Wavelength-adjustable Tamm laser based on two-dimensional perovskite material and preparation method thereof

Abstract

The invention discloses a wavelength-adjustable Tamm laser based on a two-dimensional perovskite material and a preparation method thereof, the laser sequentially comprises a substrate, a DBR reflecting layer formed by alternating titanium dioxide and silicon dioxide, a two-dimensional perovskite absorbing layer and a silver reflecting layer from bottom to top, the bottom silicon dioxide layer is in contact with the substrate, and the bottom silicon dioxide layer is in contact with the silver reflecting layer. The top titanium dioxide layer is in contact with the two-dimensional perovskite absorption layer, and the thickness of the top titanium dioxide layer is smaller than that of the other titanium dioxide layers; the silver reflecting layer and the DBR reflecting layer form a Tamm state, and the high exciton binding energy of the two-dimensional perovskite material and the optical Tamm state form a strong coupling effect. The DBR structure introduced by the laser has high reflectivity for a target optical wave band, light is limited in the perovskite layer, and the Tamm state promotes the enhancement of the optical field intensity near the perovskite layer, so that the lasing and reduction of the thickness of top titanium dioxide are realized, the phase round-trip condition is met, and the maximization of the enhancement of an electric field in the perovskite layer is realized; and a low laser threshold is realized.

Description

Technical Field

[0001] This invention relates to a laser, its fabrication method and application, and particularly to a wavelength-tunable Tamm laser based on two-dimensional perovskite material, its fabrication method and application. Background Technology

[0002] Traditional semiconductor lasers rely on the fundamental physical process of population inversion, which requires the injection of a large amount of energy from the outside to increase the number of excited-state particles in the gain medium to exceed that of the ground state, thereby generating laser light through stimulated emission. This process itself determines its high energy threshold, and achieving effective optical feedback and mode control usually requires the growth of high-quality epitaxial layers. This results in complex and costly laser fabrication processes, making it difficult to integrate with mainstream photonic platforms such as silicon-based lasers at low cost. Furthermore, the emission wavelength of traditional lasers is strictly locked by the inherent band structure of the gain medium. To achieve laser emission in different bands, it is necessary to develop novel group III-V or multi-quantum-well material systems with lattice matching and band structure adaptation for each specific wavelength. This not only means high and complex epitaxial growth and process development costs, but also means that a single device can usually only output a fixed narrowband wavelength. If a multi-wavelength laser system is to be built, multiple independent lasers must be physically integrated in a bulky manner, resulting in a sharp increase in system complexity, power consumption, and size. Summary of the Invention

[0003] Objectives of the Invention: The first objective of this invention is to provide a wavelength-tunable Tamm laser based on two-dimensional perovskite material with low threshold and tunable wavelength emission; the second objective of this invention is to provide a method for fabricating the wavelength-tunable Tamm laser based on two-dimensional perovskite material.

[0004] Technical Solution: The wavelength-tunable Tamm laser based on two-dimensional perovskite material described in this invention comprises, from bottom to top, a substrate, a DBR reflective layer composed of alternating titanium dioxide and silicon dioxide, a two-dimensional perovskite absorber layer, and a silver reflective layer. The bottom silicon dioxide layer is in contact with the substrate, and the top titanium dioxide layer is in contact with the two-dimensional perovskite absorber layer. The thickness of the top titanium dioxide layer is lower than that of the other titanium dioxide layers. The silver reflective layer and the DBR reflective layer form Tamm states. The high exciton binding energy of the two-dimensional perovskite material forms a strong coupling effect with the optical Tamm states. The exciton-polaritons formed under this effect generate laser light after condensation.

[0005] The exciton-polaritons formed by the strong coupling effect between the high exciton binding energy of two-dimensional perovskite materials and optical Tamm states can generate lasers immediately after condensation, which is a lower threshold compared to perovskite materials that require population inversion to generate lasers. Since the (PBA)₂PbI₄ layer added between the metal layer and the DBR cavity alters the original Tamm plasma localization effect, the thickness of the titanium dioxide layer in contact with the (PBA)₂PbI₄ layer is adjusted. This ensures both the quality factor of the lasing peak and the Tamm resonance excitation condition with the Ag reflector layer, while simultaneously forming two-dimensional perovskite excitons. Exciton-photon coupling forms exciton-polaritons, thus achieving a low-threshold laser.

