A metal quantum well based neuron-like optical switch

Abstract

This invention discloses a neuron-like optical switch based on a metal quantum well, comprising a substrate, and a dual-ring resonator and a metal quantum well located on the substrate. The dual-ring resonator includes a first straight waveguide, a first ring waveguide, a second straight waveguide, and a second ring waveguide. The first straight waveguide includes a first input terminal, and the second straight waveguide includes a second input terminal and an output terminal. The first straight waveguide is coupled to the first ring waveguide, and the first ring waveguide is coupled to the second ring waveguide. The metal quantum well is located between the second ring waveguide and the second straight waveguide. Incident light enters the first straight waveguide from the first input terminal, and after coupling, enters the first and second ring waveguides. Pump light enters the second straight waveguide from the second input terminal to irradiate the metal quantum well. By changing the intensity of the pump light, the refractive index of the metal quantum well is modulated, thereby modulating the intensity of the light output from the output terminal. This optical switch exhibits high optical modulation speed and modulation efficiency.

Description

Technical Field

[0001] This invention belongs to the field of micro-nano optoelectronics technology, specifically relating to a neuron-like optical switch based on a metal quantum well. Background Technology

[0002] With the rapid development of micro / nano on-chip integration technology and in-depth research in silicon photonics, photonic interconnects have the potential to become one of the development solutions to overcome electronic limitations. Optical modulators are an important research direction for short-distance optical interconnect devices. Among them, all-optical modulators, which use light to control light, have shown great potential in improving modulation speed and overcoming the inherent limitations of electronic devices.

[0003] In various applications of all-optical modulators, optical nonlinear neurons represent one of the cutting-edge areas of research in optical information processing. The function of an all-optical nonlinear neuron is to mimic the working mode of a biological synapse, achieving an all-optical input-output function with high modulation ratio and modulation speed. Research on optical neurons can fundamentally overcome the limitations of traditional computers in brain-like processing and will create more possibilities for neural network computing in the field of optics, greatly promoting the development of high-efficiency optical chips.

[0004] However, compared to existing electronic neural networks, the practical performance of current optical neural networks remains unsatisfactory. More specifically, stronger interactions require relatively large device size, and the lack of efficient nonlinear operations and slow response limit the performance of optical neurons, leading to model bias and the accumulation of computational errors in practice. Therefore, the current challenge is to achieve integrated, highly modulated, high-speed nonlinear optical neurons.

[0005] For efficient on-chip optical nonlinear neurons, the most commonly used nonlinear effects include saturable absorption, optical bistableness, and Kerr-type nonlinearity. Compared to saturable absorption and optical bistableness methods, Kerr-type nonlinearity offers faster response and simpler network structure design. However, common materials typically exhibit very weak nonlinearity. Therefore, to achieve efficient nonlinear neurons, it is necessary to design resonant structures or directly enhance the nonlinear response.

[0006] Patent application CN113391469A discloses an all-optical switch based on a linearly coupled dielectric-based metasurface. Its basic structure consists of a periodically arranged array of two-dimensional dielectric polymer metasurfaces on a substrate. When a signal electromagnetic wave (light) is incident alone, the light intensity transmitted through the sample is relatively high, and the optical switch is in a conducting state. When a control electromagnetic wave (light) is incident simultaneously, the light intensity transmitted through the sample is extremely low, and the optical switch switches from a conducting state to a blocking state, thus achieving an all-optical switch. By changing the structure of the polymer metasurface, the response wavelength of the target electromagnetic wave can be adjusted, and the adjustable range can cover the radio frequency to visible light band. This all-off switch has a low switching threshold and a high response speed. However, since this invention does not involve the optical nonlinearity of the material, the modulation efficiency is difficult to meet very high requirements. Summary of the Invention

[0007] This application provides a neuron-like optical switch based on a metal quantum well. This optical switch combines the field enhancement effect of a double-ring resonator with the high nonlinear effect of a metal quantum well (MQW), giving it high optical modulation speed and modulation efficiency.

