IL259366A - Hybrid fiber-coupled diode pump laser module - Google Patents

Description

Monitor Fig. 1 Prior Arty X Fig. 2A zTop view X Fig. 2B zFront view Fig. 2C y XFig. 2Dy X z Fig. 3Ay X z Fig. 3By X Fig. 3C zy X Fig. 4 zy X Fig. 5 zy X Fig. 6 zLaser Amplifying System 740 Seed Pump Dump 300 400 703 704 702 Fig. 7Fiber Laser Systems 840 Pump Dump 500 600 803 804 Fig. 8A 840 FGB Pump Dump 500 803 804 804 Fig. 8BP-574981-IL 259366/2 HYBRID FIBER-COUPLED DIODE PUMP LASER MODULE BACKGROUND OF THE INVENTION

[001] High power fiber lasers and fiber amplifiers require high brightness pump source and efficient techniques to be coupled with a doped fiber, in order to excite the ions and initiate a lasing process. Coupling a signal power with a fiber core is also critical.

[002] A common method to couple a pump and/or a signal light with a doped fiber is via a fused coupler, which is a fiber combiner or a fused tapered fiber bundle (TFB), based on end face pumping technique. A TFB combiner with signal feedthrough includes a central input signal fiber and an output pigtail (curled) double-clad (DC) fiber, which combines the signal and pump light in a single pigtail fiber. The use of a TFB includes guiding the signal light, surrounded by several multi-mode fibers and guiding the pump light. In order to match the diameter of the fiber bundle to the diameter of the output pigtail fiber, the bundle is slowly melted and tapered. After the tapering process the fiber bundle is cleaved around the taper waist and fusion spliced to the output pigtail DC fiber. However, tapering of the fiber bundle inherently involves increasing the numerical aperture (NA) of the pump light and a change of the mode field diameter (MFD) of the signal light. Hence, the necessary optical matching and mechanical alignment requirements between the tapered fiber bundle and the output pigtail DC fiber can lead to several drawbacks of the TFB structure, for example: ₋ less flexibility in the choice of input fibers that can match the output pigtail DC fiber, after the tapering process; ₋ a slight mismatch or misalignment between the signal mode field diameters (MFD) of the tapered input signal fiber and the output pigtail DC fiber leads to a degradation of the beam quality, primarily in conjunction with signal insertion loss and which could also lead to catastrophic damage to the fiber at high power operation; ₋ in the case of a backward propagating signal, e.g. for a counter-propagation pumped fiber amplifier, the signal insertion loss (up to 10%) can cause damage to the pump diodes due to their insufficient isolation against amplified signal light. 1 P-574981-IL 259366/2

[003] Another common technique includes a monolithic all-fiber combiner like a gradually transferred (GT) wave coupler, with the employment of a tapered capillary around a multi-clad fiber or direct fusion of one or more tapered multi-mode fibers to the outermost cladding of multi-clad fibers.

[004] However, the coupling efficiencies of the current combiners are not sufficient to permit their use in very high-power amplifiers and lasers. In addition, as the signal fiber is tapered down along with the pump fibers, the resulting small core diameter of the signal fiber creates significant mismatch problems for coupling with large mode area double clad fibers. These large mode field diameter mismatches cause unacceptably high signal loss, which probably cause temperature increase and damage to the TFB.

[005] Another drawback is their susceptibility to parasitic non-linear processes, primarily stimulated Brillouin scattering (SBS), which occurs when the laser signal has a line-width narrower than a few tens of megahertz. This is due to the long interaction length (due to the component additional fiber length) of the optical signal field and the core material of the fiber

[006] Accordingly, there is a need for a new technique that overcome the above- mentioned deficiencies, can reduce the number of fusion points and can reduce energy loss.

SUMMARY OF THE INVENTION

[007] In some embodiments of the invention, a hybrid fiber-coupled diode pump laser module (and in short, a pump module) is provided, configured to be coupled to an optical fiber having a core and at least one clad, the pump module comprising: ₋ at least one focusing lens in optical path with the optical fiber; ₋ plurality of diode modules, each configured to output a multi-mode beam in optical path with the clad; ₋ at least one core associated module in optical path with the core configured to provide a function selected from a group of consisting of: a) to output a single-mode beam towards the core; 2 P-574981-IL 259366/2 b) to receive a beam from the core, and to couple the received beam to an output optical fiber; c) to receive a beam from the core, and to reflect the received beam back to the core, and d) to receive a beam from the core, and to reflect a part of the received beam back to the core, and to couple another part of the received beam to an output optical fiber.

