Ceramic fiber laser gain medium sheet and method of making same

Abstract

The application provides a ceramic fiber laser gain medium sheet and a preparation method thereof. The ceramic fiber laser gain medium sheet comprises a doped gain region, a substrate region and a substrate. The doped gain region comprises a ceramic substrate and active ions doped in the substrate, and the doped gain region is in the shape of a curved filament. The substrate region is made of ceramic material and is coated on the radial outer side of the doped gain region. The doped gain region and the substrate region are both arranged on the substrate. The ceramic fiber laser gain medium sheet has a pump light injection end, a laser injection end and a laser output end. Pump light and seed light are injected into the doped gain region through the pump light injection end and the laser injection end respectively. After the seed light is amplified by the doped gain region, the amplified seed light is output from the laser output end. The ceramic fiber laser gain medium sheet has a greatly improved nonlinear threshold, damage threshold and thermal conductivity, and the output power of the fiber laser is greatly improved. The devices are integrated on a heat sink plate, and complex shaping optical elements are not needed, so that the volume of the laser is greatly compressed.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of laser technology, in particular to a ceramic fiber laser gain medium sheet and a preparation method thereof. BACKGROUND

[0002] The fiber laser is a laser with a long and thin doped rare earth fiber as a laser gain medium. The surface area and volume ratio of the fiber laser is very large, which is very beneficial to heat dissipation. Due to the growth process limitation, it is extremely difficult to prepare a laser crystal fiber with a crystal as a material, and there is no feasible solution at present. Therefore, the gain medium of the current fiber laser is a glass material. Because the glass has good ductility, it can be easily drawn into a fiber. However, the nonlinear threshold of the glass material is low. When the peak power of the laser is greater than 100kW, the fiber laser produces nonlinear effects such as stimulated Raman scattering, and the fiber laser will be damaged. In addition, the thermal conductivity of the glass is one order of magnitude lower than that of the crystal and ceramic materials. Therefore, the output power of the single fiber laser is limited. The average power of the narrow linewidth continuous fiber laser is below 5kW, and the peak power of the pulsed fiber laser is below 100kW. SUMMARY

[0003] The technical problem to be solved by the present application is how to improve the performance of the fiber laser. The present application provides a ceramic fiber laser gain medium sheet and a preparation method thereof.

[0004] The ceramic fiber laser gain medium sheet according to the embodiments of the present application comprises:

[0005] The doped gain region comprises a ceramic matrix and active ions doped in the matrix, and the doped gain region is in the form of a curved filament;

[0006] The matrix region is made of ceramic material and is coated on the radial outer side of the doped gain region;

[0007] The substrate is provided with the doped gain region and the matrix region;

[0008] The ceramic fiber laser gain medium sheet has a pump light injection end, a laser injection end and a laser output end. Pump light and seed light are injected into the doped gain region through the pump light injection end and the laser injection end respectively. The seed light is amplified by the doped gain region and then output from the laser output end.

[0009] According to some embodiments of the present application, the intersection overlap part of the doped gain region is provided with a matrix thin layer.

[0010] In some embodiments of the present application, the ceramic fiber laser gain medium sheet further comprises a cooling plate provided with a cooling flow channel with a predetermined shape.

[0011] According to some embodiments of the present application, the refractive index n2 of the substrate region is less than the refractive index n1 of the doped gain region.

[0012] In some embodiments of the present application, the radius of the curved portion of the doped gain region is R, the thickness of the doped gain region is d, the laser divergence angle of the transmission in the doped gain region is θ, and the following is satisfied:

[0013] θ+(d / R)*(180 / π)<(90-sin -1 (n2 / n1).

[0014] According to some embodiments of the present application, the diameter of the doped gain region is in the order of hundreds of microns.

[0015] In some embodiments of the present application, the laser injection end and the laser output end are each provided with a laser anti-reflection film, and the pump light injection end is provided with a second anti-reflection film.

[0016] According to some embodiments of the present application, the ceramic substrate and the substrate region are both made of YAG or LuAG material.

