiation fields at a pump laser radiation field rotation angle 180 or at a seed laser radiation field rotation angle 182, each relative to a symmetry plane 184 running perpendicular to the top surface plane 140 and the bottom surface plane 142. For a disk-shaped solid body 112 with a diameter of 25 mm and an inclination angle 144 of 1° and a pump laser radiation field rotation angle 180 and a seed laser radiation field rotation angle 183 of 5°, the radiation fields follow a course as shown schematically in the Figures 5 and 6 are shown. In these two figures, beams exceeding 83% of the power of the seed laser radiation field 132 and 93% of the power of the pump laser radiation field 122 are shown merely as examples.

[0111] Figure 5 shows the beam path in a view from the y-direction. In Figure 6 As an example, a close-up view of the solid body 112 is shown, which is rotated by 45 degrees relative to the y-axis.

[0112] In Figure 5 It is clearly visible that the seed laser radiation field 132 emerging from the solid body 112 forms a small angle with the incident seed laser radiation field 132 and can thus be easily separated spatially.

[0113] A profile of the pump laser radiation field 122 and the seed laser radiation field 132 in the wedge-shaped solid 112 is shown in Figure 6 shown schematically. The path here follows an arc, so that the pump laser radiation field 122 exits the solid 112 at a different angle.

[0114] The number of reflections is essentially independent of the position on the solid. Only the size of the arcuate path, and thus the light path, is determined by the local thickness of the solid.

[0115] To compensate for excess light paths, the solid body 112 can optionally be doped with a uniform effective thickness. In this case, the doping is selected such that the doping density increases with decreasing thickness of the wedge-shaped solid body 112.

[0116] Alternatively, the second coating 146 could also be formed on a second solid or substrate. However, without the possibility of effective cooling, the amplified seed laser radiation field 132 would have to pass through it.

[0117] In principle, the seed laser radiation field 132 and the pump laser radiation field 122 do not have to lie in the same plane of incidence. Furthermore, the rotation of the wedge-shaped solid body 112 relative to the plane of symmetry 184 should preferably not be chosen too large, since in the worst case, this would lead to an increase in the reflection angle rather than a decrease.

[0118] Preferably, both the pump laser radiation field 122 and the seed laser radiation field 132 can be collimated. A beam divergence of less than 1° is preferably achieved.

[0119] If the pump light source is a non-monochromatic pump light source, only a portion of the radiation generated by it, i.e., a portion of the spectrum, is captured in the solid 112 in the manner described. The uncaptured portion of the pump laser radiation field 132, i.e., the portion reflected back from the solid 112 by the second coating 146, can be redirected onto the solid 112, for example, via one or more mirrors, and upon this second incidence, strike the solid 112 at an angle optimized for the remaining spectrum, which enables the capture of this portion of the spectrum of the pump laser radiation field 132.

[0120] For such pump light sources, one possible option is to provide a dispersive element, such as a prism, grating, lens, or a suitable glass block, which approximates the spectral angular behavior from the above equation for describing the tilt behavior of the coating across the spectrum of the pump light source. Thus, the dispersive element makes it possible to collimate the different wavelengths at different angles, which, at least theoretically, enables the coupling of a non-monochromatic pump laser radiation field 122 into the solid-state 112 in a single step.

[0121] If further rotations are to be made, the amplified seed laser radiation field 132 can, for example, be redirected onto the solid body 112 via additional mirrors 136a and 136b. This is shown schematically in Figure 7 shown.

[0122] In Figure 8A schematic diagram of an arrangement for testing the system's susceptibility to deformation of the solid body 112 is shown. Here, a slight curvature on the top side 138 and the bottom side 116 was computationally taken into account as an example to achieve a defocusing effect for the seed laser radiation field 132. A focus offset according to an ideal lens was considered as a quality criterion and compared with the offset of a beam reflected once. Figure 8 shows such a spherical deformation with a defocus caused by wedge curvature with a radius of r=500 mm. Figure 8 The beam designated by reference numeral 186 results for a wavelength of 780 nm with multiple reflections. Figure 8The beam, designated by reference numeral 188, has a wavelength of 700 nm and is reflected once at the surface of the solid. Ideal lenses with a focal length f=10 mm are schematically drawn as rectangles and designated by reference numeral 190. A reference plane 192 for defocus determination is drawn as a circle.