[0008] This application provides a neuron-like optical switch based on a metal quantum well, comprising a substrate, and a double-ring resonator and a metal quantum well located on the substrate, wherein;

[0009] The dual-ring resonator includes a first straight waveguide, a first ring waveguide, a second straight waveguide, and a second ring waveguide. The first straight waveguide includes a first input terminal, and the second straight waveguide includes a second input terminal and an output terminal. The first straight waveguide is coupled to the first ring waveguide, and the first ring waveguide is coupled to the second ring waveguide.

[0010] The metal quantum well is located between the second ring waveguide and the second straight waveguide;

[0011] Incident light enters the first straight waveguide from the first input end, and after coupling, enters the first and second ring waveguides. Pump light enters the second straight waveguide from the second input end to irradiate the metal quantum well. By changing the intensity of the pump light, the refractive index of the metal quantum well is controlled, thereby modulating the intensity of the light output from the output end.

[0012] Furthermore, the intensity of the pump light is 0-123 GW / cm². 2 The transmittance of the incident light is 0.008-0.64.

[0013] Furthermore, the intensity of the pump light is 0-123 GW / cm². 2 The modulation depth of the optical switch is 3-18.78 dB.

[0014] Furthermore, the length of the metal quantum well is 600-2000 nm, and the wavelength of the pump light is 600-2000 nm; the length of the metal quantum well being an integer multiple of the pump light wavelength is intended to ensure that the pump light can exist stably in the metal quantum well, forming a resonant mode.

[0015] Furthermore, the center width of the metal quantum well is 35-45 nm, and the height is 360-380 nm. The center width of the metal quantum well is in the range of 35-45 nm to avoid excessive width leading to increased losses, and to avoid an excessively small width hindering the pump light from forming a stable resonant mode within the metal quantum well. The height of the metal quantum well, 360-380 nm, is intended to match the height of the double-ring resonator, avoiding mode mismatch and energy loss during light propagation within the metal quantum well.

[0016] Furthermore, the dimensions of the dual-ring resonator are as follows: the width of the first straight waveguide is 450-480nm and the height is 380-400nm; the width of the second straight waveguide is 460-480nm and the height is 380-400nm; the radius of the first ring waveguide is 2730-2740nm and the height is 370-390nm; the radius of the second ring waveguide is 2730-2740nm and the height is 370-390nm.

[0017] Furthermore, the minimum spacing between the second straight waveguide and the second ring waveguide is 35-45 nm. This minimum spacing is designed to be consistent with the center width of the metal quantum well, so as to avoid energy leakage caused by gaps between the metal quantum well and the second straight waveguide and the second ring waveguide.

[0018] Furthermore, the metal quantum well unit is constructed by alternating stacks of nanoscale-thick metal layers and insulating layers. The materials of the metal / insulator layers are metal / insulator nanomaterials compatible with micro / nano fabrication processes. The thickness ratio of the metal layer to the insulating layer is 3:7-1:1. This thickness ratio aims to change the refractive index of the metal quantum well under pump light intensity. When the thickness ratio is small, the refractive index change decreases, the modulation steepness decreases, but the modulation depth is large due to lower loss. When the thickness ratio is large, the refractive index change increases, the modulation steepness increases, but the modulation depth is small due to higher loss. Therefore, considering both the modulation steepness and modulation depth, a thickness ratio of 3:7-1:1 for the metal layer to the insulating layer can achieve better modulation performance.

[0019] Furthermore, the two sides of the metal quantum well that are parallel to the staggered stacking direction of the metal quantum well are respectively attached to the second micro-ring waveguide and the second straight waveguide.

[0020] Furthermore, the metal layer is a titanium nitride, gold, silver, aluminum, or indium tin oxide film, and the insulating layer is an aluminum oxide film or a silicon dioxide film.

[0021] Furthermore, the metal quantum well unit is formed by alternating stacks of several titanium nitride thin films with a thickness of 0.5-5.0 nm and aluminum oxide thin films with a thickness of ≥ single atomic layer - 50 nm.

