A surface plasmon laser emitter based on metal nanowire array and a preparation method thereof

Abstract

The application discloses a kind of based on metal nanowire array surface plasmon laser emitter, including metal nanowire array-gain medium composite layer;In the metal nanowire array-gain medium composite layer, metal nanowire array is vertically distributed in gain medium composite layer, the diameter of metal nanowire is not less than 2nm, height is same with the thickness of the metal nanowire array-gain medium composite layer, the spacing of adjacent metal nanowire is 1~15nm, and the volume percentage of metal nanowire in the metal nanowire array-gain medium composite layer is 20%~60%.The preparation method of the disclosed laser emitter is simple in operation, and is convenient for practical preparation and application.The excitation power density threshold of the laser emitter prepared is only 20W / cm 2 .

Description

TECHNICAL FIELD

[0001] The application belongs to the field of nanomaterials, and particularly relates to a surface plasmon laser emitter based on a metal nanowire array and a preparation method thereof. BACKGROUND

[0002] At present, the miniaturization of a laser by using surface plasmons is very effective. Through the resonance effect of metal nanoparticles, the light beam can be bound to a volume much smaller than the wavelength of light, thereby realizing the function of a nanometer optical cavity. The surface plasmon laser (Spasers) material can not only become the core device of a high-power nanolaser, but also can expand the plasmon in the fields of optoelectronic circuits, quantum information communication, biological medical probes, and ultra-micro-nano chips, which are important applications of the plasmon laser in the field of functional material science.

[0003] In addition to the traditional semiconductor-insulator-metal waveguide structure, the plasmonic nanocavity integrated with the gain medium is also of great significance. It can produce subwavelength scale coherent light beyond the diffraction limit, thereby breaking the limitation of the semiconductor mode volume and promoting the development of the ultimate miniaturized nanodevice of the laser.

[0004] Teri W. Odom et al. once reported an ultralow-threshold, continuous-wave upconverting lasing from subwavelength plasmons (https: / / doi.org / 10.1038 / s41563-019-0482-5). Yb 3+ / Er 3+ upconversion particles were coated on a silver nanocolumn array. Each silver nanocolumn can act as a local surface plasmon resonance unit, and meanwhile, the collective coherent coupling between the units can be realized through the specific periodic arrangement, thereby producing narrow lattice plasmon resonance, effectively suppressing radiation loss, and obtaining near-field enhancement. The excitation power density threshold reaches 70 W / cm 2 , which is several orders of magnitude lower than other small lasers. However, the formation process of the nanocolumn array is very complex, and a series of nanofabrication processes such as photolithography, Si etching, metal deposition, and metal film stripping are required, which makes it difficult to mass-produce. In addition, the upconversion particles form the gain medium on the array in the form of solution dripping, which not only makes it difficult to ensure the consistency of the thickness of the medium on each array, but also makes the stability poor due to the open design.

[0005] A Chinese patent document with publication number CN111934185A discloses a random laser based on silver nanorod metamaterial and luminescent coupling. An anodic oxidation method is used to prepare an aluminum oxide hole template, and a silver nanorod array is embedded in the hole as a surface plasmon resonance cavity. A mixed solution of nile red / PMMA is then added on top as a light gain medium. This nanoscale resonance cavity has good constraint and enhancement effect on the optical field, and can obtain a lower threshold and high output power. However, this method based on an anodic aluminum oxide template has natural defects, such as the difficulty in further scaling the inter-nanopillar spacing, which not only limits the further improvement of the output power, but also is not conducive to the integration with other functional devices. In addition, the light gain medium is also grown by solution drop method, and the stability of practical application is severely challenged. SUMMARY

[0006] In view of the above, the present application aims to provide a metal nanowire array surface plasmon laser emitter and a preparation method thereof. The preparation method is simple to operate, and is convenient for actual preparation and application. The excitation energy of the prepared laser emitter is only 1 mJ, and the calculated excitation power density threshold is only 20 W / cm 2 .

[0007] To achieve the above-mentioned application purposes, the embodiments provide a metal nanowire array surface plasmon laser emitter, which comprises a metal nanowire array-gain medium composite layer.

[0008] In the metal nanowire array-gain medium composite layer, the metal nanowire array is vertically distributed in the gain medium composite layer. The diameter of the metal nanowire is not less than 2 nm, the height of the metal nanowire is the same as the thickness of the metal nanowire array-gain medium composite layer, the spacing between adjacent metal nanowires is 1-15 nm, and the volume percentage of the metal nanowire in the metal nanowire array-gain medium composite layer is 20%-60%.