[0123] To compare this with normal reflection, the change in the focal plane was determined by applying a curvature with a radius r = 500 mm to the solid 112. This results in the amplified seed laser radiation field 132, represented by beam 186, resulting in a shift from 10 mm to 10.161 mm, while the reflected beam 188 results in a shift from 10 mm to 10.444 mm. Expressed in refractive power, this translates to -1.58 diopters for the amplified beam 186 and -4.25 diopters for the reflected beam. The smaller the refractive power, the better the result.

[0124] In a second step, the curvature of solid body 112 is further reduced, i.e., a radius of r = 5 m is assumed, in order to more accurately examine the phase behavior of beams 186 and 188. All unproblematic imaging errors were not taken into account in this analysis. The result is an astigmatism on the order of approximately 3 wavelengths. The phase error of reflected beam 188 is slightly larger than that of beam 186. Despite the increased number of revolutions of the amplified beam 186, a phase image similar to that of reflected beam 188 is obtained. This makes it possible to provide sufficient measurement information for adaptive beam correction from the outputs from intermediate reflections.

[0125] Figure 9 shows a grayscale representation of higher order phase errors without tilt and defocus in radians. A surface curvature with a radius of r = 5 m is assumed. The image field width is 10 mm. Figure 9 On the left, a reference beam 188 with a wavelength of 700 nm and a single reflection at the coating 146 is shown. On the right, the result for beam 186 with a wavelength of 780 nm and multiple reflections is shown.

[0126] In the Figures 10 to 20 Possible variants for the coupling of pump laser radiation fields 122 and seed laser radiation fields 132 into a wedge-shaped solid body 112, which is provided with the coatings 118 and 146, are shown schematically.

[0127] Figure 10shows the impingement of a pump laser radiation field 122 with multiple pump beams that are coupled into the solid-state 112 at slightly tilted angles. This approach has an advantage because pump light sources often do not have an ideal beam profile, which would result in the angle requirements of the second coating 146 being exceeded. However, along a conical surface, the required angle of incidence is always maintained.

[0128] In Figure 11An arrangement for a seed laser radiation field 132 is shown as an example. It impinges on the solid body 112 at a seed laser radiation field angle 176 and a seed laser radiation field rotation angle 182. The beam path for the seed laser radiation field 132 without a second deflecting mirror arrangement 134 is shown in solid lines. The beam path with a second deflecting mirror arrangement 134 comprising two deflecting mirrors 136a and 136b is shown in dotted lines. The deflecting mirrors 136a and 136b enable a second pass with a defined number of multiple reflections through the solid body 112.

[0129] The described effect of multiple passes through the solid body 112 by using two coatings 118 and 146 can also be used in laser resonators 148. The multiple reflections in the solid body 112 increase the effective thickness of the amplifying medium, so that fewer resonator passes are necessary to enable stable laser operation.

[0130] In the Figures 13 to 15 In each case, a solid body 112 is schematically shown, the first coating 118 of which is highly reflective and the second coating 146 of which is in the form of a bandpass filter.

[0131] Figure 13shows the incidence of a radiation field 194 at a radiation field angle 196 relative to the surface normal 174 of the upper side 138. Here, the entrance condition is met. The upper side 138 forms a full-surface coupling opening 154 for the radiation field 194. This can be, in particular, the pump laser radiation field 122 or the seed laser radiation field 132. Here, as explained in detail above, several reflections are enabled in the solid body 112 before the radiation field 194 exits the solid body 112 again.

[0132] Figure 14 shows schematically that the second coating 146, in the form of a bandpass filter, is highly reflective and thus impermeable for radiation field angles 196 that are too flat or too steep. Therefore, the radiation field 194 cannot penetrate the solid body 112 if the radiation field angle 196 is not adjusted.

[0133] If the radiation field angle is 196, as shown schematically in Figure 15shown, not close enough to a flank of the optical density profile of the second coating 146, for example to the flanks 160 or 162 or 168 or 170, the radiation field 194 can couple out of the solid body 112 again unhindered after reflection at the first coating 118.

