An intracooling flake laser and method of manufacture

Abstract

The application discloses an inner-cooling thin-plate laser and a preparation method thereof. The inner-cooling thin-plate laser comprises, from one side to the other side, a heat sink, a high-reflection layer, an inner-cooling thin-plate gain medium, a high-transmission layer, a passive layer and an output mirror. The inner-cooling thin-plate gain medium is connected with a pump light source through an optical coupling system. The inner-cooling thin-plate gain medium comprises a thin-plate gain medium. Periodic micropores, cooling micropores and microchannels are formed on the thin-plate gain medium. The periodic micropores are perpendicular to the light-out surface of the thin-plate gain medium to form a photonic crystal array, which is used for limiting the generation of an optical field in the thin-plate gain medium and forming an array optical field. The cooling micropores are arranged in an array outside the periodic micropores and are perpendicular to the light-out surface of the thin-plate gain medium. The cooling micropores are connected with the microchannels to form inner-cooling channels. The heat sink is provided with a cooling liquid inlet and a cooling liquid outlet which are connected with the inner-cooling channels. The cooling liquid flowing in the inner-cooling channels does not disturb the propagation of light in the thin-plate gain medium.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of laser technology, in particular to an internal cooling thin disk laser and a preparation method. BACKGROUND

[0002] The thin disk laser is considered as one of the most famous progresses in laser technology in recent years, which is based on a revolutionary design concept of solid-state laser. The thermal gradient direction of the thin disk gain medium is parallel to the output laser direction. The thin disk gain medium has high pump power density without obvious temperature gradient. Theoretically, the thin disk laser can overcome the contradiction between high power and high brightness, and has the potential to output a beam close to the diffraction limit. In recent years, the thin disk laser has become a powerful assistant for scientific research and industrial processing.

[0003] In order to realize high power and high beam quality laser output of the thin disk gain medium under strong pumping condition, good heat dissipation is necessary. At present, the gain medium is usually fixed on a heat sink by welding or mechanical method, and water cooling, air cooling, semiconductor refrigeration and other heat dissipation means are used. Temperature gradient is generated in the medium and the heat conduction section. The traditional heat dissipation means cannot effectively remove the waste heat in the medium. The increase of pump power leads to the continuous rise of temperature in the gain medium, which forms a non-uniform temperature field distribution in the medium and causes thermal stress in the medium. The thermal stress can cause thermal lens effect, thermal birefringence and thermal stress damage in the solid gain medium, which causes distortion of the laser wavefront passing through the gain medium, reduces the beam quality of the output laser of the laser, and also reduces the service life of the gain medium, which is not conducive to the long-term stable operation of the laser.

[0004] Therefore, the effective heat dissipation of the thin disk laser has become a problem to be solved for the high power thin disk laser. SUMMARY

[0005] In view of the deficiencies in the prior art, the present application provides an internal cooling thin disk laser and a preparation method.

[0006] The present application discloses an internal cooling thin disk laser, comprising: a heat sink, a high reflection layer, an internal cooling thin disk gain medium, a high transmission layer, a passive layer and an output mirror arranged in sequence from one side to the other side, the internal cooling thin disk gain medium being connected with a pump light source through an optical coupling system.

[0007] The internal cooling thin disk gain medium comprises a thin disk gain medium, and the thin disk gain medium is formed with periodic micropores, cooling micropores and microchannels; wherein,

[0008] The periodic micropores are perpendicular to the light-emitting surface of the thin gain medium to form a photonic crystal array for limiting the generation of light field in the thin gain medium and forming an array light field; the cooling micropores are arranged in an array outside the periodic micropores and are perpendicular to the light-emitting surface of the thin gain medium, and the cooling micropores are connected with the microchannels to form an internal cooling channel; the heat sink is provided with a cooling liquid inlet and a cooling liquid outlet connected with the internal cooling channel, and the cooling liquid flowing in the internal cooling channel does not disturb the propagation of light in the thin gain medium.

