CN206076718U - A kind of middle-infrared band optical fiber pumping/signal bundling device - Google Patents

Abstract

The purpose of this utility model is to provide a kind of mid-infrared band optical fiber pumping/signal beam combiner, including signal optical fiber, pumping optical fiber, quartz glass casing and output optical fiber; The fiber core material of described signal optical fiber is pure germanium dioxide Material, the tapered ratio of the tapered area of the optical fiber bundle is between 1 and 3; the optical fiber bundle and the output optical fiber can be welded by asymmetric electrode discharge heating or low temperature fusion, and the fusion loss of the signal optical fiber is low less than 10%; the utility model can realize the combined output of the signal light of the mid-infrared band laser and the pump laser, realize the passage of the signal light with high power and low loss, and the pass rate of the pump laser in the optical fiber bundle can usually be controlled at 98% % or more, it can couple pumping laser light greater than 100 watts into the output fiber to ensure the realization of high-power mid-infrared fiber amplifier.

Description

A mid-infrared band optical fiber pumping/signal combiner

technical field

The utility model belongs to the field of fiber lasers, in particular to a mid-infrared band fiber pumping/signal combiner.

Background technique

In recent years, fiber lasers in the mid-infrared band have played an increasingly important role in meteorological monitoring, lidar, biomedicine, material processing, national defense and security and other fields. Soft glass fibers based on non-quartz materials (such as fluoride glass, tellurite glass, sulfide glass, etc.) do not have the strong phonon resonance absorption loss of silica fibers in the mid-infrared band, and can support the generation of fiber lasers in the mid-infrared band and low loss transmission. In particular, ZBLAN fiber doped with rare earth ions such as Er ³⁺ , Ho ³⁺ and Dy ³⁺ in recent years (a kind of fluoride fiber, the specific composition is ZrF ₄ -BaF ₂ -LaF ₃ -AlF ₃ -NaF) The rapid development of the technology has made many domestic and foreign research institutes report mid-infrared lasers with output power in the order of watts (see SD Jackson, Towards high-power mid-infrared emission from a fiber laser, Nature Photonics, 6(7), 423- 431(2012). (SD Jackson, Towards high-power mid-infrared fiber laser output, Nature Photonics, 2012, Issue 6, Vol. 7)). These doped ZBLAN fibers can provide laser radiation with a gain between 2.7 and 3.1 μm. However, limited by the physical characteristics of soft glass optical fibers, there is still a lack of a series of key optical fiber components (such as fiber gratings, optical isolators, optical fiber pumping/signal combiners, mode field adapters, etc.) and core technologies based on soft glass optical fibers ( Such as soft glass fiber processing, soft glass fiber fusion, etc.). This has led to the vast majority of mid-infrared fiber laser research using a space-pumped structure, which loses the advantages of simple structure, high stability, and easy integration that fiber lasers should have.

In recent years, the world's first Er ³⁺ doped 3 μm fiber laser with all-fiber structure reported by Laval University in Canada obtained a laser output with a working wavelength of 2.94 μm and an average power of 30.5 W (see V.Fortin, M.Bernier , STBah, and R.Vallée, 30W fluoride glass all-fiber laser at 2.94μm, OpticsLetter 40(12), 2882-2885(2015); V.Fortin et al., 30W, 2.94μm all-fiber fluoride fiber laser, Optics Letters , 2015, Issue 40, Vol. 12). However, the heat and quality degradation caused by the fiber grating will limit the further improvement of the laser power output directly from the resonator. The main oscillation power amplification (MOPA) structure is a common structure for further realizing high-power fiber laser amplification output. This structure usually consists of an oscillator and one or more stages of amplifiers. The core component is a high-power optical fiber pumping/signal combiner, which can efficiently couple signal light and pumping light into the double-clad gain fiber to achieve an all-fiber structure and high-efficiency laser amplification output . In the multi-stage main oscillation power amplification structure, the pump/signal beam combiner is particularly required to have low signal light insertion loss and high pump light coupling efficiency. At present, based on the MOPA structure, a laser with a single fiber output power greater than 10KW in the 1μm band has been realized. Inevitably, using the MOPA structure to increase the power of fiber lasers in the mid-infrared band will bring higher power mid-infrared laser output.

The signal optical fiber, pumping optical fiber and output optical fiber of the existing optical fiber pumping/signal combiner are all made of silica optical fiber. Due to the enhanced phonon resonance absorption loss of the quartz fiber at a wavelength greater than 2.4 μm, it cannot be used to transmit laser signals with a wavelength above 2.4 μm, which means that the existing quartz fiber pump/signal combiner cannot be used Amplification of fiber lasers in the mid-infrared region. According to the technical information, there is no design or report about the optical fiber pumping/signal combiner in the mid-infrared band.

