A nanowire vector beam laser and a preparation method thereof

Abstract

The application discloses a nanowire vector beam laser and a preparation method thereof. The laser specifically comprises a substrate, which is a gallium arsenide substrate or a silicon substrate; a silicon dioxide film coated on a substrate surface of the substrate, wherein an opening is arranged in the silicon dioxide film, and a gallium arsenide nanowire vertically grown from the opening of the substrate; wherein the gallium arsenide nanowire is a high-uniformity gallium arsenide Fabry-Perot nanowire cavity, and a plurality of indium gallium arsenide quantum discs are embedded in the gallium arsenide nanowire. The volume of the vector beam laser is effectively reduced, and the stability and expandability of the vector beam laser are improved.

Description

Technical Field

[0001] This invention belongs to the field of laser technology, specifically relating to a nanowire vector beam laser and its fabrication method. Background Technology

[0002] Laser is amplified light through stimulated emission, possessing advantages such as high intensity, high directionality, and monochromaticity. Today, laser technology has made significant progress and plays an important role in various fields. However, miniaturization of laser devices still faces many challenges that need to be addressed.

[0003] Vector beams, also known as vector light beams, refer to light beams with different polarization states at different positions on the wavefront at the same moment. Due to the polarization characteristics of vector beams, the application of optical systems in fields such as super-resolution imaging, optical tweezers, high-capacity optical interconnects, and quantum communication has been expanded. The methods for generating vector beams can be summarized into active and passive methods. Active methods involve specially designing the optical resonator of the laser, integrating optical components in free space or the resonator, and selecting the desired mode within the laser. Passive methods include interferometry, spatial light modulator wavefront reconstruction, and crystal birefringence. However, regardless of whether it is an active or passive method, the required devices or systems are too large to be used in photonic integrated chips, and their stability and scalability are relatively low.

[0004] Therefore, how to reduce the size of nanowire vector beam lasers and improve their stability and scalability is a technical problem that needs to be solved by those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to solve the technical problems of existing nanowire vector beam lasers being too large to be applied in photonic integrated chips, and having low stability and scalability.

[0006] To achieve the above-mentioned technical objectives, the present invention provides a nanowire vector beam laser, the laser comprising:

[0007] The substrate is specifically a gallium arsenide substrate or a silicon substrate;

[0008] A silicon dioxide thin film is coated on the substrate surface of the substrate, and the silicon dioxide thin film has openings, and gallium arsenide nanowires are vertically grown from the substrate through the openings, wherein the gallium arsenide nanowires are highly uniform gallium arsenide Fabry-Perot nanowire cavities, and multiple indium gallium arsenide quantum disks are embedded in the gallium arsenide nanowires.

[0009] Furthermore, the gallium arsenide nanowire is a hexagonal prism, the aperture diameter is 100 nm, the average diameter of the gallium arsenide nanowire is 300 nm, and the length is 2.3 μm. The gallium arsenide nanowire also includes a top mirror and a bottom mirror. The bottom mirror is the bottom part of the gallium arsenide nanowire excluding the part located inside the aperture of the silicon dioxide film. The bottom mirror is gallium arsenide and is in contact with the silicon dioxide film. The top mirror is gallium arsenide and is in contact with the air.

[0010] Furthermore, the indium gallium arsenide quantum disk is uniformly embedded in the gallium arsenide nanowire.

[0011] Furthermore, the number of indium gallium arsenide quantum disks is ten.

[0012] Furthermore, the ratio of arsenic:gallium:indium in the indium gallium arsenide quantum disk is 50.8:38.8:10.4.

[0013] Furthermore, the thickness of the indium gallium arsenide quantum disk is 15 nm.

[0014] Furthermore, the effective refractive index of the bottom mirror can be adjusted.

[0015] Furthermore, the effective refractive index of the bottom mirror is adjusted by adjusting the ratio of the bottom mirror to the bottom area of ​​the gallium arsenide nanowire.

[0016] On the other hand, the present invention also provides a method for fabricating a nanowire vector beam laser, for fabricating the nanowire vector beam laser as described above, the method comprising:

[0017] A 30 nm silicon dioxide thin film is deposited on the substrate surface of the substrate;

[0018] After the array pattern is transferred to the silicon dioxide thin film by reactive ion etching, a first process is performed, which specifically involves removing the oxide layer, oxides, and adsorbed gases.