[0009] As a further improvement of the present application, the periodic micropores have a smaller aperture than the cooling micropores, and the periodic micropores are formed by a plurality of polygonal micropore arrays, and the micropores of each polygonal micropore array penetrate the thickness direction of the thin gain medium; the cooling micropores are arranged in the same polygonal array outside each polygonal micropore array, and each cooling micropore penetrates the thickness direction of the thin gain medium; the microchannels are formed on the surface of the thin gain medium and are connected with the adjacent two cooling micropores at both ends.

[0010] As a further improvement of the present application, the heat sink is provided with cooling liquid channels corresponding to the cooling micropores, and the cooling liquid channels are connected with the cooling liquid inlet and the cooling liquid outlet, or one or more of the cooling liquid channels are used as the cooling liquid inlet and the remaining one or more channels are used as the cooling liquid outlet.

[0011] As a further improvement of the present application, the heat sink includes but is not limited to one of diamond, silicon carbide and aluminum, and the internal cooling thin gain medium is fixed on the heat sink by a mechanical clamping method; cooling liquid is injected into the internal cooling channel of the internal cooling thin gain medium through the heat sink, and the cooling liquid includes but is not limited to one of water, alcohol and freon;

[0012] The passive layer is made of a transparent material for blocking the cooling liquid to prevent it from flowing out from the rear end surface, so that the cooling liquid circulates in the internal cooling channel.

[0013] As a further improvement of the present application, the thin gain medium is made of a transparent material containing one or more doping elements, and the doping elements include but are not limited to one or more of Yb, Er and Y, and the transparent material includes but is not limited to one of glass material, sapphire and crystal;

[0014] The pump light source includes but is not limited to one of a semiconductor laser, a mercury lamp, a xenon lamp, a krypton lamp and a flash lamp, and the pumping method is end-face pumping.

[0015] As a further improvement of the present application, the high-reflection layer has high reflection to the oscillation laser formed by the internal cooling thin gain medium, and the high-transmission layer has high transmission to the oscillation laser formed by the internal cooling thin gain medium.

[0016] The output mirror forms a semi-reflection and semi-transmission of the oscillation laser to the inner cooling wafer gain medium, and the output mirror is prepared on the back surface of the passive layer or uses a separate optical lens.

[0017] The application further discloses a preparation method of the inner cooling wafer laser.

[0018] The inner cooling wafer gain medium is prepared.

[0019] The femtosecond laser beam is focused on the inside or surface of the wafer gain medium, and the periodic micropore and the cooling micropore region are modified by laser direct writing; the upper and lower surfaces of the wafer gain medium are polished, and the modified region is exposed; the wafer gain medium is placed in an etching solution, and the etching solution selectively etches the modified region to obtain the periodic micropore and the cooling micropore; and the microchannel is obtained on the surface of the wafer gain medium by laser processing.

[0020] High reflection layers and high transmission layers are respectively coated on two surfaces of the inner cooling wafer gain medium.

[0021] The high reflection layer side of the inner cooling wafer gain medium is mounted on a heat sink.

[0022] The high transmission layer side of the inner cooling wafer gain medium is sequentially provided with a passive layer and an output mirror.

[0023] The pump light source is incident into the inner cooling wafer gain medium through an optical coupling system.

[0024] As a further improvement of the application, the spot of the femtosecond laser is focused on the inside or surface of the wafer gain medium by using an immersion lens, wherein the size of the focused spot is less than 1 um, the laser power is 1-10 mW, and the polarization is linear polarization or circular polarization.

[0025] As a further improvement of the application, the etching solution includes but is not limited to one of phosphoric acid, hydrofluoric acid and hydrochloric acid, and the etching temperature includes but is not limited to room temperature or heating.