[0022] Furthermore, the substrate is made of silicon dioxide or aluminum oxide.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] This invention places a metal quantum well between the second ring waveguide and the second straight waveguide of a dual-ring resonator. The metal quantum well is irradiated with pump light, and the refractive index of the metal quantum well is adjusted by regulating the intensity of the pump light, thereby enabling efficient modulation of the transmittance of the transmitted light output from the output end of the second straight waveguide.

[0025] The neuron-like optical switch based on a metal quantum well provided by this invention can achieve a high modulation depth, i.e., a high modulation steepness, by changing the light intensity of the pump light with relatively little change. Furthermore, by combining the field enhancement effect of the dual-ring resonator with the maximum Kerr nonlinearity of the metal quantum well, the extinction ratio of the optical switch based on the metal quantum well provided by this invention can reach 18.78 dB. That is, the ratio of the light intensity at the output terminal when the optical switch of the metal quantum well is in the off state to the light intensity at the output terminal when the optical switch of the metal quantum well is in the on state can reach 18.78 dB. The above two points demonstrate that the optical switch based on the metal quantum well provided by this invention has high sensitivity. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of a neuron-like optical switch based on a metal quantum well, provided as an embodiment of this application.

[0027] Figure 2 This is a schematic diagram of the structure of a metal quantum well provided in an embodiment of this application.

[0028] Figure 3 A schematic diagram of the structural parameters of a neuron-like optical switch based on a metal quantum well provided in an embodiment of this application.

[0029] Figure 4 The graph shows the refractive index variation of the neuron-like optical switch based on a metal quantum well provided in the embodiments of this application under different light intensities when irradiated onto the metal quantum well.

[0030] Figure 5 The resonance peak curves of the neuron-like optical switch based on a metal quantum well provided in the embodiments of this application under pump illumination and no pump illumination.

[0031] Figure 6 The modulation test diagram of the neuron-like optical switch based on a metal quantum well provided in the embodiments of this application, wherein, Figure 6 'a' represents the normalized energy flux distribution under no-pump light conditions. Figure 6 b represents the pump light at 123 GW / cm. 2 Lower normalized energy flow distribution diagram.

[0032] Figure 7 A schematic diagram illustrating the modulation performance of a neuron-like optical switch based on a metal quantum well, provided in an embodiment of this application, wherein... Figure 7 'a' represents the transmittance as the ratio of the titanium nitride layer to the total thickness of the titanium nitride and aluminum oxide layers increases from 0.1 to 0.6, and the pump light intensity increases from 0 to 123 GW / cm². 2 And the changing curve, Figure 7 b represents the transmittance derivative when the titanium nitride content is 0.4% (corresponding to the portion shown in the black dashed box on the right). The right side shows the transmittance and fitted curve when the titanium nitride content is 0.4%.

[0033] Among them, the substrate is 100, the double-ring resonator is 200, the first straight waveguide is 210, the first input terminal is 211, the first ring waveguide is 220, the second ring waveguide is 230, the second straight waveguide is 240, the second input terminal is 241, the output terminal is 242, and the metal quantum well is 300. Detailed Implementation

[0034] 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.

[0035] To achieve high-efficiency and high-speed modulation of the optical switch, this application introduces a metal quantum well into a dual-ring resonator. By adjusting the intensity of the pump light, the refractive index of the metal quantum well is controlled, thereby enabling rapid and efficient modulation of the transmitted light intensity. This achieves a high-efficiency and high-speed modulated optical switch. In a specific embodiment, this application provides a neuron-like optical switch based on a metal quantum well, such as... Figure 1 As shown, it includes a substrate 100, and a double-ring resonator 200 and a metal quantum well 300 located on the substrate 100, wherein:

[0036] The dual-ring resonator 200 provided in this application includes a first straight waveguide 210, a first ring waveguide 220, a second straight waveguide 240, and a second ring waveguide 230. The first straight waveguide 210 includes a first input terminal 211, and the second straight waveguide 240 includes a second input terminal 241 and an output terminal 242. The first straight waveguide 210 is coupled to the first ring waveguide 220, and the first ring waveguide 220 is coupled to the second ring waveguide 230.

