An inelastic tunneling on-chip light source based on hyperbolic nanoantennas

Abstract

This invention discloses an inelastic tunneling on-chip light source based on a hyperbolic nanoantenna, comprising a hyperbolic nanoantenna, which includes two sub-nanoantennas: each sub-nanoantenna is a quasi-quadrangular prism structure with its upper and lower surfaces arranged at an angle; the sub-nanoantennas are constructed by alternating stacks of metal and dielectric layers; an air-insulating region is formed between the shortest vertical edges of the quasi-quadrangular prism structures corresponding to the two sub-nanoantennas, through which light waves are output, excited by inelastic tunneling; and a plasma-channel waveguide located at one end of the hyperbolic nanoantenna, used to receive the light waves output through the air-insulating region and transmit them in a predetermined direction. This on-chip light source exhibits both high optical modulation speed and high modulation efficiency, i.e., high external quantum efficiency.

Description

Technical Field

[0001] This invention belongs to the field of micro-nano optoelectronics technology, specifically relating to an inelastic tunneling on-chip light source based on a hyperbolic nanoantenna. Background Technology

[0002] When light waves (electromagnetic waves) are incident on the interface between a metal and a dielectric, the free electrons on the metal surface undergo collective oscillation. The electromagnetic waves couple with the free electrons on the metal surface to form a near-field electromagnetic wave that propagates along the metal surface. If the oscillation frequency of the electrons matches the frequency of the incident light wave, resonance will occur. In the resonant state, the energy of the electromagnetic field is effectively converted into the collective vibrational energy of the free electrons on the metal surface. This forms a special electromagnetic mode: the electromagnetic field is confined to a very small area on the metal surface and is enhanced. This phenomenon is called the surface plasmon resonance phenomenon.

[0003] With the development of surface plasmon research and the advancement of nanoscale microfabrication technology, on-chip plasmonic circuits provide an extremely effective strategy for miniaturized devices to achieve efficient integration while possessing a large information capacity.

[0004] Among various plasmon-based devices, electrically driven plasma sources have received widespread attention. As an on-chip light source, a plasma source modulates the input electrical signal onto an optical signal of the desired operating wavelength through electro-optic conversion.

[0005] Chinese patent CN115296138A discloses a silicon-based on-chip light source with an integrated end-face coupler. Its basic structure consists of an inverted-ridge waveguide silicon laser and an end-face coupler. This invention designs the inverted-ridge waveguide laser and the end-face coupler on the same substrate. The inverted-ridge waveguide laser is fabricated through selective epitaxy, providing a silicon-based on-chip light source scheme that can be coupled into a silicon waveguide. The emitting surface and the silicon waveguide are on the same plane, which is beneficial for improving the coupling efficiency of light from the laser to the silicon waveguide. However, since this invention still belongs to a traditional laser light source, the modulation rate is difficult to meet very high requirements.

[0006] However, as described in the aforementioned patent, currently widely used electronically driven plasma sources, such as nanoLEDs and nanolasers, have significant limitations in modulation speed, which also limits their application in information rates above GHz.

[0007] The inelastic tunneling mechanism of electrons offers the possibility of breaking through the operating frequency limitations of on-chip plasma light sources. Electrons undergo both elastic and inelastic tunneling when passing through tunneling junctions. Inelastic tunneling, as a photoelectric conversion pathway, can achieve direct electrical excitation of surface plasmons in a very short time. On-chip light sources utilizing the inelastic tunneling mechanism of electrons will possess advantages such as ultra-high photon modulation speed, large-scale integration capability, and potential tunability of operating wavelength.

[0008] However, the commonly used indicator for measuring the photoelectric conversion efficiency of a light source is its external quantum efficiency, and the external quantum efficiency of previous inelastic tunneling light sources is much lower than that of the aforementioned nano-LEDs and nano-lasers. Summary of the Invention

[0009] This invention provides an inelastic tunneling on-chip light source based on a hyperbolic nanoantenna. This on-chip light source has both high optical modulation speed and high modulation efficiency, i.e., high external quantum efficiency.