[0017] The preparation method of the ceramic fiber laser gain medium sheet according to the embodiments of the present application is used to prepare the ceramic fiber laser gain medium sheet as described above, and the preparation method comprises the following steps:

[0018] S100, using YAG or LuAG material as a ceramic substrate to form a filament in the order of hundreds of microns, and laying the filament on a substrate according to a design pattern to form an integrated fiber ceramic green sheet that satisfies fiber laser waveguide transmission;

[0019] S200, performing ceramic sintering on the integrated fiber ceramic green sheet to form a ceramic fiber laser sheet;

[0020] S300, thinning the ceramic fiber laser sheet to a preset thickness;

[0021] S400, cutting a cooling channel according to a preset pattern;

[0022] S500, coating the ceramic fiber laser sheet.

[0023] According to some embodiments of the present application, step S500 comprises coating a pump light anti-reflection film on the pump light injection end of the ceramic fiber laser sheet, coating a laser anti-reflection film on the laser injection end and the laser output end, and coating an evanescent wave elimination film on the side surface of the ceramic fiber laser sheet.

[0024] The present application has the following beneficial effects:

[0025] Compared with the glass fiber gain medium, the ceramic fiber laser gain medium sheet has greatly improved nonlinear threshold, damage threshold and thermal conductivity, and can greatly improve the output power of the fiber laser, especially the output power of the pulse fiber laser and the narrow linewidth laser. The ceramic fiber gain medium of the application can be integrated with a laser diode pump source on a heat sink plate, without the need for complex shaping optical elements, greatly reducing the size of the laser. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The basic structure of the ceramic fiber laser gain medium sheet according to the embodiment of the application is shown in the figure.

[0027] Figure 2 The coating diagram of the ceramic fiber laser gain medium sheet according to the embodiment of the application is shown in the figure.

[0028] Figure 3 The schematic diagram of the bidirectional pumped ceramic fiber laser gain medium sheet according to the embodiment of the application is shown in the figure.

[0029] Figure 4 The schematic diagram of the side scattering pumped integrated ceramic fiber laser sheet according to the embodiment of the application is shown in the figure.

[0030] Figure 5 The flow chart of the preparation method of the ceramic fiber laser gain medium sheet according to the embodiment of the application is shown in the figure.

[0031] Reference signs:

[0032] The ceramic fiber laser gain medium sheet 100, the pump light injection end 101, the laser injection end 102, the laser output end 103, the cross-overlapping part 104,

[0033] The doped gain region 10,

[0034] The matrix region 20, the pump light 21, the seed light 22, the output laser 23,

[0035] The cooling plate 30, the laser diode 41, the laser seed source 42. DETAILED DESCRIPTION

[0036] In order to further illustrate the technical means and effects taken by the application to achieve the predetermined purposes, the application will be described in detail below in combination with the drawings and preferred embodiments.

[0037] The commonly used solid laser gain medium materials are crystal, glass and ceramic, the laser crystal is widely used in various lasers, especially in pulse lasers, due to the good thermal conductivity, mechanical strength and high damage threshold, the laser glass has very good ductility, and is mainly made into optical fiber for lasers, and the laser ceramic has characteristics similar to the laser crystal, although the laser ceramic has the advantages of short preparation period and low cost, but due to the difficulty in preparation, the yield is not high, so the laser ceramic is rarely used in lasers at present.

[0038] The laser ceramic is fired from a blank, with the increasing maturity of the additive manufacturing technology, if the additive manufacturing technology is used, the laser ceramic blank is flexibly prepared according to a specific design scheme, and after firing, various optical functions such as crystal fiber waveguide, self-Q, spatial filtering and spontaneous emission suppression can be realized on a single laser material, so that a complex laser is miniaturized and integrated.

[0039] The application discloses a kind of ceramic fiber laser gain medium sheet 100 made by using the principle of additive manufacturing.The single ceramic fiber laser gain medium sheet 100 made can realize 100kW level laser output, and the output laser of multiple ceramic fiber laser gain medium sheet 100 can also be carried out spectrum or coherent beam combination, to realize the scaling of laser power.The description of method flow in the specification and the steps of flow chart in the drawings of the specification of the present application do not have to be strictly executed according to step label, the execution order of method steps can be changed.Moreover, certain steps can be omitted, multiple steps can be combined into one step for execution, and / or one step can be divided into multiple steps for execution.

[0040] As shown in Figures 1-4 The ceramic fiber laser gain medium sheet 100 according to the embodiment of the application includes a doped gain region 10, a matrix region 20 and a substrate.

[0041] The doped gain region 10 includes a ceramic matrix and active ions doped in the matrix, and the doped gain region 10 is in the form of a curved filament.The matrix region 20 is made of ceramic material and covers the radial outer side of the doped gain region 10, and the doped gain region 10 and the matrix region 20 are both arranged on the substrate.