[0009] The metal nanowire array surface plasmon laser emitter is incident light through the metal nanowire array-gain medium composite layer, causing collective oscillation of free electrons in the metal nanowire, exciting surface plasmon resonance, enhancing the local electric field between the nanowires, thereby enhancing the band transition energy radiation of the gain medium, and further enhancing the photon emission, resulting in surface plasmon laser.

[0010] The metal nanowire array-gain medium composite layer has strong dependence on the excitation wavelength of the gain medium material. The incident light needs to meet the laser excitation wavelength of the gain medium. After the gain medium is excited, the photon absorbs energy to jump from the ground state to the Fermi level, and then the photon jumps to the excited state, and then returns to the ground state from the excited state. In this process, surface plasmon resonance is involved. The energy band is generated through the joint action of the two composite layers to produce surface plasmon laser.

[0011] In the surface plasmon laser emitter, the metal nanowire array is orderly and densely distributed in the metal nanowire array-gain medium composite layer. The size and arrangement of the metal nanowire and the type of the gain medium will affect the response of the plasmon laser emitter to the incident light. The diameter of the metal nanowire and the spacing between adjacent nanowires affect the resonance frequency of the surface plasmon, and the resonance frequency of the plasmon needs to match the specific excitation wavelength of the gain medium to produce plasmon laser. Therefore, in order to better produce plasmon laser, the diameter of the metal nanowire in the metal nanowire array-gain medium composite layer is 2-5 nm, the spacing between the metal nanowires is 1-7 nm, the height is not less than 100 nm, and the volume percentage of the metal nanowire in the metal nanowire array-ceramic composite layer is 30%-40%. Further preferably, the diameter of the metal nanowire is between 2-3 nm, the spacing between the metal nanowires is 1-3 nm, the height is greater than 200 nm, and the volume percentage of the metal nanowire in the metal nanowire array-ceramic composite layer is 35%-40%.

[0012] Preferably, the thickness of the metal nanowire array-gain medium composite layer is 150-300 nm. Further preferably, the thickness is 200-250 nm.

[0013] Preferably, the metal nanowire material is one of gold, platinum, silver, tungsten, copper, and aluminum; the gain medium material can be selected from a variety of materials, including red powder Y2O3:Eu 3+ , green powder CeMgAl 11 O 19 : Tb 3+ or (La, Ce, Tb)PO4, blue powder BaMgAl 10 O 17 :Eu or Sr5(PO4)3Cl:Eu 2+ , Y2O3:Pr 3+ , Y2O3:Sm 3+ , Y2O3:Gd 3+ , Y2O3:Tb 3+ , Y2O3:Dy 3+ , Y2O3:Ho 3+ , Y2O3:Er 3+ , Y2O3:Tm 3+NaYF4:Yb 3+ / Er 3+ The substrate material can be selected from a variety of materials, including quartz glass, silicon wafer, sapphire, etc.

[0014] To achieve the above-mentioned purposes, the embodiment further provides a preparation method of the above-mentioned surface plasmon laser emitter based on a metal nanowire array, comprising the following steps:

[0015] (1) pretreating the substrate;

[0016] (2) selecting metal and gain medium as target materials, setting the power density range of the metal target at 1-5 W / cm 2 , the power density range of the gain medium target at 4-20 W / cm 2 , the sputtering gas pressure range at 0.1-1 Pa, the target base distance greater than 65 mm, the substrate bias power density range at 1-4 W / cm 2 , and the self-bias voltage higher than -60 V;

[0017] (3) controlling the metal target and the gain medium target to work simultaneously for more than 3 hours, magnetron sputtering depositing a metal nanowire array-gain medium composite layer to obtain the plasmon laser emitter.

[0018] During the magnetron sputtering, the metal target is driven by pulse, radio frequency or direct current power supply, and the gain medium target is driven by radio frequency power supply. Compared with common micro-nano processing methods, the magnetron sputtering has the advantages of simple operation, low cost, convenient parameter adjustment and wide selection range of sputtering target materials. Through the power control of the compound ceramic target and the metal target in the sputtering process and the selective etching effect of low-energy ion bombardment, the size and arrangement of the metal nanowire in the composite layer can be conveniently adjusted in a wide range.

[0019] Preferably, the substrate can be a metal material, an inorganic non-metal material or a flexible material, wherein the metal material includes aluminum, copper, zinc alloy, stainless steel, etc., or the inorganic non-metal material includes ceramic, glass, oxide, nitride, etc., and the flexible material includes PET, PI, etc.