Utility model content

The purpose of the utility model is to provide a mid-infrared band optical fiber pumping/signal combiner with low loss of signal light and high coupling efficiency of pumping light.

In order to solve the above technical problems, the utility model adopts the following technical solutions:

A mid-infrared band optical fiber pumping/signal combiner includes a signal optical fiber, a pumping optical fiber, a quartz glass sleeve and an output optical fiber. One end of the signal optical fiber and one end of the pumping optical fiber are inserted and fixed from the same end of the quartz glass sleeve, melted and tapered, and combined into an optical fiber bundle with a tapered region (including a tapered region and a waist region) ; cutting the optical fiber bundle at the waist region, the cutting plane is perpendicular to the geometric center line of the optical fiber bundle, and connecting the cut optical fiber bundle with the output optical fiber through fusion splicing.

The core material of the signal optical fiber is pure germanium dioxide material, and the cladding material is a mixed material of germanium dioxide and quartz or pure quartz material.

The signal optical fiber is a single-clad optical fiber.

The core of the signal fiber supports single-mode or few-mode laser transmission of 2.7-3.1 μm, and the numerical aperture of the core of the signal fiber can effectively confine the laser inside the core to ensure low-loss transmission.

The core diameter of the signal optical fiber ranges from 2.5 to 30 μm, and the cladding diameter ranges from 125 to 300 μm. The fiber core diameter is selected so that the laser mode field area supported by it is the same as the laser mode field area supported by the output fiber of the mid-infrared signal laser. same.

The pumping fiber is of the same type as the coupling fiber of the mid-infrared fiber amplifier pumping laser.

The pumping fiber is a multimode silica fiber, and the number of fibers can be 6 or 18. The pumping fiber can support the transmission of 793nm, or 976nm, or 1150nm, or 1550nm laser.

The output optical fiber is a non-doped double-clad fluoride optical fiber, the core and cladding of the optical fiber are made of fluoride glass, the numerical aperture of the core of the optical fiber is between 0.15 and 0.35, and the numerical aperture of the cladding is between 0.4 and 0.7 between.

The core diameter of the output optical fiber ranges from 2.5 to 30 μm, the outer cladding diameter ranges from 125 to 600 μm, the inner cladding diameter ranges from 100 to 300 μm, and the inner cladding diameter is smaller than the outer cladding diameter. The core and cladding diameters of rare-earth-doped gain fibers required for mid-infrared fiber amplifiers are the same.

In the utility model, after the coating layer is stripped off one end of the pumping optical fiber and the signal optical fiber, they are inserted into a quartz glass tube, wherein the pumping optical fiber is evenly arranged around the signal optical fiber; the pumping optical fiber, signal optical fiber, The central axes of the quartz glass sleeves are parallel to each other. Then, the quartz glass tube inserted with the optical fiber is fused and tapered to form a bundle of optical fibers with a tapered region.

In the utility model, the ratio of the diameter of the circumscribed circle of the cross section at the input end (the end where the quartz glass tube is inserted into the optical fiber) and the output end (the place where the output optical fiber is welded) of the tapered region of the optical fiber bundle is drawn The taper ratio, its value is generally between 1 and 3, and the selection of the length of the tapered region should meet the condition that the signal fiber and the pump fiber have no tapered loss during the tapering process.

In the utility model, the diameter of the circumscribed circle of the cross section of the optical fiber bundle at the waist region of the tapered region is smaller than or equal to the diameter of the output optical fiber.

In the utility model, before the fiber bundle is fused with the output fiber through the end face, heating and core expansion operations need to be performed, and the mode field diameter of the signal fiber at the end of the fiber bundle after core expansion is the same as the core diameter of the output fiber .

In the utility model, the welding of the optical fiber bundle and the output optical fiber can adopt asymmetric electrode discharge heating welding or low temperature welding, the welding loss of the signal optical fiber is less than 10%, and the passing rate of the pumping light is above 98%.

Compared with the existing optical fiber pumping/signal combiner technology, the utility model has the beneficial effects of:

1. The utility model can realize the combined output of the signal light and the pump laser of the mid-infrared band laser. The signal fiber is a germanium dioxide fiber, which can support low-loss transmission with a wavelength of 2.7-3.1 μm. The output fiber is double-wrapped One-layer fluoride optical fiber, which can be fusion-spliced with the subsequent doped fluoride optical fiber;

2. In the fiber bundle of the present invention, the signal fiber can be heated and core expanded after the bundle is completed, so that the mode field diameter finally matches the core diameter of the output fiber, which can ensure that the signal laser is pumped through the fiber with low loss. The transport/signal beam combiner realizes the passage of high-power and low-loss signal light.

