Low-threshold laser and preparation method thereof
By epitaxially growing a hexagonal boron nitride layer and a monolayer crystal sandwich structure on a silicon dioxide substrate, the problems of poor stability and high threshold of existing organic laser devices are solved, and continuous laser emission with low threshold and improved stability are achieved.
Patent Information
- Application Number
- CN202510867535.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-26
- Publication Date
- 2025-11-14
AI Technical Summary
Existing organic laser devices have poor stability and high lasing thresholds, making it difficult to achieve continuous laser emission at room temperature. Moreover, most of them rely on pulsed laser excitation and cannot achieve continuous laser emission with low thresholds.
A low-threshold laser is fabricated using a sandwich structure consisting of a hexagonal boron nitride layer and a monolayer crystal epitaxially grown on a silicon dioxide substrate and physical vapor deposition technology. An optical resonator is formed by the J-aggregated monolayer crystal and the hexagonal boron nitride layer. Combined with the optical field localization effect of the micro-nano resonator, continuous laser excitation is achieved.
Stable continuous laser emission was achieved at a low threshold of 1.6 nW, with a wavelength range of 580 nm to 780 nm. The emission stability was high, and the emission peak intensity decayed by only 10% after 5000 s of continuous operation. The thermal management and optical loss of the laser device were reduced.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of laser technology, and particularly relates to a low-threshold laser and its fabrication method. Background Technology
[0002] Since the first ruby laser was invented in 1960, laser technology has been a focus of attention in the field of optics, attracting scientists to explore its broad application prospects. Compared with other materials, organic materials possess abundant excited-state photophysical and photochemical processes, giving them high tunability in photoluminescence (PL) spectra. Furthermore, organic materials allow for the adjustment of growth conditions to form long-range ordered crystals, achieving narrow-band emission, thus making them more advantageous for laser design and fabrication. However, organic lasers typically face challenges such as poor device stability, high lasing threshold, and difficulty in achieving room-temperature continuous laser lasing.
[0003] To improve laser performance, researchers have focused on gain materials, striving to develop lasers with superior performance. For example, by designing molecular structures, an optimized energy level system has been established using intramolecular proton transfer in excited states to achieve population inversion and efficient optical gain, thereby lowering the laser threshold. However, this method has low proton conversion efficiency, is difficult to excite with continuous-wave lasers, and has limited effect on lowering the laser threshold. Therefore, to realize low-threshold continuous-wave organic lasers, researchers have focused on improving the radiative rate and fluorescence quantum yield of gain materials.
[0004] Guo Qingwei et al. achieved rapid excited-state intramolecular proton transfer (ESITP) during molecular luminescence using the organic dye 1,5-dihydroxyanthraquinone, and constructed an optimized energy level system based on this to achieve high-efficiency optical gain. Furthermore, they successfully achieved deep red laser emission at a wavelength of approximately 672 nm by forming a square microdisk structure through the self-assembly of the dye molecules, with a laser threshold as low as 0.39 μJ. However, this device currently only operates under pulsed laser excitation conditions and has not yet achieved continuous laser emission.
[0005] Xuedong Wang et al. synthesized a small amphiphilic organic molecule, (E)-3-(4-(di-p-tolylamino)phenyl)-1-(1-hydroxynaphth-2-yl)prop-2-en-1-one (DPHP). Based on this molecule, they prepared self-assembled micro-hemispherical structures in which molecules arranged themselves in a J-aggregate manner, thereby improving the emissivity of the DPHP hemispheres and eliminating the exciton-exciton annihilation process. At room temperature, a single DPHP hemisphere achieved low-threshold near-infrared laser emission. However, a limitation of this technique is that its laser excitation method remains pulsed laser, and laser emission cannot be achieved under low-threshold continuous laser excitation.
[0006] Patent CN 116093718A discloses a low-threshold whispering-gallery laser and its fabrication method. This laser uses a gold nanofilm as a substrate, on which polymer fibers doped with the laser dye PM597 are fabricated via electrospinning to form a whispering-gallery microcavity structure. Under pump light excitation, this structure can achieve stable whispering-gallery laser output. Simultaneously, the surface plasmons excited by the gold nanofilm enhance the evanescent field of the polymer fiber whispering-gallery microcavity, thereby lowering the laser's threshold. However, this laser currently still relies on pulsed laser excitation and cannot achieve continuous laser excitation.
