Preparation method of erbium ion doped mid-infrared microsphere laser

Abstract

The invention relates to a preparation method of an erbium-ion-doped mid-infrared microsphere laser. The preparation method comprises the following steps: step 1, preparing erbium-ion-doped low-hydroxyl fluorotellurite glass; wherein the lowest absorption coefficient of hydroxyl is 0.009 cm <-1 >; step 2, preparing the low-hydroxyl fluorotellurite glass into powder, and then sequentially melting and cooling the powder to prepare erbium ion doped fluorotellurite glass microspheres; step 3, preparing the fluorotellurite optical fiber into an optical fiber taper with a taper area by utilizing an arc discharge assisted local heating stretching method; and step 4, placing the fluorotellurite glass microspheres in a taper area of an optical fiber taper, and exciting erbium ions in the fluorotellurite glass microspheres through an optical fiber taper coupling method under 976nm laser pumping to realize 2.7 [mu] m laser emission. The invention has the advantages that 2.7 mu m laser output can be realized, and the coupling efficiency is high.

Description

Technical Field

[0001] The present invention belongs to the field of laser preparation, and particularly relates to a method for preparing an erbium ion-doped mid-infrared microsphere laser. Background Art

[0002] Mid-infrared lasers (2-5 μm) have important strategic significance in the fields of scientific research and applications. They not only have strong penetration ability for biological tissues, but also because the fingerprint characteristic peaks of many atoms / molecules and the blackbody radiation range of missile / aircraft tail flames are also located in the mid-infrared band, making this band have unique scientific and application values in the fields of gas sensing, environmental monitoring, medical detection, military confrontation, etc. Mid-infrared light sources have become one of the forefront hotspots in the current optical research field.

[0003] Currently, the mainstream mid-infrared lasers on the market include fiber lasers, quantum cascade lasers, rare-earth doped crystal lasers, crystal optical parametric oscillators, chemical lasers, gas lasers, semiconductor lasers, etc., and they have achieved varying degrees of development in their respective fields. However, these lasers still face many challenges, such as the complexity of the growth and manufacturing of semiconductor materials, working in a low-temperature environment, pumping with a pulsed laser source, and high energy consumption. In addition, in some specific applications, these traditional mid-infrared lasers also have limitations, especially in applications that require high integration, miniaturization, or high-selectivity control of resonant modes, and they often cannot meet the requirements. In contrast, glass-based optically pumped whispering gallery mode (WGM) microcavity lasers are very attractive due to their relatively simple manufacturing process, extremely low surface roughness, no absorption and scattering losses, high quality factor of the microcavity, ultra-narrow linewidth, rare-earth ion-doped glass as the gain medium, and no need to design any other optical feedback micro / nano structures. The microcavities of WGM optical microcavity lasers mainly include microsphere cavities, micro-ring cavities, micro-disk cavities, micro-core ring cavities, micro-bottle cavities, etc. In particular, microsphere cavity lasers have received extensive attention due to their unique physical structure and excellent optical properties. Microsphere cavity lasers not only have an extremely high quality factor (Q value), but also can achieve highly localized optical field enhancement, and are particularly suitable for fields such as cavity quantum dynamics, low-threshold / narrow-linewidth lasers, highly sensitive optical detection, and nonlinear optics.