[0037] The metal quantum well 300 provided in this application is located between the second ring waveguide 230 and the second straight waveguide 240, with one side of the metal quantum well 300 in close contact with the second ring waveguide 230 and the other side of the metal quantum well 300 in close contact with the second straight waveguide 240, so that the second ring waveguide 230 and the second straight waveguide 240 can be efficiently coupled with the metal quantum well 300, avoiding light leakage and loss in the air.

[0038] like Figure 2 As shown, the metal quantum well 300 provided in this application is composed of several layers of 2.4 nm thick titanium nitride (TiN) thin films and several layers of 0.5 nm thick aluminum oxide (Al2O3) thin films stacked alternately. This stacking method is along the z-direction, designed to minimize the change in the out-of-plane component of the refractive index (along the z-direction) under pump light intensity, while maximizing the change in the in-plane component (in the xy plane). Since the probe light signal propagates in the xy plane, the in-plane component of the refractive index plays a dominant role. Therefore, the metal quantum well stacked along the z-direction provides a significantly varying in-plane component of the refractive index, improving modulation efficiency. Consequently, the curved surface of the metal quantum well 300 along the x-direction is in close contact with the second ring waveguide 230, and the parallel surface of the metal quantum well 300 along the x-direction is in close contact with the second straight waveguide 240.

[0039] For conventional metal / insulator nanomaterials compatible with micro / nano fabrication processes, MQWs can be constructed when the thickness of the metal material is 5 nm or less.

[0040] like Figure 1 As shown in the embodiment of this application, the probe light is incident from the first input end 211 along the y-direction into the first straight waveguide 210, and after coupling, it enters the first ring waveguide 220 and the second ring waveguide 230. The pump light is incident from the second input end 241 along the y-direction into the second straight waveguide 240 to irradiate the metal quantum well 300. By changing the light intensity of the pump light, the refractive index of the metal quantum well 300 is controlled, thereby modulating the light intensity of the transmitted light emitted from the output end 242.

[0041] Example 1

[0042] like Figure 3As shown, the specific dimensions of the dual-ring resonator 200 provided in this application are as follows: the width W of the first straight waveguide 210 is... Si =470nm, height is H Si =380nm, the width W of the second straight waveguide is 240. Si =470nm, height is H Si =380nm, the radius R of the first ring waveguide 220 is 2720nm, return Figure 1 Height H Si =380nm, the radius of the second ring waveguide 230 is R = 2720nm, and the height is H. Si =380nm, and the spacing between the first straight waveguide 210 and the first ring waveguide 220 is 0, and the spacing between the first ring waveguide 220 and the second ring waveguide 230 is 0. By limiting the size of the first and second straight waveguides and the first and second ring waveguides, the light propagates in the fundamental mode during the propagation of the dual-ring resonator 200, avoiding the generation of multimode propagation and intermode dispersion, thus attenuating and losing energy diffusion.

[0043] like Figure 3 As shown, the specific dimensions of the metal quantum well 300 provided in this application are as follows: the length of the metal quantum well 300 is L. MQW =1997nm, with a center width of T MQW =40nm, height is 380nm.

[0044] The dual-ring resonator 200 provided in this application is made of silicon, the substrate is made of silicon dioxide, the metal layer of the metal quantum well unit is a titanium nitride layer, and the insulating layer is an aluminum oxide layer, with a thickness ratio of 2:3 between the titanium nitride layer and the aluminum oxide layer. If the metal layer thickness is relatively large, the light loss is greater, the transmittance is lower, and the extinction ratio is lower. If the metal layer thickness is relatively small, the sensitivity to refractive index changes is lower, which also affects the modulation efficiency. Figure 7 As shown in b, when the thickness ratio of the titanium nitride layer to the aluminum oxide layer is 2:3, it exhibits both high modulation steepness and large modulation depth. Figure 7 As shown in b, a modulation depth of 3dB can be achieved, which doubles the transmittance, requiring only a pump light intensity of 13GW / cm². 2 .

