Micro-ring modulator and method of fabrication

Abstract

The application discloses a kind of micro-ring modulators and preparation method.The micro-ring modulator includes: at least one straight waveguide and at least one surface plasmon micro-ring resonator with the coupling relationship of straight waveguide each other;Straight waveguide is used to transmit optical signal;Surface plasmon micro-ring resonator is used to modulate the intensity of optical signal corresponding to the wavelength of surface plasmon micro-ring resonator.The technical scheme of the application can realize a kind of modulator with small loss to optical signal and small device size.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of communication technology, and in particular to a microring modulator and a preparation method. BACKGROUND

[0002] With the increasingly mature optical interconnection technology between cabinets, boards and modules, people have gradually shifted their research focus to optical interconnection within chips. Due to the low optical loss characteristics of silicon in the near-infrared band, silicon-on-insulator is the most important platform for on-chip photonics in the current industry, which is not only compatible with CMOS technology, but also facilitates the fabrication of high refractive index waveguides and various active (mainly lasers, modulators and detectors) and passive (couplers, polarization beam splitters, wavelength division multiplexing / demultiplexing, multimode interferometers, etc.) photonic devices.

[0003] As an active core device of optical interconnection on chip, the modulator needs to achieve a large modulation depth on the optical signal under the action of the electrical signal on the premise of meeting the low insertion loss and high modulation bandwidth. However, the size of the existing silicon microring modulator is about 10 microns, which cannot further reduce the device size.

[0004] Therefore, there is an urgent need for a modulator with small device size and small loss to the optical signal. SUMMARY

[0005] The main purpose of the embodiment of the present application is to provide a microring modulator and a preparation method, aiming to realize a modulator with small device size and small loss to the optical signal.

[0006] To achieve the above purpose, the embodiment of the present application provides a microring modulator, comprising:

[0007] At least one straight waveguide and at least one surface plasmon microring resonator in a coupling relationship with the straight waveguide;

[0008] The straight waveguide is used for transmitting an optical signal;

[0009] The surface plasmon microring resonator is used for modulating the intensity of the optical signal corresponding to the wavelength of the surface plasmon microring resonator.

[0010] To achieve the above purpose, the embodiment of the present application further provides a preparation method of a microring modulator, comprising the following steps:

[0011] Preparation of at least one straight waveguide, the straight waveguide is used for transmitting an optical signal;

[0012] At least one surface plasmon resonance (SPR) microring resonator coupled to the straight waveguide is fabricated. The SPR is used to modulate the intensity of an optical signal with a wavelength corresponding to the SPR.

[0013] The microring modulator and its fabrication method proposed in this invention include a straight waveguide and a surface plasmon resonance microring resonator coupled to the straight waveguide. The straight waveguide is used to propagate the optical signal, and the surface plasmon resonance microring resonator is used to modulate the intensity of the optical signal corresponding to the wavelength of the surface plasmon resonance microring resonator. In this invention, the straight waveguide significantly reduces the transmission loss of the optical signal compared to the surface plasmon resonance device. Compared to the silicon microring modulator, the surface plasmon resonance microring resonator can confine the optical signal to a smaller scale for propagation, thereby reducing the size of the microring resonator. Attached Figure Description

[0014] Figure 1 This is a top view of a micro-ring modulator provided in an embodiment of the present invention;

[0015] Figure 2 This is a top view of another micro-ring modulator provided in an embodiment of the present invention;

[0016] Figure 3 This is a schematic diagram illustrating the principle of optical signal transmission and modulation using a micro-ring modulator provided in an embodiment of the present invention;

[0017] Figure 4 This is a schematic diagram of a straight waveguide structure provided in an embodiment of the present invention;

[0018] Figure 5 This is a top view of a micro-ring modulator provided in an embodiment of the present invention;

[0019] Figure 6 yes Figure 5 Cross-sectional view along the A-A' direction;

[0020] Figure 7 This is a top view of another micro-ring modulator provided in an embodiment of the present invention;

[0021] Figure 8 yes Figure 7 Cross-sectional view along the B-B' direction;

[0022] Figure 9 This is a top view of another micro-ring modulator provided in an embodiment of the present invention;

[0023] Figure 10 This is a flowchart of a method for fabricating a microring modulator according to an embodiment of the present invention;

[0024] Figure 11This is a flowchart of a method for fabricating a straight waveguide according to an embodiment of the present invention;

[0025] Figure 12 This is a flowchart illustrating a method for fabricating a surface plasmon resonance microring resonator according to an embodiment of the present invention;

[0026] Figure 13 This is a flowchart of another method for fabricating a surface plasmon microring resonator provided in an embodiment of the present invention;

[0027] Figures 14-19 This is a schematic diagram of the structure corresponding to each step of the fabrication method of a micro-ring modulator provided in an embodiment of the present invention;

[0028] Figure 20 This is a schematic diagram of the structure corresponding to each step of the fabrication method of a straight waveguide provided in an embodiment of the present invention;

[0029] Figure 21 This is a schematic diagram of the structure corresponding to each step of the method for fabricating a surface plasmon microring resonator provided in an embodiment of the present invention;

[0030] Figure 22 This is a schematic diagram of the structure corresponding to each step of another method for fabricating a surface plasmon microring resonator provided in this embodiment of the invention. Detailed Implementation

[0031] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0032] In the following description, the use of suffixes such as "module," "part," or "unit" to denote elements is solely for the purpose of illustrative purposes and has no inherent meaning. Therefore, "module," "part," or "unit" may be used interchangeably.

[0033] As mentioned in the background section, existing silicon microring modulators are around 10 micrometers in size, making further reduction in device size impossible. This is because existing silicon-based optical modulators are limited by the weak plasmon dispersion effect of silicon, making it difficult to achieve large modulation depths at smaller scales. Surface plasmon polariton (SPP) photonics reveals the potential of metallic nanostructures to address the scale mismatch between diffraction-limited dielectric optical systems and nanoscale on-chip electronic components. SPP modulators can achieve large optical modulation amplitudes at a size of only a few micrometers. However, due to the inherent free carrier absorption in the active layer that generates the SPP, these modulators generally exhibit high on-chip losses. Therefore, there is an urgent need for a modulator with low optical signal loss and small device size.