[0004] Early research on glass-based WGM microsphere lasers mainly focused on the visible and near-infrared bands. Traditional silica-based glass is not suitable for fabricating mid-infrared microsphere lasers because of the strong multi-phonon absorption when the wavelength is greater than 2 μm, which leads to a sharp increase in loss. Although chalcogenide glass has advantages such as a good transmission window, low phonon energy, and high nonlinearity in the mid-infrared band, its low solubility of rare-earth ions reduces the fluorescence emission efficiency and also has deficiencies in the laser applications of optical devices. With the progress in the synthesis, doping, and processing of high-quality mid-infrared transparent glass, glass-based WGM microsphere lasers have been extended to the mid-infrared band, and common ones include telluride glass, nanocrystalline glass, and fluoride glass. Since 2004, ~2 μm WGM microsphere lasers based on single / double-doped rare-earth ion glass have been widely studied. However, with the increasing specific application requirements, WGM microsphere lasers operating in longer mid-infrared bands are gradually becoming a development trend. Among them, erbium ions (Er 3+ ) have unique luminescence advantages in the 2.7 μm band, and its emission peak matches the absorption peak of water molecules, making it very suitable for laser surgery and tissue ablation in the medical field. In addition, the energy level structure of Er 3+ enables it to achieve high laser conversion efficiency, thereby obtaining mid-infrared lasers with low thresholds and high output powers.

[0005] Currently, in the research process of fabricating erbium-ion-doped mid-infrared microsphere lasers, different glass materials are usually used to fabricate microspheres and fiber tapers respectively. In 2014, Deng et al. based on highly Er 3+ -doped ZBLAN glass microspheres, combined with tapering a special low-hydroxyl multimode quartz fiber, and for the first time realized a mid-infrared WGM microsphere laser operating at 2718.5 nm through the evanescent wave coupling method of the fiber taper, obtaining a laser threshold lower than 150 μW and an ultra-narrow linewidth less than 1.1 MHz, but the highest output power was only 600 nW. In 2018, Behzadi et al. used a single-mode germanium-doped tapered fiber with comparable loss to replace the low-hydroxyl multimode quartz fiber taper to couple with highly Er 3+ -doped ZBLAN glass microspheres, and by using a high-gain Er / Pr:ZBLAN fiber amplifier, successfully increased the output power of the 2.71 μm microsphere laser to 1 mW, significantly improving its application potential in high-sensitivity sensors and high-signal-to-noise ratio trace detection.

[0006] Although the above methods of fabricating mid-infrared microsphere lasers based on different combinations of glass materials can achieve a certain degree of optical coupling, in actual operation, because the coupling efficiency of the evanescent wave is affected by factors such as the refractive indices of different materials, mismatched optical losses, and interface scattering, the coupling efficiency is low, and the phenomenon of unstable laser modes is likely to occur.

[0007] Therefore, it is necessary to further improve the existing method for preparing mid-infrared microsphere lasers. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a method for preparing an erbium-ion-doped mid-infrared microsphere laser in view of the current situation of the prior art. The method for preparing the erbium-ion-doped mid-infrared microsphere laser can not only achieve high coupling efficiency but also realize the output of 2.7 μm laser.

[0009] The technical solution adopted by the present invention to solve the above technical problem is: a method for preparing an erbium-ion-doped mid-infrared microsphere laser, characterized by including the following steps:

[0010] Step 1, prepare a low-hydroxyl fluorotellurite glass doped with erbium ions; wherein, the absorption coefficient of the hydroxyl group is at least 0.009 cm-1;

[0011] Step 2, make the low-hydroxyl fluorotellurite glass into powder, and then perform melting and cooling treatments on the powder in sequence to prepare a fluorotellurite glass microsphere doped with erbium ions;

[0012] Step 3, use the arc-discharge-assisted local heating and stretching method to prepare an optical fiber taper with a tapered region from the fluorotellurite optical fiber;

[0013] Step 4, place the fluorotellurite glass microsphere at the tapered region of the optical fiber taper, and under the pumping of 976 nm laser, excite the erbium ions in the fluorotellurite glass microsphere through the optical fiber taper coupling method to realize the laser emission of 2.7 μm.

[0014] Preferably, in step 1, specifically, in a dry atmosphere or under argon protection, the rare earth erbium raw material and the fluorotellurite glass raw material are melted together and then cooled to prepare the low-hydroxyl fluorotellurite glass doped with erbium ions. In a dry atmosphere or under argon protection, the purity of the glass can be improved and the water absorption can be reduced.