[0006] Preferably, the two-dimensional perovskite material is (PBA)₂PbI₄. The band gap of the perovskite material can be precisely controlled by adjusting the chemical composition and layer thickness, resulting in tunable light absorption characteristics. Two-dimensional perovskite materials with higher band gaps, such as (PEA)₂PbI₄ and (PEA)₂PbBr₄, can also be selected, but at the same perovskite thickness, this will cause a blue shift in the device's lasing peak.

[0007] Preferably, the thickness of the two-dimensional perovskite material is 12-30 nm, and the emission wavelength of the laser is 515-540 nm. In the Tamm structure, increasing the thickness of the perovskite material leads to a higher exciton content in the coupling system. A higher exciton content facilitates effective energy relaxation through interparticle scattering, thereby achieving low-threshold lasers at lower pump power. However, excessively strong exciton interactions can also lead to phase space filling and exciton ionization, thus disrupting strong coupling at higher densities. This is why the perovskite layer thickness cannot exceed 30 nm. Conversely, thinning the perovskite material results in a higher cavity mode photon composition in the coupling system. A higher photon composition means tighter coupling between polaritons and the cavity photon field, resulting in a longer coherence time, as photons escape more easily from the cavity. This is beneficial for achieving long-range coherence and narrower linewidth. However, due to the reduced exciton content, particles encounter a relaxation bottleneck when relaxing to the ground state, thus increasing the lasing threshold. Therefore, the perovskite layer thickness cannot be less than 12 nm. The bandgap of perovskite materials can be precisely controlled by adjusting the chemical composition and layer thickness, resulting in adjustable light absorption characteristics. The emission wavelength of lasing during strong coupling can be affected by adjusting various influencing factors of perovskite.

[0008] Preferably, the DBR reflective layer in the laser has eight alternating groups of titanium dioxide and silicon dioxide, wherein the thickness of the titanium dioxide in direct contact with the silver layer is 10-15 nm, the thickness of the remaining titanium dioxide is 50-55 nm, the thickness of the silicon dioxide is 80-90 nm, and the thickness of the silver layer is 30-40 nm. The thickness of titanium dioxide and silicon dioxide is determined by the exciton peak of the perovskite in the device structure. Taking (PBA)₂PbI₄ perovskite as an example, its exciton peak is at 515 nm. According to the Bragg diffraction principle, the thickness of each layer of the DBR should be one-quarter of the exciton peak wavelength divided by the refractive index of that layer. Therefore, the titanium dioxide layer thickness is calculated to be 80-90 nm, and the silicon dioxide layer thickness is calculated to be 50-55 nm. A slight deviation does not affect the high reflectivity of the DBR. The titanium dioxide layer in direct contact with the silver layer is relatively thin to act as a high-reflectivity layer together with the perovskite layer and to compensate for the phase detuning caused by the addition of the active layer in the Tamm structure. Therefore, the thickness of the titanium dioxide layer in direct contact with the silver layer is chosen to be 10-15 nm. The silver layer, together with the DBR structure, acts as a Fabry-Perot cavity and forms the Tamm structure to confine light. This requires that the silver layer cannot be too thin, otherwise it will not be able to confine light. If it is too thick, it will lead to excessive metal loss in the structure, thus affecting the laser threshold. 30-40 nm is the optimal thickness.

[0009] The method for fabricating a wavelength-tunable Tamm laser based on two-dimensional perovskite material according to the present invention includes the following steps:

[0010] (1) Deposit alternating SiO2 and TiO2 layers on the substrate;

[0011] (2) A two-dimensional perovskite precursor solution is spin-coated onto the top TiO2 layer, and then annealed to form a perovskite absorber layer;

[0012] (3) An Ag layer is deposited on the surface of the perovskite absorption layer to form the wavelength-tunable Tamm laser based on the two-dimensional perovskite material.

[0013] Preferably, in step (1), the alternating SiO2 and TiO2 layers are deposited using an electron beam evaporation system with an initial evaporation power of 1~2 kW, an evaporation rate of 0.1~0.5 nm / s, and a film thickness monitoring system sampling interval of 0.1~0.5s.