[0020] Preferably, in step (1), the pretreated substrate comprises: for a rigid substrate, sequentially performing ultrasonic cleaning with acetone, ethanol and deionized water, then performing heat desorption and plasma sputtering cleaning to optimize the substrate surface cleanliness; for an organic or flexible substrate, performing ultrasonic cleaning with a cleaning agent and deionized water, and performing surface activation treatment on the substrate. After the above-mentioned pretreatment, the substrate surface is more conducive to the growth of the metal thin film.

[0021] Preferably, in step (2), magnetron sputtering is performed under an argon atmosphere. By adjusting the power of the metal target and gain medium target used for sputtering, combining different substrate bias voltages for selective etching, and varying the deposition time, the microstructure characteristics of the metal nanowires in the metal nanowire array-gain medium composite layer, such as size, spacing, and volume fraction, can be significantly altered. Metal nanowire array-gain medium composite layers with different microstructure characteristics can achieve the expected modulation of the plasmon resonance peak, thus matching it with the specific excitation wavelength of the gain medium to generate plasmonic laser. Preferably, when sputtering and depositing the metal nanowire array-gain medium composite layer, the power density of the metal target is in the range of 1-3 W / cm². 2 The power density range used for ceramic targets is 4-8 W / cm². 2 The sputtering pressure range is 0.2-0.5 Pa, the target-substrate distance is higher than 80 mm, and the deposition sputtering time is 3-5 h.

[0022] Preferably, when the substrate is insulating, the substrate bias type is radio frequency (RF) bias; when the substrate is conductive, the substrate bias type is RF or pulse bias. The substrate bias power density ranges from 3 to 4 W / cm². 2 The self-bias voltage is higher than -60V. When the substrate bias power density is lower than the preferred range, selective growth of metal is difficult, and nanowire structures cannot be obtained.

[0023] Compared with the prior art, the beneficial effects of the present invention include at least the following:

[0024] (1) Compared with common laser devices, the magnetron sputtering method used in this invention is simple to prepare, has mature technology, can form a film in one step, has controllable size, high film quality, high integration, and is suitable for large-area preparation.

[0025] (2) The range of metals and gain medium materials in this invention is wide. Different combinations of metals and gain medium materials can obtain laser devices with different wavelengths of light. Therefore, different metals or ceramic materials can be selected to construct laser devices according to the needs of different situations.

[0026] (3) There are no special requirements for the selection of substrate materials in this invention. Common rigid or flexible, insulating or conductive, organic or inorganic materials can all be used as substrates, which greatly expands the application range of related devices while reducing the difficulty of preparation.

[0027] (4) After testing, the excitation power density threshold of the laser emitter prepared in this invention is only 20 W / cm². 2 This indicates that the power reaches 20W / cm. 2 It can emit laser light at the same time, which is something that other laser devices cannot achieve. This reduces the energy required for excitation and saves on device usage costs. Attached Figure Description

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort based on these drawings.

[0029] Figure 1 Structure diagram of the metal nanowire array-surface plasmon laser emitter designed for the embodiment;

[0030] Figure 2 Low-magnification TEM morphology of the cross section of the plasmon laser emitter prepared for the embodiment 1;

[0031] Figure 3 High-magnification TEM morphology of the cross section of the metal nanowire array-ceramic composite layer in the plasmon laser emitter prepared for the embodiment 1;

[0032] Figure 4 Fluorescence spectrum of the plasmon laser emitter prepared for the embodiment 1;

[0033] Figure 5 Low-magnification TEM morphology of the cross section of the plasmon laser emitter prepared for the embodiment 2;

[0034] Figure 6 High-magnification TEM morphology of the cross section of the metal nanowire array-ceramic composite layer in the plasmon laser emitter prepared for the embodiment 2;

[0035] Figure 7 Fluorescence spectrum of the plasmon laser emitter prepared for the embodiment 2. DETAILED DESCRIPTION

[0036] In order to make the objects, technical solutions and advantages of the present application clearer, the following will further describe the present application in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and do not limit the protection scope of the present application.

[0037] The structure of the metal nanowire array-gain medium composite layer prepared for the embodiment is shown in Figure 1 In the metal nanowire array-gain medium composite layer, the metal nanowire array is vertically distributed in the gain medium composite layer. The following embodiments take silicon wafer and quartz wafer as the substrate, gold and silver as the metal material, and Y2O3:Eu as the gain medium material. 3+ By adjusting the relevant sputtering parameters, the size and distribution of the metal nanowire in the metal ceramic film layer are changed, and the metal nanowire array-surface plasmon laser emitter is prepared, and the fluorescence characteristics are characterized.