[0015] Preferably, step 3 includes the following steps in sequence:

[0016] Step 31, take the fluorotellurite optical fiber, remove the coating layer in the middle part thereof, and wipe the middle part where the coating layer is removed clean;

[0017] Step 32, fix the first end of the fluorotellurite optical fiber on the optical fiber clamping platform, and fix the second end of the fluorotellurite optical fiber on the stepping motor;

[0018] Step 33: Move the electrode of the arc discharge device close to the middle part of the fluorotellurite optical fiber and generate local arc heating. During the arc heating process, use a stepper motor to stretch the second end of the fluorotellurite optical fiber, making the middle part of the fluorotellurite optical fiber gradually thinner to form an optical fiber taper with the said tapered region.

[0019] Step 34: Place a U-shaped aluminum block with the opening facing upward on the three-dimensional adjustment platform. Adjust the three-dimensional adjustment platform until the optical fiber taper touches the upper end of the U-shaped aluminum block, and fix the optical fiber taper to the upper end of the U-shaped aluminum block with molten salicylic acid.

[0020] Preferably, the said Step 4 includes the following steps:

[0021] Step 41: Screen the fluorotellurite glass microspheres, and use a truncated optical fiber to pick out the spherical fluorotellurite glass microspheres with a smooth surface.

[0022] Step 42: Place the selected fluorotellurite glass microspheres at the tapered region of the optical fiber taper prepared in Step 3.

[0023] Step 43: Select a pump light source of a 976 nm laser diode, direct the pump light emitted by this pump light source into the optical fiber taper, and then perform non-contact optical coupling on the fluorotellurite glass microspheres through the evanescent wave field of the optical fiber taper to achieve laser emission at 2.7 μm.

[0024] Preferably, in Step 3, an optical fiber taper preparation device is used to prepare the fluorotellurite optical fiber into an optical fiber taper with a tapered region. Among them, this optical fiber taper preparation device includes:

[0025] An optical fiber clamping platform for clamping the first end of the fluorotellurite optical fiber

[0026] A stepper motor, whose output end is used to connect to the second end of the fluorotellurite optical fiber;

[0027] An electrode for heating the fluorotellurite optical fiber;

[0028] A three-dimensional adjustment platform for placing the U-shaped aluminum block.

[0029] Preferably, in Step 4, a microsphere laser device is used to achieve 976 nm laser pumping. This microsphere laser device includes:

[0030] A pump light source for connecting to one end of the optical fiber taper. Among them, this pump light source selects a 976 nm laser diode;

[0031] A spectrometer for connecting to the other end of the optical fiber taper;

[0032] A microscope for observing the positions of the fluorotellurite glass microspheres and the optical fiber taper.

[0033] The microsphere laser device has a high integration level, which is beneficial to the miniaturization of the device.

[0034] Compared with the prior art, the advantages of the present invention are as follows:

[0035] 1. In the preparation method of the mid-infrared microsphere laser of the present invention, the fluorotellurite glass microsphere and the fluorotellurite optical fiber adopt the same matrix, avoiding the coupling problem caused by the mismatch of the matrix between the glass microsphere and the fiber taper, thereby significantly improving the coupling efficiency; while in the prior art, the glass microsphere and the fiber taper adopt different matrices, resulting in low coupling efficiency.

[0036] 2. The present invention improves the laser threshold and Q value of the mid-infrared microsphere laser by optimizing the fiber taper design and the microsphere coupling technology.

[0037] 3. Using low-hydroxyl fluorotellurite glass can reduce optical loss and improve laser efficiency; when the hydroxyl content in the fluorotellurite glass is high, the hydroxyl may chemically react with other ions in the optical medium, resulting in an increase in optical loss; especially at 2.7 μm, the hydroxyl will cause strong absorption, leading to an increase in the optical loss of the glass; selecting low-hydroxyl fluorotellurite glass helps to reduce this additional absorption caused by the hydroxyl, thereby improving the efficiency of the laser.