[0010] A specific embodiment of the present invention provides an inelastic tunneling on-chip light source based on a hyperbolic nanoantenna, comprising:

[0011] Hyperbolic nanoantenna, comprising two sub-nanoantennas:

[0012] The sub-nanoantenna is a quasi-quadrangular prism structure, with its upper and lower surfaces arranged at an angle. The sub-nanoantenna is composed of alternating stacked metal and dielectric layers. An air-insulating region is formed between the shortest vertical edges of the quasi-quadrangular prism structures corresponding to two sub-nanoantennas. Light waves are output through this air-insulating region, and these light waves are obtained through inelastic tunneling excitation.

[0013] A plasma channel waveguide, located at one end of a hyperbolic nanoantenna, is used to receive light waves output through an air-insulated region and transmit the light waves in a predetermined direction.

[0014] Furthermore, the inelastic tunneling on-chip light source based on the hyperbolic nanoantenna also includes a reflecting antenna located at the other end of the hyperbolic nanoantenna, which is used to reflect the light waves output through the air-insulated region to the plasma channel waveguide.

[0015] Furthermore, a base plane is provided on the quasi-quadrangular prism structure corresponding to the sub-nanoantenna. The base plane is perpendicular to the four vertical prisms. The angle between the upper surface of the quasi-quadrangular prism structure and the base plane is α, where 0 < α ≤ 10°. The angle between the lower surface of the quasi-quadrangular prism structure and the base plane is β, where 0 ≤ β ≤ 10°.

[0016] Furthermore, the length of the long diagonal of the upper surface of the quasi-prismatic structure is a2, where 120≤a2≤320nm; the edge intersecting the long diagonal on the upper surface is projected onto the base plane to form an included angle θ, where 40≤θ≤55°.

[0017] Furthermore, the length ratio of the longest vertical edge to the shortest vertical edge among the four vertical edges is 1-40.

[0018] This invention improves the internal quantum efficiency by rationally setting the size of the long diagonal of the upper surface of each sub-antenna and the size of the apex angle through which the long diagonal passes, so that the proportion of inelastic tunneling experienced by electrons through the hyperbolic nanoantenna is relatively high. This means that more energy is used for the conversion of electrons into photons, exciting more photons, and the photons can be coupled to the plasma channel waveguide with high efficiency, thereby achieving a high external quantum efficiency.

[0019] Furthermore, the operating wavelength of the light output by the hyperbolic nanoantenna is 900-1700 nm. By reasonably setting the size of the sub-nanoantenna, the peak of the local density of states and the peak of the radiation efficiency are made as close as possible within this wavelength range, thereby achieving a high external quantum efficiency. This allows for adjustment of any operating wavelength within the 900-1700 nm range, exhibiting strong tunability.

[0020] Furthermore, the thickness of the sub-nanoantenna is 1-40 nm.

[0021] Furthermore, the thickness ratio of the metal layer to the dielectric layer is 0.9-1.1.

[0022] More preferably, the metal layer is made of gold, silver, aluminum, titanium nitride (TiN), ITO, etc., and the dielectric layer is made of silicon, silicon dioxide (SiO2), aluminum oxide (Al2O3), silicon carbide (SiC), etc.

[0023] The sub-nano antenna is obtained by means of the following methods:

[0024] An initial sub-nanoantenna is obtained, which is formed by alternating stacking of metal layers and dielectric layers. The structure of the initial sub-nanoantenna is a quadrangular prism with both the upper and lower surfaces being rhomboid.

[0025] Define the long diagonal a2 of the upper surface and the long diagonal a3 of the lower surface of the sub-nanoant. Cut along the long diagonal a2 of the upper surface, or cut along the long diagonal a2 of the upper surface and the long diagonal a3 of the lower surface respectively, such that the ratio of the longest vertical edge d1 to the shortest vertical edge d2 of the resulting quadrangular prism is 1-40, thus obtaining the sub-nanoant.

[0026] Furthermore, the apex angle θ through which the long diagonal of the upper or lower surface of the initial sub-nanoantane passes is 40-55°.