3. The selection of the tapering ratio in the optical fiber bundle of the present utility model is mainly based on ensuring the high pass rate of the pumping laser in the fiber bundle (taper region), and the pass rate can be controlled above 98% usually; due to the signal optical fiber Different from the parameters of the pumping fiber, the control of the insertion loss of the signal fiber is mainly guaranteed by the thermal core expansion technology after the fiber is bundled.

4. The pumping fiber of the present utility model is a quartz multimode fiber, which can support 793nm, or 976nm, or 1150nm, or 1550nm laser transmission, and the selection of the specific laser wavelength is determined by the absorption spectrum of the gain fiber connected to the output fiber. Since the output power of semiconductor lasers and fiber lasers at these wavelengths can reach the order of tens of watts, through this optical fiber pump/signal beamer, at least pumping lasers greater than 100 watts can be coupled into the output fiber to ensure high Realization of a power mid-infrared fiber amplifier.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description These are only some embodiments of the utility model, and those skilled in the art can also obtain other drawings according to these drawings without any creative effort.

Fig. 1 is the cross-sectional front schematic diagram of the optical fiber group bundle after tapering in the utility model embodiment;

Fig. 2 is a cross-sectional schematic diagram of a mid-infrared optical fiber pumping/signal combiner according to an embodiment of the present invention;

Fig. 3 is a schematic cross-sectional view at A-A in Fig. 2;

Fig. 4 is a schematic cross-sectional view at B-B in Fig. 2;

Fig. 5 is a schematic cross-sectional view at C-C in Fig. 2;

illustration:

1. Signal optical fiber; 2. Pumping optical fiber; 3. Quartz sleeve; 4. Output optical fiber; 5. Cone area; 6. Waist area; 7. Cutting position of waist area; 81. Equivalent optical fiber cladding in waist area; 82. Equivalent optical fiber core in waist area; 41. Output optical fiber cladding; 42. Output optical fiber core.

detailed description

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. example. Based on the embodiments of the present utility model, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the scope of protection of the present utility model.

In the embodiment shown in Figure 1, one end of the input signal optical fiber 1 and one end of the pumping optical fiber 2 are inserted into the quartz glass sleeve 3 and fixed, and then melted and bonded into a tapered region (comprising a tapered Fiber bundles in Zone 5 and Waist Zone 6). And vertically cut the optical fiber bundle at position 7 in the waist region, and then connect the cut optical fiber bundle with the output optical fiber 4 through end face fusion to obtain a mid-infrared band optical fiber pumping/signal as shown in Figure 2 Combiner.

In this embodiment, the coating materials of one signal optical fiber 1 and six pumping optical fibers 21-26 are removed and then bundled and inserted into the quartz glass tube 3 to ensure that the input signal optical fiber 1 is located in the center of the optical fiber bundle. As shown in Figure 3; and the optical fiber bundle is heated to a molten state for tapering, the tapering ratio is 2, and the length of the tapered region 5 is 1cm; when the outer diameter of the optical fiber bundle is 250 μm, reduce the heating intensity, The heating and tapering process was stopped when the length of the waist region was 5 mm. The selection of the tapered ratio in the optical fiber bundle can ensure that the pass rate of the pumping laser in the optical fiber bundle (the tapered region) is 99%. The fiber bundle after tapering is shown in Figure 1.

In this embodiment, when the quartz glass sleeve 3 is tapered, the core diameter of the signal optical fiber 1 becomes smaller in proportion, and the core diameter of the signal optical fiber 1 at the waist region 6 is only 5 μm; To realize the passage of low-loss signal light, the waist region 6 needs to be heated and core expanded; the waist region 6 is heated with an oxyhydrogen flame for 20 minutes, and two of the cores of the signal optical fiber 1 at the waist region 6 are heated. Expanding the core of germanium oxide into the cladding increases the size of the core mode field area, making the mode field area of the signal fiber at position 7 of the taper region equal to the core mode field area of the output fiber 4 . Reduce the loss of the signal laser passing through the optical fiber pumping/signal combiner, and realize the passage of high-power and low-loss signal light.

In this embodiment, after heating and expanding the core, the tapered optical fiber bundle is vertically cut at the middle position 7 of the waist region 6; the fiber bundle at the cutting position 7 forms an equivalent optical fiber 8 in the waist region, and its cross-section As shown in Figure 4. The cross-sectional structure of the equivalent optical fiber 8 in the waist region is composed of an equivalent optical fiber cladding 81 and an equivalent optical fiber core 82 in the waist region. The cladding of the signal optical fiber 1, the pumping optical fibers 21-26 and the glass sleeve 3 form the equivalent optical fiber cladding 81 of the equivalent optical fiber 8 in the waist region after heating and tapering. The core of the tapered signal optical fiber 1 is heated and expanded to form an equivalent optical fiber core 82 .

In this embodiment, the optical fiber bundle and the output optical fiber 4 are fused at the cutting position 7 using warm fusion technology to obtain the mid-infrared band optical fiber pumping/signal combiner provided by the utility model.

