Hybrid plasmonic hollow-core waveguide-based nanolaser and preparation method thereof

Abstract

The application discloses a kind of nanolaser based on hybrid plasmonic hollow core waveguide, including substrate, nanowire and dome;The substrate is provided with recess, the dome is elliptical dome, recess and elliptical dome constitute hollow core cavity, and the nanowire is arranged in the hollow core cavity.The application can improve the light field local ability of nanolaser, and reduce gain threshold.

Description

Technical Field

[0001] This invention relates to a nanolaser, belonging to the field of subwavelength lasers, and particularly to a nanolaser based on a hybrid plasmonic hollow waveguide and its fabrication method. Background Technology

[0002] Since its invention, the laser has become one of the core devices in modern science, technology, and industrial applications. However, traditional semiconductor lasers are limited by the optical diffraction limit, making it difficult to achieve nanoscale optical field confinement, which restricts the integration density and performance improvement of photonic devices. In recent years, plasmonic nanolasers have attracted widespread attention because they can compress the optical field to the subwavelength or even nanoscale. Surface plasmons can break the diffraction limit at the metal-dielectric interface, guiding and forming a local electromagnetic field, which provides a possibility for realizing ultra-miniature lasers.

[0003] However, traditional plasmonic waveguides often face an inherent contradiction between high transmission loss and low optical confinement, resulting in high laser gain thresholds and limited energy efficiency. Hybrid plasmonic waveguides, by combining the advantages of dielectric waveguides and plasmonic structures, localize energy to the vicinity of air and dielectric media. Maintaining a certain distance from the metal achieves lower propagation loss. In summary, hybrid plasmonic waveguides achieve nanoscale optical field confinement while maintaining low propagation loss, providing a new approach for the design of high-performance nanolasers.

[0004] Currently, various plasmonic waveguide structures have been proposed, such as wedge-shaped, ridge-shaped, grooved, and slotted waveguides, whose mode area can be compressed to a fraction of the total area. The order of magnitude. Nevertheless, how to further reduce the laser gain threshold while achieving deep subwavelength optical field localization remains a key challenge for on-chip integrated nanolasers. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a nanolaser based on a hybrid plasmonic hollow waveguide and its fabrication method, which can improve the optical field localization capability and reduce the gain threshold.

[0006] Technical solution: The present invention discloses a nanolaser based on a hybrid plasmonic hollow waveguide, comprising a substrate, nanowires, and a dome; the substrate is provided with a groove, the dome is an elliptical dome, the groove and the elliptical dome form a hollow cavity, and the nanowires are disposed in the hollow cavity.

[0007] Furthermore, the nanowires are gallium arsenide nanowires.

[0008] Furthermore, the substrate is a metal substrate.

[0009] Furthermore, the dome is an alkali metal dome.

[0010] Furthermore, the hollow cavity is made of a low-refractive-index medium.

[0011] Furthermore, it also includes a two-dimensional material layer disposed on the upper surface of the nanowire.

[0012] Furthermore, the two-dimensional material layer is made of single-layer graphene material.

[0013] Furthermore, the depth of the recess in the substrate, as well as the bulge width and height of the hollow cavity, are determined based on the radius of the nanowire.

[0014] Furthermore, the depth of the groove drilling The width of the bulge in the hollow cavity The height of the hollow cavity bulge ;

[0015] in, It is the radius of the nanowire. It is the distance between the nanowires and the highest point of the dome. It is the distance between the nanowire and the groove on its adjacent side.

[0016] The method for fabricating a nanolaser based on a hybrid plasmonic hollow waveguide according to the present invention is characterized by comprising the following steps: etching grooves on a substrate, placing nanowires in the grooves, and fabricating an elliptical dome above the substrate.

[0017] Beneficial effects: Compared with the prior art, the advantages of the present invention are: (1) The hybrid plasmonic hollow waveguide structure proposed in the present invention has a grooved metal substrate and a bent alkali metal dome forming a hollow cavity. The hexagonal gallium arsenide nanowire of two-dimensional material graphene is located in the center. The nanowire and the hollow cavity are combined to propose a hybrid plasmonic alkali metal hollow waveguide, which combines the advantages of dielectric waveguide and surface plasmon resonance, and effectively controls the balance between optical mode confinement, propagation loss and structural size. It has the advantages of supporting nanoscale optical mode confinement, maintaining low propagation loss, that is, compressing the mode area and having low propagation loss. Graphene has a strong mode field effect and field enhancement capability. By adding a single layer of graphene, the strong hybridization between the hollow plasmonic mode, the gallium arsenide nanowire mode and the graphene plasmonic mode makes energy localization in the nanogap possible.