[0019] The flow rates of trimethylgallium and triarsenide were set to 1.006 × 10⁻⁶, respectively. -5 mol / min and 1.998×10 - 5 Gallium arsenide nanowire pillars were grown on the substrate after the first treatment at a flow rate of mol / min and a growth temperature of 750℃ for 20 minutes; then, indium gallium arsenide quantum disks were grown with a trimethylindium flow rate of 2.529 × 10⁻⁶ mol / min. -6 The growth rate was mol / min, with growth times of 30 seconds for the gallium arsenide barrier, 15 seconds for the indium gallium arsenide quantum disk, and a total of 10 cycles; finally, gallium arsenide was grown for 5 minutes to embed the indium gallium arsenide quantum disk in the gallium arsenide nanowire.

[0020] This invention provides a nanowire vector beam laser, which, compared with the prior art, includes a substrate, specifically a gallium arsenide substrate or a silicon substrate; a silicon dioxide thin film coated on the substrate surface, wherein the silicon dioxide thin film has openings; and gallium arsenide nanowires vertically grown from the substrate through the openings. The gallium arsenide nanowires are highly uniform gallium arsenide Fabry-Perot nanowire cavities, and multiple indium gallium arsenide quantum disks are embedded within the gallium arsenide nanowires. This effectively reduces the size of the nanowire vector beam laser and improves its stability and scalability. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments or prior art of this specification, the drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this specification. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 The diagram shown is a schematic representation of the nanowire vector beam laser provided in the embodiments of this specification.

[0023] Figure 2 The image shown is a spectrum observed under weak pump flow in an embodiment of this specification;

[0024] Figure 3 The figure shown is a minority carrier lifetime diagram of gallium arsenide nanowires in the embodiments of this specification;

[0025] Figure 4 The image shown is a bright spot formed by the emission of light from the top of the gallium arsenide nanowire under the condition that the pumping rate is below the threshold in the embodiments of this specification.

[0026] Figure 5 The image shown is a speckled pattern formed by light emitted from the top of the nanowire when the pumping rate exceeds a threshold in an embodiment of this specification.

[0027] Figure 6 The image shown is an optical imaging diagram of the annular laser spot emitted by the nanowire under the condition of collecting the optical path without a polarizer in the embodiment of this specification;

[0028] Figure 7 The image shown is an optical imaging diagram of the laser beam emitted from the nanowire under the condition that the optical path is placed with polarizers at the top and bottom positions in the embodiment of this specification.

[0029] Figure 8 The image shown is an optical imaging diagram of the laser beam emitted from the nanowire under the condition that the optical path is equipped with polarizers placed in the left and right directions in the embodiment of this specification.

[0030] Figure 9 The diagram shown is a schematic flowchart of the nanowire vector beam laser fabrication method provided in this embodiment. Detailed Implementation

[0031] To enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0032] As described in the background section, nanowire vector beam lasers require devices or systems that are too large, primarily due to the diffraction limit of light. The subwavelength scale of vector beam nanolasers presents a challenge because the laser modes in nanowire vector beam lasers should be laterally distributed. Unidirectional light transmission requires additional complex refractive index modulation to achieve a vector beam, necessitating complex and precise optical cavity fabrication processes. Microdisk or microring cavities are candidate structures that can support and circulate whispering-gallery modes. However, to support large-volume optical whispering-gallery modes, the dimensions of these cavities cannot be scaled down to the wavelength scale, failing to meet the ever-growing miniaturization requirements of photonic integrated chips. Moreover, the emission direction of optical whispering-gallery modes is tangential to the ring cavity, resulting in poor laser directionality. Reported nanowire lasers cover the ultraviolet to mid-infrared spectral range; however, these nanowires support multiple intrinsic modes that compete with each other during lasing. In nanowires, TE... 01 The intrinsic modes (with the same electromagnetic field distribution as the angularly polarized cylindrical vector beam) exhibit the properties of vector modes. However, TE 01 The mode is a high-order mode that selectively lases TE. 01 It is a challenge. Selective region epitaxy refers to the local epitaxial growth after depositing and patterning a dielectric mask on a semiconductor substrate. This can produce high-quality nanowires with uniform morphology and controllable size, which is beneficial for realizing vector modes.

[0033] Therefore, this application proposes a nanowire vector beam laser, such as Figure 1 As shown, the laser includes:

[0034] The substrate is specifically a gallium arsenide substrate or a silicon substrate;

[0035] A silicon dioxide thin film is coated on the substrate surface of the substrate, and the silicon dioxide thin film has openings, and gallium arsenide nanowires are vertically grown from the substrate through the openings, wherein the gallium arsenide nanowires are highly uniform gallium arsenide Fabry-Perot nanowire cavities, and multiple indium gallium arsenide quantum disks are embedded in the gallium arsenide nanowires.