[0038] 4. Using the arc discharge-assisted local heating and stretching method to prepare the fiber taper can reduce the surface defects of the fiber taper, which often lead to light scattering loss, further increasing the laser threshold and decreasing the Q value.

[0039] Using the arc discharge-assisted local heating and stretching method to prepare the fiber taper has the following advantages compared with the traditional U-shaped ceramic heater and oxyhydrogen flame heating - stepping motor preparation:

[0040] Local precise heating: The arc discharge can concentrate the heat at a specific position of the optical fiber, avoiding over-wide or over-heated heating areas; compared with the traditional U-shaped ceramic heating method, the U-shaped ceramic heater has a larger heating surface and lacks precise control of specific areas, easily leading to local overheating or uneven heating, which will have an adverse impact on the quality and shape of the fiber taper. Although the oxyhydrogen flame heating can also provide high temperature, the flame stability is poor, having an adverse impact on the heating effect.

[0041] Temperature control stability: The arc discharge can provide a stable high temperature, and during the heating process, the temperature distribution is relatively uniform, avoiding uneven stretching of the optical fiber caused by temperature fluctuations; in contrast, the temperature control of the U-shaped ceramic heater depends on the response speed and heat conduction effect of the heater itself, resulting in temperature control delay or instability in some cases; the oxyhydrogen flame heating - stepping motor method depends on the temperature of the combustion flame, and this flame temperature is easily affected by external factors (such as hydrogen and oxygen supply, combustion intensity), resulting in unstable temperature control.

[0042] Ease of operation: The arc discharge device is easy to control and relatively simple to operate. In contrast, the U-shaped ceramic heater requires fine adjustment of the heater distance and temperature control, with complex operation and more monitoring needed. The hydrogen-oxygen flame heating - stepper motor method requires continuous monitoring of the flame stability and combustion state, which increases the complexity and difficulty of operation.

[0043] 5. The 2.7-μm laser obtained by the laser in the present invention can be applied to many fields such as integrated photonics, low-threshold lasers, highly sensitive biosensing, cavity optomechanics, etc. Its application will greatly promote the innovation and development of micro-nano photonics devices and further expand the application scope of mid-infrared lasers. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a schematic flow chart of the preparation method of the mid-infrared microsphere laser according to the embodiment of the present invention;

[0045] Figure 2 It is a schematic structural diagram of the optical fiber taper preparation device used in step 3 of the preparation method of the mid-infrared microsphere laser according to the embodiment of the present invention;

[0046] Figure 3 It is a schematic diagram of the microsphere laser device used in step 4 of the preparation method of the mid-infrared microsphere laser according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0047] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Refer to Figure 1 As shown, the preparation method of the erbium-ion-doped mid-infrared microsphere laser in this embodiment includes the following steps 1 to 4.

[0048] Step 1: Prepare low-hydroxyl fluorotellurite glass doped with erbium ions; among them, the absorption coefficient of the hydroxyl group is at least 0.009 cm-1; specifically, in a dry atmosphere or under argon protection, the rare-earth erbium raw material and the fluorotellurite glass raw material are melted together and then cooled to prepare low-hydroxyl fluorotellurite glass doped with erbium ions;

[0049] Step 2: Make the low-hydroxyl fluorotellurite glass into powder, and then perform melting and cooling treatments on the powder in sequence to prepare fluorotellurite glass microspheres 100 doped with erbium ions; that is, microspheres are prepared using the principle that the surface tension of the glass droplet shrinks into a sphere under high-temperature conditions, specifically including steps such as apparatus cleaning, powder grinding / sieving / washing and drying, high-temperature melting, cooling and collection, cleaning and bottling.