[0007] Therefore, developing lasers with better stability and the ability to achieve continuous laser excitation at a lower threshold will be a major breakthrough in the field of lasers. Summary of the Invention
[0008] To address the aforementioned technical problems, this invention provides a low-threshold laser and its fabrication method.
[0009] The first objective of this invention is to provide a low-threshold laser, comprising:
[0010] Silica substrate;
[0011] A first hexagonal boron nitride layer is disposed on the surface of the silicon dioxide substrate;
[0012] A monolayer crystal is disposed on the surface of the first hexagonal boron nitride layer; the monolayer crystal is composed of N,N′-dimethyl-3,4,9,10-perylenedicarboximide molecules, wherein the N,N′-dimethyl-3,4,9,10-perylenedicarboximide (Me-PTCDI) molecules are arranged in a long-range ordered manner according to J aggregation;
[0013] A second hexagonal boron nitride layer is disposed on the surface of the monolayer crystal;
[0014] The sandwich structure formed by the first hexagonal boron nitride layer, the monolayer crystal, and the second hexagonal boron nitride layer is an optical resonator.
[0015] In one embodiment of the present invention, the 3,4,9,10-perylenetetracarboxylic dianhydride and its derivatives are selected from 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA), N,N′-dimethyl-3,4,9,10-perylenedicarboximide (Me-PTCDI), N,N'-dipentyl-3,4,9,10-perylenetetracarboximide (PTCDI-C5), or N,N'-di(tetranyl)-3,4,9,10-perylenetetracarboximide (PTCDI-C13).
[0016] In one embodiment of the present invention, the thickness of the silicon dioxide substrate is 250nm-300nm.
[0017] In one embodiment of the present invention, the thickness of the first hexagonal boron nitride layer is 300nm-350nm.
[0018] In one embodiment of the present invention, the thickness of the second hexagonal boron nitride layer is 300nm-350nm.
[0019] In one embodiment of the present invention, the diameter of the low-threshold laser is 2.5 μm-5 μm.
[0020] In one embodiment of the present invention, a first hexagonal boron nitride layer is used as an epitaxial growth substrate for the organic crystal, while a second hexagonal boron nitride layer is used to protect the organic crystal. Hexagonal boron nitride possesses chemical stability and high-temperature resistance, effectively resisting chemical corrosive conditions during the subsequent fabrication of low-threshold lasers, protecting the organic crystal from damage, and without negatively impacting the luminescence properties of the organic crystal. Since both the upper and lower layers use hexagonal boron nitride, their optical refractive indices are identical. This not only reduces optical losses but also ensures that the strongest field enhancement of the device's optical cavity is located precisely in the center of the hexagonal boron nitride layer, i.e., at the location of the organic crystal, thereby further enhancing the function of the optical cavity.
[0021] A second objective of this invention is to provide a method for fabricating the aforementioned low-threshold laser, comprising the following steps:
[0022] S1. Prepare a first hexagonal boron nitride layer on the surface of a silicon dioxide substrate;
[0023] S2. A monolayer molecular crystal is epitaxially grown on the surface of a first hexagonal boron nitride layer using physical vapor deposition (PVD) technology.
[0024] S3. Prepare a second hexagonal boron nitride layer on the surface of a monolayer molecular crystal;
[0025] S4. Prepare a protective layer on the surface of the second hexagonal boron nitride layer;
[0026] S5. Polystyrene microspheres are spin-coated onto the surface of the protective layer as a mask, and the low-threshold laser is obtained by reactive ion etching.