[0036] Specifically, the vector beam laser material fabrication in this application is controllable and boasts high crystal quality. Compared to traditional top-down fabrication processes such as focused ion beam etching and electron beam lithography, it features a simpler process, easier operation, stronger controllability, and easier post-defect introduction and promotion. Nanowires, as a natural nanoscale resonant cavity, can form sufficient optical feedback through end-face reflection, enabling laser miniaturization. The laser in this application utilizes the intrinsic modes supported by nanowires, thereby eliminating the need for post-processing of complex structures to ensure high optical performance. Compared to traditional microdisk or microring cavities, the structure proposed in this invention is scaled down to the subwavelength scale and well confined within the nanowire cavity, achieving efficient laser excitation and obtaining a vector beam laser with a low threshold.

[0037] Secondly, the gallium arsenide nanowires in the vector beam laser of this application are grown using a vertical growth technique within selected region epitaxy, enabling direct bottom-up epitaxial growth of the nanowire optical cavity without subsequent processing. Furthermore, different mask openings can be designed and fabricated for laser modes with varying mode field distributions to achieve mode selection, which will greatly promote the development of nanolasers with other complex optical fields.

[0038] Furthermore, the nanowire vector beam laser of this application uses a uniform, regular, and smooth nanowire shape without any conical or lattice distortion, minimizing optical losses in the cavity to achieve a high quality factor. Due to the small volume of the nanowire cavity, the number of guided modes in the resonant cavity is minimized, making it suitable for achieving single-mode laser output.

[0039] In some embodiments, the gallium arsenide nanowire is a hexagonal prism, the aperture diameter is 100 nm, the average diameter of the gallium arsenide nanowire is 300 nm, the length is 2.3 μm, and the gallium arsenide nanowire further includes a top mirror and a bottom mirror. The bottom mirror is the portion of the bottom of the gallium arsenide nanowire excluding the portion located inside the aperture of the silicon dioxide film. The bottom mirror is gallium arsenide and is in contact with the silicon dioxide film. The top mirror is gallium arsenide and is in contact with air.

[0040] In some embodiments, the indium gallium arsenide quantum disks are uniformly embedded in the gallium arsenide nanowires, the number of indium gallium arsenide quantum disks is ten, the ratio of arsenic:gallium:indium in the indium gallium arsenide quantum disks is 50.8:38.8:10.4, and the thickness of the indium gallium arsenide quantum disks is 15 nm.

[0041] In some embodiments, the effective refractive index of the bottom mirror can be adjusted.

[0042] In some embodiments, the effective refractive index of the bottom mirror is adjusted by adjusting the proportion of the bottom area of ​​the bottom mirror to that of the gallium arsenide nanowire.

[0043] In specific application scenarios, the designed nanowires were simulated using finite-difference time-domain (FDTD) simulations to analyze the threshold gain for different nanowire diameters and select suitable intrinsic modes. The threshold gain was divided into three intervals based on the nanowire diameter. The lowest threshold eigenmodes corresponding to the nanowire diameter ranges of 200–230 nm, 230–320 nm, and 320–400 nm were HE, respectively. 11a / b TE 01 HE 21a / b When the nanowire diameter is less than 230 nm, higher-order guided modes are no longer supported in the nanowire; only HE modes are allowed. 11a / b The modes resonate within the nanowire cavity. As the nanowire diameter increases, the number of modes supported within the nanowire cavity begins to increase. Due to HE... 11a / b Most of the energy distribution in the mode is concentrated along the central axis of the nanowire. When it propagates to the bottom surface of the nanowire, most of the energy flow leaks into the substrate through the SiO2 openings, causing a rapid decrease in the reflectivity of the bottom surface. However, due to TE... 01 The mode exhibits a donut-shaped mode field distribution, which can be well reflected by the bottom facet of the nanowire / SiO2. Therefore, the effective refractive index can be modulated by changing the shape of the bottom facet (i.e., the diameter of the nanowire and the mask opening) to customize and select the laser mode, ultimately leading to the successful realization of a vector beam laser.

[0044] The laser properties of a single nanowire grown vertically on a substrate were evaluated using a confocal microphotoluminescence (μ-PL) system, and the PL spectra under different pump intensities were plotted and analyzed. Figure 2 A broad fluorescence spectrum centered at 1000 nm and 75 nm wide was observed under weak pumping current. Due to the band-filling effect in the indium gallium arsenide quantum disk, this peak shifts to shorter wavelengths with increasing pumping current. At 1 μJ / cm²... 2 At excitation pumping rates around 980 nm, a Fabry-Pérot (FP) resonance peak appeared, centered at 980 nm. The intensity of this resonance peak increased with increasing pump power and rapidly dominated the entire fluorescence spectrum. Simultaneously, below the lasing threshold, the full width at half maximum (FWHM) of the emission peak increased with increasing excitation, decreased abruptly at the onset of stimulated emission, and then increased again with further increases in pumping rate, consistent with lasing characteristics.