[008] In some embodiments, the pump module further comprises a volume Bragg grating (VBG), configured to narrow and lock beams to a predetermined range of wavelength.

[009] In some embodiments, the plurality of diode modules and the core associated module are arranged in at least one row, such that their output beams are parallel one to another, per each row.

[0010] In some embodiments, in the case of two rows or more, the pump module further comprises: ₋ at least one polarizer beam combiner, in the path of a first beams' row; ₋ one or more folding mirrors, each folding-mirror for each additional row, wherein each folding mirror is configured to redirect its corresponding row of parallel beams into the respective polarizer beam combiner.

[0011] In some embodiments, each of the diode modules comprises: ₋ a broad area laser (BAL); ₋ a BAL associated folding-mirror, configured with an optical path between its associated BAL and the clad; and ₋ optionally, at least one lens arranged between the BAL and its associated folding- mirror, configured to adjust shape of the BAL's beam.

[0012] In some embodiments, the core associated module comprises a seed module comprising: ₋ at least one seed input, configured to be coupled to a seed laser device; ₋ a seed associated folding-mirror, configured for optical path between the seed input and the core; and 3 P-574981-IL 259366/2 ₋ optionally, at least one lens arranged between the seed input and its associated folding-mirror, configured to adjust shape of the seed's beam.

[0013] In some embodiments, the seed associated module further comprises at least one of: ₋ a beam amplifier, configured to amplify the seed beam; ₋ a tap (not shown) or a partial mirror, configured to sample the seed beam, and a monitor configured monitor and alert of backward beam transmission; and ₋ an isolator, configured to allow transmission of light in one direction only.

[0014] In some embodiments, the core associated module comprises an output module comprising: ₋ an output fiber, optionally comprising an end-cap element; ₋ a folding-mirror associated with the output fiber, configured for optical path between the core and the output fiber; ₋ optionally, at least one lens, arranged between the output fiber and its associated folding-mirror, configured to adjust shape of the received core beam; and ₋ optionally, a pump dump.

[0015] In some embodiments, the core associated module comprises a high reflecting (HR) module comprising: ₋ an HR mirror; ₋ a folding-mirror associated with the HR mirror, configured for optical path between the core and the HR mirror; and ₋ optionally, at least one lens arranged between the HR mirror and its associated folding-mirror, configured to adjust shape the associated beams.

[0016] In some embodiments, the HR module further comprises an intra cavity modulator arranged between the HR mirror and its associated folding-mirror, configured to modulate the reflected beam.

[0017] In some embodiments, the core associated module comprises a partial reflecting (PR) module comprising: 4 P-574981-IL 259366/2 ₋ an output fiber, optionally comprising an end-cap; ₋ a PR mirror, in optical path with the output fiber; ₋ a folding mirror associated with the PR mirror, configured for optical path between the core and the PR mirror; and ₋ optionally, at least one lens, arranged between the PR mirror and its associated folding-mirror, configured to adjust shape the associated beams.

[0018] In some embodiments, the pump module further comprises at least one heat dispensing element selected from a group consisting: base surface, ribs, screws, and any combination thereof.

[0019] In some embodiments of the invention, a fiber amplifying system is provided comprising: ₋ an optical fiber, comprising a core and at least one clad; ₋ the pump module according to at least some of the above embodiments, coupled to a first end of the optical fiber.

[0020] In some embodiments, the system further comprises at least one selected from: a pump dump, an end-cap element.

[0021] In some embodiments, the fiber amplifying system, further comprises the pump module according to at least some of the above embodiments, coupled to a second end of the optical fiber.

[0022] In some embodiments of the invention, a fiber laser system is provided comprising: ₋ an optical fiber, comprising a core and at least one clad; ₋ the pump module according to at least some of the above embodiments, coupled to a first end of the optical fiber; and ₋ a Fiber Bragg Grating (FBG) or the hybrid pump module according to at least some of the above embodiments, coupled to a second end of the optical fiber.

[0023] In some embodiments, the fiber laser system further comprises at least one of: a pump dump and an end-cap element.