[0034] To address the aforementioned technical problems, this application provides a micro-ring modulator that reduces device size while ensuring low modulation loss of optical signals.

[0035] Figure 1 This is a schematic diagram of a micro-ring modulator provided in an embodiment of the present invention. Figure 2 This is a schematic diagram of another micro-ring modulator provided in an embodiment of the present invention. Figure 1 and Figure 2 As shown, the microring modulator includes: at least one straight waveguide 10 and at least one surface plasmon resonance microring resonator 20 coupled to the straight waveguide; the straight waveguide 10 is used to transmit optical signals; the surface plasmon resonance microring resonator 20 is used to modulate the intensity of the optical signal corresponding to the wavelength of the surface plasmon resonance microring resonator 20.

[0036] It should be noted that, Figure 1 and Figure 2 The example shown is merely a schematic diagram of a microring modulator formed by coupling a surface plasmon resonance microring resonator 20 and a straight waveguide 10. Figure 1 As shown, the surface plasmon resonator 20 is located at a predetermined distance above the straight waveguide 10, and the surface plasmon resonator 20 and the straight waveguide 10 are perpendicularly coupled to each other. Figure 2 The surface plasmon microring resonator 20 and the straight waveguide 10 are located on the same plane and are separated by a preset distance. The surface plasmon microring resonator 20 and the straight waveguide 10 are horizontally coupled to each other.

[0037] Figure 3 This is a schematic diagram illustrating the principle of optical signal transmission and modulation using a micro-ring modulator, as provided in an embodiment of the present invention. Figure 3 An exemplary schematic diagram of the optical signal transmission and modulation principle of the simplest micro-ring modulator is shown. Figure 3 The illustrated microring modulator is composed of a single surface plasmon resonance microring resonator 20 coupled to a straight waveguide 10. The embodiments of the present invention do not limit the number of plasmon resonance microring resonators 20 and straight waveguides 10; those skilled in the art can set them according to actual needs. It should be noted that the embodiments of the present invention use one straight waveguide 10 and one surface plasmon resonance microring resonator 20 as examples for illustration. For example, see [link to example description]. Figure 3An optical signal with a wavelength corresponding to the surface plasmon resonance (SPR) microring resonator 20 is input from the input terminal 10A of the straight waveguide 10. After passing through the SPR 20, it is output from the output terminal 10B of the straight waveguide 10 after one revolution. Since the SPR 20 and the straight waveguide 10 are coupled (either horizontally or vertically), the optical signal with a wavelength corresponding to the SPR 20 is in a resonant state during transmission. The SPR 20 can modulate the intensity of the optical signal with the corresponding wavelength. The wavelength corresponding to the SPR 20 is related to the size of the SPR 20. The difference between the length of one revolution of the optical signal in the surface plasmon resonator 20 and the length of the surface plasmon resonator 20 in the coupling region 30 is an integer multiple of the wavelength corresponding to the surface plasmon resonator.

[0038] For example, straight waveguide 10 is a silicon-on-insulator (SOI) photonic straight waveguide, using silicon as the waveguide layer and silicon dioxide as the cladding. Due to the large refractive index difference between silicon and silicon dioxide (approximately 2), optical signals can be transmitted within the silicon without entering the low-refractive-index silicon dioxide dielectric layer. Furthermore, due to silicon's low optical loss characteristics in the near-infrared band, SOI is currently the most important on-chip photonics platform in the industry. This reduces losses during optical signal transmission and ensures compatibility with CMOS processes, lowering device costs and enabling optoelectronic integrated circuits.

[0039] Surface plasmon polariton (SPP) photonics reveals the potential of metallic nanostructures to address the scale mismatch between diffraction-limited dielectric optical systems and nanoscale on-chip electronic components. SPP modulators can achieve large optical modulation amplitudes at a size of only a few micrometers. Specifically, a SPP microring resonator 20 typically includes an active layer and a dielectric layer. Under the influence of an electrical signal, surface plasmons exist at the interface between the active and dielectric layers. The relative permittivity of the active layer approaches zero, resulting in near-zero impedance for the optical signal and an infinitesimally small phase change. This allows for directional emission of the optical signal and confinement to a small scale. Specifically, while existing silicon microring modulators are around 10 micrometers in size, the SPP microring resonator 20 reduces the microring size to around 1 micrometer. Therefore, when the optical signal is in a resonant state, it can propagate at the interface between the active and dielectric layers, with the surface plasmons as the propagation medium. Furthermore, the active layer exhibits good ion dispersion, meaning that the surface plasmon resonance (SPR) microring resonator 20 can generate charge carriers under the influence of an electrical signal, thereby altering the effective refractive index at the interface between the active layer and the dielectric layer to modulate the intensity of the optical signal. In addition, compared to non-microring SPR, the SPR can function as an optical switch, eliminating the signal loss caused by the SPR in a non-resonant state.

[0040] The technical solution in this embodiment of the invention includes a straight waveguide 10 and a surface plasmon resonance (SPR) microring resonator 20 coupled to the straight waveguide. The straight waveguide 10 is used to propagate the optical signal, and the SPR 20 is used to modulate the intensity of the optical signal at a wavelength corresponding to the SPR 20. Compared to SPR devices, the straight waveguide 10 significantly reduces the transmission loss of the optical signal. Compared to silicon microring modulators, the SPR 20 can confine the optical signal to a smaller scale for propagation, reducing the size of the microring resonator. It should be noted that, compared to silicon-based resonators, the technical solution in this embodiment of the invention, while reducing the device size and slightly reducing losses, increases the modulation bandwidth of the microring modulator. Therefore, the above technical solution achieves a modulator with low optical signal loss, high modulation bandwidth, and small device size.

[0041] In the above technical solution, the straight waveguide 10, compared with the surface plasmon resonance device, greatly reduces the optical signal transmission loss. The specific structure of the straight waveguide 10 is described in detail below.