[0027] In one embodiment of the present invention, in step S2, the method for preparing the monolayer molecular crystal specifically includes the following steps: under vacuum conditions, the silicon dioxide substrate after the preparation of the first hexagonal boron nitride layer and N,N′-dimethyl-3,4,9,10-perylenedicarboximide are subjected to segmented heating to obtain a monolayer molecular crystal epitaxially grown on the surface of the first hexagonal boron nitride layer; hexagonal boron nitride has a flat and long-range ordered lattice structure, which can induce Me-PTCDI molecules to form an in-plane herringbone lattice structure, thereby facilitating the acquisition of high-quality J-aggregated monolayer molecular crystals through epitaxial growth. Furthermore, hexagonal boron nitride has a large bandgap, which does not affect the luminescence of the crystal itself when growing crystals in the visible light band.
[0028] In one embodiment of the present invention, the segmented heating is to first raise the temperature to 95°C-105°C within 28-32 minutes, then raise the temperature to 195°C-205°C within 28-32 minutes, and finally raise the temperature to 235°C-245°C within 14-16 minutes and hold the temperature for 14-16 minutes.
[0029] In one embodiment of the present invention, after S5, a step of cleaning the low threshold laser is further included; after etching, acetone is used for rinsing to remove the polystyrene microspheres and protective layer, thereby obtaining the low threshold laser; the polystyrene microspheres, with their excellent spherical regularity and surface smoothness, can be used as reactive ion etching (RIE) masks to prepare high-quality factor microdisk resonant cavities.
[0030] The technical solution of the present invention has the following advantages compared with the prior art:
[0031] (1) The low-threshold laser of this invention employs physical vapor deposition (PVD) to epitaxially grow a Me-PTCDI monolayer molecular crystal on the surface of a hexagonal boron nitride (BN) layer. The Me-PTCDI molecules are arranged in a long-range ordered manner with J-aggregates, endowing the monolayer molecular crystal with superradiative properties, thereby accelerating the radiation rate and effectively suppressing triplet exciton accumulation caused by intersystem crossing, achieving continuous-wave laser excitation and an ultra-low threshold at the nanowatt level. Hexagonal boron nitride possesses high optical transparency (especially in the visible light band) and a suitable dielectric constant, enabling the construction of a low-optical-loss resonant cavity; its high thermal conductivity also efficiently manages the laser's heat dissipation, ensuring the long-term stability of continuous laser emission. By embedding the monolayer molecular crystal in the middle of the hexagonal BN layer structure, spatial overlap between the exciton dipole and the resonant cavity optical field is achieved, significantly enhancing the efficiency of light-matter interaction.
[0032] (2) The low-threshold laser of this invention utilizes the high fluorescence quantum yield and fast emission rate of a monolayer molecular crystal. Its ultrafast emission characteristics can effectively suppress triplet exciton accumulation and the exciton-exciton annihilation process it induces. This accumulation effect is the key physical bottleneck hindering the realization of continuous-wave organic lasers. In addition, during continuous laser operation, thermal accumulation leads to photodegradation of organic materials, thereby interrupting laser emission. Hexagonal boron nitride not only serves as a low-loss optical resonator substrate, but also ensures the long-term emission stability of the laser due to its high thermal conductivity and efficient heat dissipation. Therefore, the sandwich structure formed by the monolayer molecular crystal and the hexagonal boron nitride layer constitutes an optical resonator. Combined with the optical field localization effect of the micro / nano resonator, the pump energy can be concentrated in the gain region, significantly reducing the threshold. The advantages of the aggregated monolayer molecular crystal as the emitting layer, combined with the advantages of hexagonal boron nitride as a resonator and thermal management material, jointly promote the realization of continuous-wave organic lasers.
[0033] (3) The low-threshold laser described in this invention enables the excitation and output of continuous laser light, covering a wide wavelength range (580nm-780nm), with a laser threshold as low as 1.6nW (corresponding to a power density of 0.2W / cm²). 2 Furthermore, the laser emission stability is high (after 5000s of continuous operation, the emission peak intensity decreases by about 10%). Attached Figure Description
[0034] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein:
[0035] Figure 1 This is a schematic diagram of the low-threshold laser of Embodiment 1 of the present invention;
[0036] Figure 2 This is a diagram showing the J-aggregate arrangement of Me-PTCDI molecules in the monolayer crystal of this invention;
[0037] Figure 3 This is a fluorescence optical image of a low-threshold laser with a diameter of 4 μm used in Test Example 1 of this invention;
[0038] Figure 4 The normalized fluorescence spectra of the monolayer crystal and the low-threshold laser in Test Example 1 of this invention are shown below.