P-574981-IL 259366/2 BRIEF DESCRIPTION OF THE DRAWINGS

[0024] 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:

[0025] Fig. 1 schematically illustrates a prior art example for a fiber amplifying system;

[0026] Fig. 2A, 2B, 2C and 2D schematically illustrate hybrid pump modules, according to various embodiments of the invention;

[0027] Fig. 3A, 3B and 3C schematically illustrate hybrid pump modules, where a core associated module is a seed associated module, according to some embodiments of the invention;

[0028] Fig. 4 schematically illustrates a hybrid pump module, where a core associated module is an output module, according to some embodiments of the invention;

[0029] Fig. 5 schematically illustrates a hybrid pump module, where a core associated module is a high reflecting module, according to some embodiments of the invention;

[0030] Fig. 6 schematically illustrates a hybrid pump module, where a core associated module is a partial reflecting module, according to some embodiments of the invention;

[0031] Fig. 7 schematically illustrates a fiber amplifying system, according to some embodiments of the invention; and

[0032] Figs. 8A and 8B schematically illustrate fiber laser systems, according to some embodiments of the invention.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0033] 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 6 P-574981-IL 259366/2 other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure the present invention.

[0034] The present invention relates to methods and apparatuses configured to provide optical signal amplifiers and more specifically a hybrid fiber-coupled diode pump laser module (and in short, a hybrid pump module), configured to be coupled to an optical fiber.

A skilled artisan would appreciate that the term "hybrid" refers may refer to according to some embodiments the combination of pump and signal.

[0035] A skilled artisan would appreciate that a fiber amplifying system is configured to absorb and couple energy from several multi-mode pumps and usually one single-mode seed device, and amplify it to output a high-power single-mode beam.

[0036] A general or typical model/design for a fiber amplifying system is demonstrated in Fig. 1. The fiber amplifying system 100 includes: a seed lasing device 110, connected via optical fibers (marked with lines ˗ and fusion point signs ×) to an amplifier 120, an isolator 130, a tap element 140 and a monitor 141, and mode field adaptor (MFA) 150, all as an input for a multi-mode combiner (MMC) 170, which is configured to combine the optical fibers of the six pump modules 160 together with the one optical fiber originating from the seed device into the active fiber 180. The active fiber is configured to receive an input signal and generate an output signal with higher optical power. As shown, the active fiber is connected at first end to the MMC (as mentioned above) and at the second end to a pump dump 190, configured to dump the residual pump power and scattered signal in the clad, where the output of the system is usually via an output fiber having an end-cap 191. As demonstrated the use of optical fibers for transferring light beams require multiple fusion points 192, symbolically signed with an "×".

[0037] A skilled artisan would appreciate that the above mentioned "fusion points" are also known as fusion splices. A skilled artisan would appreciate that fusion splicing is the act of joining two optical fibers end-to-end using heat. The goal is to fuse the two fibers together in such a way that light passing through the fibers is not scattered or reflected back by the splice, and so that the splice and the region surrounding it are almost as strong as the original fiber itself. Prior to the removal of the spliced fiber from the fusion splicer, a proof-test is performed to ensure that the splice is strong enough to survive handling, 7 P-574981-IL 259366/2 packaging and extended use. The bare fiber area is protected either by recoating or with a splice protector. Accordingly, there is a need for a fiber amplifying system that can reduce the number of fusion points, can reduce energy loss and production costs.

[0038] A skilled artisan would appreciate that the term “multi-mode combiner (MMC)” may refer to an optical component configured to combine the several fibers into one fiber (in the example of Fig. 1: six pump connected fibers + one seed connected fiber), which is compatible with a fiber amplifier, such that the light from the pump modules enters the clad and the light from the seed enters the core. The MMC is a complicated device (e.g. need special features to dispense heat) and therefore expensive.

[0039] A skilled artisan would appreciate that the term “fiber amplifier” or “active fiber amplifier” may refer, according to some embodiments, to a doped fiber that receives power from several pump modules and a seed module (e.g. Fig. 1: six multi-mode beams+ one single-mode beam) and outputs a single-mode beam (due to the single-mode seed) having enhancement. Over all diameter can be about 400 micro-meter where the core diameter can be about 20 micro-meter. The light from the pump modules enters the clad and the light from the seed enters the core. For example, fiber amplifiers are based on “active” fibers, having a fiber core, which is doped with laser-active ions such as Er3+, Nd3+ or Yb3+. Normally a fiber coupler is used to introduce some “pump light” in addition to the input signal light.

This pump light is absorbed by the laser-active ions, transferring them into excited electronic states and thus allowing the amplification of light at other wavelengths via stimulated emission.

[0040] A skilled artisan would appreciate that the term “pump dump” may refer, according to some embodiments of the invention, to a beam dump, which is a device designed to absorb or deflect residual un-absorbed pump power or scattered signal in the clad. For the example of Fig. 1, absorbing emission left in the clad of the active fiber.