[0134] If the second coating 146 is designed in the form of a double bandpass, as in Figure 16 schematically shown, the radiation field 194 is coupled in at a flat angle at a rising edge and coupled out of the solid body 112 at a steep angle at a falling edge.

[0135] Instead of providing a double bandpass as coating 146, both coating 118 and 146 can each be designed as a single bandpass, as shown schematically in Figure 17is shown. Coupling of the radiation field 194 into the solid body 112 then occurs at a radiation angle 196, which is greater than an exit angle of the exiting radiation field 194.

[0136] Instead of providing one or more dichroic coatings 118 or 146, both the first coating 118 and the second coating 146 can be designed in the form of highly reflective coatings. To enable the coupling of the radiation field 194 into the solid body 112, a coupling opening 154 is formed by an uncoated coupling or surface area 198. Only in this surface area 198 is the upper side 138 permeable to the radiation field 194, as shown by way of example in Figure 18The capture of the radiation field 194 is achieved by appropriate angular conditions, which, after a back reflection at the first coating 118, result in the radiation field 194 striking the second coating 146 outside the surface area 198. The radiation field 194 then passes through the coupling opening 154 again after a multiple reflection. If the radiation field 194 strikes the second coating 146 next to the surface area 198, it is reflected by the latter, as shown in Figure 18 schematically shown, reflected so that the radiation field 194 cannot penetrate into the solid body 112.

[0137] The proposed design of the solid body 112 with a highly reflective coating 118 and a dichroic coating 146 can also be used to form the seed laser radiation field 132, as shown schematically in Figure 19shown, into a cuboid-shaped solid body through a side surface 200 which runs transversely, in particular perpendicularly or substantially perpendicularly, to the upper surface plane 140 or to the lower surface plane 142. This corresponds to the procedure for a slab laser. The pump laser radiation field 122 can then be arranged as in the variant shown in Figure 13 is shown, are coupled into the solid body 112 through the second coating 146, which defines the coupling opening 144 in a wavelength-selective manner.

[0138] In Figure 20A further variant is shown, which can be used particularly with non-monochromatic and spectrally broad pump light sources. Here, the pump laser radiation field 122 is split into its spectral components using a dispersive element 202. These impinge on the solid-state body 112 at different radiation field angles 196a and 196b. However, since the coating 146 is designed to be angle-of-incidence and wavelength-dependent, both spectral components of the pump laser radiation field 142 can be coupled into the solid-state body 112 simultaneously and captured therein in the manner described. The dispersive element 202 can be designed in the form of a prism or a grating.

[0139] The dispersive element 202 can optionally be applied directly to the top side 138 of the solid body 112 for adaptation to a spectrum of the pump light source, in particular in the form of a transmission grating.

[0140] The inclination angle 144 is preferably specified as a function of the optical density profile of the coating 118 or the coating 146. Depending on the angle of incidence, the spectral angle dependence, the effective refractive index of the coating, and the refractive index of the substrate, the inclination angle 144 can thus be individually determined and optimized for the solid.

[0141] In Figure 21 Another exemplary embodiment of a solid body 112 is shown. For the sake of clarity, Figure 21 For some components of the solid body, the same reference numerals are used as in the above-described embodiments of the integrally formed solid body 112.

[0142] Unlike the ones in the Figures 2 to 19 shown and described above, the solids 112 is the one in Figure 21The solid body 112 shown is formed in several parts, namely two parts. It comprises a first part 204 and a second part 206. Parts 204 and 206 are also referred to below as the first solid body element 208 and the second solid body element 210.

[0143] The solid-state elements 208 and 210 are disk-shaped or cuboid-shaped. The first solid-state element 208 has a first top side 212 and a first bottom side 214. The second solid-state element 210 has a second top side 216 and a second bottom side 218.

[0144] The first top side 212 and the first bottom side 214 run parallel to each other. The second top side 216 and the second bottom side 218 also run parallel to each other. This defines plane-parallel solid elements 208 and 210.