[0042] Figure 4 This is a schematic diagram of a straight waveguide provided in an embodiment of the present invention. See also... Figure 4The straight waveguide includes: a substrate 101; a lower cladding 102 located on the surface of the substrate 101; a first waveguide layer 103 located on the surface of the lower cladding 102 away from the substrate 101, wherein the first waveguide layer 103 includes a first planar waveguide 1031 and a ridge waveguide 1032 located on the surface of the first planar waveguide 1031; and an upper cladding 104 located on the surface of the first waveguide layer 103 away from the lower cladding 102, wherein the surface of the upper cladding 104 away from the first waveguide layer 103 is planar.

[0043] For example, substrate 101 can be made of silicon. Lower cladding 102 can be made of silicon dioxide, first waveguide layer 103 can be made of silicon, and upper cladding 104 can be made of silicon dioxide. Lower cladding 102 and first waveguide layer 103, as well as first waveguide layer 103 and upper cladding 104, respectively constitute silicon-on-insulator structures. Such structures have significant performance advantages, mainly reflected in the following points: (1) In the band of light wavelength greater than 1.12 micrometers, the intrinsic absorption loss of silicon is extremely small, and it is almost transparent and lossless in the 1550 nanometer communication band. (2) The refractive index of the materials of first waveguide layer 103 and lower cladding layer 102 or upper cladding 104 differs greatly, about 2. The high refractive index difference enhances its ability to confine the light field. (3) The fabrication process of silicon-based photonic devices is fully compatible with the mature CMOS process in the microelectronics field, greatly reducing device support and providing the possibility of realizing optoelectronic integrated circuits.

[0044] In the above technical solution, the surface plasmon resonance microring resonator 20 and the straight waveguide 10 are coupled to each other and are used to modulate the intensity of the optical signal corresponding to the wavelength of the surface plasmon resonance microring resonator. The following section will use... Figure 4 Taking the straight waveguide 10 as an example, the specific structure of the surface plasmon resonator 20 when the surface plasmon resonator 20 and the straight waveguide 10 are perpendicularly coupled is explained.

[0045] Figure 5 This is a top view of a micro-ring modulator provided in an embodiment of the present invention. Figure 6 for Figure 5 A cross-sectional view along the A-A' direction. (See image.) Figure 5 and Figure 6As shown, the microring modulator includes a surface plasmon resonator 20 comprising: a grooved conductive microring 201, a first dielectric layer 202, and a first surface plasmon active layer 203; the grooved conductive microring 201 includes a conductive inner ring 201A, an annular groove 201B, and a conductive outer ring 201C arranged sequentially from the inside to the outside; the first dielectric layer 202 is located on the surface of the conductive inner ring 201A, the sidewalls and bottom surface of the annular groove 201B, and the surface of the conductive outer ring 201C. The conductive inner ring 201A and the conductive outer ring 201C are connected to the first electrical signal through the conductive via 20A passing through the first dielectric layer 202; the first surface plasmon active layer 203 is located on the surface of the first dielectric layer 202 away from the annular groove 201B within the annular groove 201B. The first surface plasmon active layer 203 is used to connect the second electrical signal, and the contact surface between the first surface plasmon active layer 203 and the first dielectric layer 202 is used to generate surface plasmons for modulating optical signals.

[0046] Specifically, the conductive microring 201 can be a metal microring, and the metal can be one or more of gold, silver, and copper. Among them, gold has the most stable chemical properties, silver has the lowest surface plasmon loss, and copper is compatible with CMOS processes. This invention does not limit the choice of materials and can select them according to actual application requirements.

[0047] The first dielectric layer 202 can be, for example, silicon dioxide or hafnium dioxide (HFO2). The thickness of the first dielectric layer 202 can be greater than or equal to 5 nanometers and less than or equal to 15 nanometers. This range ensures that the surface plasmon resonance microring resonator 20 has sufficient modulation bandwidth while also taking into account the modulation efficiency of the surface plasmon resonance microring resonator 20.

[0048] The first surface plasmon active layer 203 can generate plasmons under the influence of an electrical signal, exemplarily a material with a near-zero dielectric constant. Near-zero dielectric materials (ENZ) refer to a class of metamaterials whose relative dielectric constant approaches zero. With a relative dielectric constant approaching zero, the impedance to the optical signal is close to zero, and the phase change is infinitesimally small, allowing for directional emission of the optical signal and confinement to a smaller scale. Therefore, when the optical signal is in a resonant state, it can propagate at the interface between the first surface plasmon active layer 203 and the first dielectric layer 202, with the surface plasmons being the propagation medium. Furthermore, the first surface plasmon active layer 203 exhibits good ion dispersion, meaning that under the influence of an electrical signal, the first surface plasmon active layer 203 can generate charge carriers, thereby altering the effective refractive index at the interface between the first surface plasmon active layer 203 and the first dielectric layer 202 to modulate the intensity of the optical signal. Transparent conductive oxide (TCO) films are commonly used near-zero dielectric materials. These films possess common optoelectronic properties such as wide bandgap, high transmittance in the visible spectrum, and low resistivity. Examples of TCO films include indium tin oxide (ITO), aluminum-doped zinc oxide (AZO), and cadmium oxide (CdO).

[0049] Optionally, see Figure 6 The surface plasmon resonance microring resonator 20 also includes multiple pads 20B. Each conductive via 20A corresponds to one pad 20B. The first surface plasmon active layer 203 is also provided with pads 20B. The conductive via 20A and the first surface plasmon active layer 203 obtain corresponding electrical signals through the pads 20B. It should be noted that... Figure 5 The conductive via 20A and pad 20B are not shown in the diagram.

[0050] Optionally, the first electrical signal connected to the conductive inner ring 201A and the conductive outer ring 201C through the conductive via 20A passing through the first dielectric layer 202 can be a positive power supply signal, and the second electrical signal connected to the first surface plasmon active layer 203 can be a negative power supply signal. By controlling the difference between the first electrical signal and the second electrical signal, the concentration of charge carriers in the first surface plasmon active layer 203 can be changed, thereby changing the effective refractive index at the interface between the first surface plasmon active layer 203 and the first dielectric layer 202, so as to achieve intensity modulation of the optical signal.