[0014] Preferably, in step (2), the two-dimensional perovskite is (PBA)2PbI4, and the concentration of its precursor solution is 0.1~0.3mol / L.

[0015] Preferably, the annealing temperature of the two-dimensional perovskite is 60~70℃ and the annealing time is 5~10 min.

[0016] Preferably, in step (3), the evaporated Ag layer is deposited using a high-vacuum thermal evaporation coating system.

[0017] Invention Mechanism:

[0018] Two-dimensional perovskite materials (PBA)₂PbI₄ possess high exciton binding energies, meaning a strong attraction between electrons and holes, with excitons remaining stable, especially at room temperature. This results in significant strong coupling effects in light-matter interactions. The exciton-polaron coupling generated by this strong coupling enables coherent radiation with ultra-low threshold and ultrafast response without population inversion, combining the advantages of both photons and excitons. Furthermore, it operates at room temperature and has wide applications in laser devices. The band gap of perovskite materials can be precisely controlled by adjusting the chemical composition and layer thickness, leading to tunable light absorption characteristics. This has a significant impact on designing laser emission bands and optimizing optoelectronic device performance.

[0019] The laser of this invention is based on perovskite material and a DBR reflective layer. The DBR consists of alternating layers of titanium dioxide (TiO2) and silicon dioxide (SiO2), providing high reflectivity and enhancing the optical field intensity within the perovskite absorption layer. A metal layer is used to induce optical Tamm states between the perovskite layer and the DBR. The two-dimensional perovskite material (PBA)₂PbI₄, with its high exciton binding energy, couples with the Tamm states to generate exciton-polariton states. This strong coupling allows the formed exciton-polaritons to achieve laser emission without population inversion, unlike excitons. This strong coupling effectively reduces the laser threshold. Simultaneously, the high stability, low energy consumption, and tunable bandgap of the two-dimensional perovskite material ensure the stability and wavelength tunability of the laser during long-term use.

[0020] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) The laser of the present invention is based on the formation of Tamm state by perovskite material and DBR reflective layer. The high exciton binding energy of two-dimensional perovskite material forms a strong coupling effect with optical Tamm state. The exciton-polaritons formed generate laser after condensation, which has the characteristics of low threshold and tunable band emission; (2) Compared with vertical cavity surface-emitting laser, the laser of the present invention only requires a single-sided DBR with a metal layer. The structure is simple. It can be precisely tuned by adjusting the metal thickness or DBR period. Moreover, the strong light field is localized at the metal interface, and the coupling is stronger; (3) Compared with traditional surface plasmon laser, the Tamm mode of the laser of the present invention exists at the metal-DBR interface. The light field is mainly distributed in the medium rather than in the metal, which reduces metal loss. It can also achieve visible light or even near-infrared band lasing by adjusting the DBR design and metal type; (4) The Tamm laser preparation method proposed in the present invention has the advantages of simple process, low cost and readily available commercial products as raw materials, which is conducive to industrial production. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the wavelength-tunable Tamm laser based on two-dimensional perovskite material in this invention.

[0022] Figure 2 The reflectance spectra of the Tamm structure composed of silver and DBR without the perovskite layer and the single DBR structure;

[0023] Figure 3 Absorption spectrum and normalized photoluminescence peak diagram of a single two-dimensional perovskite (PBA)2PbI4;

[0024] Figure 4 (a) is the absorption spectrum of the laser prepared in Example 1; 4(b) is the electric field diagram corresponding to each absorption peak;

[0025] Figure 5 (a) is the absorption spectrum of a wavelength-tunable Tamm laser based on two-dimensional perovskite material as the thickness of the perovskite layer varies; 5(b) is the calculated composition ratio of excitons and Tamm plasmons. Detailed Implementation

[0026] The technical solution of the present invention will be further described below with reference to the embodiments.