[0145] The solid-state elements 208 and 210 are arranged slightly tilted relative to each other, with the first bottom side 214 facing the second top side 216 and vice versa. This arrangement allows the first bottom side 214 and the second top side 216 to form an angle of inclination 144 between them.

[0146] The second underside 218 of the first solid-state element 208 forms in the Figure 21 illustrated two-part solid body 112, the underside 116 defined in the other embodiments. The first underside 114 of the second solid body element 210 forms the top side 138 of the solid body 112.

[0147] The upper side 138 in turn defines the upper side plane 140. The lower side 116 defines the lower side plane 142. Accordingly, in the embodiment of the solid body 112 shown in Figure 21, the lower side 116 is provided with the first reflective coating 118 and the upper side 138 is provided with the second reflective coating 146.

[0148] In particular, the second solid-state element 210 may contain the laser-active material. The first solid-state element 208 may be formed from glass, for example, and then essentially serves as a substrate for the second reflective coating 146.

[0149] Even with the Figure 21In the illustrated embodiment of the solid body 112, the top side 138 and / or the bottom side 116 optionally comprise at least one optical coupling opening for coupling a seed laser radiation field 132 and / or a pump laser radiation field 122 into the solid body 112 between the reflective coatings 118 and 146. For the sake of clarity, Figure 21 The radiation field 194 is shown as an example for the three possible options.

[0150] The described configuration of the solid-state body 112 with the two solid-state elements 208 and 210 enables the coupling of a radiation field 194 through the optical coupling opening 154, which can be designed as in the embodiments described above, for example by the special coating 146.

[0151] In order to be able to couple the radiation field 194 as completely as possible into the second solid-state element 210, it is advantageous if the second upper side 216 is provided or equipped with an anti-reflection layer 220 in order to avoid back-and-forth reflections between the first lower side 214 and the second upper side 216 as far as possible.

[0152] The coatings 118 and 146 can be selected in particular as in the above-described embodiments of solid bodies 112, as can the angle of inclination 144.

[0153] In Figure 22 A further embodiment of a two-part solid body, designated overall by reference numeral 112, is schematically illustrated. It again comprises a first solid body element 208 and a second solid body element 210, which are provided with coatings 118 and 146 in an analogous manner.

[0154] For the sake of clarity, Figure 22the same reference numerals are used as in the Figure 21 illustrated embodiment of the two-part solid body 112.

[0155] Optionally, the second top side 216 can be provided with the anti-reflection layer 220.

[0156] The mutually inclined solid elements 208 and 210 in turn define the angle of inclination 144 between the top surface plane 140 and the bottom surface plane 142.

[0157] In contrast to the solid 112, as it is found in Figure 21 As shown, the solid 112 is in Figure 22 the solid-state elements 208 and 210 are arranged further apart from each other.

[0158] An imaging device 222 is arranged between the solid-state elements 208 and 210. This can, for example, be designed as a 4f imager and serve as a so-called relay optic. Figure 22The imaging device 222 is shown as an example with two lenses 224 and 226. It can also comprise other optical elements, in particular lenses.

[0159] The imaging device 222 serves, in particular, to bridge the spatial distance, also referred to as the free light path, between the first underside 214 and the second top side 216. The imaging device 222 is preferably arranged and configured such that the radiation field 194 is imaged from the top side plane 140 onto the bottom side plane 142.

[0160] The imaging device 222 enables a larger usable area of ​​the second solid-state element 210, particularly when designed in the form of a 4f image.

[0161] The functionality of the two-part solid body 112 corresponds to the functionality of the above-described embodiments of one-piece solid bodies 112.

[0162] The solid body 112 is to be formed in several parts, in particular in two parts, as in connection with the Figures 21 and 22 described, has the particular advantage that the components used have a lower geometric complexity.

[0163] Finally, it should be emphasized again that the use of a solid body 112 according to the invention, which has a coupling opening 154, is suitable for both pumping and removing the laser-active material. Whether the solid body 112 is formed in one piece or in multiple parts is irrelevant.

[0164] A particular advantage of the invention lies in a significantly reduced complexity of the optical structure of the laser amplification system 128, so that high-power laser sources can be manufactured with significantly lower equipment and associated costs.

