A laser system

Abstract

An optical configuration including axiconical elements that serve as parts of a resonator or an optical chain of an amplifier for an active laser volume with a large transverse dimension. The system may include a single-fold or multiple-folds axiconical elements. One of the system's advantages is providing the means to produce, even with a stable resonator, a high-quality and well-controlled beam, utilizing efficiently a wide active laser medium.

Claims

1. An optical system that comprises: an axicon reflector having a center aperture; a waxicon reflector that has an even number of stages; an amplifying unit; an excitation unit that is configured to excite the amplifying unit; wherein an optical axis of the waxicon reflector differs from an optical axis of the axicon reflector; wherein the optical axis of the waxicon reflector and the optical axis of the axicon reflector belong to a continuous folded optical path; wherein different stages of the waxicon reflector are configured to reflect a laser beam, during different amplifying iterations, towards different regions of the amplifying unit; wherein some of the different regions of the amplifying unit are configured to amplify the laser beam, during the different amplifying iterations, and direct the laser beam towards different regions of the axicon reflector; wherein one region of the amplifying unit is configured to amplify the laser beam and direct the laser beam from the waxicon reflector through the center aperture; wherein different regions of the axicon reflector are configured to reflect the laser beam, during the different amplifying iterations, towards the different regions of the amplifying unit; wherein the different regions of the amplifying unit are configured to amplify the laser beam, during the different amplifying iterations, and direct the laser beam towards different regions of the waxicon reflector.

2. The optical system according to claim 1 further comprising an output mirror.

3. The optical system according to claim 2 wherein the output mirror belongs to a stable resonator.

4. The optical system according to claim 2 wherein the output mirror belongs to an unstable resonator.

5. The optical system according to claim 1 wherein a first stage of the waxicon reflector is configured to reflect a laser beam towards a first region of the first amplifying disc; wherein the first region of the amplifying unit is configured to amplify the laser beam and direct the laser beam towards a first region of the axicon reflector; wherein the first region of the axicon reflector is configured to receive the laser beam and reflect the laser beam towards a second region of the first amplifying disc; wherein the second region of the amplifying unit is configured to amplify the laser beam and to direct the laser beam towards a second stage of the waxicon reflector.

6. The optical system according to claim 1 wherein the waxicon reflector and the axicon reflector are positioned on opposite sides of an optical axis of the amplifying unit.

7. The optical system according to claim 1 wherein the optical axis of the waxicon reflector and the optical axis of the axicon reflector are parallel to each other.

8. The optical system according to claim 1 wherein the optical axis of the waxicon reflector and the optical axis of the axicon reflector are oriented at each other.

9. The optical system according to claim 1 wherein a number of stages of the waxicon reflector minus one equals a number of stages of the axicon reflector.

10. The optical system according to claim 1 wherein all stages of the waxicon and the axicon are configured to reflect the laser beam, during the different amplifying iterations.

11. The optical system according to claim 1 wherein the amplifying unit consists essentially of an amplifying and reflecting disc.

12. The optical system according to claim 11 wherein the different stages of the waxicon reflector are configured to reflect the laser beam towards different regions of the amplifying disc; wherein some of the different regions of the amplifying disc are configured to amplify the laser beam and direct the laser beam towards different regions of the axicon reflector; wherein one central region of the amplifying disc is configured to amplify the laser beam and direct the laser beam from the waxicon reflector through the center aperture; wherein different regions of the axicon reflector are configured to reflect the laser beam towards the different regions of the amplifying disc; and wherein the different regions of the amplifying disc are configured to amplify the laser beam and direct the laser beam towards different regions of the waxicon reflector.

13. The optical system according to claim 1 wherein the amplifying unit comprises a set of amplifying disks that are configured to amplify the laser beam.

14. The optical system according to claim 13 wherein each amplifying disk of the set comprises multiple regions; wherein the amplifying unit is configured to amplify the laser beam by utilizing, during the different amplifying iterations, at least a majority of the multiple regions of each of the multiplying disks.

15. The optical system according to claim 13 wherein the amplifying unit is configured to amplify the laser beam by using all amplifying disks of the set during each one of the different amplifying iterations.

