Patent ID: 12237642

SPECIFIC DESCRIPTION

Reference will now be made in detail to the embodiments of the invention. Wherever possible, same or similar reference numerals are used in the drawings and the description to refer to the same or like parts or steps. The drawings are in simplified form and are not to precise scale. For purposes of convenience and clarity only, directional (up/down, etc.) or motional (forward/back, etc.) terms may be used with respect to the drawings. The term “couple” and similar terms do not necessarily denote direct and immediate connections, but also include connections through intermediate elements or devices.

In accordance with the inventive concept shown inFIGS.1,2and3, the disclosed ultra-high power all fiber laser system10may include any number of fiber laser sources14p-14climited only by practical considerations. The laser sources14are arranged in a configuration having one or more central lasers sources14cand multiple peripheral laser sources14pwhich may flank, surround or just simply be spaced from the central source(s) without any specific order. The operational regime of laser sources14may be selected from one of continuous wave (CW) or quasi CW (QCW) or pulsed regimes. The scope of the disclosure provides for laser sources14operate in respective different regimes or all source may have the same regime. For example, central laser14cmay be a QCW laser, whereas peripheral laser sources14ccan operate in a CW regime. The laser sources may output respective laser beams simultaneously or sequentially in a single transverse mode (SM) or multiple transverse modes (MM) which necessitates either SM fibers or MM fibers. The configuration including a combination of SM and MM laser sources along with respective SM and MM fibers is also contemplated within the scope of this disclosure. The output powers of respective laser sources14may be either the same or different from one another. The laser sources are controlled by a central processing unit12in a manner known to one of ordinary skill in software and laser arts. The configuration of individual laser sources may include a master oscillator power amplifier architecture or just an oscillator.

The laser sources14generate respective laser outputs guided along light paths through respective central and peripheral output fibers16cand16p, the downstream ends of which are spliced to respective feeding fibers18cand18p. To prevent losses, the cores of respective spliced output and feeding fibers are aligned with one another and uniformly dimensioned.

The feeding fibers18pand18care coupled to a tapered fiber-bundle including a plurality of guiding fibers which are fused together to define a downstream tapered fiber bundle20. The tapered fiber bundle, as known to one ordinary skill and shown inFIG.2, is configured with a central guiding fiber22c, which is spliced to the downstream end of central feeding fiber18c, and a plurality of peripheral guiding fibers22psurrounding central fiber22cand spliced to peripheral feeding fibers18p. The input and output faces24and26(FIG.1), respectively, define therebetween the body of fiber bundle20. Depending on the number of feeding fibers18, fiber bundle20may have a 3×1 or 7×1 or 19×1 configuration or even more individual fibers20c,20pcoupled to more than one second cores of delivery fiber28provided the technological circumstances allow the desired number of fibers20. The reduction of input face24of fiber bundle20is determined by the outer peripheries of respective spaced and co-extending feeding fibers18. A particularly advantageous ratio between input and output faces24,26, respectively, of combiner20may v within a 2 to 10 range. The determining factors of the actual reduction of face26include alignment and dimension of (1) the core of central feeding fiber18c(FIG.2) and central core34of delivery fiber28, and (2) the cores of respective peripheral feeding fibers18pas well as second core32of deliver fiber28. Completing the structure of fiber bundle20is a protective sleeve52of polymer material covering the splice region between combiner20and delivery fiber28in a known to one of ordinary skill manner.

Referring toFIG.3in addition toFIGS.1and2, output face26of downstream fiber fiber bundle20(FIG.1) is spliced to a multicore delivery fiber28. The latter is configured with at least two concentric cores. One of the cores is a central core34which receives light guided through a central fiber train including at least one output of central laser sources14cand central fiber20cof fiber bundle20. At least one second core32of deliver fiber28receives light guided through outputs of respective peripheral laser sources14pand central fiber20pof bundle20. The central and second cores34,32respectively are separated by an inner cladding36which along with outer clad38sandwiches second core32. The refractive index of delivery fiber28is shown at the bottom ofFIG.3and includes a uniform index for both cores32,34which is higher than a uniform index of inner and outer cladding36,38respectively.