[0027] Example 1

[0028] like Figure 1 As shown, the wavelength-tunable Tamm laser based on two-dimensional perovskite material of the present invention comprises, from bottom to top, a quartz glass substrate, a DBR reflective layer composed of eight alternating layers of titanium dioxide and silicon dioxide, a two-dimensional perovskite absorber layer, and a silver reflective layer. The bottom silicon dioxide layer is in contact with the substrate, and the top titanium dioxide layer is in contact with the two-dimensional perovskite absorber layer. In the DBR reflective layer, the top TiO2 layer is 12 nm thick, the remaining TiO2 layers are 52 nm thick, and the SiO2 layer is 88 nm thick. The two-dimensional perovskite absorber layer is made of (PBA)₂PbI₄ and has a thickness of 18 nm. The silver reflective layer has a thickness of 40 nm.

[0029] The preparation method includes the following steps:

[0030] Step 1: Quartz glass substrate treatment: In an ultrasonic cleaner, the substrate is cleaned sequentially with cleaning agent, deionized water, acetone and isopropanol for 20 minutes. Then it is dried in a 100°C drying oven. Finally, the dried quartz glass substrate surface is irradiated with UV light for 15 minutes. The purpose of this step is to increase the wettability of the quartz glass substrate surface and remove organic and inorganic impurities.

[0031] Step 2: Place the cleaned and dried substrate evenly on the workpiece holder, ensuring a tight contact between the substrate and the holder without any movement. Install the crucible containing the evaporation material onto the crucible holder of the electron beam evaporation source, adjusting the crucible position so that the electron beam focus accurately falls on the surface of the evaporation material. Close the vacuum chamber door, ensuring the door seal is intact and undamaged or deformed, and then start the vacuum system. First, turn on the mechanical pump and open the fore-stage valve to perform a rough evacuation of the vacuum chamber. When the vacuum level drops to 1×10⁻⁶... -2 When the pressure is below 1 Pa, close the fore-stage valve, stop the mechanical pump, then start the molecular pump and open the molecular pump inlet valve to perform deep evacuation. During the evacuation process, monitor the vacuum level changes in real time via the touchscreen. When the vacuum level reaches 1 × 10⁻⁶ Pa, [the system will continue evacuating]. -4 When the Pa is below the specified value, the coating conditions are met, and the next step can be performed.

[0032] Step 3: Access the coating parameter setting interface on the touchscreen. Set the relevant parameters according to the type of optical film to be prepared. When preparing a silicon dioxide film, set the initial evaporation power to 2 kW, the evaporation rate to 0.5 nm / s, and the target film thickness to 88 nm. When preparing a titanium dioxide silicon film, set the initial evaporation power to 2 kW, the evaporation rate to 0.5 nm / s, the thickness of the top TiO2 layer to 12 nm, and the thickness of other layers to 52 nm. Simultaneously, set the sampling interval of the film thickness monitoring system to 0.1 s to ensure real-time monitoring of film thickness growth. After setting the parameters, start the electron gun and gradually increase the electron gun power to preheat the evaporation material. During preheating, control the power increase rate at 0.2 kW / min to avoid splashing of the evaporation material due to a sudden increase in power. At the same time, observe the surface state of the evaporation material. When the material surface begins to slightly melt, stop increasing the power and maintain the current power for preheating for 5-10 minutes to ensure uniform material temperature.

[0033] Step 4: After preheating, gradually increase the electron gun power to bring the evaporation rate to the set value (0.5 nm / s) and begin the formal coating process. During the coating process, monitor the film thickness growth curve, evaporation rate change curve, and electron gun power change curve in real time via the touch screen. If any parameters deviate from the set values, the equipment control system will automatically adjust the electron gun power to ensure that the evaporation rate and film thickness growth meet the requirements. At the same time, observe the surface condition of the substrate. If abnormal film color or uneven surface occurs, the coating process must be stopped immediately to analyze the cause and resolve the issue.

[0034] Step 5: Based on the required film structure, repeat the above TiO2 and SiO2 deposition steps, alternately depositing 8 groups of TiO2 and SiO2 to form a multilayer periodic structure.

[0035] Step 6: When the film thickness monitoring system shows that the film thickness has reached the target value, the equipment will automatically reduce the electron gun power and gradually stop evaporation; at this time, maintain the vacuum state of the vacuum chamber and allow the film to cool in the vacuum environment for 10-15 minutes to avoid stress cracking of the film due to sudden temperature drop.