[0051] In the above technical solution, the surface plasmon resonance microring resonator 20 and the straight waveguide 10 are coupled to each other and are used to modulate the intensity of the optical signal corresponding to the wavelength of the surface plasmon resonance microring resonator 20. The following section will use...Figure 4 Taking the straight waveguide 10 as an example, the specific structure of the surface plasmon resonator 20 when the surface plasmon resonator 20 and the straight waveguide 10 are horizontally coupled is illustrated.

[0052] Figure 7 This is a top view of another micro-ring modulator provided in an embodiment of the present invention. Figure 8 for Figure 7 A cross-sectional view along the B-B' direction. (See attached image.) Figure 7 and Figure 8 As shown, the microring modulator includes a surface plasmon resonator 20 comprising: a second waveguide layer 210, a second dielectric layer 211, and a second surface plasmon active layer 212; the second waveguide layer 210 includes a second horizontal waveguide 210A and a microring waveguide 210B located on the surface of the second horizontal waveguide 210A, wherein the microring waveguide 210B is provided with a groove 213, the bottom surface of the groove 213 exposing a portion of the surface of the second horizontal waveguide 210A; the second dielectric layer 211 is located on the second waveguide... A second horizontal waveguide 210A, located on the surface 210 of the second dielectric layer and surrounding the microring waveguide 210B, is connected to a third electrical signal via a conductive via passing through the second dielectric layer. A second surface plasmon active layer 212, located on the surface of the second dielectric layer 211 on the microring waveguide 210B away from the microring waveguide 210B, is used to connect a fourth electrical signal. The contact surface between the second surface plasmon active layer 212 and the second dielectric layer is used to generate surface plasmons for modulating optical signals. It should be noted that the second horizontal waveguide 210A, located on the periphery of the microring waveguide 210B, is connected to the third electrical signal via a conductive via passing through the second dielectric layer. Since the microring waveguide 210B and the second horizontal waveguide 210A are electrically connected, the microring waveguide 210B is connected to the third electrical signal.

[0053] Specifically, the second waveguide layer 210 is made of silicon and is the same layer as the first waveguide layer 103 in the straight waveguide 10. The micro-ring waveguide 210B and the ridge waveguide 1032 are separated by a preset distance L1, which affects the coupling state. The smaller the preset distance L1, the stronger the coupling between the surface plasmon resonance micro-ring resonator 20 and the straight waveguide 10, and the higher the modulation efficiency of the surface plasmon resonance micro-ring resonator 20 for optical signals. Conversely, the smaller the preset distance L1, the weaker the coupling between the surface plasmon resonance micro-ring resonator 20 and the straight waveguide 10, and the lower the modulation efficiency of the surface plasmon resonance micro-ring resonator 20 for optical signals.

[0054] The second dielectric layer 211 can be, for example, silicon dioxide or hafnium dioxide (HFO2). The thickness of the second dielectric layer 211 can be greater than or equal to 5 nanometers, or less than or equal to 15 nanometers. This range ensures that the surface plasmon resonance microring resonator 20 has sufficient modulation bandwidth while also taking into account the modulation efficiency of the surface plasmon resonance microring resonator 20.

[0055] The second surface plasmon active layer 212 can generate plasmons under the influence of an electrical signal, exemplified by a near-zero dielectric constant material. Near-zero dielectric constant materials (ENZ) refer to a class of metamaterials whose relative dielectric constant approaches zero. With a relative dielectric constant approaching zero, the impedance to the optical signal is close to zero, and the phase change is infinitesimally small, allowing for directional emission of the optical signal and confinement to a smaller scale. Therefore, when the optical signal is in a resonant state, it can propagate at the interface between the second surface plasmon active layer 212 and the second dielectric layer 211, with the propagation medium being surface plasmons. Furthermore, the second surface plasmon active layer 212 exhibits good ion dispersion; that is, under the influence of an electrical signal, the second surface plasmon active layer 212 can generate charge carriers to change the effective refractive index at the interface between the second surface plasmon active layer 212 and the second dielectric layer 211, thereby modulating the intensity of the optical signal. Transparent conductive oxide (TCO) films are commonly used materials with near-zero dielectric constants. These films share common optoelectronic properties such as wide bandgap, high transmittance in the visible spectrum, and low resistivity. Exemplary TCO films include indium tin oxide (ITO) films, aluminum-doped zinc oxide (AZO) films, and cadmium oxide (CdO) films.

[0056] Figure 9 This is a top view of yet another micro-ring modulator provided in an embodiment of the present invention. Figure 9As shown, the surface plasmon resonance microring resonator 20 also includes multiple pads 20B, with each conductive via corresponding to a pad 20B. The conductive vias acquire corresponding electrical signals through the pads 20B. The second horizontal waveguide 210A, located around the microring waveguide 210B, includes two conductive vias passing through the second dielectric layer 211, symmetrically arranged with respect to the surface plasmon resonance 20. Therefore, the corresponding pads 20B are symmetrically arranged with respect to the surface plasmon resonance 20. Optionally, the surface plasmon resonance microring resonator 20 also includes an active connection layer 20C. The active connection layer 20C is made of the same material as the second surface plasmon active layer 212 and is partially located on the second surface plasmon active layer 212. The second surface plasmon active layer 212 is connected to the fourth electrical signal through the pads 20B on the active connection layer 20C. To avoid direct electrical connection between the second surface plasmon active layer 212 on the micro-ring waveguide 210B and the pad 20B, which could damage the second surface plasmon active layer 212 and affect the modulation efficiency of the surface plasmon micro-ring resonator 20 for optical signals, it is important to note that... Figure 7 and Figure 8 Conductive vias and pads are not shown. Figure 9 Conductive vias are not shown. Optionally, the pads 20B located around the microring waveguide 210B are spaced approximately 500 nanometers apart from the microring waveguide 210B, and the pads 20B on the active interconnect layer 20C are also spaced approximately 500 nanometers apart from the microring waveguide 210B. This avoids damage to the microring waveguide 210B during the etching of the metal layer during the fabrication of the pads 20B, which would affect the modulation efficiency of the surface plasmon resonance microring resonator 20 for optical signals.

[0057] Optionally, the third electrical signal can be a positive power supply signal, and the fourth electrical signal can be a negative power supply signal. By controlling the difference between the third and fourth electrical signals, the concentration of charge carriers in the second surface plasmon active layer 212 is changed, thereby changing the effective refractive index at the interface between the second surface plasmon active layer 212 and the second dielectric layer 211, and thus modulating the intensity of the optical signal.

