Pump-gain integrated fiber and method for manufacturing the same

Abstract

The application relates to the technical field of fiber lasers, in particular to a pump-gain integrated optical fiber and a preparation method thereof. The cross section of the integrated optical fiber comprises, from outside to inside, a coating layer, an inner cladding layer, an outer cladding layer and a fiber core. The optical fiber comprises a light total reflection zone, a pump-gain zone and a light partial reflection zone along the central axis. The inner cladding layer wraps the fiber core. The outer cladding layer surrounds the inner cladding layer, and a plurality of groups of pump units are embedded in the outer cladding layer and are uniformly distributed around the central axis. The refractive index of the fiber core is greater than that of the inner cladding layer, and the refractive index of the inner cladding layer is greater than that of the outer cladding layer. Different groups of pump units are distributed on different cross sections in the pump-gain zone of the optical fiber. The application changes the traditional semiconductor pumping generation and fiber laser output mode, and then realizes the change of the waveguide structure in the optical fiber through the optical fiber post-processing mode, realizes the single-fiber resonant cavity, and realizes the laser output under the action of an external electric field.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fiber laser, in particular to a pump gain integrated fiber and a preparation method thereof. BACKGROUND

[0002] In the late 1980s, with the maturity of fiber manufacturing process and the development of solid-state lasers, fiber lasers have become a hot spot of people's attention. With the gradual maturity of double-clad fiber and cladding pumping technology, high-power fiber lasers have made breakthrough progress. Due to the advantages of small size, good compactness, convenient heat management, good beam quality and the like, in recent years, high-power fiber lasers outputted by fiber have been widely applied in optical communication, material processing, medical diagnosis and treatment, information storage, laser printing, laser measurement and control, laser spectroscopy and nonlinear frequency conversion and the like.

[0003] In a high-power fiber laser system, cladding pumping technology has become a common key technology. The current double-clad pumping coupling technology mainly includes the following three kinds: (1) spatial light coupling; (2) pump combiner; (3) GTWave fiber. Among them, the spatial light coupling has two points of deficiency, the first is that in the process of coupling, the light path needs to be accurately adjusted on site, and the high-power fiber and optical mirror are exposed to the air, which increases the risk of the whole laser system, reduces the stability of the system, and the system structure is complex; the second is that the coupling end of the gain fiber needs to be cut at an angle and polished, which increases the process difficulty of the whole system. Compared with the spatial light coupling, the pump combiner is a full-fiber structure, which uses the fusion between the pump fiber and the signal fiber to replace the spatial light coupling, which increases the stability, safety and integration level of the whole system. However, the current high-power fiber pump combiner is limited by the manufacturing process, and the highest power that can be tolerated is about 10kW, which limits the further improvement of laser power. The existing process is complex and requires a relatively long fiber length, which will cause strong nonlinear effects at high power, limiting the further improvement of laser power.

[0004] Now the high-power fiber laser, fiber amplifier mainly adopts double-clad doped fiber, compared with the divergence angle of the multimode pump beam emitted by the semiconductor pump laser, the inner cladding diameter is small, therefore how to couple the pump light to the inner cladding of the double-clad fiber is the core technology to obtain high-power fiber laser output. Researchers have proposed a variety of schemes, including: fused-taper end-pumped coupling technology, GT-wave technology, attached prism side-pumped coupling, V-shaped groove side-pumped coupling, pump fiber angle polishing side-coupling, diffraction grating side-coupling, tapered quartz tube side-coupling and embedded mirror side-coupling, etc. However, the existing fiber coupling technology can only realize a single function-pump laser coupling, limited by factors such as thermal load, light conversion mode, electro-optical conversion efficiency, the higher the power of the fiber laser, the larger the volume and weight, and the miniaturization of the fiber laser becomes more difficult. SUMMARY

[0005] The application provides a pump gain integrated fiber and a preparation method thereof, to solve the defects in the prior art that the fiber laser is limited by factors such as thermal load, light conversion mode, electro-optical conversion efficiency, and the volume and weight of the fiber laser become larger as the power of the fiber laser becomes higher. The PN type semiconductor is embedded in the fiber preform rod stage, and then the pump gain integrated fiber is prepared through the drawing tower. The CO2 laser irradiation, femtosecond laser writing, hydrogen-loaded ultraviolet mask irradiation and other fiber post-processing methods are used to realize the change of the waveguide structure inside the fiber, and then the single fiber resonant cavity is realized, and the laser output is realized under the action of the external electric field.