[0026] As a further improvement of the application, the cooling micropore is larger than the modified region of the periodic micropore after the femtosecond laser direct writing by means of multiple writing or power increase, and the diameter of the cooling micropore after etching is larger than that of the periodic micropore.

[0027] Compared with the prior art, the application has the following beneficial effects:

[0028] The application combines femtosecond laser processing, chemical etching and laser processing technology to prepare an internal cooling thin sheet gain medium containing periodic micropores, cooling micropores and microchannels, wherein the periodic micropores constitute a photonic crystal array for limiting the light field generated in the thin sheet gain medium to form an array light field, which can reduce thermal stress caused by uneven temperature field distribution; the cooling micropores are connected with the microchannel structure to form a cooling channel, and the cooling liquid can be injected into the cooling channel through heat sink circulation to efficiently lead out the heat deposition in the thin sheet and weaken the thermal lens effect in the gain medium; the application can greatly increase the thickness of the thin sheet gain medium to increase the number of gain ions, which is conducive to realizing the high-power, fast-cooling and output beam stable thin sheet laser and its industrial production and application. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The structure schematic diagram of the internal cooling thin sheet gain medium disclosed by an embodiment of the application is shown in the figure.

[0030] Figure 2 The structure schematic diagram of the internal cooling thin sheet laser disclosed by an embodiment of the application is shown in the figure.

[0031] In the figure:

[0032] 1, thin sheet gain medium; 2, cooling micropore; 3, periodic micropore; 4, microchannel; 5, high transmission layer; 6, high reflection layer; 7, passive layer; 8, heat sink; 9, pump light source; 10, optical coupling system; 11, output mirror. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical scheme and advantages of the embodiments of the application clearer, the technical scheme of the embodiments of the application will be described clearly and completely below in combination with the drawings of the embodiments of the application. Obviously, the described embodiments are part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0034] The application will be described in further detail below in combination with the drawings:

[0035] As Figure 1 , 2As shown, this invention provides an internally cooled thin-film laser, comprising: an internally cooled thin-film gain medium, a high-transparency layer 5, a high-reflectivity layer 6, a passive layer 7, a heat sink 8, an output mirror 11, an optical coupling system 10, and a pump source 9; wherein, the internally cooled thin-film gain medium includes a thin-film gain medium 1, on which periodic micro-holes 3, cooling micro-holes 2, and microchannels 4 are formed; the high-transparency layer 5 and the high-reflectivity layer 6 are respectively deposited on both sides of the internally cooled thin-film gain medium, a heat sink 8 is installed on one side of the high-reflectivity layer 6 of the internally cooled thin-film gain medium, and a passive layer 7, a heat sink 8, and an output mirror 11 are sequentially disposed on one side of the high-transparency layer 5 of the internally cooled thin-film gain medium; the internally cooled thin-film gain medium is connected to the pump source 9 through the optical coupling system 10; the pump light generated by the pump source 9 performs end-face pumping on the internally cooled thin-film gain medium, and a stable oscillating laser is formed in the internally cooled thin-film gain medium and output from the output mirror 11.

[0036] Specifically:

[0037] like Figure 2 As shown, the periodic micropores 3 of the present invention are perpendicular to the light-emitting surface of the thin-film gain medium 1 to form a photonic crystal array, used to confine the light field generated in the thin-film gain medium 1 and form an array light field; preferably, the periodic micropores 3 are composed of multiple polygonal micropore arrays, such as Figure 2 The hexagonal micro-hole array shown; the micro-holes of each polygonal micro-hole array penetrate the thickness direction of the thin-film gain medium; cooling micro-holes 2 are arranged in an array outside the periodic micro-holes 3 and perpendicular to the light-emitting surface of the thin-film gain medium 1. The cooling micro-holes 2 are arranged in the same polygonal array (such as a hexagonal array) outside each polygonal micro-hole array, and each cooling micro-hole 2 penetrates the thickness direction of the thin-film gain medium. The aperture of the periodic micro-holes 3 is smaller than the aperture of the cooling micro-holes 2. The arrangement of the cooling micro-holes 2 and the periodic micro-holes 3 can ensure that the cooling micro-holes 2 can fully dissipate heat from the thin-film gain medium 1. The cooling micro-holes 2 are connected to the microchannels 4 to form an internal cooling channel. Preferably, the microchannels 4 are formed on the surface of the thin-film gain medium 1 and are connected to two adjacent cooling micro-holes 2 at both ends.