[0045] To further understand the characteristics of lasers, Figure 3The minority carrier lifetime of the nanowires at 5 K is shown. Since nonradiative recombination on the nanowire surface is suppressed at 5 K, the minority carrier lifetime at 0.1 p is significantly reduced. th A long lifetime of approximately 1.38 ns can be obtained, indicating that most charge carriers are consumed by spontaneous emission at a pump flow rate of 1.3 P. th At this point, the lifetime is shortened to 45 ps (the system resolution is ~50 ps), and carrier recombination is dominated by stimulated emission. Figure 4 When the pumping rate is below a threshold, light emission forms a bright spot at the top of the gallium arsenide nanowire. When the pumping rate exceeds the threshold, light emitted from the top surface of the nanowire, i.e., the top mirror, forms a bright spot. Figure 5 The displayed speckled stripes confirm that the emitted light is coherent. Because the emitted laser is saturated during camera acquisition, the expected dark spot at the center of the vector beam cannot be observed here. Therefore, a neutral density filter is inserted along the acquisition path for attenuation, preventing camera oversaturation and allowing identification of the vector beam's intensity distribution. Inserting a linear polarizer before the camera splits the original gallium arsenide nanowire laser's emitted vector beam into a bilobed pattern perpendicular to the polarizer's axis. Figures 6-8 The diagram shows a double-leaf pattern rotating with the linear polarizer while remaining perpendicular. The polarization direction for each image is marked, confirming that the emitted laser mode is an angularly polarized vector spot. Figure 6 The image shown is an optical imaging diagram of the annular laser spot emitted by the nanowire under the condition of collecting the optical path without a polarizer, as described in the embodiments of this specification. Figure 7 The image shown is an optical imaging diagram of the nanowire-emitted laser beam under the condition of upper and lower polarizers in the optical path placement in the embodiments of this specification. Figure 8 The image shown is an optical imaging diagram of the laser beam emitted from the nanowire under the condition that the optical path is equipped with polarizers placed in the left and right directions in the embodiment of this specification.

[0046] The vector beam laser proposed in this application utilizes a bottom-up direct epitaxial growth method for nanowire optical cavities without post-processing, providing greater feasibility for the development of nanolasers. Its fabrication method is compatible with current CMOS processes, exhibits high efficiency per unit area, and can be well applied to photonic chip integration. The proposed emission wavelength is 980 nm, and the threshold is ~1 μJ / cm². 2 The single-mode vector beam nanolaser is realized using multi-quantum dot nanowires with a diameter of 290–315 nm. Since the nanowires have a subwavelength diameter, they can be considered the smallest vector beam generators. In summary, this vector beam nanowire laser has the advantages of simple fabrication, ease of operation, high controllability, low cost, and ease of promotion.

[0047] Furthermore, this application also provides a method for fabricating a nanowire vector beam laser, such as... Figure 9As shown, the method for fabricating the nanowire vector beam laser as described above includes:

[0048] Step S901: Deposit a 30 nm silicon dioxide thin film on the substrate surface of the substrate.

[0049] Step S902: After transferring the array pattern to the silicon dioxide thin film by reactive ion etching, a first process is performed, specifically the removal of the oxide layer, oxide, and adsorbed gas.

[0050] Step S903: Set the flow rates of trimethylgallium and triarsenide to 1.006 × 10⁻⁶ respectively. -5 mol / min and 1.998×10 -5 Gallium arsenide nanowire pillars were grown on the substrate after the first treatment at a flow rate of mol / min and a growth temperature of 750℃ for 20 minutes; then, indium gallium arsenide quantum disks were grown with a trimethylindium flow rate of 2.529 × 10⁻⁶ mol / min. -6 The growth rate was mol / min, with growth times of 30 seconds for the gallium arsenide barrier, 15 seconds for the indium gallium arsenide quantum disk, and a total of 10 cycles; finally, gallium arsenide was grown for 5 minutes to embed the indium gallium arsenide quantum disk in the gallium arsenide nanowire.