[0027] Furthermore, the spacing between the two sub-nanoantennas is 1-10 nm. By setting a reasonable spacing, the two sub-nanoantennas can form a tunnel junction, thereby enabling the outward transmission of light waves excited by inelastic tunneling.

[0028] Furthermore, the plasma channel waveguide is a sandwich structure composed of a metal cladding layer and a silicon dioxide core layer. More preferably, the metal cladding layer is made of metallic materials such as gold, silver, aluminum, and titanium nitride (TiN) that can provide good reflectivity.

[0029] Furthermore, the distance between the plasma channel waveguide and the hyperbolic nanoantenna is 190-210 nm, the thickness of the plasma channel waveguide is 240-260 nm, the length is 1-10 μm, the plasma channel waveguide is etched with a channel, and the light wave output from the air-insulated region is guided through the channel to propagate in a set direction, and the width of the channel is 90-110 nm.

[0030] By setting reasonable dimensions for the plasma channel waveguide and the spacing between the plasma channel waveguide and the hyperbolic nanoantenna, the plasma channel waveguide can be better coupled with the hyperbolic nanoantenna, reducing the optical wave transmission loss to a maximum of no more than 2 dB / µm.

[0031] Furthermore, the distance between the reflecting antenna and the hyperbolic nanoantenna is 190-210 nm, the thickness of the reflecting antenna along the light wave propagation direction is 190-210 nm, and the length perpendicular to the light wave propagation direction is 390-410 nm.

[0032] Furthermore, the material of the reflective antenna is a metallic material such as gold, silver, aluminum, or titanium nitride (TiN) that can provide good reflective performance.

[0033] Furthermore, one end of the hyperbolic nanoantenna is connected to an electrical signal source, and the other end is grounded. The potential difference across the hyperbolic nanoantenna causes inelastic tunneling of the electrical signal at the antenna. Part of the energy is converted into photons, which are coupled into the channel waveguide as plasmons, or coupled into the channel waveguide after reflection by the reflecting antenna.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] This invention provides a quadrangular prism structure with an included angle between the upper and lower surfaces as the structure of each sub-nanoantenna, which enables a high rate of inelastic tunneling to generate a large number of plasmons when an electrical signal passes through the tunnel junction, thus achieving a high external quantum efficiency. Furthermore, since the process of inelastic tunneling to generate plasmons can reach the THz level, it is possible to convert ultra-high frequency electrical signals into modulated optical signals of a specified wavelength, thus achieving a high modulation speed. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the structure of an inelastic tunneling on-chip light source based on a hyperbolic nanoantenna provided in an embodiment of the present invention;

[0037] Figure 2 This is a schematic diagram of the hyperbolic nanoantenna provided in an embodiment of the present invention;

[0038] Figure 3 The graph shows the radiation efficiency and local state density of the hyperbolic nanoantenna provided in Embodiment 1 of the present invention as a function of wavelength.

[0039] Figure 4 This is a three-dimensional structural diagram of the inelastic tunneling on-chip light source based on a hyperbolic nanoantenna provided in Embodiment 1 of the present invention;

[0040] Figure 5 These are the local density of states versus wavelength diagrams provided in Embodiments 2, 3, and 4 of the present invention.

[0041] Among them, the plasma channel waveguide is 100, the hyperbolic nano-antenna is 200, and the reflective antenna is 300. Detailed Implementation

[0042] Exemplary embodiments of the present invention will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0043] In order to achieve optical signal modulation at ultra-high frequencies and energy conversion efficiency with application value, this application uses a hyperbolic nanoantenna as a plasmonic light source. By designing the nanoantenna, electrons have a considerable inelastic tunneling probability and radiation efficiency, thereby enabling the rapid and efficient modulation of optical signals by electrical signals.

[0044] According to one embodiment of the present invention, an inelastic tunneling on-chip light source based on a hyperbolic nanoantenna is provided. Figure 1This is a schematic diagram showing the structure of an inelastic tunneling on-chip light source based on a hyperbolic nanoantenna, as shown below. Figure 1 As shown, it includes a plasma channel waveguide 100, a hyperbolic nanoantenna 200, a reflective antenna 300, an electrical signal source, and a ground. The air-insulated region of the hyperbolic nanoantenna 200, the plasma channel waveguide 100, and the reflective antenna 300 are located on the same axis. The electrical signal source and the ground are respectively connected to the two ends of the hyperbolic nanoantenna 200 in the X direction.