[0045] In this embodiment, the MQWs unit consists of multiple pairs of ultrathin TiN layers and Al2O3 layers. The MQWs, composed of alternating stacks of metal and insulating films, can first be grown on a substrate using magnetron sputtering. The TiN layers can be grown at a reaction growth temperature of 350°C and a nitrogen / argon volume ratio of 7:3. The Al2O3 layers are deposited by sputtering in the same chamber as the TiN layer, with the Al2O3 layer growth temperature set at 350°C. Under a chamber pressure of 5 mTorr and argon gas pressure of 5 sccm, the growth power is 150 W, and the growth rate is approximately 0.4 nm / min. The MQWs can then be obtained through photolithography or focused ion beam milling. The thickness of the MQWs can be reduced by sacrificing the extinction ratio to lower the difficulty of actual manufacturing.

[0046] Figure 4 This illustrates the change in the refractive index of a metal quantum well as the intensity of light incident on it, such as... Figure 4 As shown, the light intensity illuminating the metal quantum well increases to 150 GW / cm². 2 At this point, the imaginary part of the refractive index of the metal quantum well is significantly affected in its in-plane component, decreasing to a minimum. The refractive index drops from 4.5 to 0.099, thus minimizing the refractive index of the metal quantum well, corresponding to a pump light intensity of 123 GW / cm². 2 Due to the field-effect enhancement of the metal quantum well, the light intensity when irradiated by the metal quantum well increases to 150 GW / cm². 2 Because the intensity of the pump light is only 123 GW / cm². 2 When the refractive index of the metal quantum well is minimized, the neuron-like optical switch based on the metal quantum well provided in this application has a better modulation steepness.

[0047] like Figure 5 As shown, without pump light illumination, the high light loss of the metal quantum well prevents the second ring waveguide 230 from resonating, resulting in only one peak and low transmittance; when the pump intensity is 123 GW / cm², the second ring waveguide 230 fails to resonate. 2 Under pump light illumination, due to the slightly different resonant environments of the first ring waveguide 220 and the second ring waveguide 230, there are two resonance peaks. In this embodiment, the resonant peaks are taken at a wavelength of 1997 nm. The transmittance of the probe light can reach 0.64, and the Q value can reach 153.6. The high Q value of the dual-ring resonator enables the metal quantum well to have a field enhancement effect, which can further enhance the nonlinear effect of the metal quantum well and increase the refractive index change. Therefore, the field enhancement effect of the dual-ring resonator can further improve the transmittance of the probe light under high light intensity, and achieve a high modulation efficiency of the optical switch. n / / and k / / are the in-plane components of the real and imaginary parts of the refractive index, respectively, while n⊥ and k⊥ are the out-of-plane components of the real and imaginary parts of the refractive index.

[0048] like Figure 6 As shown in Figure a, under the illumination of no pump light, due to the high loss of light entering the second ring waveguide 230 by the metal quantum well, the second ring waveguide 230 cannot resonate. Therefore, the transmittance of the transmitted light emitted from the output port is extremely low, at 0.008, and the energy flux of the transmitted light is almost zero. The neuron-like optical switch based on the metal quantum well provided in this application is in the off state. Figure 6 As shown in b, when the pump light is 123 GW / cm 2 At that time, due to the huge nonlinear response of the metal quantum well and the enhancement effect of the double-ring resonator, the transmittance increases sharply to 0.64, the energy flow of the transmitted light output from the input end increases, and the neuron-like optical switch based on the metal quantum well provided in this application is in the on state.