[0041] A skilled artisan would appreciate that the term “isolator” may refer, according to some embodiments of the invention, to an optical element configured to allow transmission of light in one direction only. 8 P-574981-IL 259366/2

[0042] A skilled artisan would appreciate that the term “pump modules” may refer, according to some embodiments of the invention, to modules with diodes therein providing multi-mode beams. A skilled artisan would appreciate that the term “broad area laser (BAL) diodes” may refer to diodes providing multi-mode beams with an oval shape cross section. BALs (also called broad stripe or broad emitter laser diodes, single-emitter laser diodes, and high brightness diode lasers) are edge-emitting laser diodes, where the emitting region at the front facet has the shape of a broad stripe.

[0043] A skilled artisan would appreciate that the term “single-mode” may refer, according to some embodiments of the invention, an optical beam having only one transverse mode excited.

[0044] A skilled artisan would appreciate that the term “polarizer beam combiner” may refer, according to some embodiments of the invention, to an optical element that is configured to combine together two signals with perpendicular polarizations.

[0045] A skilled artisan would appreciate that the term “volume Bragg grating (VBG)” may refer, according to some embodiments of the invention, to an optical means comprising a grating within a glass block configured to reflect an incident beam with an angel relative to the incident beam wavelength. A typical application of volume Bragg gratings is the wavelength stabilization of lasers, most often of laser diodes.

[0046] A skilled artisan would appreciate that the term “end cap” may refer, according to some embodiments of the invention, to an optical means configured to expand a beam's cross section. Fiber end caps are created by fusion splicing or laser fusing short lengths of material to the fiber end face. Fiber end caps are required for a number of applications including the creation of collimators, to allow expansion of high power fiber laser beams to reduce the power density at the air/silica interface and to protect structured fibers against environmental ingress.

[0047] A skilled artisan would appreciate that the term “phase modulator/s” may refer, according to some embodiments of the invention, to an optical modulator, which can be used to control the optical phase of a laser beam. Frequently used types of phase modulators are electro-optic modulators based on Pockels cells, Litium Niobate (LiNbO3) Electro Optic 9 P-574981-IL 259366/2 Modulatorsd and liquid crystal modulators, but it is also possible e.g. to exploit thermally induced refractive index changes or length changes e.g. of an optical fiber or induce length changes by stretching. Various kinds of phase modulators are used within the area of integrated optics, where the modulated light propagates in waveguides.

[0048] A skilled artisan would appreciate that the term “beam splitter” may refer, according to some embodiments of the invention, to an optical device, which is configured to split an incident light beam (e.g. a laser beam) into two or more beams, which may or may not have the same optical power. According to some embodiments, beam splitters are used as beam combiners, for combining few beams into a single beam. According to some embodiments, beam splitters are required for interferometers, auto-correlators, cameras, projectors and laser systems. According to some embodiments, beam splitters can include: ₋ dielectric mirror, which may be any partially reflecting mirror that can be used for splitting light beams. In laser technology, dielectric mirrors are often used for such purposes. The angle of incidence, also determining the angular separation of the output beams, for example 45°, which is often convenient, but it can also have other values, and influences the characteristics of the beam splitter. A wide range of power splitting ratios can be achieved via different designs of the dielectric coating. ₋ cubes, where the beam separation occurs at an interface within the cube. Such a cube is often made of two triangular glass prisms, which are glued together with some transparent resin or cement. The thickness of that layer can be used to adjust the power splitting ratio for a given wavelength. ₋ fiber optic splitter, which is a type of fiber coupler that is used as fiber-optic beam splitters. Such a device can be made by fusion-combining fibers, and may have two or more output ports. As for bulk devices, the splitting ratio may or may not strongly depend on the wavelength and polarization of the input. ₋ grating is an optical component with a periodic structure that splits and diffracts light into several beams travelling in different directions. The emerging coloration is a form of structural coloration. The directions of these beams depend on the spacing of the grating and the wavelength of the light so that the grating acts as the dispersive element.

According to some embodiments, grating can be used as beam combiner as well.

P-574981-IL 259366/2

[0049] A skilled artisan would appreciate that the term “fiber coupler” or “coupler” may refer, according to some embodiments of the invention, to an optical fiber device with one or more input fibers and one or several output fibers. Light from an input fiber can appear at one or more outputs, with the power distribution potentially depending on the wavelength and polarization.