[0045] The electrical signal output from the electrical signal source is input to the hyperbolic nanoantenna 200. Due to the potential difference between the two ends of the hyperbolic nanoantenna 200, electrons undergo inelastic tunneling at the antenna. Part of the energy of the electrical signal is converted into photons and coupled into the plasma channel waveguide 100 in the form of plasmons. At the same time, the light wave directed towards the reflecting antenna 300 is reflected and coupled into the plasma channel waveguide 100 through the reflecting antenna 300. As a result, the forward-reverse emission ratio of the on-chip light source, i.e., the hyperbolic nanoantenna 200, is greater than 7dB.

[0046] Figure 2 This is a structural diagram of the hyperbolic nanoantenna 200, as shown below. Figure 2 As shown, the hyperbolic nanoantenna 200 includes a first sub-nanoantenna and a second sub-nanoantenna. Both the first and second sub-nanoantennas are quasi-quadrangular prism structures. The upper and lower surfaces of the quasi-quadrangular prism structures are set at an angle. The sub-nanoantennas are composed of alternating stacked metal layers and dielectric layers. An air-insulating region is formed between the shortest vertical edges d2 of the quasi-quadrangular prism structures corresponding to the two sub-nanoantennas. The two sub-nanoantennas and the air-insulating region form a tunnel junction. When the electrical signal passes through the tunnel junction, a large proportion of inelastic tunneling occurs. The energy lost by the electrical signal is converted into light waves and output outward through the air-insulating region.

[0047] In one specific embodiment, such as Figure 2As shown, a base plane is set on the quadrangular prism-like structure corresponding to the sub-nanoantenna. This base plane is perpendicular to the four vertical prisms. The angle α between the upper surface of the quadrangular prism-like structure and the base plane is 0 < α ≤ 10°, and the angle β between the lower surface of the quadrangular prism-like structure and the base plane is 0 ≤ β ≤ 10°. The length of the long diagonal of the upper surface of the quadrangular prism-like structure is a2, where 120 ≤ a2 ≤ 320 nm. The edges intersecting the long diagonal of the upper surface are projected onto the base plane to form an angle θ, where 40 ≤ θ ≤ 55°. The four vertical prisms are perpendicular to the plane, and the ratio of the length of the longest vertical edge d1 to the shortest vertical edge d2 among the four vertical prisms is 1-40. By setting the parameters of the quadrangular prism-like structure described above, the operating wavelength of the light wave output by the hyperbolic nanoantenna can be obtained as 900-1700 nm. The peaks of local density of states and radiative efficiency both fall on specific wavelengths within the operating wavelength range, resulting in a higher proportion of inelastic tunneling in the tunnel junction. This allows for the excitation of more light waves, achieving a higher external quantum efficiency. Furthermore, the wide operating wavelength range provides high tunability.

[0048] In one specific embodiment, the sub-nanoantenna is obtained in the following manner:

[0049] An initial sub-nanoantenna is obtained, formed by alternating stacks of metal and dielectric layers. The initial sub-nanoantenna has a structure of a quadrangular prism with both its upper and lower surfaces being rhomboid. The vertex angle θ of the long diagonal of either the upper or lower surface of the initial sub-nanoantenna is 40-55°.

[0050] Define the long diagonal a2 of the upper surface and a3 of the lower surface of the sub-nanoant. Cut along the long diagonal a2 of the upper surface and the long diagonal a3 of the lower surface, respectively, such that the ratio of the longest vertical edge d1 to the shortest vertical edge d2 of the resulting quadrangular prism is 1-40. This yields the sub-nanoant, where both the upper and lower surfaces after cutting are made of dielectric and metallic materials, respectively. The length of the long diagonal of the cut upper surface is a2, where 120 ≤ a2 ≤ 320 nm.