[0006] The application provides a pump gain integrated fiber, the cross section of the fiber from outside to inside comprises a coating layer, an inner cladding layer, an outer cladding layer and a core; the fiber comprises a light total reflection area, a pump gain area and a light partial reflection area along the central axis direction;

[0007] The central axes of the coating layer, the pump layer, the inner cladding layer and the core are coincident with the central axis of the fiber;

[0008] The inner cladding layer wraps the core; the outer cladding layer surrounds the inner cladding layer, a plurality of groups of pump units are embedded in the outer cladding layer and uniformly distributed around the central axis; the refractive index of the core is greater than that of the inner cladding layer, and the refractive index of the inner cladding layer is greater than that of the outer cladding layer;

[0009] Different groups of pump units are distributed on different cross sections in the pump gain area of the fiber.

[0010] According to the pump gain integrated fiber provided by the application, preferably, the core is doped with a predetermined kind of rare earth ion, and the cross-sectional shape of the core is circular.

[0011] The pump-gain integrated optical fiber provided by the application has a central symmetric cross section shape, preferably a circular shape, an octagonal shape, a rectangular shape, etc.

[0012] The pump-gain integrated optical fiber provided by the application has a pump unit comprising, from top to bottom, a total reflection layer, a PN semiconductor and a partial reflection layer, and metal wires are respectively arranged on both sides of the PN semiconductor.

[0013] The PN semiconductor is used to generate pump light and to optically stimulate rare earth ions in the core to convert the wavelength of input laser light.

[0014] The pump-gain integrated optical fiber provided by the application has a pump-gain integrated optical fiber, preferably, the metal wires on both sides of the PN semiconductor are closely attached to non-light-emitting positions of the P-type semiconductor and the N-type semiconductor, respectively, and the PN semiconductor can be driven to emit light by an external electric field.

[0015] In another aspect, the application also provides a preparation method of a pump-gain integrated optical fiber, comprising:

[0016] The pump-gain integrated optical fiber preform is prepared, and the whole after the combination of the PN semiconductor or the P-type semiconductor and the N-type semiconductor is respectively embedded on the outer surface of the doped optical fiber preform according to the design.

[0017] The optical fiber preform after embedding the PN semiconductor is placed in a glass sleeve, and the two are closely attached, and the pump-gain integrated optical fiber is formed through pretreatment and optical fiber drawing.

[0018] The formed pump-gain integrated optical fiber is treated by a CO2 laser, a femtosecond laser or a hydrogen-loaded ultraviolet mask irradiation method to form a PN junction in the pump layer of the pump-gain integrated optical fiber and a waveguide structure having selective transmission of pump light and laser wavelength, so that the pump light is directly irradiated into the core when emitting, and the rare earth doped ions in the core and the refractive index changes between layers are used to form electrically excited light emission of the pump unit and optically excited light emission in the core, respectively, so that the single optical fiber realizes the integration of pump-resonant cavity.

[0019] The application also provides a non-transitory computer readable storage medium having a computer program stored thereon, wherein the computer program is executed by a processor to implement the steps of the preparation method of the pump-gain integrated optical fiber as described above.

[0020] The application provides a pump gain integrated optical fiber and a preparation method thereof, wherein a PN type semiconductor is embedded in an optical fiber preform rod stage, and then a pump gain integrated optical fiber is prepared through a drawing tower, and then a CO2 laser irradiation, a femtosecond laser writing, hydrogen-loaded ultraviolet mask irradiation and other optical fiber post-processing methods are used to realize the change of the waveguide structure in the optical fiber, and then a single optical fiber resonant cavity is realized, and laser output is realized under the action of an external electric field. The traditional semiconductor pumping generation and optical fiber laser output mode is changed, the semiconductor pumping source is compressed to the optical fiber scale, the metal wire is embedded in advance to realize driving, and the pumping light emission direction is adjusted to be directly embedded and acted on the doped optical fiber, laser generation is realized, and a new implementation mode is provided for the light weight and miniaturization of the optical fiber laser. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the present application or prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0022] Fig. 1 is one of the structure schematic diagrams of the pump gain integrated optical fiber provided by the present application;