[0042] As shown in Figure 2 and Figure 3 The ceramic fiber laser gain medium sheet 100 has a pump light injection end 101, a laser injection end 102 and a laser output end 103, the pump light 21 and the seed light 22 are injected into the doped gain region 10 through the pump light injection end 101 and the laser injection end 102 respectively, and the seed light 22 is amplified in the doped gain region 10 and then output from the laser output end 103.

[0043] Compared with the glass fiber gain medium, the ceramic fiber laser gain medium sheet 100 has a high nonlinear threshold, a high damage threshold and a high thermal conductivity, and can greatly improve the output power of the fiber laser, especially the output power of the pulse fiber laser and the narrow line width laser.

[0044] According to some embodiments of the present application, as shown in Figure 1 As shown in Figure 1 As shown in the figure, the intersection of the light path of the doped gain region 10 (i.e. the above-mentioned intersection overlapping part 104) needs to be laid with a thin layer of matrix in the middle of the intersection, which separates the doped gain region 10.

[0045] In some embodiments of the present application, the ceramic fiber laser gain medium sheet 100 further comprises a cooling plate 40 provided with a cooling flow channel of a predetermined shape. It should be noted that in order to improve the cooling effect of the ceramic fiber laser gain medium sheet 100, the substrate can also be provided with a cooling flow channel.

[0046] According to some embodiments of the present application, the refractive index n2 of the matrix region 20 is less than the refractive index n1 of the doped gain region 10. The thickness of the matrix region 20 is greater than 3μm, which ensures that the evanescent wave can be unaffected, and in order to increase the mechanical strength, the thickness of the matrix region 20 can be increased accordingly.

[0047] In some embodiments of the present application, the radius of the curved part of the doped gain region 10 is R, the thickness of the doped gain region 10 is d, and the laser divergence angle transmitted in the doped gain region 10 is θ, which satisfies:

[0048] θ+(d / R)*(180 / π)<(90-sin -1 (n2 / n1))).

[0049] In this way, total reflection of laser can occur at the interface between the doped gain region 10 and the matrix region 20, so that the laser always remains in the doped gain region 10 for transmission, without entering the matrix region 20.

[0050] According to some embodiments of the present application, the diameter of the doped gain region 10 is in the order of hundreds of microns.

[0051] In some embodiments of the present application, the laser injection end 102 and the laser output end 103 are each provided with a laser anti-reflection film, and the pump light injection end 101 is provided with a second anti-reflection film. For example, the first anti-reflection film can be a 940nm anti-reflection film, and the second anti-reflection film can be a 1030nm anti-reflection film.

[0052] According to some embodiments of the present application, the ceramic matrix and the matrix region 20 are both made of YAG or LuAG material.

[0053] AsFigures 1-4 As shown, the outer cladding of the ceramic optical fiber is a matrix region 20 without doped active ions, the matrix region 20 can adopt YAG, LuAG or spinel and other transparent materials, the fiber core is a doped gain region 10, the matrix material is doped with active ions, the active ions can be Nd, Yb, Er or Tm and the like, and the shrinkage coefficients of the matrix region 20 and the doped region are made the same through auxiliary material matching, so as to prevent material cracking during sintering.

[0054] The preparation method of the ceramic optical fiber laser gain medium sheet 100 according to the embodiment of the present application is used for preparing the ceramic optical fiber laser gain medium sheet 100 as described above, and the preparation method comprises:

[0055] S100, YAG or LuAG material is used as a ceramic matrix to form a hundred-micron-level filament, which is laid on a substrate according to a design pattern to form an integrated optical fiber ceramic green sheet meeting the optical fiber laser waveguide transmission;

[0056] S200, the integrated optical fiber ceramic green sheet is sintered to form a ceramic optical fiber laser sheet;

[0057] S300, the ceramic optical fiber laser sheet is thinned to a preset thickness;

[0058] S400, a cooling channel is cut out according to a preset pattern;

[0059] S500, the ceramic optical fiber laser sheet is coated.