[0039] Figure 5 This is the power-dependent spectrum of a low-threshold laser with a diameter of 4 μm in Test Example 1 of this invention;
[0040] Figure 6 Power-dependent intensity and full width at half maximum (FWHM) analysis of a low-threshold laser with a diameter of 4 μm in Test Example 1 of this invention;
[0041] Figure 7 The power-dependent spectrum of the low-threshold laser with a diameter of 2.5 μm in Test Example 2 of this invention is shown.
[0042] Figure 8 The power-dependent intensity and full width at half maximum (FWHM) analysis of the low-threshold laser with a diameter of 2.5 μm in Test Example 2 of this invention;
[0043] Figure 9 This is the power-dependent spectrum of a low-threshold laser with a diameter of 5 μm in Test Example 3 of this invention;
[0044] Figure 10 Analysis of power-dependent intensity and full width at half maximum (FWHM) of a low-threshold laser with a diameter of 5 μm in Test Example 3 of this invention;
[0045] Figure 11 The fluorescence spectrum in Fourier space of the low-threshold laser in Test Example 4 of the present invention is shown; where a is the fluorescence spectrum in Fourier space of the low-threshold laser below the threshold power, and b is the fluorescence spectrum in Fourier space of the low-threshold laser above the threshold power.
[0046] Figure 12 The polarization-dependent fluorescence spectrum of the low-threshold laser with power above the threshold in Test Example 4 of this invention;
[0047] Figure 13 This is the polarization polarization diagram of the low-threshold laser with power above the threshold in Test Example 4 of the present invention;
[0048] Figure 14 The curve showing the decay of the luminous intensity of the low-threshold laser over time in Test Example 5 of this invention is shown.
[0049] Figure 15 The emission spectra of the low-threshold laser in Test Example 5 of this invention are shown at 0s and after 5000s of operation. Detailed Implementation
[0050] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.
[0051] Example 1
[0052] Reference Figure 1 As shown, the low-threshold laser and its fabrication method in this embodiment specifically include the following steps:
[0053] S1. First, a hexagonal boron nitride layer with a thickness of 300 nm is transferred onto a SiO2 / Si substrate with a thickness of approximately 300 nm / 500±25 μm using a dry transfer method.
[0054] S2. Then, the transferred substrate is placed in a tube furnace and positioned 10 cm away from the source region. A quartz boat containing N,N′-dimethyl-3,4,9,10-perylenedicarboximide (Me-PTCDI) powder is placed in the source region. The tube furnace cavity is then closed, and the cavity is purged with argon gas. After purging, the cavity is evacuated until the vacuum reaches 2 × 10⁻⁶. - 3 Below Pa, the tube furnace is started, and the temperature is increased in stages: first, the temperature is raised to 100℃ after 30 minutes, then to 200℃ after 30 minutes, and then to 240℃ after 15 minutes, and held at 240℃ for 15 minutes. This allows Me-PTCDI molecules to epitaxially grow into a monolayer crystal along the surface of the hexagonal boron nitride layer, wherein the Me-PTCDI molecules are arranged in a long-range ordered manner according to the J-aggregate pattern. Figure 2 );
[0055] S3. Subsequently, a hexagonal boron nitride layer with a thickness of 300 nm is transferred onto the monolayer molecular crystal.
[0056] S4. Spin-coat a layer of PMMA as a protective layer on the hexagonal boron nitride surface at a spin speed of 2000 rpm for 60 s. Immediately after spin-coating, bake the product at 180°C for 180 s using a heating table.
[0057] S5. Finally, a 4μm polystyrene microsphere is spin-coated onto the stacked region of the monolayer crystal and two layers of hexagonal boron nitride as a mask, and reactive ion etching (RIE) is performed. After etching for 20 min, the polystyrene microsphere is removed by ultrasonic rinsing with acetone for 5 s, resulting in a low threshold laser with a diameter of 4μm.