[0165] Solid-state lasers 110 with solid bodies 112 according to the invention can be used particularly in materials processing and, furthermore, in particular, in laser cutting, laser joining, laser sintering, and laser engraving. Furthermore, they are also suitable for laser ablative propulsion and space debris removal. List of reference symbols

[0166] 10 Solid-state laser 12 Solid-state 14 Cooling arrangement 16 Bottom side 18 First coating 20 Pump laser 22 Pump laser radiation field 24 First deflection mirror arrangement 26a, 26b, 26c Deflection mirror 28 Laser amplification system 30 Seed laser 32 Seed laser radiation field 34 Second deflection mirror arrangement 36a, 36b, 36c, 36d Deflection mirror 110 Solid-state laser 112 Solid-state 114 Cooling arrangement 116 Bottom side 118 First coating 120 Pump laser 122 Pump laser radiation field 124 First deflection mirror arrangement 126a Deflection mirror 128 Laser amplification system 130 Seed laser 132 Seed laser radiation field 134 Second Deflecting mirror arrangement 136a,136bDeflection mirror 138Top side 140Top surface plane 142Bottom surface plane 144Inclination angle 146Second coating 148Resonator 150End mirror 152Output mirror 154Injection aperture 156Coating 158Bandpass filter 160Flank 162Flank 164Transmission region 166Transmission region 168Flank 170Flank 172Pump laser radiation field angle 174Surface normal 176Seed laser radiation field angle 178Surface normal 180Pump laser radiation field rotation angle 182Seed laser radiation field rotation angle 184Plane of symmetry 186Beam 188Beam 190Lens 192Reference plane 194Radiation field 196a, 196bRadiation field angle 198Surface area 200Side surface 202Dispersive element 204First part 206Second part 208First solid element 210Second solid element 212First top side 214First bottom side 216Second top side 218Second bottom side 220Antireflection layer 222Imaging device 224Lens 226Lens,

Claims

1. Discoidal or cuboidal solid body (112) for a laser amplification system (128), which solid body (112) contains at least one laser-active material, has an upper side (138) defining an upper side plane (140) and a lower side (116) defining a lower side plane (142), wherein the upper side plane (140) and the lower side plane (142) are inclined in relation to each other and enclose an angle of inclination (144), wherein the lower side (116) is provided with a first reflective coating (118), and wherein the upper side (138) is provided with a second reflective coating (146), wherein the upper side (138) and / or the lower side (116) has at least one optical input coupling opening for input coupling a seed laser radiation field (132) and / or a pump laser radiation field (122) into the solid body (112) between the first and the second reflective coating (118, 146), and wherein the at least one optical input coupling opening (154) is configured in the form of a wavelength- and angle of incidence-dependent input coupling opening for a pump laser radiation field (122) and / or seed laser radiation field (132), wherein the first reflective coating (118) and / or the second reflective coating (146) define / defines the at least one wavelength-dependent and angle of incidence-dependent input coupling opening (154), wherein the first reflective coating (118) is configured in the form of a highly reflective coating or in the form of a wavelength- and angle of incidence-dependent reflective coating, and wherein the second reflective coating (146) is configured in the form of a highly reflective coating or in the form of a wavelength- and angle of incidence-dependent reflective coating (156).

2. Solid body in accordance with Claim 1, wherein it (112) is integrally formed.

3. Solid body in accordance with Claim 1, wherein it (112) is of two- or multi-part configuration.

4. Solid body in accordance with Claim 1 or 3, wherein the solid body (112) comprises at least one first solid body element (208) and at least one second solid body element (210).

5. Solid body in accordance with Claim 4, wherein a) at least one of the at least two solid body elements (208, 210) contains the laser-active material, and / or b) at least one of the at least two solid body elements (208, 210) is formed of a material translucent to the seed laser radiation field (132) and / or the pump laser radiation field (122), and / or c) the at least one first solid body element (208) and the at least one second solid body element (210) are configured plane-parallel and / or d) the at least one first solid body element (208) has a first upper side (212) and a first lower side (214), wherein the at least one second solid body element (210) has a second upper side (216) and a second lower side (218), wherein the first lower side (214) and the second upper side (216) are arranged or formed facing each other, and wherein the first lower side (214) forms the upper side (138) defining the upper side plane (140), and wherein the second lower side (218) forms the lower side (116) defining the lower side plane (142), and / or e) an imaging device (222) is arranged or formed between the at least one first solid body element (208) and the at least one second solid body element (210).