[0018] (2) The present invention is based on a laser with a hybrid plasmonic hollow waveguide, which forms a strong confinement structure for the optical field in the x / y direction, realizes the unity of a very small mode area and a long transmission distance, significantly reduces the laser gain threshold and improves the Purcell factor, and obtains an on-chip nanolaser with an ultra-low gain threshold. Attached Figure Description

[0019] Figure 1This is a schematic diagram of the nanolaser structure in Embodiment 2 of the present invention.

[0020] Figure 2 This is a graph showing the trend of the real and imaginary parts of the effective refractive index of the nanolaser in Embodiment 2 of the present invention as a function of the structural parameter r.

[0021] Figure 3 This is a graph showing the trend of the electric field intensity of the laser changing with the y-axis inside the metal under different radii r in Embodiment 2 of the present invention.

[0022] Figure 4 This is a graph showing the variation of the electric field intensity of the laser with the x-axis under different radii r in Embodiment 2 of the present invention.

[0023] Figure 5 This is a schematic diagram of different electric field vectors at the hollow cavity in Embodiment 2 of the present invention.

[0024] Figure 6 This is a graph showing the trend of propagation distance and mode area as a function of r in Embodiment 2 of the present invention.

[0025] Figure 7 This is a graph showing the trend of the constraint factor as r changes in Embodiment 2 of the present invention.

[0026] Figure 8 This is a graph showing the trend of the gain threshold as r changes in Embodiment 2 of the present invention.

[0027] Figure 9 This is a graph showing the trend of the Purcell factor as a function of r in Embodiment 2 of the present invention. Detailed Implementation

[0028] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0029] Example 1

[0030] The nanolaser based on hybrid plasmon hollow waveguide of the present invention includes a substrate, nanowires and a dome; the substrate is provided with a groove, the dome is an elliptical dome, the groove and the elliptical dome form a hollow cavity, and the nanowires are disposed in the hollow cavity.

[0031] In this embodiment, the substrate is a metal substrate, such as gold or silver, preferably silver.

[0032] In this embodiment, the dome is an alkali metal dome, preferably sodium.

[0033] In this embodiment, the nanowire is gallium arsenide nanowire, which has a regular hexagonal structure.

[0034] In this embodiment, the hollow cavity uses a low refractive index medium, such as air or porous silica.

[0035] In this embodiment, a two-dimensional material, such as monolayer graphene, bandgap transition metal chalcogenides, or black phosphorus, is also disposed on the upper surface of the nanowire.

[0036] In this embodiment, the depth of the groove in the substrate, as well as the width and height of the hollow cavity bulge, are determined based on the radius of the nanowire.

[0037] In this embodiment, a metal layer is formed on a low refractive index dielectric substrate by magnetron sputtering.

[0038] In this embodiment, grooves are etched on a metal substrate using focused ion beam technology.

[0039] In this embodiment, a whole bonded by van der Waals forces is formed on gallium arsenide nanowires by peeling and transferring two-dimensional materials.

[0040] In this embodiment, gallium arsenide nanowires are transferred into a metal groove.

[0041] In this embodiment, by spin-coating a heated and molten liquid alkali metal material over a metal substrate, an alkali metal dome is formed at the metal groove due to the surface tension of the liquid.

[0042] Example 2

[0043] Reference Figure 1 In this embodiment of the nanolaser, the nanowires are made of GaAs, the noble metal substrate is made of metallic silver, the alkali metal dome is made of sodium, the internal hollow cavity is made of air or silicon with a refractive index close to that of air, and the two-dimensional material is graphene. Figure 1 The nanowires protrude from the hollow cavity for ease of demonstration. In the actual design, the nanowires and the outer shell are flush, meaning that the substrate, nanowires, dome, and two-dimensional material layer have the same length in the z-direction.

[0044] The radius of the nanowire is set as r. As r increases, the nanowire increases in size from the geometric center point outwards. The cross-sectional dimensions of the laser are 500 nm wide (x direction), 500 nm high (y direction), and 200 μm long (z direction). Designed for 5nm Designed for 40nm. Design parameters. , defined as half the height of the nanowire. The cavity bulge is related to r, and the bulge width... bulge height Drilling depth The inner diameter of the substrate is 3 μm (i.e., the length of the groove in the x direction).