[0058] In order to reduce the contact resistance between the conductive via and the second horizontal waveguide 210A surrounding the micro-ring waveguide 210B, an N-type doped region or a P-type doped region is provided on the surface of the second horizontal waveguide 210A and the micro-ring waveguide 210B adjacent to the second dielectric layer 211.

[0059] Specifically, N-type or P-type doped regions are provided on the surfaces of the second horizontal waveguide 210A and the micro-ring waveguide 210B adjacent to the second dielectric layer 211 to reduce the contact resistance between the pad 20B and the second horizontal waveguide 210A surrounding the micro-ring waveguide 210B, further reducing the series resistance of the surface plasmon resonator 20. Optionally, the contact resistance between the conductive via and the second horizontal waveguide 210A surrounding the micro-ring waveguide 210B can be controlled by controlling the concentration of dopant ions. A higher dopant ion concentration results in a lower contact resistance between the pad 20B and the second horizontal waveguide 210A surrounding the micro-ring waveguide 210B, and vice versa. For example, the doping concentration is typically 10¹⁹-10²⁰ cm⁻¹. -3 The thickness of the doped layer is typically 30-70 nm. Within this concentration range, N-type or P-type heavily doped regions are formed to further reduce the contact resistance between the pad 20B and the second horizontal waveguide 210A surrounding the microring waveguide 210B.

[0060] It should be noted that, see Figure 6 The thickness L2 of the portion of the upper cladding 104 covering the ridge waveguide 1032 affects the coupling state between the surface plasmon resonance (SPR) microring resonator 20 and the straight waveguide 10. A thinner L2 of the portion of the upper cladding 104 covering the ridge waveguide 1032 results in a weaker coupling strength between the SPR and the straight waveguide 10, and a lower modulation efficiency of the SPR for optical signals. Conversely, a thicker L2 of the upper cladding 104 covering the ridge waveguide 1032 results in a stronger coupling strength between the SPR and the straight waveguide 10, and a higher modulation efficiency of the SPR for optical signals.

[0061] Optionally, see Figure 6 The thickness L2 of the portion of the upper cladding 104 covering the ridge waveguide 1032 is greater than or equal to 50 nanometers and less than or equal to 70 nanometers.

[0062] Specifically, if the thickness L2 of the portion of the upper cladding 104 covering the ridge waveguide 1032 is less than 50 nanometers, it weakens the mechanical strength of the straight waveguide 10. If the thickness L2 of the portion of the upper cladding 104 covering the ridge waveguide 1032 is greater than 70 nanometers, it results in too weak a coupling strength between the surface plasmon resonance (SPR) microring resonator 20 and the straight waveguide 10. Therefore, a thickness L2 of the portion of the upper cladding 104 covering the ridge waveguide 1032 that is greater than or equal to 50 nanometers and less than or equal to 70 nanometers avoids both the problem of too weak a mechanical strength in the straight waveguide 10 and the problem of too weak a coupling strength between the SPR and the straight waveguide 10, which would lead to lower modulation efficiency of the SPR 20 for optical signals.

[0063] In the above technical solution, the wavelength corresponding to the surface plasmon resonance (SPR) microring resonator 20 and the size of the SPR 20 are related. The difference between the length of one revolution of the optical signal in the SPR 20 and the length of the coupling region 30 is an integer multiple of the wavelength corresponding to the SPR 20.

[0064] Optionally, see Figure 5 The diameter of the conductive inner ring 201A is greater than or equal to 1.8 micrometers and less than or equal to 2.4 micrometers; and / or the diameter of the conductive outer ring 201C is greater than or equal to 2.8 micrometers and less than or equal to 3.2 micrometers; and / or the width of the annular groove 201B is greater than or equal to 80 nanometers and less than or equal to 100 nanometers.

[0065] The dimensions of the conductive inner ring 201A and the conductive outer ring 201C determine the dimensions of the annular groove 201B. The larger the diameter of the conductive inner ring 201A, the longer the circumference of the annular groove 201B; the larger the diameter of the conductive outer ring 201C, the longer the circumference of the annular groove 201B; the wider the annular groove 201B, the wider the width of the first surface plasmon active layer 203 when the thickness of the first dielectric layer 202 is constant.

[0066] Specifically, the diameter of the conductive inner ring 201A is greater than or equal to 1.8 micrometers and less than or equal to 2.4 micrometers; and / or the diameter of the conductive outer ring 201C is greater than or equal to 2.8 micrometers and less than or equal to 3.2 micrometers. This ensures that the longer the perimeter of the annular groove 201B, the more likely the wavelength corresponding to the surface plasmon resonance (SPR) is to be within a preset range. For example, the wavelength corresponding to the SPR 20 can be in the O-band and C-band. The O-band wavelength is approximately 1310 nanometers, and the C-band wavelength is approximately 1550 nanometers.

[0067] If the width of the annular groove 201B is less than 80 nanometers, and the thickness of the first dielectric layer 202 is constant, the width of the first surface plasmon active layer 203 will be too narrow, resulting in too low a carrier concentration provided by the first surface plasmon active layer 203, and thus too low a modulation efficiency of the surface plasmon microring resonator 20. If the width of the annular groove 201B is greater than 100 nanometers, and the thickness of the first dielectric layer 202 is constant, the width of the first surface plasmon active layer 203 will be too wide, resulting in too much absorption of carriers by the first surface plasmon active layer 203, and thus too low a modulation efficiency of the surface plasmon microring resonator 20.

[0068] Optionally, Figure 4In the shown straight waveguide 10, the width L3 of the ridge waveguide 1032 is greater than or equal to 400 nm and less than or equal to 500 nm. The thickness L4 of the ridge waveguide 1032 is determined by the thickness of the first waveguide layer 103. The thickness L5 of the first planar waveguide 1031 is greater than or equal to 60 nm and less than or equal to 80 nm. The thickness of the first waveguide layer 103 can be 160 nm, 220 nm, or 250 nm. The above size range ensures low transmission loss in the surface plasmon resonance modulator coupled from a single surface plasmon resonance microring resonator 20 and a straight waveguide 10.