[0050] A skilled artisan would appreciate that the term “tap" or "tap element” may refer, according to some embodiments of the invention, to a coupler configured for a coupling output ratio of 50:50, 75:25, 90:10, or 99:1. Fiber tapping may use a network tap method that extracts signal from an optical fiber without breaking the connection. Tapping of optical fiber can allow diverting some of the signal being transmitted in the core of the fiber into another fiber or a detector or a monitor.

[0051] A skilled artisan would appreciate that the term “optical amplifier” may refer, according to some embodiments of the invention, to a device which receives some input signal and generates an output signal with higher optical power. According to some embodiments, inputs and outputs are laser beams, either propagating in free space or in a fiber. The amplification occurs in a so-called gain medium, which has to be “pumped” (i.e., provided with energy) from an external source. According to some embodiments, optical amplifiers are optically, chemically or electrically pumped.

[0052] A skilled artisan would appreciate that the term “dichroic mirror” may refer, according to some embodiments, to a mirror with significantly different reflection or transmission properties at two different wavelengths.

[0053] A skilled artisan would appreciate that the term “seed laser” may refer to, according to some embodiments of the invention, a laser the output which is injected into an amplifier or another laser. Typical types of seed lasers are small laser diodes (single- frequency or gain-switched), short-cavity fiber lasers, and miniature solid-state lasers such as nonplanar ring oscillators (NPROs).

[0054] Reference is now made to Figs. 2A, 2B, 2C and 2D which schematically demonstrate a hybrid pump module configured to be coupled to an optical fiber 240. 11 P-574981-IL 259366/2 According to some embodiments, the optical fiber can be a doped (active) fiber or a passive fiber (data format transparent). The optical fiber comprises a core 241 and at least one clad 242. As shown in Figs. 2A, 2B, 2C and 2D the pump module 200 comprises: − at least one focusing lens 230 in free space optical path with the optical fiber 240; − plurality of diode modules 210, each configured to output a multi-mode beam which is in free space optical path with the clad 242 of the optical fiber, via the optical lens; − at least one core associated module 220 in free space optical path with the core 241 of the optical fiber, configured to provide a function selected from a group consisting of: a) to output a single-mode beam towards the core 241 of the optical fiber, via the optical lens; b) to receive a beam from the core 241 of the optical fiber, via the focusing lens, and to couple the received beam to an output optical fiber 411; c) to receive a beam from the core 241 of the optical fiber, via the focusing lens, and to reflect the received beam back to the core 241, again via the focusing lens; and d) to receive a beam from the core 241 of the optical fiber, via the focusing lens, and to reflect a part of the received beam back to the core, again via the focusing lens, and to couple another part of the received beam to an output optical fiber 610.

[0055] According to some embodiments, the term "single mode beam" refers to a beam consisting of one or few beam modes, in the range between 1 and 10 modes.

[0056] According to some embodiments, the plurality of diode modules 210 are in free space optical path with the clad 242 of the optical fiber. According to some embodiments this optical path does not include any optical fiber for the optical path. According to some embodiments, some of the diode modules 210 are in free space optical path with the core 241 of the optical fiber as well.

[0057] According to some embodiments, the core associated module 220 is in free space optical path with the core 241 of the optical fiber only; meaning no optical light is coupled 12 P-574981-IL 259366/2 into the clad 242 of the optical fiber 240. According to some embodiments this optical path does not include any optical fiber for the optical path.

[0058] According to some embodiments, the hybrid pump module 200 further comprises a volume Bragg grating (VBG) 250 configured to narrow and lock beams of the diodes to a narrow predetermined range of wavelength. According to some embodiments, a common VGB is a 976 wavelength locked module, which is perfectly matched to the high absorption narrow linewidth Yttrium boride (Yb) ions. According to some embodiments and as demonstrated in Fig. 2D the VGB is located between the focusing lens 230 and the optical fiber 240.

[0059] According to some embodiments, the plurality of diode modules 210 and the core associated module 220 are arranged in at least one row 281, such that their output beams are parallel one to another, per each row. Figs. 2A, 2B and 2C demonstrate an isometric view, top view and front view of the system having the plurality of diode modules 210 (in this example, eight diode modules) and the core associated module 220 are arranged in a single row. Fig. 2D demonstrates an isometric the system having the plurality of diode modules 210 (in this example, seventeen diode modules) and the core associated module 220 are arranged in two rows 281 and 282.