[0050] Step 3. Use the arc discharge-assisted local heating and stretching method to prepare a fiber taper 200 with a taper region 200a from the fluorotellurite optical fiber; wherein, the diameter of the depression in the taper region 200a is between 0.5 - 2 μm. Specifically, in this embodiment, Step 3 sequentially includes the following steps:

[0051] Step 31. Before fiber tapering, first make the two ends of the fluorotellurite optical fiber in the form of FC connectors to facilitate subsequent connection with instrument devices such as pump sources and oscilloscopes; then take the fluorotellurite optical fiber, remove the coating layer from the middle part and wipe the middle part clean;

[0052] Step 32. Fix the first end of the fluorotellurite optical fiber on the fiber clamping platform 1, and fix the second end of the fluorotellurite optical fiber on the stepping motor 2;

[0053] Step 33. Place the electrodes of the arc discharge device close to the middle part of the fluorotellurite optical fiber and generate local arc heating, with the heating temperature being 400 - 600 °C to soften the fluorotellurite optical fiber;

[0054] Among them, during the arc heating process, use the stepping motor 2 to slowly stretch the second end of the fluorotellurite optical fiber, making the middle part of the fluorotellurite optical fiber gradually thinner to form a fiber taper 200 with a taper region 200a;

[0055] Step 34. Place the U-shaped aluminum block with the opening facing upwards on the three-dimensional adjustment platform 4, adjust the three-dimensional adjustment platform 4 until the fiber taper 200 touches the upper end of the U-shaped aluminum block; and fix the fiber taper 200 on the upper end of the U-shaped aluminum block with molten salicylic acid. See Figure 2 , Step 3 uses a fiber taper preparation device to prepare a fiber taper 200 with a taper region 200a from the fluorotellurite optical fiber; wherein, the fiber taper preparation device includes a fiber clamping platform 1, a stepping motor 2, an electrode 3, and a three-dimensional adjustment platform 4. The fiber clamping platform 1 is used to clamp the first end of the fluorotellurite optical fiber; the output end of the stepping motor 2 is used to connect with the second end of the fluorotellurite optical fiber; the electrode 3 is used to heat the fluorotellurite optical fiber; the three-dimensional adjustment platform 4 is used to place the U-shaped aluminum block;

[0056] Step 4. Place the fluorotellurite glass microsphere 100 at the taper region 200a of the fiber taper 200, and under the 976 nm laser pump, through the fiber taper coupling method, excite the erbium ions in the fluorotellurite glass microsphere 100 to achieve laser emission at 2.7 μm. Specifically, Step 4 includes the following steps 41 - 43:

[0057] Step 41: Screen the fluorotellurite glass microspheres 100. Use the truncated optical fiber 300 to pick out the spherical and smooth-surfaced fluorotellurite glass microspheres 100. One end of the truncated optical fiber 300 is fixed to the inner wall of the long glass capillary with ultraviolet glue, and the long glass capillary is fixed on a high-precision three-dimensional moving adjustment bracket.

[0058] Step 42: Place the selected fluorotellurite glass microspheres 100 at the taper region 200a of the fiber taper 200 prepared in Step 3. That is, under the microscope observation, adjust the three-dimensional platform to couple the fluorotellurite glass microspheres 100 with the taper region 200a of the fiber taper 200.

[0059] Step 43: Select a 976 nm laser diode pump light source, and direct the pump light emitted by the pump light source into the fiber taper 200. Then, perform non-contact optical coupling on the fluorotellurite glass microspheres 100 through the evanescent wave field of the fiber taper 200 to achieve laser emission at 2.7 μm. See Figure 3 , Step 4 uses a microsphere laser device to achieve laser output at 2.7 μm. The microsphere laser device includes a pump light source 5, a spectrometer 6, and a microscope 7. The pump light source 5 is used to connect to one end of the fiber taper 200; among them, the pump light source selects a 976 nm laser diode; the spectrometer 6 is used to connect to the other end of the fiber taper 200; the microscope 7 is used to observe the positions of the fluorotellurite glass microspheres 100 and the fiber taper 200.