[0069] The diameter of the microring waveguide 210B determines the length of one revolution of the optical signal in the surface plasmon resonance microring resonator 20, as well as the corresponding wavelength of the surface plasmon resonance microring resonator. Optionally, the outer diameter of the microring waveguide 210B is greater than or equal to 10 micrometers and less than or equal to 12 micrometers; and / or, the width of the microring waveguide 210B is greater than or equal to 200 nanometers and less than or equal to 400 nanometers.

[0070] The larger the outer diameter of the microring waveguide 210B, the longer the optical signal travels through one revolution in the surface plasmon resonance microring resonator 20. The outer diameter L6 of the microring waveguide 210B is greater than or equal to 10 micrometers and less than or equal to 12 micrometers, which falls within a preset range corresponding to the wavelength of the surface plasmon resonance microring resonator. For example, the wavelength corresponding to the surface plasmon resonance microring resonator 20 can be in the O-band and C-band. The O-band wavelength is approximately 1310 nanometers, and the C-band wavelength is approximately 1550 nanometers.

[0071] If the width L7 of the microring waveguide 210B is less than 200 nm, the width of the second surface plasmon active layer 212 will be too narrow, resulting in insufficient carrier concentration provided by the second surface plasmon active layer 212 and thus low modulation efficiency of the surface plasmon microring resonator 20. If the width L7 of the microring waveguide 210B is greater than 400 nm, the width of the second surface plasmon active layer 212 will be too wide, resulting in excessive absorption of carriers by the first surface plasmon active layer 203 and thus low modulation efficiency of the surface plasmon microring resonator 20.

[0072] This invention also provides a method for fabricating a micro-ring modulator. Figure 10 A flowchart illustrating the fabrication method of the micro-ring modulator provided in an embodiment of the present invention is shown. Figures 14-19 This is a schematic diagram showing the structural steps corresponding to each step of a method for fabricating a microring modulator according to an embodiment of the present invention. Figure 15 for Figure 14 The left view. Among them... Figure 17 for Figure 16 A cross-sectional view along the A-A' direction. Figure 19for Figure 18 A cross-sectional view along the B-B' direction. (See attached image.) Figure 10 As shown, the fabrication method of this micro-ring modulator includes the following steps:

[0073] Step 110: Prepare at least one straight waveguide for transmitting optical signals.

[0074] See Figure 14 and Figure 15 At least one straight waveguide 10 is fabricated, which is used to transmit optical signals. Figure 14 and Figure 15 The example only shows one straight waveguide 10. The embodiments of the present invention do not limit the number of plasmonic microring resonators and straight waveguides; those skilled in the art can set them according to actual needs. It should be noted that the embodiments of the present invention are all illustrated using one straight waveguide 10 and one surface plasmonic microring resonator 20 as examples.

[0075] In this embodiment, for example, the straight waveguide 10 is a silicon-on-insulator (SiO2) photonic straight waveguide, with silicon material as the waveguide layer 10A and silicon dioxide material as the cladding layer 10B. Because the refractive index difference between silicon and silicon dioxide is relatively large, approximately 2, optical signals can be transmitted in silicon without entering the low-refractive-index silicon dioxide dielectric layer. Furthermore, due to silicon's low optical loss characteristics in the near-infrared band, SiO2 is currently the most important on-chip photonics platform in the industry. This reduces losses during optical signal transmission and is compatible with CMOS processes, reducing device costs and enabling optoelectronic integrated circuits.

[0076] Step 120: Prepare at least one surface plasmon resonance microring resonator coupled to a straight waveguide. The surface plasmon resonance microring resonator is used to modulate the intensity of an optical signal with a wavelength corresponding to the surface plasmon resonance microring resonator.

[0077] See Figure 16 and Figure 17 At least one surface plasmon microring resonator 20, perpendicularly coupled to the straight-wave 10-guide, is fabricated. (See also...) Figure 18 and Figure 19 At least one surface plasmon microring resonator 20, horizontally coupled to the straight-wave 10-guide, is fabricated. Figure 16 and Figure 17 As shown, the surface plasmon resonator 20 is located at a predetermined distance above the straight waveguide 10, and the surface plasmon resonator 20 and the straight waveguide 10 are perpendicularly coupled to each other. Figure 18 and Figure 19The surface plasmon microring resonator 20 and the straight waveguide 10 are located on the same plane and are separated by a preset distance. The surface plasmon microring resonator 20 and the straight waveguide 10 are horizontally coupled to each other.

[0078] In this embodiment, the surface plasmon resonance microring resonator 20 typically includes an active layer 20D and a dielectric layer 20E. Surface plasmons exist at the interface between the active layer 20D and the dielectric layer 20E. The relative permittivity of the active layer 20D approaches zero, resulting in near-zero impedance for optical signals and infinitesimal phase change. This allows for directional emission of optical signals and confinement of the signals to a smaller scale. Therefore, when the optical signal is in a resonant state, it can propagate at the interface between the active layer 20D and the dielectric layer 20E, with the surface plasmons as the propagation medium. Furthermore, the active layer 20D exhibits good ion dispersion, meaning that under the influence of an electrical signal, the surface plasmon resonance microring resonator can generate charge carriers to change the effective refractive index at the interface between the active layer 20D and the dielectric layer 20E, thereby modulating the intensity of the optical signal.

[0079] The technical solution in this embodiment of the invention includes a straight waveguide 10 and a surface plasmon resonance (SPR) microring resonator 20 coupled to the straight waveguide 10. The straight waveguide 10 is used to propagate the optical signal, and the SPR 20 is used to modulate the intensity of the optical signal at a wavelength corresponding to the SPR 20. Compared to SPR devices, the straight waveguide 10 significantly reduces the transmission loss of the optical signal. The SPR 20 can confine the optical signal to a smaller scale for propagation, reducing the size of the microring resonator. It should be noted that, compared to silicon-based resonators, the technical solution in this embodiment of the invention, while reducing the device size and slightly reducing losses, increases the modulation bandwidth of the microring modulator. Therefore, the above technical solution achieves a modulator with low optical signal loss, high modulation bandwidth, and small device size.