[0038] Furthermore, the thin-film gain medium 1 of the present invention is composed of a transparent material containing one or more doped elements, including but not limited to one or more of Yb, Er, and Y, and the transparent material including but not limited to one of glass, sapphire, and crystal; the diameter of the periodic micropores 3 is about 0.1 mm, the diameter of the cooling micropores 2 is about 1 mm, and the diameter of the microchannels 4 is about 0.5 mm.

[0039] The heat sink 8 of the application is provided with a cooling liquid inlet and a cooling liquid outlet communicated with the internal cooling channel, so that the cooling liquid flowing in the internal cooling channel does not disturb the propagation of light in the thin slice gain medium 1; wherein the heat sink 8 is provided with cooling liquid channels corresponding to the cooling micro-holes 2, the cooling liquid channels are communicated with the cooling liquid inlet and the cooling liquid outlet, or one or more of the cooling liquid channels are used as the cooling liquid inlet and the remaining one or more channels are used as the cooling liquid outlet. Preferably, the heat sink 8 includes but is not limited to one of diamond, silicon carbide and aluminum, and the internal cooling thin slice gain medium is fixed on the heat sink 8 by mechanical clamping; the cooling liquid including but not limited to one of water, alcohol and freon is injected into the internal cooling channel of the internal cooling thin slice gain medium through the heat sink 8, and the cooling speed of the thin slice gain medium can be controlled by changing the flow rate of the cooling liquid; the passive layer 7 of the application is made of transparent material and is used to block the cooling liquid to prevent it from flowing out from the rear end surface, so that the cooling liquid circulates in the internal cooling channel.

[0040] The pump light source of the application includes but is not limited to one of a semiconductor laser, a mercury lamp, a xenon lamp, a krypton lamp and a flash lamp, and the pumping method is end face pumping; the high reflection layer 6 has high reflection to the oscillation laser formed by the internal cooling thin slice gain medium, and the high transmission layer 5 has high transmission to the oscillation laser formed by the internal cooling thin slice gain medium; the output mirror 11 has semi-reflection and semi-transmission to the oscillation laser formed by the internal cooling thin slice gain medium, and the output mirror 11 is prepared on the rear surface of the passive layer or uses a separate optical lens.

[0041] The application provides a preparation method of an internal cooling thin slice laser, which comprises the following steps:

[0042] Step 1, preparing an internal cooling thin slice gain medium:

[0043] Step 11, focusing a femtosecond laser beam to the inside or surface of the thin slice gain medium; wherein the spot of the femtosecond laser is focused in the inside or surface of the thin slice gain medium by immersion lens focusing, the size of the focused spot is less than 1 um, the laser power is 1-10 mW, and the polarization is linear polarization or circular polarization;

[0044] Step 12, modifying the periodic micro-hole and the cooling micro-hole region by laser direct writing; wherein the modification region of the cooling micro-hole after the femtosecond laser direct writing is larger than that of the periodic micro-hole by multiple writing or increasing the power, so that the diameter of the cooling micro-hole after etching is larger than that of the periodic micro-hole;

[0045] Step 13, polishing the upper and lower surfaces of the thin slice gain medium to leak out the modification region;

[0046] Step 14, the wafer gain medium is placed in an etching liquid, the etching liquid selectively etches the modified region, and periodic micropores and cooling micropores are obtained; wherein the etching liquid includes but is not limited to one of phosphoric acid, hydrofluoric acid and hydrochloric acid, and the etching temperature includes but is not limited to room temperature or heating;