[0023] Fig. 2 is the second structure schematic diagram of the pump gain integrated optical fiber provided by the present application. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the present application more clear, the technical scheme in the present application will be described clearly and completely in the following with reference to the drawings in the present application. Obviously, the described embodiments are some embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0025] The terms "include" and "have" and any variations thereof in the specification and claims of the present application and the above drawings are intended to cover the non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or modules is not limited to the listed steps or modules, but optionally includes other steps or modules not listed or optionally includes other steps or modules inherent to the process, method, product or device.

[0026] It should be noted that the terms "first" and "second" used in this invention merely distinguish similar objects and do not represent a specific ordering of objects. It is understood that "first" and "second" can be interchanged in a specific order or sequence where permissible. It should be understood that the objects distinguished by "first" and "second" can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those described or illustrated herein.

[0027] In one embodiment, such as Figs. 1-2 As shown, the present invention provides a pump-gain integrated optical fiber, the cross-section of which includes a coating layer, an inner cladding layer, an outer cladding layer, and a core from the outside to the inside; the optical fiber includes a total internal reflection region, a pump gain region, and a partial internal reflection region along the central axis.

[0028] The central axis of the coating layer, the pump layer, the inner cladding layer, and the fiber core all coincide with the central axis of the optical fiber.

[0029] The inner cladding encloses the fiber core; the outer cladding surrounds the inner cladding, and a plurality of pump units uniformly distributed around the central axis are embedded in the outer cladding; the refractive index of the fiber core is greater than that of the inner cladding, and the refractive index of the inner cladding is greater than that of the outer cladding;

[0030] Different groups of pump units are distributed on different cross sections in the pump gain region of the optical fiber.

[0031] The technical solution principles involved in this invention include:

[0032] Pump-gain integrated optical fiber is produced by embedding P-type semiconductors, N-type semiconductors, and metal electrodes at specific locations in the doped optical fiber preform during the fiber preform stage, and then drawing the fibers using a wire drawing technique.

[0033] The integrated pump-gain fiber is manufactured in one piece. After molding, it undergoes post-processing techniques such as CO2 laser irradiation, F5-second laser writing, and hydrogen-loaded ultraviolet mask irradiation to achieve PN junction and pump-gain integration.

[0034] The process involves using selective reflective structures and laser wavelength selective reflective structures. Finally, through pre-embedded metal electrodes, the PN-type semiconductor emits light under the influence of an external electric field, directly acting on the rare-earth-doped fiber core. Combined with the laser wavelength selective reflective structure, a resonant cavity is formed, ultimately emitting laser light.

[0035] 0. In the pump-gain integrated optical fiber provided by this invention, the fiber core is doped with a preset seed.

[0036] The fiber core contains rare earth ions and has a circular cross-sectional shape.

[0037] Optionally, the cross-sectional shape of the inner cladding is a central symmetric figure, including but not limited to a circle, a regular polygon, and other figures that satisfy the condition of pumping light filling the inner cladding and the outer cladding.

[0038] The present application does not limit the structure of the inner cladding to the above, and the effect of the present application is not affected by the structure of the inner cladding.

[0039] Correspondingly, the cross-sectional shape of the inner surface of the outer cladding is the same as that of the outer surface of the inner cladding.

[0040] Specifically, the core 1, the inner cladding 2, the outer cladding 4, and the coating layer 5 form a conventional gain fiber waveguide transmission structure.

[0041] The refractive index of the core 1, the inner cladding 2, and the outer cladding 4 is ncore> ninerciading> nouterciadding, and the numerical aperture between the three is determined according to the design of the optical fiber.

[0042] Specifically, the core 1 is doped with rare earth ions, which are used for energy level conversion between the pumping light in the pumping layer and the rare earth ions, thereby generating laser.