[0080] In the above technical solution, the straight waveguide 10, compared with the surface plasmon resonance device, greatly reduces the optical signal transmission loss. The fabrication method of the straight waveguide 10 is described in detail below.

[0081] Figure 11 This is a flowchart illustrating a method for fabricating a straight waveguide according to an embodiment of the present invention. Figure 2 The diagram shows the structural schematics corresponding to each step of the fabrication method of the straight waveguide provided in the embodiment of the present invention. Figure 20 In the figures, Figure (1b) is a left view of Figure (1a). Figure (2b) is a left view of Figure (2a). Figure (3b) is a left view of Figure (3a). Figure (4b) is a left view of Figure (4a). See also Figure 11The fabrication method of this straight waveguide includes the following steps:

[0082] Step 1101: Provide a substrate.

[0083] See Figure 20 Figures (1a) and (1b) show a substrate 101. For example, the substrate 101 may be made of silicon.

[0084] Step 1102: Form a lower cladding layer on the substrate surface.

[0085] See Figure 20 As shown in Figures (2a) and (2b), a lower cladding layer 102 is formed on the surface of substrate 101. The lower cladding layer 102 can be a silicon dioxide material formed by a thermal oxidation process.

[0086] Step 1103: A first waveguide layer is formed on the surface of the lower cladding layer away from the substrate, wherein the first waveguide layer includes a first planar waveguide and a ridge waveguide located on the surface of the first planar waveguide.

[0087] See Figure 20 As shown in Figures (3a) and (3b), a first waveguide layer 103 is formed on the surface of the lower cladding layer 102 away from the substrate 101. The first waveguide layer 103 includes a first planar waveguide 1031 and a ridge waveguide 1032 located on the surface of the first planar waveguide. The lower cladding layer 102 and the first waveguide layer 103 constitute a silicon-on-insulator structure.

[0088] The first waveguide layer 103 includes a first planar waveguide 1031 and a ridge waveguide 1032 located on the surface of the first planar waveguide. The formation process of the first waveguide layer 103 includes: forming a silicon material layer on the surface of the lower cladding layer 102 away from the substrate 101; and forming the first waveguide layer 103, including the first planar waveguide 1031 and the ridge waveguide 1032 located on the surface of the silicon material layer away from the lower cladding layer 102, through an etching process. Exemplarily, the etching process may include electron beam lithography (EBL) and reactive ion etching (RIE). In electron beam lithography, a photomask is first formed using a negative photoresist, wherein the spin-coating speed of the photoresist is approximately 3000 rpm, and the pre-baking temperature is approximately 95°C. In the exposure and development process of the negative photoresist, the base dose exposure is 1100 μC / cm. 2 The developing solution is approximately 25% tetramethylammonium hydroxide (TMAH) solution, followed by immersion in deionized water and isopropanol for cleaning. The etching gases used in the reactive ion etching process are C4F8 and SF6 in a ratio of approximately 8:8. To achieve a balance between the etching and passivation gas processes, an etching rate of approximately 3.2 nm / s is employed.

[0089] Step 1104: An upper cladding is formed on the surface of the first waveguide layer away from the lower cladding layer. The surface of the upper cladding away from the first waveguide layer is planar.

[0090] See Figure 20 In Figures (4a) and (4b), an upper cladding 104 is formed on the surface of the first waveguide layer 103 away from the lower cladding 102, and the surface of the upper cladding 104 away from the first waveguide layer 103 is planar. The upper cladding 104 can be made of silicon dioxide. The first waveguide layer 103 and the upper cladding 104 constitute a silicon-on-insulator structure.

[0091] The preparation process of the upper cladding 104 specifically includes: forming a silicon dioxide material layer on the surface of the first waveguide layer 103 away from the lower cladding 102 through a thermal annealing process, and then planarizing the silicon dioxide material layer through an etching process to form an upper cladding 104 with a planar surface on the side away from the first waveguide layer 103.

[0092] In the above technical solution, the surface plasmon resonance microring resonator 20 and the straight waveguide 10 are coupled to each other and are used to modulate the intensity of the optical signal corresponding to the wavelength of the surface plasmon resonance microring resonator. The following describes in detail the fabrication method of the surface plasmon resonance microring resonator 20 when the surface plasmon resonance microring resonator 20 and the straight waveguide 10 are perpendicularly coupled to each other.

[0093] Figure 12 A flowchart illustrating a method for fabricating a surface plasmon microring resonator according to an embodiment of the present invention. Figure 21 This is a schematic diagram of the structure corresponding to each step of the fabrication method of a surface plasmon microring resonator provided in an embodiment of the present invention. Figure 21 Figure (1b) is a cross-sectional view of Figure (1a). Figure (2b) is a cross-sectional view along the A-A' direction in Figure (2a). See also Figure 12 The method for fabricating a surface plasmonic microring resonator perpendicularly coupled to a straight waveguide includes the following steps:

[0094] Step 1201: Form a conductive microring with grooves, wherein the conductive microring with grooves includes a conductive inner ring, an annular groove and a conductive outer ring arranged sequentially from the inside to the outside.

[0095] See Figure 21As shown in Figures (1a) and (1b), a grooved conductive microring 201 is formed on the surface of the upper cladding 104 away from the first waveguide layer 103. The grooved conductive microring 201 includes a conductive inner ring 201A, an annular groove 201B, and a conductive outer ring 201C arranged sequentially from the inside out. Specifically, the conductive microring 201 can be a metal microring, and the metal can be one or more of gold, silver, and copper. Gold has the most stable chemical properties, silver has the lowest surface plasmon resonance loss, and copper is compatible with CMOS processes. This invention does not limit the choice of material and can select it according to actual application requirements. The thickness L2 of the portion of the upper cladding 104 covering the ridge waveguide 1032 affects the coupling state between the surface plasmon resonance microring resonator 20 and the straight waveguide 10. The thinner the portion of the upper cladding 104 covering the ridge waveguide 1032, the weaker the coupling strength between the surface plasmon resonator 20 and the straight waveguide 10, and the lower the modulation efficiency of the surface plasmon resonator 20 for optical signals. Conversely, the thicker the portion of the upper cladding 104 covering the ridge waveguide 1032, the stronger the coupling strength between the surface plasmon resonator 20 and the straight waveguide 10, and the higher the modulation efficiency of the surface plasmon resonator 20 for optical signals.