[0036] Step 7: Place the substrate in the center of the spin coater stage, drop the (PBA)₂PbI₄ precursor solution at the center, and spin coat the (PEA)₂PbI₄ precursor solution at a high speed of 6000 rpm for 90 s to spread it evenly. During the high-speed spin coating process, anneal the substrate on a 70°C heating stage for 5 min to form a perovskite layer with a thickness of 18 nm.

[0037] The (PBA)2PbI4 precursor solution was prepared according to the following steps:

[0038] S7-1: Weigh PbI2 powder (46.1 mg) and PBAI powder (55.43 mg) in a 1:2 molar ratio using an electronic balance, slowly pour them into a glass bottle, add 1 mL of DMF organic solvent, and heat and stir on a heating platform at 70°C under a nitrogen atmosphere for 12 h until completely dissolved.

[0039] S7-2: The completely dissolved solution was filtered with 0.22 μm PTFE to obtain the (PBA)2PbI4 precursor solution.

[0040] Step 8: On the (PBA)2PbI4 perovskite layer, a 40 nm thick Ag layer is deposited by thermal evaporation to finally obtain a wavelength-tunable Tamm laser based on two-dimensional perovskite material.

[0041] Example 2

[0042] Based on Example 1, by changing the thickness of the perovskite layer to 12~30 nm, we can obtain the device coupling results corresponding to perovskite films of different thicknesses. From this, we can infer the influence of perovskite thickness on the lasing emission band.

[0043] like Figure 2As shown, the reflection spectra of the Tamm structure composed of silver and DBR (which differs from the laser in Example 1 in that it lacks a perovskite layer, but otherwise remains the same) and the reflection spectrum of a single DBR structure were calculated separately without the perovskite layer. The reflection spectra show that the bandgap of the designed DBR structure is 430-630 nm (the range with higher reflectivity of the curve), while the Tamm structure is simply a DBR structure with an added silver layer. However, a reflection peak appears at 505 nm in the reflection spectrum, indicating that the Tamm structure absorbs light at this point and can confine photons in the 505 nm band inside the device. This lays the foundation for using the photon energy in this band to generate strong coupling with perovskite excitons.

[0044] Figure 3 The absorption spectrum and normalized photoluminescence peak of a single-layer two-dimensional perovskite (PBA)₂PbI₄ are shown. The perovskite is composed of (PBA)₂PbI₄ directly spin-coated on a quartz glass substrate. Its absorption spectrum (505 nm) and photoluminescence peak (515 nm) are both in the high reflectivity range (430-630 nm) of the DBR. This indicates that the photons that generate excitons in the perovskite (corresponding to the absorption peak at 505 nm) do not pass through the DBR, but are reflected back to the perovskite layer to continue promoting exciton generation. This improves photon utilization, which is a prerequisite for realizing low threshold laser. The photoluminescence peak at 515 nm is within the DBR, which proves that the Tamm structure of this invention can provide a Fabry-Perot cavity to form an optical resonant cavity, thereby realizing a large amount of exciton-polaritons condensation and thus generating laser light.

[0045] like Figure 4 As shown in (a), the absorption spectrum of the laser after combining the Tamm structure prepared in Example 2 with two-dimensional perovskite (PBA)2PbI4 is shown. Two obvious absorption peaks appear in the visible light band, namely A1 (489nm) and A2 (517nm). The positions of these two absorption peaks are completely different from the absorption peak of 505nm of the single perovskite thin film and the absorption peak of 505nm of the single Tamm device. This proves that the structure has been coupled, causing the two originally identical energy levels to split and generate two different energy levels. Figure 4 (b) shows the electric field distribution corresponding to the absorption peak wavelengths A1 (489 nm) and A2 (517 nm). It can be seen that the electric field corresponding to the two absorption peaks of the device is enhanced near the perovskite layer. This indicates that photons are indeed confined within the perovskite layer. The introduction of the Tamm structure has an effect. The confined photons and perovskite excitons together form new particles exciton-polaritons. With the condensation of new particles and the optical resonance of the Tamm structure, the device generates laser emission.