[0043] As shown in FIG. 1, the pumping unit includes, from top to bottom, a total reflection layer, a PN semiconductor, and a partial reflection layer. Fig. 2

[0044] Metal wires are mounted on both sides of the PN semiconductor.

[0045] The PN semiconductor is used to generate pumping light, which is used for optical excitation of rare earth ions in the core to convert the wavelength of input laser.

[0046] Specifically, the metal wires on both sides of the PN semiconductor are closely attached to the non-light-emitting positions of the P-type semiconductor and the N-type semiconductor, respectively, and can drive the PN semiconductor to emit light through an external electric field.

[0047] As shown in FIG. 1, in one specific embodiment, the pumping layer 3 is located in the middle of the outer cladding and includes a PN semiconductor 31, a partial reflection layer 32, a total reflection layer 33, and metal wires 34. Fig. 2 The PN semiconductor 31 is generated by combining a P-type semiconductor and an N-type semiconductor, and is used to generate pumping light that can optically excite rare earth ions in the core 1 to generate wavelength conversion.

[0048] The PN semiconductor 31 is generated by combining a P-type semiconductor and an N-type semiconductor, and is used to generate pumping light that can optically excite rare earth ions in the core 1 to generate wavelength conversion.

[0049] ​The partially reflective layer 32 and the total reflective layer 33 are generated from the outer cladding glass portion. The reflectivity of the pump light generated by the PN-type semiconductor is changed by using fiber optic post-processing methods such as femtosecond laser writing and hydrogen-loaded ultraviolet mask irradiation.

[0050] The metal wire 34 is formed by integrally drawing a conductive metal with the pump gain fiber after embedding it in the preform stage. It is closely attached to the non-light-emitting positions of the P-type semiconductor and the N-type semiconductor, and can drive the PN-type semiconductor to emit light through an external electric field.

[0051] All optical fibers are placed on the optical fiber cold plate and grooved. According to the design of power, beam quality and nonlinear effect suppression, optical fiber grooves are made on the surface of the optical fiber cold plate to place the optical fiber part, while ensuring that each splice point is within a straight optical fiber groove within 10cm before and after.

[0052] On the other hand, the present invention also provides a method for fabricating an integrated pump-gain optical fiber, comprising the following steps:

[0053] To prepare an integrated pump gain optical fiber preform, either PN-type semiconductors are bonded together on the outer surface of the doped optical fiber preform as a whole, or P-type and N-type semiconductors are embedded separately on the outer surface of the doped optical fiber preform.

[0054] The fiber preform with embedded PN semiconductor is placed in a glass sleeve and the two are tightly bonded together. After pretreatment and fiber drawing, the pump gain integrated fiber is formed.

[0055] The formed pump-gain integrated fiber is treated with CO2 laser, femtosecond laser or hydrogen-loaded ultraviolet mask to form a PN junction and a waveguide structure that selectively transmits pump light and laser wavelength in the pump layer of the pump-gain integrated fiber. This allows the pump light to directly irradiate into the fiber core. By utilizing the rare earth doping ions in the fiber core and the changes in refractive index between the layers, the electro-excited emission of the pump unit and the optically excited emission inside the fiber core are formed respectively, so that the pump-resonant cavity is integrated in a single fiber.

[0056] In one specific embodiment, the pump-gain integrated optical fiber provided by the present invention includes:

[0057] The pump-gain integrated fiber is designed with a core size of 20 μm, an octagonal inner cladding cross-section with an circumscribed circle diameter of 400 μm, and pump units in the pump layer with a cross-section of 100 μm × 400 μm. P-type and N-type semiconductors, along with metal wires, are embedded on the outer surface of the inner cladding of the doped fiber. The fiber length is 500 cm, with a 300 cm pump-gain region and 100 cm optical transmission regions. The core numerical aperture is 0.06, and the inner cladding numerical aperture is 0.46. After the optical fiber is drawn, a PN junction is formed on the outer surface of the inner cladding of the doped optical fiber by CO2 laser irradiation, with the P-type and N-type semiconductors intact. Then, a structural region with partial reflection function of pump light is prepared near the emission position of the PN junction using femtosecond laser, and a structural region with total reflection function of pump light is prepared between the corresponding PN junction and the coating layer. Finally, fiber optic transmission regions with integrated pump gain are fiber gratings with reflectivities of >99.5% and <10%, respectively. After fabrication, since the optical fiber retains metal throughout, applying a voltage to the two metal strands using an external electric field can cause the PN junction to emit light, which directly acts on the fiber core. Under the action of pump light, the fiber core generates laser light. Simultaneously, by constraining the numerical aperture of the fiber core and selectively transmitting the laser light through the optical transmission path, the pump-resonant cavity integration of a single optical fiber can be achieved, directly generating laser light. Then, it is fused with the cladding optical filter and QBH to diffuse the remaining pump light and higher-order modes under the condition of total internal reflection failure, while the generated laser light is unaffected in its transmission within the fiber core, achieving stable output of 1080nm laser light.