[0060] In some embodiments, and as demonstrated in Fig. 2D, for the case of two rows or more 181,182, the pump module further comprises: ₋ at least one polarizer beam combiner 260, in the optical path of a first beams' row 281; ₋ one or more folding mirrors 282A, each folding-mirror for each additional row, wherein each folding mirror is configured to redirect its corresponding row of parallel beams into its' respective polarizer beam combiner. 0048 According to some embodiments, and as demonstrated in Figs. 2A and 2B, each of the diode modules 210 comprises: ₋ a broad area laser (BAL) 211, configured to output a multi-mode beam; ₋ a BAL associated folding-mirror 212, configured with an optical path between its associated BAL and the clad 242 of the optical fiber (via the focusing lens 230); and 13 P-574981-IL 259366/2 ₋ optionally, at least one lens 213,214 arranged between the BAL and its associated folding-mirror 242, configured to adjust shape of the BAL's beam.

[0061] Reference is now made to Fig. 3A, 3B and 3C, which schematically demonstrate hybrid pump modules 300, comprising at least some of the features and elements as in the hybrid pump modules 200 demonstrated in Figs. 2A-2D. According to some embodiments, the core associated module is a seed associated module 301, configured to output a single- mode beam towards the core of the optical fiber, via the optical lens. The seed associated module 301 comprising: − at least one seed input 311, configured to be coupled to a seed laser device 702 (shown in Fig. 7), via an optical fiber 310; − a seed associated folding-mirror 312, configured for optical path between the seed input and the core 241 of the optical fiber, via the focusing lens 230, and − optionally, at least one lens 313 arranged between the seed input and its associated folding-mirror 312, configured to adjust shape of the seed's beam.

[0062] According to some embodiments, wherein the seed associated module 300 further comprises at least one of: ₋ a tap (not shown) or a partial mirror 305 and a monitor 306, as demonstrated in Fig. 3A, located between the seed input 311 and the optimal lens 313 or the folding-mirror 312, configured to sample the seed beam, monitor it and alert of backward beam transmission (back to the seed input 311); ₋ a beam amplifier 315, as demonstrated in Fig. 3B, located between the seed input 311 and the optimal lens 313 or the folding-mirror 312, configured to amplify the seed beam; and ₋ an isolator 316, as demonstrated in Fig. 3C, located between the seed input 311 and the optimal lens 313 or the folding-mirror 312, configured to allow transmission of light in one direction only.

[0063] Reference in snow made to Fig. 4 schematically demonstrates a hybrid pump module 400, comprising at least some of the features and elements as in the hybrid pump modules 200 demonstrated in Figs. 2A-2D. According to some embodiments, the core associated module is an output module 401, configured to receive a beam from the core of 14 P-574981-IL 259366/2 the optical fiber, via the focusing lens, and to couple the received beam to an output optical fiber 411. The output module 401 comprising: ₋ an output fiber 411, optionally comprising an end-cap element 409; ₋ a folding-mirror 412 associated with the output fiber 411, configured for optical path between the core 241 of the optical fiber and the output fiber 411; ₋ optionally, at least one lens 413, arranged between the output fiber 411 and its associated folding-mirror 409, configured to adjust shape of the received core beam; and ₋ optionally, a pump dump (not shown).

[0064] According to some embodiments, the output module 400 further comprises a tap (not shown) or a partial mirror 405 and a monitor 406, located between the output fiber 411 and the optimal lens 413 or the folding-mirror 412, configured to sample the seed beam, monitor it and alert of backward beam transmission (back to the folding mirror 412).

[0065] Reference in snow made to Fig. 5 schematically demonstrates a hybrid pump module 500, comprising at least some of the features and elements as in the hybrid pump modules 200 demonstrated in Figs. 2A-2D. According to some embodiments, the core associated module is a high reflecting (HR) module 501, configured to receive a beam from the core 241 of the optical fiber, via the focusing lens, and to reflect the received beam back to the core 241, again via the focusing lens. The (HR) module 501 comprising: ₋ an HR mirror 511, ₋ a folding-mirror 512 associated with the HR mirror 511, configured for optical path between the core 241 of the optical fiber and the HR mirror, and ₋ optionally, at least one lens 513 arranged between the HR mirror 511 and its associated folding-mirror 512, configured to adjust shape the associated beams.

[0066] According to some embodiments the (HR) module 501 is configured to reflect the received beam back and forth in a form of fiber resonator.

[0067] According to some embodiments, the HR module 501 further comprises an intra cavity modulator 510 arranged between the HR mirror 511 and its associated folding- mirror 512, configured to modulate the reflected beam's amplitude, or phase, or polarization or any combination thereof. According to some embodiments the intra cavity P-574981-IL 259366/2 modulator comprises an acusto-optic modulator, or an electro-optic modulator. According to some embodiments, the intra cavity modulation allows pulse laser behavior.