[0046] Figure 5 (a) and Figure 5(b) shows the absorption spectrum and exciton and Tamm plasmon composition ratios of the Tamm laser at perovskite layer thicknesses of 12–30 nm, respectively. Figure 5 (a) and Figure 5 (b) It can be seen that when the thickness of the perovskite layer changes in the range of 12~30nm, the structure always has two absorption peaks that are different from the absorption peak of the single perovskite film (505nm) and the absorption peak of the single Tamm device (505nm). This indicates that the cavity structure is always coupled, but the position of the double absorption peaks will change with the change of the thickness of the perovskite layer. This leads to the fact that the positions of exciton generation and exciton-exciton polaritrile condensation are necessarily different. Specifically, since the low energy level after the coupling of exciton-exciton polaritrile condensation occurs, the laser emission band will gradually redshift as the thickness of the perovskite layer increases. Therefore, the laser emission band based on this design is from the perovskite photoluminescence peak at 515nm to the coupling critical 540nm, which can be achieved by adjusting the thickness of the perovskite layer.

Claims

1. A wavelength-tunable Tamm laser based on two-dimensional perovskite material, characterized in that, From bottom to top, the structure includes a substrate, a DBR reflective layer composed of alternating layers of titanium dioxide and silicon dioxide, a two-dimensional perovskite absorber layer, and a silver reflective layer. The bottom silicon dioxide layer is in contact with the substrate, and the top titanium dioxide layer is in contact with the two-dimensional perovskite absorber layer. The thickness of the top titanium dioxide layer is less than that of the other titanium dioxide layers. The silver reflective layer and the DBR reflective layer form a Tamm state. The high exciton binding energy of the two-dimensional perovskite material forms a strong coupling effect with the optical Tamm state. The exciton-polaritons formed under this effect generate laser light after condensation.

2. The wavelength-tunable Tamm laser based on two-dimensional perovskite material according to claim 1, characterized in that, The two-dimensional perovskite material is (PBA)2PbI4.

3. The wavelength-tunable Tamm laser based on two-dimensional perovskite material according to claim 2, characterized in that, The thickness of the two-dimensional perovskite material is 12~30 nm, and the emission wavelength of the laser is 515~540 nm.

4. The wavelength-tunable Tamm laser based on two-dimensional perovskite material according to claim 3, characterized in that, The laser's DBR reflective layer contains eight alternating layers of titanium dioxide and silicon dioxide. The titanium dioxide layer in direct contact with the silver layer has a thickness of 10-15 nm, while the remaining titanium dioxide layers have a thickness of 50-55 nm. The silicon dioxide layer has a thickness of 80-90 nm, and the silver layer has a thickness of 30-40 nm.

5. The wavelength-tunable Tamm laser based on two-dimensional perovskite material according to claim 1, characterized in that, The substrate is quartz glass.

6. A method for fabricating a wavelength-tunable Tamm laser based on two-dimensional perovskite material as described in any one of claims 1 to 5, characterized in that, Includes the following steps: (1) Deposit alternating SiO2 and TiO2 layers on the substrate; (2) A two-dimensional perovskite precursor solution is spin-coated onto the top TiO2 layer, and then annealed to form a perovskite absorber layer; (3) An Ag layer is deposited on the surface of the perovskite absorption layer to form the wavelength-tunable Tamm laser based on the two-dimensional perovskite material.

7. The method for fabricating a wavelength-tunable Tamm laser based on two-dimensional perovskite material according to claim 5, characterized in that, In step (2), the two-dimensional perovskite is (PBA)2PbI4, and the precursor solution concentration is 0.1~0.3 mol / L.

8. The method for fabricating a wavelength-tunable Tamm laser based on two-dimensional perovskite material according to claim 7, characterized in that, The annealing temperature of the two-dimensional perovskite is 60~70℃, and the time is 5~10 min.

9. The method for fabricating a wavelength-tunable Tamm laser based on two-dimensional perovskite material according to claim 6, characterized in that, In step (1), the alternating SiO2 and TiO2 layers are deposited using an electron beam evaporation system with an initial evaporation power of 1~2 kW, an evaporation rate of 0.1~0.5 nm / s, and a film thickness monitoring system sampling interval of 0.1~0.5s.

10. The method for fabricating a wavelength-tunable Tamm laser based on two-dimensional perovskite material according to claim 6, characterized in that, In step (3), the vapor-deposited Ag layer is deposited using a high-vacuum thermal evaporation coating system.

Images