[0058] On the other hand, the present invention also provides a computer program product, the computer program product comprising a computer program stored on a non-transitory computer-readable storage medium, the computer program comprising program instructions, which, when executed by a computer, enable the computer to perform the steps of the pump-gain integrated optical fiber fabrication method provided by the above methods.

[0059] In another aspect, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the method for fabricating the pump-gain integrated optical fiber provided by the above methods.

[0060] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0061] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A pump-gain integrated optical fiber, characterized in that, The cross-section of the optical fiber, from the outside to the inside, includes a coating layer, an outer cladding layer, a pump layer, an inner cladding layer, and a fiber core; the optical fiber, along the central axis, includes a total internal reflection region, a pump gain region, and a partial internal reflection region. The central axis of the coating layer, the pump layer, the inner cladding layer, and the fiber core all coincide with the central axis of the optical fiber. The inner cladding encloses the fiber core; the outer cladding surrounds the inner cladding, and a plurality of pump units uniformly distributed around the central axis are embedded in the outer cladding; the refractive index of the fiber core is greater than that of the inner cladding, and the refractive index of the inner cladding is greater than that of the outer cladding; Different groups of pump units are distributed on different cross sections in the pump gain region of the optical fiber; The pumping unit includes a total reflection layer, a PN type semiconductor, and a partial reflection layer connected sequentially from top to bottom, with metal wires installed on both sides of the PN type semiconductor. The PN-type semiconductor is used to generate pump light, which is used to optically excite rare earth ions in the fiber core to perform wavelength conversion on the input laser.

2. The pump-gain integrated optical fiber according to claim 1, characterized in that, The fiber core is doped with a predetermined type of rare earth ions, and the cross-sectional shape of the fiber core is circular.

3. The pump-gain integrated optical fiber according to claim 1, characterized in that, The cross-sectional shape of the inner cladding is a centrally symmetrical figure.

4. The pump-gain integrated optical fiber according to claim 1, characterized in that, The metal lines on both sides of the PN semiconductor are closely attached to the non-light-emitting positions of the P-type and N-type semiconductors, respectively, and the PN semiconductor can be driven to emit light by an external electric field.

5. A method for fabricating an integrated pump-gain optical fiber as described in any one of claims 1 to 4, characterized in that, include: To prepare an integrated pump gain optical fiber preform, either PN-type semiconductors are bonded together on the outer surface of the doped optical fiber preform as a whole, or P-type and N-type semiconductors are embedded separately on the outer surface of the doped optical fiber preform. The fiber preform with embedded PN semiconductor is placed in a glass sleeve and the two are tightly bonded together. After pretreatment and fiber drawing, the pump gain integrated fiber is formed. The formed pump-gain integrated fiber is treated with CO2 laser, femtosecond laser or hydrogen-loaded ultraviolet mask to form a PN junction and a waveguide structure that selectively transmits pump light and laser wavelength in the pump layer of the pump-gain integrated fiber. This allows the pump light to directly irradiate into the fiber core. By utilizing the rare earth doping ions in the fiber core and the changes in refractive index between the layers, the electro-excited emission of the pump unit and the optically excited emission inside the fiber core are formed respectively, so that the pump-resonant cavity is integrated in a single fiber.

6. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the method for fabricating an integrated pump-gain optical fiber as described in claim 5.

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