[0058] Test Example 1
[0059] (1) Irradiate a low-threshold laser with a diameter of 4 μm using a mercury lamp with a filter, and take a photo under a 100x magnification lens. The fluorescence optical image of the low-threshold laser is shown below. Figure 3 As shown. From Figure 3 It can be seen that the edge of the low threshold laser exhibits uniform and continuous red emission, which indicates that Me-PTCDI molecules emit light under laser excitation in the low threshold laser, and the emission of molecules is then coupled through the disk structure to form a whispering galvanic mode (WGM) laser.
[0060] (2) A low-threshold laser with a diameter of 4 μm was excited using a 532 nm continuous laser, and its spectrum was acquired. The results are as follows: Figure 4 As shown. From Figure 4As can be seen, unlike monolayer crystals, the spectrum of low-threshold lasers exhibits typical sawtooth emission peaks, further proving the formation of WGM lasers within low-threshold lasers. This also indicates that sawtooth emission peaks, i.e., the peak shape of lasers, cannot be generated with only Me-PTCDI molecules; this sawtooth spectral morphology only appears when a disk-like structure, i.e., a low-threshold laser, is formed.
[0061] (3) A low-threshold laser with a diameter of 4 μm was subjected to variable power testing and excited with 532 nm continuous lasers of different powers. The laser power was modulated by the laser power module on a confocal microspectrometer. The light spot was focused on the edge of the 4 μm low-threshold laser, and the emission spectrum of the low-threshold laser was collected. The spectral results collected at different powers are shown below. Figure 5 As shown. From Figure 5 It can be seen that at lower laser power, the emission peak is weak and no sawtooth emission peak is generated. As the laser power gradually increases, a sawtooth emission peak appears when the threshold laser power is reached. This is further analyzed by examining the intensity and full width at half maximum (FWHM) of the emission peak at different powers. Figure 6 The threshold power of the laser was found to be 1.6 nW, corresponding to a threshold power density of 0.20 W / cm². 2 This laser's threshold power is 300 times lower than that of previously reported continuous-wave laser-excited lasers. This ultra-low threshold power primarily stems from two aspects. First, the monolayer crystal is epitaxially grown under low vacuum, resulting in high-quality crystals with a J-gathering arrangement, exhibiting superradiative properties, high absorptivity, high emissivity, short lifetime, and near-100% fluorescence quantum yield. This allows it to overcome the effects of triplet quenching and achieve low-threshold continuous-wave laser excitation. Second, the WGM optical cavity, constructed with hexagonal boron nitride layers on both the top and bottom, has a higher quality factor, enhancing the interaction between light and matter and allowing light to reside within it for extended periods, thereby further reducing the threshold power.
[0062] Test Example 2
[0063] Based on Example 1, a low-threshold laser with a diameter of 2.5 μm was fabricated using 2.5 μm polystyrene microspheres as a mask. The 2.5 μm low-threshold laser was subjected to variable power testing and excited with 532 nm continuous-wave lasers of different powers. The laser power was modulated by the laser power module on a confocal microspectrophotometer, focusing the light spot onto the edge of the 2.5 μm low-threshold laser. The emission spectrum of the low-threshold laser was collected, and the spectral results collected at different powers are shown below. Figure 7 As shown. From Figure 7It can be seen that as the laser peak gradually intensifies, the emission peak exhibits a sawtooth-like characteristic at the threshold power. Unlike the emission peak of a low-threshold laser with a diameter of 4 μm, the low-threshold laser with a diameter of 2.5 μm has a larger peak spacing, which is its mode free spectral range (FSR). Where λ is the emission peak wavelength, R is the low-threshold laser radius, and n is the refractive index of hBN, the emission peak intensity and half-width at half-maximum (WHM) are analyzed at different powers. Figure 8 The threshold power density of the laser was found to be 0.20 W / cm². 2 .