In this embodiment, the signal optical fiber 1 is a single-clad optical fiber, and its core material is pure germanium dioxide, which can support low-loss transmission with a wavelength of 2.7-3.1 μm. The cladding material is pure quartz material, and the core/cladding diameter is 10μm/125μm.

The inner diameter of the quartz glass sleeve 3 is 400 μm, and the outer diameter is 500 μm.

The output optical fiber 4 is a non-doped double-clad fluoride optical fiber, the core and the inner cladding of which are made of fluoride glass, and can be fusion-spliced with subsequent doped fluoride optical fibers. The diameter of the core/inner cladding is 20 μm/250 μm, and the numerical aperture of the core/cladding is 0.27/0.46; the outer cladding of the output fiber 4 is a coating layer of acrylic resin material, and the diameter is 450 μm; after the coating material is removed The cross-sectional view of the optical fiber is shown in Figure 5, wherein 41 is the inner cladding of the output optical fiber, and 42 is the core of the output optical fiber.

The pumping fiber 2 is a multimode silica fiber with a core/cladding diameter of 105 μm/125 μm, a core numerical aperture of the fiber is 0.15, and the number of fibers is 6. Multimode silica fiber can support 793nm, or 976nm, or 1150nm, or 1550nm laser transmission, the specific laser wavelength selection is determined by the absorption spectrum of the gain fiber connected to the output fiber. Since the output power of semiconductor lasers and fiber lasers at these wavelengths can reach the order of tens of watts, through this optical fiber pump/signal beamer, at least pumping lasers greater than 100 watts can be coupled into the output fiber to ensure high Realization of a power mid-infrared fiber amplifier.

The above is only a specific embodiment of the utility model, but the scope of protection of the utility model is not limited thereto, and any skilled person familiar with the technical field can easily think of changes within the technical scope disclosed in the utility model Or replacement, all should be covered within the scope of protection of the present utility model. Therefore, the protection scope of the present utility model should be based on the protection scope of the claims.

Claims (7)

1. a kind of middle-infrared band optical fiber pumping/signal bundling device, including output optical fibre, signal optical fibre, quartz glass sleeve and At least one pump fibres；One end of the signal optical fibre is with one end insertion quartz glass sleeve of pump fibres and fixed, takes out Fortune optical fiber is evenly spaced in around signal optical fibre；The signal optical fibre, pump fibres, quartz glass sleeve Jing fused biconical tapers are combined It is the optical fiber beam combination with La Zhui areas；The optical fiber beam combination passes through end face welding with the output optical fibre in the lumbar region in La Zhui areas； The core material of the signal optical fibre be pure germanium dioxide material, clad material be germanium dioxide and quartz mixing material or Pure quartz material.

2. middle-infrared band optical fiber pumping/signal bundling device as claimed in claim 1, it is characterised in that the signal optical fibre For single cladding structure optical fiber；The fibre core of the signal optical fibre supports 2.7～3.1 μm of single mode or few mould Laser Transmission；The letter The core diameter scope of number optical fiber is 2.5～30 μm, and cladding diameter scope is 125～300 μm.

3. middle-infrared band optical fiber pumping/signal bundling device as claimed in claim 1, it is characterised in that the signal optical fibre It is identical with the core area of the output optical fibre in the mode field area of outfan.

4. middle-infrared band optical fiber pumping/signal bundling device as claimed in claim 1, it is characterised in that the pump fibres For multimode silica fibre；The quantity of the pump fibres can be 6 or 18；The pump fibres support 793nm, or 976nm, or the transmission of 1150nm or 1550nm laser.

5. middle-infrared band optical fiber pumping/signal bundling device as claimed in claim 1, it is characterised in that the output optical fibre For undoped double clad fluoride fiber；The fibre core and covering of optical fiber is fluoride glass material；The fibre core numerical aperture of optical fiber Between 0.15～0.35, covering numerical aperture is between 0.4～0.7 in footpath；The core diameter scope of the output optical fibre is 2.5 ～30 μm, outer cladding diameter scope is 125～600 μm, and inner cladding diameter scope is 100～300 μm, and inner cladding diameter is less than outer Cladding diameter.

6. middle-infrared band optical fiber pumping/signal bundling device as claimed in claim 1, it is characterised in that the optical fiber beam combination La Zhui areas input and outfan cross section circumcircle diameter ratio between 1～3, it is transversal at the lumbar region in La Zhui areas The circumscribed circular diameter in face is less than or equal to output optical fibre diameter.

7. middle-infrared band optical fiber pumping/signal bundling device as claimed in claim 1, it is characterised in that the optical fiber beam combination With the welding of output optical fibre, asymmetric electrode electric discharge heat welded or low-temperature welding method can be adopted.