[0038] Example 1

[0039] The silicon wafer and quartz wafer were ultrasonically cleaned sequentially with acetone, ethanol, and deionized water for 15 minutes each to remove surface contaminants. The cleaned silicon wafer and quartz wafer were then dried with nitrogen gas and fixed onto a substrate tray. The tray was placed into the deposition chamber of the magnetron sputtering equipment, and a pre-vacuum was applied to 10 °C. -4 Below Pa; argon gas flow is introduced to maintain the deposition chamber pressure at 0.4 Pa, and the gold target and Y2O3:Eu are cleaned by radio frequency sputtering. 3+ Etching of the target material lasted 10 minutes, followed by substrate cleaning with a substrate bias voltage for 5 minutes. After etching and cleaning, the gas flow was adjusted to bring the deposition chamber pressure to 0.3 Pa, and the gold target and Y₂O₃:Eu were then activated. 3+ A baffle plate in front of the target; co-sputtering of two targets; adjustment of the silver target and Y2O3:Eu. 3+ The sputtering power of the target is 1.2 W / cm². 2 and 5W / cm 2 The substrate bias power density is 3.2 W / cm². 2 After 4 hours of deposition, the gold target and Y2O3:Eu were switched off. 3+ The target and bias drive power supply are used to finally obtain a plasmonic laser emitter.

[0040] The cross-sectional morphology of the above samples was observed and analyzed using transmission electron microscopy (TEM). Figure 2 The TEM image shows the cross-sectional morphology of the metal nanowire array-ceramic composite layer in Example 1. It can be observed that the nanowires are embedded in the matrix and exhibit a typical periodic arrangement structure. The thickness of the metal nanowire array-ceramic composite layer is 250 nm. Figure 3 A high-magnification TEM image of its cross-section shows that the average diameter of the nanowires is about 2.8 nm and the edge spacing is 1.5–2 nm.

[0041] Figure 4 The fluorescence spectrum of the plasmonic laser emitter in the embodiment shows that Y2O3:Eu 3+ Several characteristic emission peaks, the strongest of which is at 611nm.

[0042] Example 2

[0043] The silicon wafer and quartz wafer were sequentially immersed in acetone, ethanol, and deionized water, and ultrasonically cleaned for 15 minutes to remove surface contaminants. The cleaned silicon wafer and quartz wafer were then dried with nitrogen gas and fixed onto a substrate tray. The tray was placed into the deposition chamber of the magnetron sputtering equipment, and a pre-vacuum of 10⁻⁶ ppm was applied. -4 Below Pa; argon gas is introduced to maintain the deposition chamber pressure at 0.4 Pa, and the silver target and Y2O3:Eu are cleaned by radio frequency sputtering. 3+Target 10 min, and the substrate bias cleaning substrate 5 min; etching cleaning after the end, adjust the airflow to make the deposition chamber pressure to 0.3 Pa, open silver target and Y2O3:Eu 3+ The baffle in front of the target, two targets sputtering, adjust the silver target and Y2O3:Eu 3+ Sputtering power of the target is 1 W / cm 2 And 4.5 W / cm 2 , the substrate bias power density is 3.2 W / cm 2 , after 4 h of deposition, close the silver target and Y2O3:Eu 3+ Target and bias driving power, finally get the plasmonic laser emitter.

[0044] The cross-section morphology of the above film samples is observed and analyzed by TEM. Figure 5 The cross-section TEM morphology of the metal nanowire array-ceramic composite layer in Example 2 is given, and the corresponding high-magnification TEM morphology is shown in Figure 6 The average diameter of the nanowire is about 2.3 nm, and the edge spacing is 2 nm.

[0045] Figure 7 The fluorescence spectrum of the plasmonic laser emitter in the example is given, and a stronger characteristic emission peak at 611 nm can be observed.

[0046] The above specific embodiments have described the technical solutions and beneficial effects of the present application in detail. It should be understood that the above description is only the most preferred embodiment of the present application, and is not intended to limit the present application. Any modifications, supplements and equivalent replacements made within the principle range of the present application shall be included in the protection scope of the present application.