[0051] In one specific embodiment, such as Figure 2 As shown, the spacing h between the two sub-nanoantennas provided in this embodiment is 1-10 nm. By setting a reasonable spacing, the two sub-nanoantennas can form a tunnel junction, thereby enabling the outward transmission of light waves excited by inelastic tunneling.

[0052] return Figure 1In one specific embodiment, the plasma channel waveguide 100 provided in this embodiment is a sandwich structure composed of a metal cladding layer and a silicon dioxide core layer. The metal cladding layer is made of metallic materials such as gold, silver, aluminum, and titanium nitride (TiN), which can provide good reflectivity. The thickness of the plasma channel waveguide is 240-260 nm, and the length is 1-10 μm. The plasma channel waveguide is etched with channels, through which light waves output from the air-insulated region are guided to propagate in a predetermined direction. The width of the channels is 90-110 nm. By setting reasonable dimensions for the plasma channel waveguide and the spacing between the plasma channel waveguide and the hyperbolic nanoantenna, the plasma channel waveguide can better couple with the hyperbolic nanoantenna, reducing the light wave transmission loss to a maximum of no more than 2 dB / μm.

[0053] return Figure 1 In one specific embodiment, the reflective antenna provided in this embodiment is located at the other end of the hyperbolic nanoantenna 200 in the z-direction, at a distance of 190-210 nm from the hyperbolic nanoantenna 200. The reflective antenna is made of metallic materials that can provide good reflectivity, such as gold, silver, aluminum, and titanium nitride (TiN). The thickness of the reflective antenna along the light wave propagation direction is 190-210 nm, and its length perpendicular to the light wave propagation direction is 390-410 nm. Using the reflective antenna, the forward-reverse emission ratio of the on-chip light source is greater than 7 dB.

[0054] Example 1

[0055] Figure 4 This shows a three-dimensional structural diagram of an inelastic tunneling on-chip light source based on a hyperbolic nanoantenna, such as... Figure 4 As shown, the specific dimensions of the inelastic tunneling on-sheet light source for the hyperbolic nanoantenna are provided, and the channel width d of the plasma channel waveguide 100 is shown. g =100nm, height c g =250nm, total width 2b g +d g =1300nm, the length a of the reflective antenna 300 along the channel direction r =200nm, width b r =400nm, height c r =150nm, the distance d from the far end of the reflector antenna 300 to the near end of the channel waveguide r =400nm. This series of dimensions has been optimized to maximize coupling efficiency. The figure shows three cross-sections within the waveguide and displays the normalized energy flux density at these cross-sections to illustrate its low propagation loss.

[0056] The sub-nanoant provided in this embodiment is composed of eight layers of alternating metal and dielectric layers, with a total thickness of 40 nm. The materials of the metal / dielectric layers are metal / dielectric nanomaterials compatible with micro / nano fabrication processes, wherein the thickness ratio of the metal layer to the dielectric layer is 1:1.

[0057] In this embodiment, the edges of the upper surfaces of the two sub-nanoantennas corresponding to the quasi-prismatic structure intersecting with the long diagonal are projected onto the base plane, forming an angle θ of 30°. The length of the long diagonal of the upper surface of the quasi-prismatic structure is a2 = 320 nm. The longest vertical edge of the quasi-prismatic structure is d1 = 40 nm, and the shortest vertical edge is d2 = 10 nm. Through the above-mentioned dimensional design, as... Figure 3 As shown, the radiation efficiency peak and local density of states peak of the hyperbolic nanoantenna 200 can simultaneously fall on the operating wavelength of 1550 nm. In this example, the external quantum efficiency of the device is 19%.

[0058] Example 2

[0059] Unlike Example 1, the angle formed by the projection of the edge where the upper surface of the prism-like structure intersects the long diagonal onto the base plane and the length of the long diagonal of the upper surface of the prism-like structure are changed, with three possible combinations of parameters, such as... Figure 5 The diagram shows the peak values ​​of the equivalent local density of states (IDS) for three sets of parameters (here, IDS is defined as the product of local density of states and radiative efficiency, a quantity that directly reflects the external quantum efficiency of the device). The first set: θ = 55°, a2 = 120 nm, with the peak value of IDS falling at an operating wavelength of 1300 nm. The second set: θ = 45°, a2 = 170 nm, with the peak value falling at an operating wavelength of 1550 nm. The third set: θ = 40°, a2 = 210 nm, with the peak value falling at an operating wavelength of 1700 nm. This means that by changing the feature size of the nanoantenna, the operating wavelength of the light source can be adjusted within the range of 900-1700 nm while maintaining high coupling efficiency. For the three sub-examples corresponding to the three parameter combinations, their external quantum efficiencies are 15%, 23%, and 24%, respectively.