The longitudinal cross-section of delivery fiber28, as shown inFIGS.1and2, has preferably a double bottleneck shape which is configured with input and output tapered sections or portions44,46gradually expanding inwards and terminating at a distance from one another. A mid-section42has a diameter larger than that of each input and output faces29of the delivery fiber and bridges tapered sections44and46, respectively. The input and output sections44,46each extend outwards directly from mid-section42of delivery fiber28, as shown inFIG.1. Alternatively, delivery fiber28may be provided with opposite input and output elongated cylindrical end sections48,50(FIG.2), respectively which extend outwards from input and output faces29(FIG.1) of respective tapered portions44,46. The delivery fiber28may be up to at least 20 m long without showing any degradation in a 100 kW CW laser system10. The protective sleeve52envelopes fiber bundle20and extends over its opposite faces24and26, respectively to cover a splice54with delivery fiber28and at least downstream portions of respective feeding fibers (FIG.2). An end block or beam expander40is spliced to the output face of delivery28and configured to minimize the environmental hazard in the known manner.

The feeding fibers18c,18pare disclosed above as being directly coupled to respective central and peripheral guiding fibers of downstream combiner20. Alternatively, a plurality of central laser sources14cand plurality of peripheral laser sources14pmay be grouped together, as shown inFIG.1. The feeding fibers18guiding light from respective laser sources of each group are, in turn, coupled to respective second or upstream combiners60. Accordingly, system10may be provided with central and peripheral combiners60cand60phaving respective output fibers62cand62pspliced to central and peripheral guiding fibers of combiner20. Combining multiple laser outputs into a single output fiber of each combiner may increase the intensity of light delivered to downstream combiner20. The number of feeding fibers18of each group may vary and limited only by technological and practical considerations. For example,FIG.1illustrates the 3×1 configuration of each combiner60c, p. The delivery fiber28may be provided with a clad-mode absorber, as known in the art, which is configured to remove propagation of modes along the outer clad that can be detrimental to the protective layer of delivery fiber28.

FIGS.4A-4Din combination withFIGS.1and2illustrate respective cross-sections of the illustrated structure. In particular,FIG.4Aillustrates a cross-sectional view of output face26of 7×1 fiber bundle20provided with a central fiber20cand six (6) peripheral fibers20paround central fiber20c. The inputs of respective fibers20cand20pare spliced to respective outputs of laser sources14ofFIG.1, and each fiber20guides the received light beam toward downstream face26of bundle20. The latter is reduced such that individual beams delivered by respective peripheral fibers20pare coupled into second core32of delivery fiber28, whereas the central beam propagating along central fiber20centers into central core34of fiber28, as shown inFIG.4C. Turning toFIG.4B, central core34has a diameter which is substantially equal to or greater than that of central guiding fiber20cofFIG.4Ashowing fiber bundle downstream face26. The second core32of delivery fiber28is dimensioned to receive peripheral guiding fibers20pof fiber bundle20, as shown inFIG.4C. The refractive index profile of delivery fiber28is illustrated inFIG.4D.

FIGS.5A-5Dillustrate respective views corresponding to the views of respectiveFIGS.4A-4D. However, the shown configurations of fiber bundle20includes nineteen (19) guiding fibers20cand20parranged concentrically with the inner circle, which corresponds to central guiding fiber20c, and the outer circle having twelve (12) peripheral guiding fibers20p. The increased number of the guiding fibers may cause the modification of delivery fiber28. As illustrated inFIGS.5B and5D, the latter is configured with central core34and two second cores32and35. Three cladding36,38and39compete the configuration ofFIG.5B. Similar to the configuration ofFIGS.4A-4D, the core diameters of respective guiding fiber20cand central core34of delivery fiber28are dimensioned to match one another.