Claims

1. A surface plasmon laser emitter based on a metal nanowire array, characterized in that, The composite material includes a metal nanowire array-gain medium layer. When incident light passes through the metal nanowire array-gain medium layer, it causes collective oscillation of free electrons in the metal nanowires, which excites surface plasmon resonance, enhances the local electric field between the nanowires, thereby enhancing the band transition energy radiation of the gain medium, which in turn enhances photon emission, resulting in surface plasmon laser. In the metal nanowire array-gain medium composite layer, the size and arrangement of the metal nanowires, as well as the type of gain medium, all affect the response of the plasmonic laser emitter to the incident light. Therefore, the metal nanowire array is vertically distributed in the gain medium composite layer, the diameter of the metal nanowires is not less than 2 nm, the height is the same as the thickness of the metal nanowire array-gain medium composite layer, the spacing between adjacent metal nanowires is 1-15 nm, and the metal nanowires occupy 20%-60% of the volume of the metal nanowire array-gain medium composite layer. The gain medium material includes: red powder Y2O3:Eu 3+ Green powder CeMgAl 11 O 19 :Tb 3+ Or (La,Ce,Tb)PO4, blue powder BaMgAl 10 O 17 Eu or Sr5(PO4)3Cl:Eu 2+ Y2O3:Pr 3+ Y2O3:Sm 3+ Y2O3:Gd 3+ Y2O3:Tb 3+ Y2O3:Dy 3+ Y2O3:Ho 3+ Y2O3:Er 3+ Y2O3:Tm 3+ NaYF4-Yb 3+ / Er 3+ This allows for better generation of plasma lasers.

2. The surface plasmon laser emitter based on a metal nanowire array according to claim 1, characterized in that, In the metal nanowire array-gain dielectric composite layer, the diameter of the metal nanowires is 2-5 nm, the spacing between the metal nanowires is 1-7 nm, and the metal nanowires account for 30%-40% of the volume of the metal nanowire array-ceramic composite layer.

3. The surface plasmon laser emitter based on a metal nanowire array according to claim 1, characterized in that, In the metal nanowire array-gain dielectric composite layer, the diameter of the metal nanowires is 2-3 nm, the spacing between the metal nanowires is 1-3 nm, and the metal nanowires account for 35%-40% of the volume of the metal nanowire array-ceramic composite layer.

4. The surface plasmon laser emitter based on a metal nanowire array according to claim 1, characterized in that, The thickness of the metal nanowire array-gain medium composite layer is 150-300 nm.

5. The surface plasmon laser emitter based on a metal nanowire array according to claim 1, characterized in that, Metal nanowire materials are made from one of the following: gold, platinum, silver, tungsten, copper, or aluminum. Substrate materials include quartz glass, silicon wafers, and sapphire.

6. A method for fabricating a surface plasmon laser emitter based on a metal nanowire array according to any one of claims 1-5, characterized in that, Includes the following steps: (1) Pre-treatment of the substrate; (2) Select metal and gain medium as target materials, and set the power density range for the metal target to be 1-5 W / cm². 2 The power density range used for the gain dielectric target is 4-20 W / cm². 2 The sputtering pressure range is 0.1-1 Pa, the target-substrate distance is greater than 65 mm, and the substrate bias power density range is 1-4 W / cm². 2 The self-bias voltage is higher than -60V; (3) Control the metal target and the gain medium target to work simultaneously for more than 3 hours, and deposit the metal nanowire array-gain medium composite layer by magnetron sputtering to obtain a surface plasmon laser emitter based on the metal nanowire array.

7. The method for fabricating a surface plasmon laser emitter based on a metal nanowire array according to claim 6, characterized in that, When sputtering to deposit a metal nanowire array-gain dielectric composite layer, the power density used for the metal target ranges from 1 to 3 W / cm². 2 ; The power density range used in ceramic targets is 4-8 W / cm². 2 The sputtering pressure range is 0.2-0.5 Pa, the target-substrate distance is higher than 80 mm, and the deposition sputtering time is 3-5 h.

8. The method for fabricating a surface plasmon laser emitter based on a metal nanowire array according to claim 6, characterized in that, The substrate bias power density ranges from 3 to 4 W / cm². 2 The self-bias voltage is higher than -60V.

9. The method for fabricating a surface plasmon laser emitter based on a metal nanowire array according to claim 6, characterized in that, When the substrate is insulating, the substrate bias type is radio frequency bias; when the substrate is conductive, the substrate bias type is radio frequency or pulse bias.

10. The method for fabricating a surface plasmon laser emitter based on a metal nanowire array according to claim 6, characterized in that, In step (1), the pretreatment of the substrate includes: for rigid substrates, ultrasonic cleaning is performed successively with acetone, ethanol and deionized water, followed by heating desorption and plasma sputtering cleaning to optimize the surface cleanliness of the substrate; for organic or flexible substrates, ultrasonic cleaning is performed with cleaning agent and deionized water, and the substrate surface is activated.

Images