[0045] As the nanowire radius r gradually increases from 70 nm, the nanowire modes are initially far from the alkali metal cavity, resulting in no mode overlap and a relatively stable normalized mode area and propagation length. However, after r = 100 nm, the metal dome in the x-direction approaches the nanowire, causing mode overlap. This leads to a rapid increase in mode localization and propagation distance. The mode energy is well localized at the two vertices of the nanowire. Since the localized region is not within the metal, losses are lower, achieving both ultra-high mode localization and a high propagation distance. Placing the graphene layer at the location of the strongest light field further enhances the interaction between the composite structure and light.

[0046] Figure 2 This is a graph showing the trend of the real and imaginary parts of the effective refractive index of a nanolaser as a function of the structural parameter r. It is the imaginary part of the effective refractive index. This represents the real part of the effective refractive index. As can be seen from the figure, the increase in the real part of the effective refractive index corresponds to the interaction between the graphene-loaded nanowire waveguide and the cavity waveguide, with energy distributed at the two vertices of the nanowire. The decrease in the imaginary part of the effective refractive index is because the graphene-loaded hybrid plasmon waveguide confines the energy to the lossless dielectric region, thereby reducing losses to extremely low levels.

[0047] Figure 3 and Figure 4 The figures show the electric field strength as a function of the x and y axes for different radii r, where |E|(au) is the electric field strength. It can be seen from the figures that in the x-direction, the energy distribution shifts from a uniform distribution in the top voids to becoming increasingly localized at the two vertices of the top nanowire. In the y-direction, the internal loss decays faster and faster, resulting in lower overall loss.

[0048] Figure 5 This is a schematic diagram of different electric field vectors at the hollow cavity, E x E y , |E| represent the x-component, y-component, and overall electric field strength, respectively. The figure shows how the energy is distributed near the top void, primarily at the two vertices of the nanowire.

[0049] Figures 6-9 The graphs show the trends of propagation distance, mode area, confinement factor, gain threshold, and Purcell factor as a function of r. Lm represents the propagation distance, and Aeff represents the mode area. Gth is the confinement factor, Fp is the gain threshold, and Gth is the Purcell factor. The graph shows that as the propagation distance increases, the mode area decreases rapidly, reaching a minimum. The confinement factor describes the distribution of laser energy on the gain material; as the confinement factor increases, the energy becomes increasingly localized on the GaAs gain material, improving the laser's lasing capability. Meanwhile, the gain threshold steadily decreases, eventually reaching a minimum of 0.0137. This means that our low-gain-threshold laser can achieve ultra-low-gain-threshold lasing.

[0050] The nanolaser of this invention achieves ultra-low gain threshold laser excitation through a graphene-loaded hybrid plasmon hollow waveguide. The effective refractive index of the nanolaser varies with the radius r of the hexagonal nanowire, where r ranges from 80 nm to 121.4 nm. Further optimization of parameters, such as decreasing mode area and gain threshold as r increases, results in better laser performance. In this embodiment, r = 121.4 nm, and the normalized mode area is... The propagation distance reached 98.6 μm. Simultaneously, due to the strong mode area and low propagation loss, a low gain threshold laser was achieved, with a gain threshold of 0.0137. The laser input light is incident perpendicularly to this cross-section, exciting hybrid surface plasmons near the apex of the gallium arsenide nanowire and the alkali metal dome. The graphene layer enhances the light-matter interaction. With r = 110 nm, g1 = 5 nm, and g2 = 40 nm, the normalized mode area is... The propagation distance is 12.9 μm, and the laser gain threshold is 0.04. .

[0051] At a wavelength of 1550 nm, the hybrid plasmon modes are tightly confined within the gap between the nanowire and the bent alkali metal dome, enabling the structure to achieve wavelengths as low as [insert wavelength here]. The mode area and material gain threshold decreased to 0.0137. Purcell factor is as high as .

[0052] Gain threshold G th This is the minimum gain achieved by a nanolaser, and its formula is:

[0053]

[0054] Where R is the reflectance, R=(n eff -1) / (n eff +1). When the wavelength is 1550nm, n wire =3.5 (gallium arsenide), L=90μm. It is a limiting factor. .

[0055] The Purcell factor consists of three parts, Fp = F SP +F R +F LSW Among them, plasmon modes Radiation mode F R =1, lossy surface wave mode F LSW :

[0056]

[0057] It is a metallic dielectric. It is an air dielectric. It is the refractive index of air. It is a band gap.