[0064] Test Example 3
[0065] Based on Example 1, a low-threshold laser with a diameter of 5 μm was fabricated using 5 μm polystyrene microspheres as a mask. The 5 μm low-threshold laser was subjected to variable power testing and excited with 532 nm continuous lasers of different powers. The laser power was modulated by the laser power module on a confocal microspectrophotometer, focusing the light spot onto the edge of the 5 μm low-threshold laser. The emission spectrum of the low-threshold laser was collected, and the spectral results collected at different powers are shown below. Figure 9 As shown. From Figure 9 It can be seen that the WGM peak spacing in the emission spectrum of the low-threshold laser with a diameter of 5 μm is smaller, only 13.9 nm. Unlike the emission peaks of the low-threshold laser with a diameter of 4 μm, the 5 μm low-threshold laser exhibits a smaller peak spacing, meaning its free spectral range (FSR) is smaller. This is consistent with the theory that the FSR decreases with increasing diameter. Further analysis of the emission peak intensity and full width at half maximum (FWHM) at different powers... Figure 10 The threshold power density of the laser was found to be 0.20 W / cm². 2 .
[0066] In summary, the free spectral range (FSR) is negatively correlated with the diameter of the low-threshold laser. As the diameter of the low-threshold laser increases, the FSR decreases, and vice versa.
[0067] Test Example 4
[0068] (1) Based on Test Example 3, coherence tests were performed on a low-threshold laser with a diameter of 5 μm. First, the laser spot was focused at the edge of the low-threshold laser. Then, the slit of the testing instrument was limited to a small area. Fourier space spectral measurements were performed at laser powers of 3.49 μW above the threshold and 0.004 μW below the threshold, respectively. The fluorescence spectra of the low-threshold laser below and above the threshold power are as follows: Figure 11 As shown. From Figure 11As can be seen from 'a' in the diagram, below the threshold power, the angular-resolved spectrum of the low-threshold laser does not exhibit interference fringes. This indicates that below the threshold power, the stimulated emission of the low-threshold laser produces few photons that lack coherence and are therefore unable to generate interference fringes. Figure 11 As shown in b, interference fringes can be observed in the angular-resolved spectrum of the low-threshold laser above the threshold. The prominent interference fringes appear at the WGM resonance, which matches the spectrum of the low-threshold laser above the threshold. This indicates that above the threshold, stimulated emission produces population inversion, and a large number of photons belong to the same photon state, suggesting that the emission of this low-threshold laser is coherent. These results demonstrate that the photons emitted by this low-threshold laser above the laser threshold are coherent light.
[0069] (2) Based on Test Example 3, a low-threshold laser with a diameter of 5 μm was subjected to polarization testing. The test was conducted using a confocal microspectrophotometer under a 100x objective lens. By focusing the laser spot onto the edge of the low-threshold laser, and under conditions above the threshold power (0.058 μW), the sample's spectrum was acquired. The polarization angle of the probe was changed using the instrument's built-in polarization attachment, thus enabling the acquisition of the low-threshold laser's spectrum at different polarization angles. When the excitation power was above the threshold power, the polarization-dependent fluorescence spectra of the low-threshold laser at different polarization angles were as follows: Figure 12 As shown. From Figure 12 It can be seen that the intensity of the WGM emission peak differs at different polarization angles. Extracting the intensity of the same WGM emission peak at different polarization angles yields... Figure 13 The polarization emission polarization diagram of the low-threshold laser shown is from... Figure 13 It can be seen that the low-threshold laser exhibits obvious polarized emission. This is because, above the threshold power, a large number of photons generated by stimulated emission have the same photon state, i.e., the same phase, the same propagation direction, and the same polarization state. The polarization state of the low-threshold laser was verified above the threshold power. According to the formula for calculating the degree of polarization, Where I 0° I represents the intensity of the spectrum at 0° polarization. 90° This represents the intensity of the spectrum under 90° polarization. According to the formula, the polarization degree of the low-threshold laser reaches 48%, which indicates that the laser produced by this low-threshold laser has good polarization.