[0051] Specifically, 30 nm of SiO2 is deposited on the substrate surface of the substrate by plasma-enhanced chemical vapor deposition. The array pattern is transferred onto the SiO2 by reactive ion etching. The substrate surface of the substrate with the pattern array is deoxidized by acid solution and heated to 750 °C in an AsH3 atmosphere to remove oxides and adsorbed gases from the substrate surface.

[0052] Vapor-solid (VS) methods are catalyst-free growth techniques where nanowires are grown by adsorbing gas-phase atoms and diffusing them on a surface. They can be deposited at specific locations on a substrate via selective region epitaxy (SAE), enabling the creation of multi-period, uniformly sized, and tunable nanowire arrays.

[0053] First, an ordered GaAs array was fabricated, with the fluxes of TMGa and AsH3 set to 1.006 × 10⁻⁶. -5 mol / min and 1.998×10 -5 GaAs nanowire pillars were grown at a flow rate of 1.529 × 10⁻⁶ mol / min and a growth temperature of 750 °C for 20 minutes. Then, indium gallium arsenide quantum disks were grown at a flow rate of 2.529 × 10⁻⁶ mol / min. -6 The growth rate was mol / min, with growth times of 30 seconds for the gallium arsenide barrier, 15 seconds for the indium gallium arsenide quantum disk, and a total of 10 cycles; finally, gallium arsenide was grown for 5 minutes to successfully embed the indium gallium arsenide quantum disk in the gallium arsenide nanowire.

[0054] The device embodiments described above are merely illustrative. For example, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or plug-ins may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces, indirect coupling or communication connection between devices or units, and may be electrical, mechanical, or other forms.

[0055] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on describing the differences from other embodiments. In the description of this specification, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this specification. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0056] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. A nanowire vector beam laser, characterized in that, The laser includes: The substrate is specifically a gallium arsenide substrate or a silicon substrate; A silicon dioxide thin film is coated on the substrate surface of the substrate, and the silicon dioxide thin film has openings, and gallium arsenide nanowires are vertically grown from the substrate through the openings, wherein the gallium arsenide nanowires are highly uniform gallium arsenide Fabry-Perot nanowire cavities, and multiple indium gallium arsenide quantum disks are embedded in the gallium arsenide nanowires. The gallium arsenide nanowire also includes a top mirror and a bottom mirror. The bottom mirror is the portion of the bottom of the gallium arsenide nanowire excluding the portion located inside the opening in the silicon dioxide film. The bottom mirror is gallium arsenide and is in contact with the silicon dioxide film. The top mirror is gallium arsenide and is in contact with air. The effective refractive index of the bottom mirror can be adjusted, specifically by adjusting the proportion of the bottom mirror to the bottom area of ​​the gallium arsenide nanowire; thereby selecting the lasing TE 01 model.

2. The nanowire vector beam laser as described in claim 1, characterized in that, The gallium arsenide nanowire is a hexagonal prism, the aperture diameter is 100 nm, the average diameter of the gallium arsenide nanowire is 300 nm, and the length is 2.3 μm.

3. The nanowire vector beam laser as described in claim 1, characterized in that, The indium gallium arsenide quantum disk is uniformly embedded in the gallium arsenide nanowire.

4. The nanowire vector beam laser as described in claim 1, characterized in that, The number of indium gallium arsenide quantum disks is ten.

5. The nanowire vector beam laser as described in claim 1, characterized in that, The ratio of arsenic:gallium:indium in the indium gallium arsenide quantum disk is 50.8:38.8:10.

4.

6. The nanowire vector beam laser as described in claim 1, characterized in that, The thickness of the indium gallium arsenide quantum disk is 15 nm.

7. A method for fabricating a nanowire vector beam laser, characterized in that, The method for preparing the nanowire vector beam laser as described in any one of claims 1-6 comprises: A 30 nm silicon dioxide thin film is deposited on the substrate surface of the substrate; After the array pattern is transferred to the silicon dioxide thin film by reactive ion etching, a first process is performed, which specifically involves removing the oxide layer, oxides, and adsorbed gases. The flow rates of trimethylgallium and triarsenide were set to 1.006 × mol / min and 1.998× mol / min Gallium arsenide nanowire pillars were grown at a growth temperature of 750℃ on the substrate after the first treatment for 20 minutes; then, indium gallium arsenide quantum disks were grown, with the trimethylindium flux set to 2.529 × 10⁻⁶. The growth rate was mol / min, with growth times of 30 seconds for the gallium arsenide barrier, 15 seconds for the indium gallium arsenide quantum disk, and a total of 10 cycles; finally, gallium arsenide was grown for 5 minutes to embed the indium gallium arsenide quantum disk in the gallium arsenide nanowire.

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