[0060] It should be noted that the preparation method of the erbium ion-doped mid-infrared microsphere laser in this embodiment is described as follows:

[0061] 1. By making the fluorotellurite glass microspheres and the fluorotellurite fiber taper have the same matrix, the coupling problem caused by the matrix mismatch between the glass microspheres and the fiber taper is avoided, thereby significantly improving the coupling efficiency; while in the prior art, the glass microspheres and the fiber taper use different matrices, resulting in low coupling efficiency.

[0062] 2. The present invention improves the laser threshold and Q value of the mid-infrared microsphere laser by optimizing the fiber taper design and microsphere coupling technology.

[0063] 3. Using low-hydroxyl fluorotellurite glass can reduce optical loss and improve laser efficiency; when the hydroxyl content in the fluorotellurite glass is high, the hydroxyl may chemically react with other ions in the optical medium, resulting in an increase in optical loss; especially at 2.7 μm, the hydroxyl will cause strong absorption, leading to an increase in the optical loss of the glass; selecting low-hydroxyl fluorotellurite glass helps to reduce this additional absorption caused by the hydroxyl, thereby improving the efficiency of the laser.

[0064] 4. The optical fiber taper is prepared by the arc discharge assisted local heating and stretching method, which can reduce the surface defects of the optical fiber taper. These defects often lead to optical scattering loss, thereby increasing the laser threshold and reducing the Q value.

[0065] The preparation of optical fiber by the arc discharge assisted local heating and stretching method has the following advantages compared with the traditional U-shaped ceramic heater and oxyhydrogen flame heating - stepping motor preparation:

[0066] Local precise heating: The arc discharge can concentrate the heat at a specific position of the optical fiber, avoiding over-wide or over-heated heating areas. Compared with the traditional U-shaped ceramic heating method, the U-shaped ceramic heater has a larger heating surface and lacks precise control of specific areas, which easily leads to local overheating or uneven heating, thereby having an adverse impact on the quality and shape of the optical fiber taper. Although the oxyhydrogen flame heating can also provide high temperature, the flame stability is poor, which has an adverse impact on the heating effect.

[0067] Temperature control stability: The arc discharge can provide a stable high temperature, and during the heating process, the temperature distribution is relatively uniform, avoiding uneven stretching of the optical fiber caused by temperature fluctuations. In contrast, the temperature control of the U-shaped ceramic heater depends on the response speed and heat conduction effect of the heater itself, resulting in temperature control delay or instability in some cases; the oxyhydrogen flame heating - stepping motor method depends on the temperature of the combustion flame, and this flame temperature is easily affected by external factors (such as hydrogen and oxygen supply, combustion intensity), resulting in unstable temperature control.

[0068] Operation simplicity: The arc discharge device is easy to regulate and operate relatively simply. In contrast, the U-shaped ceramic heater requires fine adjustment of the distance and temperature control of the heater, with complex operation and more monitoring required; the oxyhydrogen flame heating - stepping motor method requires continuous monitoring of the flame stability and combustion state, which increases the complexity and difficulty of operation.

[0069] 5. The 2.7 μm laser obtained by the laser in the present invention can be applied to many fields such as integrated photonics, low-threshold lasers, high-sensitivity biosensing, cavity optomechanics, etc. Its application will greatly promote the innovation and development of micro-nano photonics devices and further expand the application range of mid-infrared lasers.

[0070] In summary, it can be known that by using the preparation method of the erbium ion-doped mid-infrared microsphere laser in this embodiment, the output of 2.7 μm laser can be achieved, and the coupling efficiency is high; the prepared erbium ion-doped mid-infrared glass microsphere laser can not only overcome the limitations of traditional lasers, but also open up new research directions and application prospects for fields such as integrated optics, environmental monitoring, and biomedical detection.