6. Solid body in accordance with one of the preceding Claims, wherein a) the first coating (118) is configured in the form of an angle of incidence-dependent edge filter or a single or double bandpass filter, and / or b) the second coating (146) is configured in the form of an angle of incidence-dependent edge filter or a single or double bandpass filter, and / or c) the first and / or the second coating (118, 146) are configured in the form of a dichroic coating.

7. Solid body in accordance with any one of the preceding Claims, wherein a) the first and / or the second coating (118, 146) are configured to be polarization-independent and / or b) the angle of inclination (144) is in a range of about 0° to about 3°, and / or c) the solid body (112) has a thickness, which corresponds to a distance between the upper side (138) and the lower side (116), in a range of about 100 µm to about 1000 µm.

8. Solid body in accordance with any one of the preceding Claims, wherein a) the solid body (112) is configured in the form of a crystal or is formed of glass, and / or b) the solid body (112) is doped with the laser-active material.

9. Solid body in accordance with any one of the preceding Claims, wherein a) the laser-active material comprises at least one chemical element from the group of lanthanides and / or b) the cuboidal solid body (112) has a first and a second side face (200), and wherein the first and second side face (200) run transverse to the upper side plane (140) and / or to the lower side plane (142).

10. Laser amplification system (128) comprising at least one discoidal or cuboidal solid body (112) in accordance with any one of the preceding Claims.

11. Laser amplification system in accordance with Claim 10, wherein a) the laser amplification system comprises at least one pump laser (120) for generating a pump laser radiation field (122), and / or b) the laser amplification system comprises a seed laser (130) for generating a seed laser radiation field (132), and / or c) the pump laser radiation field (122) is directed to the solid body (112) at a pump laser radiation field angle (172) in relation to a surface normal (174) of the upper side (138) or the lower side (116), wherein the seed laser radiation field (132) is directed to the solid body (112) at a seed laser radiation field angle (176) in relation to a surface normal (178) of the upper side (138) or the lower side (116), and in wherein the pump laser radiation field angle (172) and the seed laser radiation field angle (176) are different.

12. Laser amplification system in accordance with Claim 10 or 11, wherein a) the laser amplification system comprises at least one pump laser (120) for generating a pump laser radiation field (122) and at least one first deflection mirror arrangement (124) for deflecting the pump laser radiation field (122) exiting the solid body (112) back to the solid body and / or b) the laser amplification system comprises a seed laser (130) for generating a seed laser radiation field (132) and at least one second deflection mirror arrangement (134) for deflecting the seed laser radiation field (132) exiting the solid body (112) back to the solid body (112), and / or c) the solid body (112) is arranged in a resonator (148).

13. Laser amplification system in accordance with any one of Claims 10 to 12, wherein the laser amplification system comprises at least one pump laser (120) for generating a pump laser radiation field (122) and a seed laser (130) for generating a seed laser radiation field (132) and wherein a) the laser amplification system comprises at least one dispersive optical element (202) for wavelength-dependently expanding or splitting the pump laser radiation field (122) generated by the pump laser (120) and / or the seed laser radiation field (132) generated by the seed laser (130), and / or b) the pump laser radiation field (122) is directed to the solid body (112) at a pump laser radiation field rotation angle (180) deviating from 0° in relation to a symmetry plane (184) of the solid body (112) running perpendicular to the upper side plane (140) and to the lower side plane (142), and / or wherein the seed laser radiation field (132) is directed to the solid body (112) at a seed laser radiation field rotation angle (182) deviating from 0° in relation to the symmetry plane (184), and / or c) the pump laser radiation field (122) is collimated.

14. Solid-state laser (110) comprising a laser amplification system (128) in accordance with any one of Claims 10 to 13.

15. Use of a solid-state laser (110) in accordance with Claim 14 for material processing, for cutting, jointing, sintering, and / or engraving, for laser ablative drives for the removal of space debris.