[0049] Example 2

[0050] Unlike Example 1, the ratio of the titanium nitride layer to the total thickness of the titanium nitride and aluminum oxide layers in the metal quantum well is Ratio = 0.1, 0.2, 0.3, 0.4, 0.5, or 0.6. Figure 7 As shown in Figure a, when the ratio is relatively small (0.1-0.2), the proportion of titanium nitride is small, the refractive index change is small, and the modulation steepness is small, but the modulation depth is large due to the low loss. When the ratio is relatively large (0.3-0.6), the proportion of titanium nitride is large, the refractive index change is large, and the modulation steepness is large, but the modulation depth is small due to the large loss. Therefore, considering both the modulation steepness and modulation depth, a ratio of 0.3-0.5 can achieve better modulation performance. Figure 7 As shown in b, when Ratio = 0.4, the pump light intensity changes from 0 to 123 GW / cm². 2 The transmittance changed drastically from 0.008 to 0.64. The derivative of the transmittance was observed at a pump light intensity of 61 GW / cm². 2 At this point, the slope of the transmittance change reaches its peak; when the modulation depth decreases by 3dB, as shown in the figure, the transmittance increases from 0.215 to 0.43, requiring only a pump light intensity of 13GW / cm². 2 Extinction ratio (dB) = 10 * lg(ON transmittance / OFF transmittance) = 10 * lg(0.635 / 0.0084) = 18.78 dB.

[0051] 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. A neuron-like optical switch based on a metal quantum well, characterized in that, Includes a substrate, and a double-ring resonator and a metal quantum well located on the substrate, wherein; The dual-ring resonator includes a first straight waveguide, a first ring waveguide, a second straight waveguide, and a second ring waveguide. The first straight waveguide includes a first input terminal, and the second straight waveguide includes a second input terminal and an output terminal. The first straight waveguide is coupled to the first ring waveguide, and the first ring waveguide is coupled to the second ring waveguide. The metal quantum well is located between the second ring waveguide and the second straight waveguide. The metal quantum well unit is constructed by alternating stacking of metal layers and insulating layers with a thickness of nanometers. The two sides of the metal quantum well that are parallel to the alternating stacking direction of the metal quantum well are respectively attached to the second micro-ring waveguide and the second straight waveguide. Incident light enters the first straight waveguide from the first input end, and after coupling, enters the first and second ring waveguides. Pump light enters the second straight waveguide from the second input end to irradiate the metal quantum well. By changing the intensity of the pump light, the refractive index of the metal quantum well is controlled, thereby modulating the intensity of the light output from the output end.

2. The neuron-like optical switch based on a metal quantum well according to claim 1, characterized in that, The light intensity of the pump light is 0-123 GW / cm 2 The transmittance of the incident light is 0.008-0.

64.

3. The neuron-like optical switch based on a metal quantum well according to claim 2, characterized in that, The intensity of the pump light is 0-123 GW / cm. 2 The modulation depth of the optical switch is 3-18.78 dB.

4. The neuron-like optical switch based on a metal quantum well according to claim 1, characterized in that, The length of the metal quantum well is 600-2000 nm, and the wavelength of the pump light is 600-2000 nm.

5. The neuron-like optical switch based on a metal quantum well according to claim 1, characterized in that, The center width of the metal quantum well is 35-45 nm and the height is 360-380 nm.

6. The neuron-like optical switch based on a metal quantum well according to claim 1, characterized in that, The dimensions of the dual-ring resonator are as follows: the width of the first straight waveguide is 450-480 nm and the height is 380-400 nm; the width of the second straight waveguide is 460-480 nm and the height is 380-400 nm; the radius of the first ring waveguide is 2730-2740 nm and the height is 370-390 nm; the radius of the second ring waveguide is 2730-2740 nm and the height is 370-390 nm.

7. The neuron-like optical switch based on a metal quantum well according to claim 1, characterized in that, The minimum spacing between the second straight waveguide and the second ring waveguide is 35-45 nm.

8. The neuron-like optical switch based on a metal quantum well according to claim 1, characterized in that, The material of the metal layer / insulator layer is a metal / insulator nanomaterial compatible with micro-nano fabrication technology, wherein the thickness ratio of the metal layer to the insulation layer is 3:7-1:1.

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