[0047] Step 15, a microchannel is obtained on the surface of the wafer gain medium by laser processing;

[0048] Step 2, the high-reflection layer and the high-transmission layer are respectively plated on the two surfaces of the internal cooling wafer gain medium;

[0049] Step 3, the high-reflection layer side of the internal cooling wafer gain medium is mounted on a heat sink;

[0050] Step 4, the high-transmission layer side of the internal cooling wafer gain medium is sequentially provided with a passive layer and an output mirror;

[0051] Step 5, the pump light source is incident into the internal cooling wafer gain medium through an optical coupling system.

[0052] The working principle of the present application is as follows:

[0053] The pump light source reaches the internal cooling wafer gain medium through the optical coupling system, and the wafer gain medium is end-pumped; the periodic micropores in the internal cooling wafer gain medium are used to limit the generation of light field in the wafer gain medium, form an array light field, and the cooling micropores and the microchannels constitute internal cooling channels. When the pump light source is used to multi-side strong pump the wafer gain medium, a large amount of heat will be generated, if not handled, the wafer gain medium will inevitably generate a large temperature gradient, stress will be generated in the wafer gain medium, and even deformation will occur, so that the wafer laser output laser is unstable and is not conducive to the improvement of the wafer laser output power and the spot brightness. By passing a certain flow rate of cooling liquid into the wafer gain medium through the heat sink, the temperature gradient of the wafer gain medium can be rapidly and stably reduced, the heat sink material with good heat conduction performance can effectively conduct the waste heat of the wafer gain medium, has high heat exchange efficiency, and the heat sink material with low thermal expansion coefficient can effectively reduce the deformation of the wafer gain medium and reduce the internal stress, which is conducive to the stable oscillation of the laser in the wafer gain medium. After the stable oscillation laser is formed in the internal cooling wafer gain medium, the oscillation laser reaches the passive layer of the glass material through the high-transmission layer, and the oscillation laser propagates to the output mirror to realize the output of the laser.

[0054] The present application has the following advantages:

[0055] The internal cooling mode of the present application can achieve good heat conduction and cooling effect, reduce thermal effect, and further realize high-brightness and high-power laser output. The cooling mode of the internal cooling thin slice gain medium is simple and easy to operate, the cooling effect of the cooling liquid is obvious, the material is easy to obtain and low in price, the maintenance cost is low, the thin slice thickness can be greatly improved through the cooling system, the number of gain ions is increased, the output power of the thin slice laser is improved, the stability and service life of the internal cooling thin slice laser are ensured, and the large-scale production and industrialized utilization of the thin slice laser are promoted.

[0056] The above merely illustrates the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An intracooling flake laser, characterized by, It comprises: a heat sink, a high-reflection layer, an inner-cooling thin-plate gain medium, a high-transmission layer, a passive layer and an output mirror arranged in sequence from one side to the other side, the inner-cooling thin-plate gain medium being connected with a pump light source through an optical coupling system; The inner-cooling thin-plate gain medium comprises a thin-plate gain medium, and the thin-plate gain medium is formed with periodic micropores, cooling micropores and microchannels; The periodic micropores are perpendicular to the light-emitting surface of the thin-plate gain medium to form a photonic crystal array for limiting the generation of an optical field in the thin-plate gain medium and forming an array optical field; the cooling micropores are arranged in an array outside the periodic micropores and are perpendicular to the light-emitting surface of the thin-plate gain medium, and the cooling micropores are connected with the microchannels to form an inner-cooling channel; the heat sink is provided with a cooling liquid inlet and a cooling liquid outlet connected with the inner-cooling channel, and the cooling liquid circulating in the inner-cooling channel does not disturb the propagation of light in the thin-plate gain medium.