Referring briefly toFIGS.4D and5D, the refractive index of fiber28shown inFIGS.4D,5Dincludes refractive indices n1of respective central core and second core(s) equal to one another. However, the scope of the disclosure covers central and second cores configured with respective indices which differ from one another. Similarly, while inner and outer cladding38,36and39are shown to have with a uniform refractive index n2, it is foreseen that these claddings may have respective refractive indices not equal to one another.

FIGS.6A and6Billustrate the cross-sectional views of fiber bundle20and delivery fiber28, respectively. The difference between this modification and those shown inFIGS.4and5includes a different multiple central fibers20cof fiber bundle20. In particular, three (3) central fibers20ctogether define an outer circumference matching the core diameter of central core34of delivery fiber28.

FIGS.7A-7Bare analogous toFIGS.6A-6Brespectively. However, fiber bundle20has a central zone defined by seven 7 central fibers20cwhich define an outer circumference matching the core diameter of central core32of delivery fiber28. Twelve guiding peripheral fibers20pare spliced to second core32of delivery fiber28and, similar to all previously disclosed modifications, may radially extend into neighboring regions of respective claddings36,38of delivery fiber28.

As readily understood by one of ordinary skill in the laser arts, the number of central fibers20cof fiber bundle20may be increased. The increased number of central fibers20c, in turn, may require the increased core diameter of central core34of delivery fiber28. Thus those peripheral fibers20pof bundle20which are located close to central fiber20are aligned with inner second core34of fiber28and those fibers20plocated radially farther way from central fiber20care aligned with outer second core35ofFIG.5B. The core diameter of central core34of delivery fiber28may vary between 50μ and 100μ, whereas the outer diameter of delivery fiber28may range between 150μ and 300μ. These ranges, of course, are exemplary and may be adjusted in accordance with any given requirements. Note that inFIGS.4-7, the output ends of respective fibers20p, cof fiber bundle20are in mechanical contact with one another.

In use, controlling the lasers' output, light signals can be selectively guided through respective cores of feeding fibers18and coupled into the desired core or cores of delivery fiber28through respective fibers20c,20pof bundle20. As a result, delivery fiber28outputs the system beam having the desired shape. The shape of the beam incident on the workpiece to be laser treated may be represented by only a full central spot if only one or more central feeding fibers18care utilized without the help of peripheral feeding fibers18p. Alternatively, the shape may have one or multiple donut-shape beam or beams if only peripheral laser sources14pand peripheral fibers20pof bundle20are used. Of course, all source can be used simultaneously. Preferably, but not necessarily, all fibers of the combiner ofFIGS.4and7are multimode (MM) fibers. Alternatively, only central fiber20is MM whereas all peripheral fibers18are single mode (SM) fibers. Obviously other combinations of MM and SM fibers can be utilized to match the required task.

One advantageous combination of laser sources14p-14cofFIG.1may include a “central” laser14cwhich operates in a quasi-continuous (QCW) regime, whereas the “peripheral” lasers each output a CW beam. The central and peripheral lasers may operate simultaneously or sequentially. The QCW laser may be used, for example, as a piercing tool, whereas the CW peripheral lasers can be used for cutting. The configuration ofFIGS.1-7may be applied to both the piercing and cutting of the workpiece by utilizing central concentric feeding fibers. Other possible combinations of operational laser regimes may include pulsed lasers in combination with either CW of QCW lasers. The peripheral lasers may be selectively utilized with one or more peripheral lasers not outputting beams.

Having thus described several aspects of at least one example, it is to be appreciated that various alterations, modifications, and improvements will readily occur to those skilled in the art. For instance, examples disclosed herein may also be used in other contexts. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the scope of the examples discussed herein. Accordingly, the foregoing description and drawings are by way of example only.