[0060] According to some embodiments of the present application, the step S500 comprises: coating a pump light anti-reflection film on the pump light injection end 101 of the ceramic optical fiber laser sheet, coating a laser anti-reflection film on the laser injection end 102 and the laser output end 103, and coating an evanescent wave elimination film on the side surface of the ceramic optical fiber laser sheet (including the first side surface S3 and the second side surface S4 shown in the figure). Figure 2

[0061] It should be noted that, since the divergence angle of the pump light 21 is large, the matrix region 20 is divided into a strip through the way of cutting a groove, and the outside of the matrix region 20 is a low refractive index material such as water or air, so that the pump light 21 is transmitted in the matrix region 20 and the doped gain region 10.

[0062] The ceramic optical fiber laser gain medium sheet and the preparation method thereof according to the present application will be described in detail with reference to the accompanying drawings and two specific embodiments. It should be noted that the following description is only exemplary and should not be construed as a specific limitation of the present application.

[0063] Embodiment one:

[0064] As Figure 1 and Figure 3 ​As shown, the doped gain region 10 is a bendable filament, with a diameter of tens of microns to several millimeters, and the most commonly used material is YAG, in which the Yb ion concentration is related to the length of Ll, for example, the length of Ll is 100 mm, and the Yb doping concentration can be 0.2%, which ensures that most of the pump light 21 can be absorbed by the Ll section.

[0065] The matrix region 20 is generally the same material as the matrix of the doped gain region 10, and through refractive index control, it is easy to make the refractive index of the matrix region 20 and the doped gain region 10 have a difference of 0.001, for example, the refractive index of the doped gain region 10 is 1.821, and the refractive index of the matrix region 20 is 1.822, so the corresponding total reflection angle

[0066] sin -1 (n2 / n1) = 88.1°, if the diameter of the doped gain region 10 is 500 μm, and the laser divergence angle is 5 mrad, Figure 1 The minimum R in the above formula is 18 mm.

[0067] As shown in Figure 3 , the matrix material is cut at an angle, so that the pump light 21 entering the matrix region 20 satisfies the total reflection condition. When laying the doped filament slurry, due to the existence of the intersection, after laying the first layer, a layer of tens of microns of matrix slurry is covered on the first layer, and the second layer is laid, so that the doped gain region 10 does not contact, so that the laser always remains in the doped gain region 10 for transmission, avoiding the transmission loss of the laser.

[0068] As shown in Figure 2 , the laser injection end 102 and the laser output end 103 can be coated with a 1030 nm antireflection film, and the pump light injection end 101 can be coated with a 940 nm antireflection film. S3 and S4 are gain medium large faces, which can be coated with a 3 μm SiO2 film.

[0069] When Yb ions are doped, the wavelength of the pump light 21 can be 940 nm; the wavelength of the injected laser seed light 22 can be 1030 nm, and the time domain can be continuous or pulsed, and 23 is the output laser obtained after the seed light 22 is amplified by the doped gain region 10.

[0070] The material of the cooling plate 30 can be copper, aluminum, stainless steel or diamond, etc., and the inside is cooled by water, and the ceramic fiber laser gain medium sheet 100 is connected with the cooling plate 30 by bonding or welding, etc. When the 940 nm pump light 21 injection power reaches 1200 W, and the 1030 nm laser injection power is 1 W, the output laser 23 can reach more than 800 W.

[0071] Example two:

[0072] As shown in Figure 4As shown, the 940nm laser diode 41 (LD) has an output power of tens of watts in general, and the metal base plate of the LD is connected with the cooling plate 40 for heat dissipation. The injected laser seed source 42 can be a LD pumped passive Q-switched microchip laser, and other components needing heat dissipation are also connected with the cooling plate 40. The seed laser can output a pulse width of 1ns, a repetition frequency of 10kHz, and a pulse energy of 10μJ. The output seed light 22 is injected into the ceramic fiber gain module, and after amplification by the ceramic fiber gain module, laser with a pulse width of 1ns, a repetition frequency of 10kHz, and an output energy of 30mJ can be obtained, and the average power reaches 300W, and the peak power reaches 30MW.

[0073] The ceramic fiber gain medium of the embodiment can be integrated with the laser diode 41 pump source on a heat sink plate, and complex shaping optical elements are not needed, and the volume of the laser is greatly compressed.