[0070] Test Example 5
[0071] Based on Test Example 1, a stability test was conducted on a low-threshold laser with a diameter of 4 μm. The low-threshold laser was continuously irradiated with a continuous 532 nm laser with a power of 0.046 μW, while a confocal microspectrophotometer continuously collected the spectrum of the low-threshold laser. One spectrum was collected every 0.1 s, for a total of 50,000 spectra collected over a cumulative period of 5000 s. The intensity of the WGM emission peak at 671 nm was extracted from the collected spectra, and the change in emission intensity over time was analyzed. The results are as follows: Figure 14 As shown. Furthermore, Figure 15 This represents the first spectrum collected at the very beginning of laser irradiation and the last spectrum collected 5000 seconds after laser irradiation. From Figures 14-15 It can be seen that the emission decay of the low-threshold laser is very slow; even after 5000 seconds of continuous irradiation, the laser emission remains stable. This indicates that the upper hexagonal boron nitride layer in the device fabrication has a significant protective effect on the monolayer crystal in the low-threshold laser, thus enabling the low-threshold laser to achieve stable output for a long time under continuous laser irradiation. In contrast, the half-life of currently reported continuous organic lasers is only 3-4 minutes.
[0072] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.
Claims
1. A low-threshold laser, characterized in that, include: Silica substrate; A first hexagonal boron nitride layer is disposed on the surface of the silicon dioxide substrate; A monolayer crystal is disposed on the surface of the first hexagonal boron nitride layer; the monolayer crystal is composed of 3,4,9,10-perylenetetracarboxylic dianhydride and its derivatives, and the 3,4,9,10-perylenetetracarboxylic dianhydride and its derivatives are arranged in a long-range ordered manner according to J-aggregation. A second hexagonal boron nitride layer is disposed on the surface of the monolayer crystal; The sandwich structure formed by the first hexagonal boron nitride layer, the monolayer crystal, and the second hexagonal boron nitride layer is an optical resonator.
2. The low-threshold laser according to claim 1, characterized in that, The 3,4,9,10-perylenetetracarboxylic dianhydride and its derivatives are selected from 3,4,9,10-perylenetetracarboxylic dianhydride, N,N′-dimethyl-3,4,9,10-perylenedicarboximide, N,N'-dipentyl-3,4,9,10-perylenetetracarboximide, or N,N'-di(tetranyl)-3,4,9,10-perylenetetracarboximide.
3. The low-threshold laser according to claim 1, characterized in that, The thickness of the silicon dioxide substrate is 250nm-300nm.
4. The low-threshold laser according to claim 1, characterized in that, The thickness of the first hexagonal boron nitride layer is 300nm-350nm.
5. The low-threshold laser according to claim 1, characterized in that, The thickness of the second hexagonal boron nitride layer is 300nm-350nm.
6. The low-threshold laser according to claim 1, characterized in that, The diameter of the low-threshold laser is 2.5μm-5μm.
7. A method for fabricating a low-threshold laser as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Prepare a first hexagonal boron nitride layer on the surface of a silicon dioxide substrate; S2. A monolayer molecular crystal is epitaxially grown on the surface of a first hexagonal boron nitride layer using physical vapor deposition (PVD) technology. S3. Prepare a second hexagonal boron nitride layer on the surface of a monolayer molecular crystal; S4. Prepare a protective layer on the surface of the second hexagonal boron nitride layer; S5. Polystyrene microspheres are spin-coated onto the surface of the protective layer as a mask, and the low-threshold laser is obtained by reactive ion etching.
8. The method for fabricating a low-threshold laser according to claim 7, characterized in that, In S2, the method for preparing the monolayer molecular crystal specifically includes the following steps: under vacuum conditions, the silicon dioxide substrate after the preparation of the first hexagonal boron nitride layer and N,N′-dimethyl-3,4,9,10-perylenedicarboximide are subjected to segmented heating to obtain a monolayer molecular crystal epitaxially grown on the surface of the first hexagonal boron nitride layer.
9. The method for fabricating a low-threshold laser according to claim 8, characterized in that, The segmented heating process involves first raising the temperature to 95℃-105℃ within 28-32 minutes, then raising it to 195℃-205℃ within 28-32 minutes, and finally raising it to 235℃-245℃ within 14-16 minutes and holding it at that temperature for 14-16 minutes.
10. The method for fabricating a low-threshold laser according to claim 7, characterized in that, After S5, a step of cleaning the low-threshold laser is also included; after etching, acetone is used for rinsing to remove the polystyrene microspheres and protective layer, thus obtaining the low-threshold laser.