[0060] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. An inelastic tunneling on-chip light source based on a hyperbolic nanoantenna, characterized in that, include: Hyperbolic nanoantenna, comprising two sub-nanoantennas: The sub-nanoant is a quasi-quadrangular prism structure, with the upper and lower surfaces of the quasi-quadrangular prism structure forming an angle. The sub-nanoant is composed of alternating stacked metal and dielectric layers. An air-insulating region is formed between the shortest vertical edges of the quasi-quadrangular prism structures corresponding to the two sub-nanoantennas. Light waves are output through the air-insulating region. The light waves are obtained by inelastic tunneling excitation. The shortest vertical edges of the quasi-quadrangular prism structures of the two sub-nanoantennas correspond to form a hyperbolic nanoantenna. And a plasma channel waveguide, located at one end of the hyperbolic nanoantenna, for receiving light waves output through the air-insulated region and propagating the light waves in a predetermined direction; The plasma channel waveguide is a sandwich structure consisting of a metal cladding and a silicon dioxide core layer, and the plasma channel waveguide is etched with channels.

2. The inelastic tunneling on-chip light source of the hyperbolic nanoantenna according to claim 1, characterized in that, A base plane is set on the quasi-quadrangular prism structure corresponding to the sub-nanoantenna. The base plane is perpendicular to the four vertical prisms. The angle between the upper surface of the quasi-quadrangular prism structure and the base plane is α, where 0 < α ≤ 10°. The angle between the lower surface of the quasi-quadrangular prism structure and the base plane is β, where 0 ≤ β ≤ 10°.

3. The inelastic tunneling on-chip light source of the hyperbolic nanoantenna according to claim 2, characterized in that, The length of the long diagonal of the upper surface of the quasi-prismatic structure is a2, where 120≤a2≤320nm; the edge of the upper surface that intersects the long diagonal is projected onto the base plane to form an angle θ, where 40≤θ≤55°.

4. The inelastic tunneling on-chip light source of the hyperbolic nanoantenna according to claim 1, characterized in that, The ratio of the length of the longest vertical edge to the length of the shortest vertical edge is 1-40.

5. The inelastic tunneling on-chip light source of the hyperbolic nanoantenna according to claim 1, characterized in that, The operating wavelength of the light waves output by the hyperbolic nanoantenna is 900-1700nm.

6. The inelastic tunneling on-chip light source of the hyperbolic nanoantenna according to claim 1, characterized in that, The two sub-nanoantennas are spaced 1-10 nm apart.

7. The inelastic tunneling on-chip light source of the hyperbolic nanoantenna according to claim 1, characterized in that, The distance between the plasma channel waveguide and the hyperbolic nanoantenna is 150-250 nm. The thickness of the plasma channel waveguide is 200-300 nm and the length is 1-10 μm. The plasma channel waveguide is etched with channels, through which the light waves output from the air-insulated region are guided to propagate in a set direction. The width of the channels is 50-150 nm.

8. The inelastic tunneling on-chip light source of the hyperbolic nanoantenna according to claim 1, characterized in that, It also includes a reflective antenna located at the other end of the hyperbolic nanoantenna, used to reflect light waves that have passed through the air-insulated region to the reflective antenna to the plasma channel waveguide.

9. The inelastic tunneling on-chip light source of the hyperbolic nanoantenna according to claim 8, characterized in that, The distance between the reflective antenna and the hyperbolic nanoantenna is 150-250 nm, the thickness of the reflective antenna along the direction of light wave propagation is 150-250 nm, and the length perpendicular to the direction of light wave propagation is 350-450 nm.

Images