[0058] This invention integrates a finite-length graphene layer into a hollow waveguide composed of a grooved metal substrate and a curved metal dome, and embeds gallium arsenide nanowires as the gain medium, achieving strong coupling and hybridization between the hollow plasmonic mode, the nanowire waveguide mode, and the graphene plasmonic mode. This invention utilizes the excellent optoelectronic properties of graphene, including high carrier mobility, a unique band structure, and good conductivity, as an important method to improve mode localization capabilities. It offers advantages such as a wide operating bandwidth (from visible to infrared light), low insertion loss, and strong high-density integration capability. This laser is an integrated low-gain-threshold laser based on a graphene-loaded hybrid plasmonic hollow waveguide. The plasmonic waveguide can provide a smaller mode area and stronger local field enhancement. Simultaneously, the overlap of plasmonic and nanowire modes significantly enhances the optical field localization capability while achieving low propagation loss. The introduction of graphene enhances the interaction between light and the medium, ultimately realizing an ultra-low gain-threshold laser.

[0059] Example 3

[0060] This embodiment presents a method for fabricating a nanolaser based on a hybrid plasmonic hollow waveguide, which includes the following steps:

[0061] A metal layer is magnetron sputtered on a low refractive index dielectric substrate, and grooves are etched on the metal substrate using focused ion beam technology.

[0062] After a two-dimensional material layer is transferred by peeling and transferring on a high-refractive-index nanowire, a whole is formed by van der Waals forces and then transferred as a whole into a metal groove.

[0063] Finally, a heated and molten liquid alkali metal material is spin-coated onto the metal substrate. Due to the surface tension of the liquid, bulges will form at the metal grooves, and an alloy will be formed at the contact points.

[0064] In this embodiment, a silver substrate layer is formed on a silicon substrate by magnetron sputtering.

[0065] In this embodiment, silver grooves are etched on a silver substrate using focused ion beam technology.

[0066] In this embodiment, a monolayer of graphene is transferred and peeled off from gallium arsenide nanowires to form a whole bonded by van der Waals forces.

[0067] In this embodiment, gallium arsenide nanowires are transferred into silver grooves.

[0068] In this embodiment, by spin-coating heated and molten liquid sodium metal material over a silver substrate, a sodium metal dome is formed at the silver groove due to the surface tension of the liquid.

Claims

1. A nanolaser based on a hybrid plasmonic hollow waveguide, characterized in that, It includes a substrate, nanowires, and a dome; the substrate is provided with a groove, the dome is an elliptical dome, the groove and the elliptical dome form a hollow cavity, and the nanowires are disposed in the hollow cavity.

2. The nanolaser based on a hybrid plasmonic hollow waveguide according to claim 1, characterized in that, The nanowires are gallium arsenide nanowires.

3. The nanolaser based on a hybrid plasmonic hollow waveguide according to claim 1, characterized in that, The substrate is a metal substrate.

4. The nanolaser based on a hybrid plasmonic hollow waveguide according to claim 1, characterized in that, The dome is an alkali metal dome.

5. The nanolaser based on a hybrid plasmonic hollow waveguide according to claim 1, characterized in that, The hollow cavity uses a low-refractive-index medium.

6. The nanolaser based on a hybrid plasmonic hollow waveguide according to claim 1, characterized in that, It also includes a two-dimensional material layer disposed on the upper surface of the nanowire.

7. The nanolaser based on a hybrid plasmonic hollow waveguide according to claim 6, characterized in that, The two-dimensional material layer is made of single-layer graphene material.

8. The nanolaser based on a hybrid plasmonic hollow waveguide according to claim 1, characterized in that, The depth of the recess in the substrate, as well as the width and height of the hollow cavity, are determined based on the radius of the nanowire.

9. The nanolaser based on a hybrid plasmonic hollow waveguide according to claim 8, characterized in that, Groove depth The width of the bulge in the hollow cavity The height of the hollow cavity bulge ; in, It is the radius of the nanowire. It is the distance between the nanowires and the highest point of the dome. It is the distance between the nanowire and the groove on its adjacent side.

10. A method for fabricating a nanolaser based on a hybrid plasmonic hollow waveguide as described in any one of claims 1-9, characterized in that, Includes the following steps: Grooves are etched on a substrate, nanowires are placed within the grooves, and an elliptical dome is fabricated above the substrate.

Images