[0068] Reference in snow made to Fig. 6 schematically demonstrates a hybrid pump module schematically demonstrates a hybrid pump module 600, comprising at least some of the features and elements as in the hybrid pump modules 200 demonstrated in Figs. 2A- 2D. According to some embodiments, the core associated module is a partial reflecting (PR) module 601 comprising: − an output fiber 610, optionally comprising an end-cap 609; − a PR mirror 611, in optical path with the output fiber 610; − a folding mirror 612 associated with the PR mirror 611, configured for optical path between the core 241 of the optical fiber and the PR mirror 611; and − optionally, at least one lens 613, arranged between the PR mirror 611 and its associated folding-mirror 612, configured to adjust shape the associated beams.

[0069] According to some embodiments the assembly of the hybrid pump module 200, 300, 400, 500, 600 is configured to be aligned opto-mechanically, by measuring the beam paths and adjusting the location and/or orientation of the elements as mentioned above.

According to some embodiments, the adjustment is provided by a Jig vacuum catcher.

According to some embodiments, the adjusted element is at least one selected from: any one of the core modules, any one of the diode modules, any one the seed devices, any one of the BALs, any one of the folding-mirrors, any one of the lenses, any one of the beam amplifiers, any one of the taps or partial mirrors and monitors, any one of the isolators, any one of the HR mirrors, any one of the PR mirror, any one of the seed inputs, the focusing lens/es, the VGB.

[0070] According to some embodiments, at least some of the lenses 213,214,313,413,513,613, which are configured to shape a beam's cross section are selected from: fast access collimator (FAC) 213 and slow access collimator (SAC) 214.

[0071] According to some embodiments, at least some of the folding mirrors 212,312,412,512,612 are configured to tap (pass through) a fraction of the reflected beam, for further monitoring purposes (as demonstrated for example in Fig. 3 399). 16 P-574981-IL 259366/2

[0072] Reference in snow made to Fig. 7 which schematically demonstrates a fiber amplifying system 700. According to some embodiments of the invention, the fiber amplifying system 700 comprising: ₋ an active optical fiber 740, comprising a core and at least one clad; ₋ the hybrid laser pump module 300 comprising a seed module 301, according to the above embodiments, coupled to a first end 744 of the optical fiber.

[0073] As demonstrated in Fig. 7, the fiber amplifying system 700 is configured to receive a seed laser beam from a seed laser device 702 and to amplify it to high power single-mode laser beam.

[0074] According to some embodiments, the fiber amplifying system 700, further comprises the hybrid pump module 400 of comprising an output module 401, coupled to a second end 745 of the optical fiber. An artisan would appreciate that the hybrid pump module 400 is operative as a counter pump module configured to increase the beam amplification at the active optical fiber 745.

[0075] According to some embodiments, the fiber amplifying system 700 further comprises at least one selected from: a pump dump 703, an output 411 fiber with an end- cap element 704, coupled to a second end 745 of the active optical fiber 740.

[0076] An artisan would appreciate that the fiber amplifying system 700, according to the various embodiments as demonstrated above, reduces significantly the number of required fusion splices, while allowing non-dependent number of diode modules. For example, the prior art system 100 of Fig. 1 includes six diodes and requires at least nine (9) fusion splices. The current system 700 includes at least eight (can be more) diode modules and yet requires only two (2) fusion splices.

[0077] Reference in snow made to Figs. 8A and 8B, which schematically demonstrate fiber laser systems 800, according to some embodiments of the invention, comprising: ₋ an optical fiber 840, comprising a core and at least one clad; ₋ the hybrid laser pump module 500 comprising the HR module 501, coupled to a first end 844 of the optical fiber; and 17 P-574981-IL 259366/2 ₋ a fiber Bragg grating (FBG) 804 (as demonstrated in Fig. 8B), or the hybrid laser pump module 600 comprising the PR module 601 (as demonstrated in Fig. 8A), coupled to a second end 845 of the optical fiber.

[0078] An artisan would appreciate that the hybrid pump module 600 is operative as a counter pump module, configured to increase the beam amplification at the active optical fiber 840.

[0079] According to some embodiments, the fiber laser system 800 further comprises at least one of: a pump dump 803 and an output fiber comprising an end-cap element 804.