[0074] The steps for manufacturing the ceramic fiber laser sheet gain medium are as follows:

[0075] A10, using YAG or LuAG as the substrate, extruding the doped slurry from a needle hole to form a filament of hundreds of microns, and laying the filament on a substrate according to a design pattern to form an integrated fiber ceramic green plate meeting the waveguide transmission of fiber laser;

[0076] A20, performing ceramic firing to form a ceramic fiber laser;

[0077] A30, thinning the ceramic fiber laser to a sheet of about 1mm;

[0078] A40, cutting cooling channels according to the design pattern by a narrow pulse laser cold cutting method;

[0079] A50, coating a pump light anti-reflection film on the side of the ceramic fiber laser plate, and coating a laser anti-reflection film on the laser injection end 102 and the laser output end 103;

[0080] A60, coating an evanescent wave elimination film, such as a 3um SiO2 film, on the large surface of the ceramic fiber laser gain medium sheet 100, and thus the preparation of the ceramic fiber laser gain medium sheet 100 is completed.

[0081] Through the description of the specific embodiments, the technical means and effects taken by the present application to achieve the predetermined purposes can be understood more deeply and specifically. However, the accompanying drawings are provided for reference and illustration only, and are not used to limit the present application.

Claims

1. A method of making a ceramic fiber laser gain medium sheet, characterized by, The preparation method is used for preparing the ceramic fiber laser gain medium sheet; The ceramic fiber laser gain medium sheet comprises: a doped gain region comprising a ceramic matrix and active ions doped in the matrix, the doped gain region being in a curved filament shape; a matrix region made of a ceramic material and covering the radially outer side of the doped gain region; the matrix material of the matrix region is cut at a preset angle, so that the pump light entering the matrix region satisfies the total reflection condition; a substrate, the doped gain region and the matrix region are arranged on the substrate; the ceramic fiber laser gain medium sheet is prepared by auxiliary materials to make the shrinkage coefficients of the matrix region and the doped gain region the same; the ceramic fiber laser gain medium sheet has a pump light injection end, a laser injection end and a laser output end, the pump light and the seed light are injected into the doped gain region through the pump light injection end and the laser injection end respectively, and the seed light is amplified through the doped gain region and then output from the laser output end; The preparation method comprises: S100, YAG or LuAG material is used as a ceramic matrix to form a hundred-micron-level filament, which is laid on a substrate according to a design pattern to form an integrated fiber ceramic green sheet meeting the fiber laser waveguide transmission; S200, the integrated fiber ceramic green sheet is subjected to ceramic firing to form a ceramic fiber laser sheet; S300, the ceramic fiber laser sheet is thinned to a preset thickness; S400, a cooling channel is cut according to a preset pattern; S500, the ceramic fiber laser sheet is coated.

2. The method of claim 1, wherein the ceramic fiber laser gain medium sheet is prepared by the steps of: The cross-over and overlapping part of the doped gain region is provided with a matrix thin layer. ​ 3. The method of claim 1, wherein the ceramic fiber laser gain medium sheet is prepared by the steps of: The ceramic fiber laser gain medium sheet further comprises a cooling plate provided with a cooling flow channel of a preset shape. ​ 4. The method of claim 1, wherein the ceramic fiber laser gain medium sheet is prepared by the steps of: the refractive index of the doped gain region less than the refractive index of the doped gain region . ​ 5. The method of claim 4, wherein the ceramic fiber laser gain medium sheet is prepared by the steps of: The radius of the curved part of the doped gain region is R, the thickness of the doped gain region is d, and the laser divergence angle transmitted in the doped gain region is θ, which satisfies: ​ 。 6. The method of claim 1, wherein the ceramic fiber laser gain medium sheet is prepared by the steps of: The diameter of the doped gain region is in the order of hundreds of microns. ​ 7. The method of claim 1, wherein the ceramic fiber laser gain medium sheet is prepared by the steps of: providing a ceramic fiber laser gain medium sheet; and applying a coating to the ceramic fiber laser gain medium sheet. The laser injection end and the laser output end are both provided with a laser anti-reflection film, and the pump light injection end is provided with a second anti-reflection film.

8. The method of claim 1, wherein the ceramic fiber laser gain medium sheet is prepared by the steps of: The ceramic matrix and the matrix region are both made of YAG or LuAG material. ​ 9. The method of claim 1, wherein the ceramic fiber laser gain medium sheet is prepared by the steps of: Step S500 comprises: coating a pump light anti-reflection film on the pump light injection end of the ceramic fiber laser sheet, coating a laser anti-reflection film on the laser injection end and the laser output end, and coating an evanescent wave elimination film on the side surface of the ceramic fiber laser sheet. ​

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