Claims

1. A method for preparing an erbium ion-doped mid-infrared microsphere laser, characterized in that: The following steps are involved: Step 1, preparing low-hydroxyl fluorotellurite glass doped with erbium ions, wherein the absorption coefficient of hydroxyl is as low as 0.009 cm-1; Step 2, preparing low-hydroxyl fluorotellurite glass into powder, and then melting and cooling the powder in sequence to prepare fluorotellurite glass microspheres doped with erbium ions (100); Step 3: using an arc discharge assisted local heating stretching method to prepare the fluorotellurite optical fiber into an optical fiber cone (200) having a cone region (200a); Step 4: Place the fluorotellurite glass microsphere (100) at the cone region (200a) of the optical fiber cone (200), and excite the erbium ions in the fluorotellurite glass microsphere (100) by the optical fiber cone coupling method under 976nm laser pumping to achieve 2.7μm laser emission.

2. The method for preparing an erbium ion-doped mid-infrared microsphere laser according to claim 1, characterized in that: Specifically, the step 1 is to melt the rare earth erbium raw material and the fluorotellurate glass raw material together in a dry atmosphere or under the protection of argon gas, and then cool the mixture to prepare the low-hydroxyl fluorotellurate glass doped with erbium ions.

3. The method for preparing an erbium ion-doped mid-infrared microsphere laser according to claim 1, characterized in that: The step 3 comprises the following steps in sequence: Step 31, taking the fluorotellurite optical fiber, removing the coating layer from the middle portion thereof, and wiping the middle portion where the coating layer is removed; Step 32, fixing the first end of the fluorotellurite optical fiber on the optical fiber clamping platform (1), and fixing the second end of the fluorotellurite optical fiber on the stepping motor (2); Step 33, placing the electrode (3) of the arc discharge device close to the middle part of the fluorotellurite optical fiber and generating local arc heating; during the arc heating process, using the stepper motor (2) to stretch the second end of the fluorotellurite optical fiber so that the middle part of the fluorotellurite optical fiber gradually becomes thinner to form an optical fiber cone (200) having the cone region (200a); Step 34, placing the U-shaped aluminum block with the opening facing upward on the three-dimensional adjustment platform (4), adjusting the three-dimensional adjustment platform (4) until the optical fiber cone (200) contacts the upper end of the U-shaped aluminum block, and fixing the optical fiber cone (200) to the upper end of the U-shaped aluminum block with molten salicylic acid.

4. The method for preparing an erbium ion-doped mid-infrared microsphere laser according to claim 1, characterized in that: The step 4 comprises the following steps: Step 41, screening the fluorotellurite glass microspheres (100), and selecting the fluorotellurite glass microspheres (100) with spherical shape and smooth surface by cutting the optical fiber (300); Step 42, placing the selected fluorotellurite glass microspheres (100) at the taper region (200a) of the optical fiber taper (200) obtained in step 3; Step 43, a pump light source of a 976 nm laser diode is selected, and the pump light emitted by the pump light source is guided into the optical fiber cone (200), and then the fluorotellurite glass microsphere (100) is non-contact optically coupled through the evanescent wave field of the optical fiber cone (200), so as to realize 2.7 μm laser emission.

5. The method for preparing an erbium ion-doped mid-infrared microsphere laser according to claim 3, characterized in that: In step 3, a fiber taper preparation device is used to prepare the fluorotellurite optical fiber into a fiber taper (200) having a taper region (200a); wherein the fiber taper preparation device comprises: An optical fiber clamping platform (1) for clamping a first end of a fluorotellurite optical fiber; A stepper motor (2), the output end of which is used to be connected to the second end of the fluorotellurite optical fiber; An electrode (3) for heating the fluorotellurite optical fiber; The three-dimensional adjustment platform (4) is used to place the U-shaped aluminum block.

6. The method for preparing an erbium ion-doped mid-infrared microsphere laser according to claim 4, characterized in that: The step 4 uses a microsphere laser device to achieve 2.7 μm laser output; the microsphere laser device comprises: A pump light source (5) is used to be connected to one end of the optical fiber cone (200); wherein the pump light source (5) is a 976 nm laser diode; A spectrometer (6) connected to the other end of the optical fiber taper (200); A microscope (7) is used to observe the positions of the fluorotellurite glass microsphere (100) and the optical fiber taper (200).

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