2. The intracooling flake laser of claim 1, wherein, The aperture of the periodic micropores is smaller than that of the cooling micropores, the periodic micropores are formed by a plurality of polygonal micropore arrays, and the micropores of each polygonal micropore array penetrate through the thickness direction of the thin-plate gain medium; the cooling micropores are arranged in the same polygonal array outside each polygonal micropore array, and each cooling micropore penetrates through the thickness direction of the thin-plate gain medium; the microchannels are formed on the surface of the thin-plate gain medium and connected with the adjacent two cooling micropores at both ends.

3. The intracooling flake laser of claim 1 or 2, wherein, The heat sink is provided with cooling liquid channels corresponding to the cooling micropores, and the cooling liquid channels are connected with the cooling liquid inlet and the cooling liquid outlet, or one or more of the cooling liquid channels are used as the cooling liquid inlet and the remaining one or more channels are used as the cooling liquid outlet.

4. The intracooling flake laser of claim 1 or 2, wherein, The heat sink comprises one of diamond, silicon carbide and aluminum, and the inner-cooling thin-plate gain medium is fixed on the heat sink by a mechanical clamping method; cooling liquid is injected into the inner-cooling channel of the inner-cooling thin-plate gain medium through the heat sink, and the cooling liquid comprises one of water, alcohol and freon; The passive layer is made of a transparent material for blocking the cooling liquid to prevent it from flowing out from the rear end surface, so that the cooling liquid circulates in the inner-cooling channel.

5. The intracooling flake laser of claim 1 or 2, wherein, The thin-plate gain medium is made of a transparent material containing one or more doping elements, the doping elements comprise one or more of Yb, Er and Y, and the transparent material comprises one of glass material, sapphire and crystal; The pump light source comprises one of a semiconductor laser, a mercury lamp, a xenon lamp, a krypton lamp and a flash lamp, and the pumping method is end-face pumping.

6. The intracooling flake laser of claim 1 or 2, wherein, The high-reflection layer has high reflection to the oscillation laser formed by the inner-cooling thin-plate gain medium, and the high-transmission layer has high transmission to the oscillation laser formed by the inner-cooling thin-plate gain medium; The output mirror has half reflection and half transmission to the oscillation laser formed by the inner-cooling thin-plate gain medium, and the output mirror is prepared on the rear surface of the passive layer or uses a separate optical lens.

7. A method of producing an intracooling flake laser as claimed in any one of claims 1 to 6, characterized in that, It comprises: Preparation of an inner-cooling thin-plate gain medium: The femtosecond laser beam is focused inside or on the surface of the thin gain medium, and periodic micropores and cooling micropore regions are modified by laser direct writing; the upper and lower surfaces of the thin gain medium are polished to expose the modified regions; the thin gain medium is placed in an etching solution, and the etching solution selectively etches the modified regions to obtain periodic micropores and cooling micropores; and microchannels are obtained on the surface of the thin gain medium by laser processing. The high-reflection layer and the high-transmission layer are respectively coated on the two sides of the internal cooling thin gain medium. The high-reflection layer side of the internal cooling thin gain medium is mounted on a heat sink. The high-transmission layer side of the internal cooling thin gain medium is sequentially provided with a passive layer and an output mirror. The pump light source is incident into the internal cooling thin gain medium through an optical coupling system.

8. The production method according to claim 7, wherein The spot of the femtosecond laser is focused inside or on the surface of the thin gain medium by immersion lens focusing, wherein the focused spot size is less than 1 um, the laser power is 1-10 mW, and the polarization is linear or circular.

9. The production method according to claim 7, wherein The etching solution includes but is not limited to one of phosphoric acid, hydrofluoric acid, and hydrochloric acid, and the etching temperature includes but is not limited to room temperature or heating.

10. The production method according to claim 7, wherein The cooling micropore is larger than the modified region of the periodic micropore after femtosecond laser direct writing by means of multiple writing or increasing power, and the diameter of the cooling micropore after etching is larger than that of the periodic micropore.

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