16. The optical system according to claim 13 wherein the set comprises a first amplifying disc and a second amplifying disc; wherein the amplifying unit further comprises a first mirror, and a second mirror; wherein the different stages of the waxicon reflector are configured to reflect the laser beam, during the different amplifying iterations, towards different regions of the first amplifying disc; wherein the different regions of the first amplifying disc are configured to reflect the laser beam, during the different amplifying iterations, towards different regions of the first mirror; wherein the different regions of the first mirror are configured to reflect the laser beam, during the different amplifying iterations, towards different regions of the second amplifying disc; and wherein the different regions of the second amplifying disc are configured to reflect the laser beam, during the different amplifying iterations, towards different regions of the axicon reflector.

17. The optical system according to claim 1 wherein an upper half of the output mirror is transmissive and a lower half of the output les is reflective.

18. The optical system according to claim 1 further comprises a seeding beam supply unit.

19. The optical system according to claim 17 wherein the seeding beam supply unit is configured to provide a seeding beam through a central aperture of the waxicon reflector.

20. The optical system according to claim 1 wherein the excitation unit comprises laser diodes that are configured to excite the amplifying disc.

21. (canceled)

22. (canceled)

23. (canceled)

24. A method, comprising: exciting, by an excitation unit, an amplifying unit of an optical system; reflecting, by different stages of a waxicon reflector of the optical system, a laser beam, during different amplifying iterations, towards different regions of an amplifying unit of the optical system; amplifying, by some of the different regions of the amplifying unit, the laser beam, during the different amplifying iterations; directing the laser beam towards different regions of an axicon reflector of the optical system; amplifying, by one region of the amplifying unit, the laser beam and directing the laser beam from the waxicon reflector through a center aperture of the axicon reflector; wherein an optical axis of the waxicon reflector differs from an optical axis of the axicon reflector; and wherein the optical axis of the waxicon reflector and the optical axis of the axicon reflector belong to a continuous folded optical path.

25. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings in which:

[0052] FIG. 1 illustrates a prior art system;

[0053] FIG. 2 illustrates a prior art system;

[0054] FIG. 3 illustrates an example of a system;

[0055] FIG. 4A illustrates an example of a system;

[0056] FIG. 4B illustrates an example of a system;

[0057] FIG. 4C illustrates an example of a system;

[0058] FIG. 5 illustrates an example of a system;

[0059] FIG. 6 illustrates an example of a system;

[0060] FIG. 7A illustrates an example of a system;

[0061] FIG. 78 illustrates an example of a system;

[0062] FIG. 8 illustrates an example of a system; and

[0063] FIG. 9 illustrates an example of a system.

DETAILED DESCRIPTION OF THE DRAWINGS

[0064] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure the present invention.

[0065] The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings.

[0066] It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.

[0067] Because the illustrated embodiments of the present invention may for the most part, be implemented using electronic and/or optical components and circuits known to those skilled in the art, details will not be explained in any greater extent than that considered necessary as illustrated above, for the understanding and appreciation of the underlying concepts of the present invention and in order not to obfuscate or distract from the teachings of the present invention.

[0068] FIG. 1 is a schematic description of a public domain disc laser in a simple linear stable resonator configuration. The pumping and cooling arrangements of the disc element are not shown here and hereafter for simplicity. D1 11 is a thin-disc amplifying element with a fully reflective mirror on its rear side. M3 13 is an output-coupling mirror. The same nomenclature holds for the following figures as well.

[0069] FIG. 2 is a previously published description of a waxicon-axicon [M1 11 and M2 12 respectively] resonator implemented in a CO.sub.2 laser with an annular active volume. The beam is radially folded and passed through the annular active volume and central elements, and finally out coupled through the coupling mirror M3 13.

[0070] FIG. 3 is a schematic description of a single even waxicon M1 11 and axicon M2 12 resonator implemented in the embodiment of a disc laser with an amplifying disc Dl. The beam is radially folded and passed through the active volume annular and central elements, and is reflected by the rear surface of the disc, and finally out coupled through the coupling mirror M3. There may be more than one active laser disc in the resonator, or additional passive mirrors, folding the resonator.

[0071] FIG. 4A is a schematic description of a multiple even waxicon M11 111 and axicon M22 122 resonator implemented in the embodiment of a disc laser. The multiple even waxicon may have more pairs of conical folding surfaces than depicted in the figure, and corresponding folding conical surfaces in the axicon M22 122.

[0072] There may be more than one active laser disc Di in the resonator, or additional passive mirror(s) Mi, folding the resonator. A module that include one or more laser disks and one or more mirrors is denoted Di, Mi 150.