[0080] 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. 18 259366/2

Claims (17)

1. A hybrid pump module configured to be coupled to an optical fiber having a core and at least one clad, the pump module comprising: − at least one focusing lens in optical path with the optical fiber; − plurality of diode modules, each configured to output a multi-mode beam in optical path with the clad; − at least one core associated module in optical path with the core configured to provide a function selected from a group of consisting of: a) to output a single-mode beam towards the core; b) to receive a beam from the core, and to couple the received beam to an output optical fiber; c) to receive a beam from the core, and to reflect the received beam back to the core, and d) to receive a beam from the core, and to reflect a part of the received beam back to the core, and to couple another part of the received beam to an output optical fiber.

2. The hybrid pump module of claim 1, further comprises a volume Bragg grating (VBG), configured to narrow and lock beams to a predetermined range of wavelength.

3. The hybrid pump module of claim 1, wherein the plurality of diode modules and the core associated module are arranged in at least one row, such that their output beams are parallel one to another, per each row.

4. The hybrid pump module of claim 3, wherein in the case of two rows or more, the pump module further comprises: − at least one polarizer beam combiner, in the path of a first beams' row; 19 259366/2 − one or more folding mirrors, each folding-mirror for each additional row, wherein each folding mirror is configured to redirect its corresponding row of parallel beams into the respective polarizer beam combiner.

5. The hybrid pump module of claim 1, wherein each of the diode modules comprises: − a broad area laser (BAL); − a BAL associated folding-mirror, configured with an optical path between its associated BAL and the clad; and − optionally, at least one lens arranged between the BAL and its associated folding-mirror, configured to adjust shape of the BAL's beam.

6. The hybrid pump module of claim 1, wherein the core associated module comprises a seed module comprising: ₋ at least one seed input, configured to be coupled to a seed laser device; ₋ a seed associated folding-mirror, configured for optical path between the seed input and the core; and ₋ optionally, at least one lens arranged between the seed input and its associated folding-mirror, configured to adjust shape of the seed's beam.

7. The hybrid pump module of claim 6, wherein the seed associated module further comprises at least one of: − a beam amplifier configured to amplify the seed beam; − a tap or a partial mirror, configured to sample the seed beam, and a monitor configured monitor and alert of backward beam transmission; and − an isolator configured to allow transmission of light in one direction only.

8. The hybrid pump module of claim 1, wherein the core associated module comprises an output module comprising: − an output fiber, optionally comprising an end-cap element; − a folding-mirror associated with the output fiber, configured for optical path between the core and the output fiber; − optionally, at least one lens, arranged between the output fiber and its associated folding-mirror, configured to adjust shape of the received core beam; and 20 259366/2 − optionally, a pump dump.

9. The hybrid pump module of claim 1, wherein the core associated module comprises a high reflecting (HR) module comprising: − an HR mirror; − a folding-mirror associated with the HR mirror, configured for optical path between the core and the HR mirror; and − optionally, at least one lens arranged between the HR mirror and its associated folding-mirror, configured to adjust shape the associated beams.

10. The hybrid pump module of claim 9, wherein the HR module further comprises an intra cavity modulator arranged between the HR mirror and its associated folding- mirror, configured to modulate the reflected beam.

11. The hybrid pump module of claim 1, wherein the core associated module comprises a partial reflecting (PR) module comprising: − an output fiber, optionally comprising an end-cap; − a PR mirror, in optical path with the output fiber; − a folding mirror associated with the PR mirror, configured for optical path between the core and the PR mirror; and − optionally, at least one lens, arranged between the PR mirror and its associated folding-mirror, configured to adjust shape the associated beams.

12. The hybrid pump module of claim 1, further comprises at least one heat dispensing element selected from a group consisting: base surface, ribs, screws, and any combination thereof.

13. A fiber amplifying system comprising: − an optical fiber, comprising a core and at least one clad; − the hybrid pump module of claim 6, coupled to a first end of the optical fiber. 21 259366/2

14. The fiber amplifying system of claim 13, wherein the system further comprises at least one selected from: a pump dump, an end-cap element.

15. The fiber amplifying system of claim 14, further comprises the hybrid pump module of claim 8, coupled to a second end of the optical fiber.

16. A fiber laser system comprising: − an optical fiber, comprising a core and at least one clad; − the hybrid pump module of claim 9, coupled to a first end of the optical fiber; and − a Fiber Bragg Grating (FBG) or the hybrid pump module of claim 11, coupled to a second end of the optical fiber.

17. The fiber laser system of claim 16, further comprises at least one of: a pump dump and an end-cap element. 22