[0073] The additional passive mirrors, as well as appropriate curvatures in the conical surfaces of M1 1 111 and M22 122, may also be used as intra-cavity beam-expanders to facilitate matching between the size/shape of waxicon-axicon pairs and the size/shape of the amplifying disc [or discs]. The same statements hold for all the figures herein. The beam is radially folded and passed through the active volume annular and central elements, and is reflected by the rear surface of the disc(s) Di, and finally out coupled through the coupling mirror M33 133.

[0074] FIG. 4B is an explanatory presentation of the folding principle mentioned for FIG. 4A above. The optical folding of the resonator may be performed using amplifying discs or mirrors.

[0075] FIG. 4C, along with the former figures, depicts graphically the relation between the number of stages of the axicon and the number of stages of the waxicon. It follows that the number of axicon stages is as that of the waxicon, without/except the central cone of the waxicon.

[0076] FIG. 5 is a schematic description of a multiple even waxicon M11 111 and axicon M22 122 resonator implemented in the embodiment of a disc laser. The beam is radially folded and passed through the active volume annular and central elements, and is reflected by the rear surface of the disc(s) Di, and finally out coupled through half 141 of the coupling mirror. The mirror is halved through its diameter such that one half 142 is fully [100% ideally] reflecting, and the second half 141 is partially reflective [PR] according to the output coupling requirements of this resonator. There may be more than one active laser disc in the resonator, or additional passive mirrors, folding the resonator. In this arrangement the resonator, with proper design, supports a mode in the shape of TEM.sub.10, half of which is out-coupled through the mirror.

[0077] FIG. 6 depicts a similar arrangement as FIG. 5A, except that in this figure the resonator is of the Unstable Resonator configuration, the concave mirror 152 and the convex mirror 153 acting as the end-mirrors, and the out-coupling is done with a scrapper mirror 151.

[0078] An alternative coupling method can be without the scrapper, with the convex mirror 153 being a gradial-reflectivity mirror [such as but not limited to a Gaussian or a super-Gaussian mirror].

[0079] FIG. 7A is a schematic description of a multiple even waxicon M11/axicon M22 amplifier implemented in the embodiment of a disc laser. The beam is introduced into the amplifier from an external source via the folding mirror 155, then radially folded and passed through the active volume annular and central elements, and is reflected by the rear surface of the disc(s) Di, and finally out coupled with or without another folding mirror [the other folding mirror not shown in the figure]. There may be more than one active laser disc in the resonator, or an additional passive mirror, folding the amplifier.

[0080] FIG. 7B is a schematic description of a multiple even reflaxicons MRF1/MRF2 amplifier implemented in the embodiment of a disc laser. The beam is introduced into the amplifier from an external source via the central cone of MRF1, then radially folded by the external parts of MRF1 and MRF2 and passed through the active volume annular elements, and is reflected by the rear surface of the disc(s) Di, and finally out coupled with the central cone of MRF2. There may be more than one active laser disc in the resonator, or additional passive mirrors, folding the amplifier.

[0081] FIG. 8 illustrates a system in which a seeding beam SB 159 is introduced through a small aperture at the center of the central cone of the waxicon M1 or M11 respectively. There may be more than one active laser disc in the resonator, or an additional number of passive mirrors, folding the resonator. The diameter of the seed beam is small so as to ensure diffractive spread allowing the reflection from the output coupler M3 to expand and fill the resonator via the reflections from the waxicon and axicon.

[0082] FIG. 9 is a schematic description of a system that includes an Excimer Amplifying Module (denoted EAM 160) that is optically pumped and is provided as the active medium, with optical elements to couple the radiation to the waxicon-axicon resonator. This configuration provides yet another sort of capabilities to control the laser operation.

[0083] It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.

[0084] There may be provided a laser system providing a stable low-order mode output beam, said system having low sensitivity to opto-mechanical misalignments may include an active volume that may have large transversal dimensions such as, but not limited to, a solid state laser single or multiple disc amplifier; means (such as laser diodes) of exciting said active volume or volumes in a cylindrically symmetric shape to provide optical gain for laser action; means of cooling (such as water flowing behind the back [reflecting] side of the amplifying disc) said volume or volumes; a stable or an unstable resonator that may include an even-stage reflective annular axiconical end mirror, a corresponding-stage-number waxiconical reflector and a partially transmitting concave output coupling mirror, said resonator being co-axial and optically aligned with said active volume which in the case of a solid-state laser disc amplifier acts also as a folding element in said resonator, said resonator producing a low-transverse-order single mode output beam; said annular axicon, waxicon and partially transmitting mirror having radial curvatures designed for the supporting of said single mode beam; the stages of said waxicon and axicon being annuli of radial widths either equal to each other or designed for best distribution of the intra-cavity power density flux (controlling the mirror heating and/or gain saturation in the active medium) and low-transverse-mode support (by further controlling the Fresnel Number in the various sections of the resonator); mirrors acting as additional optical folding elements in said resonator; wherein all the optical chain elements of said resonator designed, mounted and aligned to ensure the production of the said desired low-transverse-mode output beam.

[0085] The laser system may produce said output beam from said active volume with an improved efficiency, by better utilizing the cumulative gain from the multiple passes through the active medium which may have a low single-pass gain.

[0086] Annular optically-attenuating rings may be introduced in the active volume according to the geometry of the waxicon mirror, in between the folding conical rings, to reduce the amplified spontaneous emission in the radial direction.

[0087] The output coupling mirror may be half diametrally fully reflective and half partially transmitting.

[0088] The laser system may be configured as an amplifier having staged reflaxicons introduced instead of the axicon, waxicon and output coupling mirror.

[0089] The laser system may act as an amplifier having input and output optical folding and/or transmitting arrangement instead of the output coupling mirror.

[0090] The laser system may receive a seeding laser beam through an opening at the tip of the central cone of said waxicon to influence the oscillating mode shape or polarization or frequency or time-modulation or any combination of the above. The laser may be induced to oscillate at a chosen wavelength, polarization, timing and/or mode shape. In the current example the seeding beam is introduced via a hole in the tip of the waxicon.

[0091] The pumping (the excitation) of the active volume is homogeneous.

[0092] The pumping of the active volume is not homogeneous to produce improved output beam quality and/or power.

[0093] An electro-optical modulation means may be introduced in the path of the central beam to enable short and ultra-short laser pulse generation.

[0094] The radial folding mirror elements may be a pair of a single stage waxicon and a single stage axicon.

[0095] The terms including, comprising, having, consisting and consisting essentially of are used in an interchangeable manner. For exampleany module may include at least the components included in the figures and/or in the specification, only the components included in the figures and/or the specification.

[0096] Any reference to the phrases may or may be should be applied to the phrases may not or may not be.

[0097] The phrase and/or means additionally or alternatively.

[0098] In the foregoing specification, the invention has been described with reference to specific examples of embodiments of the invention. It will, however, be evident that various modifications and changes may be made therein without departing from the broader spirit and scope of the invention as set forth in the appended claims.

[0099] Moreover, the terms front, back, top, bottom, over, under and the like in the description and in the claims, if any, are used for descriptive purposes and not necessarily for describing permanent relative positions. It is understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of operation in other orientations than those illustrated or otherwise described herein.

[0100] Those skilled in the art will recognize that the boundaries between components are merely illustrative and that alternative embodiments may merge components or impose an alternate decomposition of functionality upon various components. Thus, it is to be understood that the architectures depicted herein are merely exemplary, and that in fact many other architectures may be implemented which achieve the same functionality.

[0101] Any arrangement of components to achieve the same functionality is effectively associated such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality may be seen as associated with each other such that the desired functionality is achieved, irrespective of architectures or intermedial components. Likewise, any two components so associated can also be viewed as being operably connected, or operably coupled, to each other to achieve the desired functionality.

[0102] Furthermore, those skilled in the art will recognize that boundaries between the above described operations merely illustrative. The multiple operations may be combined into a single operation, a single operation may be distributed in additional operations. Moreover, alternative embodiments may include multiple instances of a particular operation, and the order of operations may be altered in various other embodiments.

[0103] However, other modifications, variations and alternatives are also possible. The specifications and drawings are, accordingly, to be regarded in an illustrative rather than in a restrictive sense.

[0104] In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word comprising does not exclude the presence of other elements or steps then those listed in a claim. Furthermore, the terms a or an, as used herein, are defined as one or more than one. Also, the use of introductory phrases such as at least one and one or more in the claims should not be construed to imply that the introduction of another claim element by the indefinite articles a or an limits any particular claim containing such introduced claim element to inventions containing only one such element, even when the same claim includes the introductory phrases one or more or at least one and indefinite articles such as a or an. The same holds true for the use of definite articles. Unless stated otherwise, terms such as first and second are used to arbitrarily distinguish between the elements such terms describe. Thus, these terms are not necessarily intended to indicate temporal or other prioritization of such elements. The mere fact that certain measures are recited in mutually different claims does not indicate that a combination of these measures cannot be used to advantage.

[0105] While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now occur to those of ordinary skill in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.