[0096] Step 1202: A first dielectric layer is formed on the surface of the conductive inner ring, the sidewalls and bottom of the annular groove, and the surface of the conductive outer ring. The conductive inner ring and the conductive outer ring are connected to the first electrical signal through conductive vias passing through the first dielectric layer.

[0097] See Figure 21 As shown in Figures (2a) and (2b), a first dielectric layer 202 is formed on the surface of the conductive inner ring 201A, the sidewalls and bottom surface of the annular groove 201B, and the surface of the conductive outer ring 201C. The conductive inner ring 201A and the conductive outer ring 201C are connected to a first electrical signal through conductive vias 20A passing through the first dielectric layer 202. The first dielectric layer 202 can be, for example, silicon dioxide or hafnium dioxide (HFO2). The thickness of the first dielectric layer 202 can be greater than or equal to 5 nanometers and less than or equal to 15 nanometers. This range ensures that the surface plasmon resonance microring resonator 20 has sufficient modulation bandwidth while also maintaining its modulation efficiency.

[0098] Step 1203: A first surface plasmon active layer is formed on the surface of the first dielectric layer away from the annular groove. The first surface plasmon active layer is used to connect the second electrical signal, and the interface between the first surface plasmon active layer and the first dielectric layer is used to generate surface plasmons for modulating optical signals.

[0099] See also Figure 20In Figures (2a) and (2b), a first surface plasmon active layer 203 is formed on the surface of the first dielectric layer 202 in the annular groove 201B away from the annular groove 201B. The first surface plasmon active layer 203 is used to connect the second electrical signal. The contact surface between the first surface plasmon active layer 203 and the first dielectric layer 202 is used to generate surface plasmons for modulating optical signals.

[0100] The first surface plasmon active layer 203 can generate plasmons under the influence of an electrical signal; for example, it can be a material with a near-zero dielectric constant. When the optical signal is in a resonant state, it can propagate at the interface between the first surface plasmon active layer 203 and the first dielectric layer 202, with the propagation medium being surface plasmons. Furthermore, the first surface plasmon active layer 203 exhibits good ion dispersion; that is, under the influence of an electrical signal, the first surface plasmon active layer 203 can generate charge carriers, thereby changing the effective refractive index at the interface between the first surface plasmon active layer 203 and the first dielectric layer 202 to modulate the intensity of the optical signal. A commonly used near-zero dielectric constant material can be a transparent conductive oxide thin film (TCO). These films possess common optoelectronic properties such as a wide bandgap, high transmittance in the visible spectrum, and low resistivity. Examples of transparent conductive oxide films include indium tin oxide (ITO) films, aluminum-doped zinc oxide (AZO) films, and cadmium oxide (CdO) films.

[0101] Optionally, see Figure 21 Furthermore, multiple pads 20B can be formed in the surface plasmon microring resonator 20, with each conductive via 20A corresponding to a pad 20B, and pads 20B formed on the first surface plasmon active layer 203. The conductive via 20A and the first surface plasmon active layer 203 obtain corresponding electrical signals through the pads 20B. Figure 21 Figure (2a) does not show pad 20B and conductive via 20A.

[0102] Optionally, the first electrical signal connected to the conductive inner ring 201A and the conductive outer ring 201C through the conductive via 20A passing through the first dielectric layer 202 can be a positive power supply signal, and the second electrical signal connected to the first surface plasmon active layer 203 can be a negative power supply signal. By controlling the difference between the first electrical signal and the second electrical signal, the concentration of charge carriers in the first surface plasmon active layer 203 can be changed, thereby changing the effective refractive index at the interface between the first surface plasmon active layer 203 and the first dielectric layer 202, so as to achieve intensity modulation of the optical signal.

[0103] In the above technical solution, the surface plasmon resonance (SPR) microring resonator 20 and the straight waveguide 10 are coupled to each other and are used to modulate the intensity of the optical signal corresponding to the wavelength of the SPR. The following describes in detail the fabrication method of the SPR 20 when the SPR and the straight waveguide 10 are horizontally coupled.

[0104] Figure 13 A flowchart illustrating another method for fabricating a surface plasmon microring resonator provided in an embodiment of the present invention. Figure 22 The diagram shows the structural schematics corresponding to each step of another method for fabricating a surface plasmon microring resonator provided in this embodiment of the invention. Figure 22 Figure (1b) is a cross-sectional view along the B-B' direction in Figure (1a). Figure (2b) is a cross-sectional view along the B-B' direction in Figure (2a). Figure (3b) is a cross-sectional view along the B-B' direction in Figure (3a).

[0105] See Figure 13 The method for fabricating a surface plasmonic microring resonator that is horizontally coupled to a straight waveguide includes the following steps:

[0106] Step 1204: Form a second waveguide layer, wherein the second waveguide layer includes a second horizontal waveguide and a micro-ring waveguide located on the surface of the second horizontal waveguide. The micro-ring waveguide is provided with a groove, and the bottom surface of the groove exposes part of the surface of the second horizontal waveguide.

[0107] See Figure 22 Figures (1a) and (1b) show a second waveguide layer 210, which includes a second horizontal waveguide 210A and a microring waveguide 210B located on the surface of the second horizontal waveguide 210A. The microring waveguide 210B has a groove 213, the bottom surface of which exposes a portion of the surface of the second horizontal waveguide 210A. It should be noted that the second waveguide layer 210 and the first waveguide layer 103 are fabricated in the same layer using the same process. A surface plasmon resonator with horizontal coupling to the straight waveguide is fabricated by setting a predetermined distance L1 between the microring waveguide 210B and the ridge waveguide 1032. The second waveguide layer 210 is made of silicon and is in the same layer as the first waveguide layer 103 in the straight waveguide 10. The predetermined distance L1 between the microring waveguide 210B and the ridge waveguide 1032 affects the coupling state. The smaller the preset distance L1, the stronger the coupling strength between the surface plasmon resonator 20 and the straight waveguide 10, and the higher the modulation efficiency of the surface plasmon resonator 20 for optical signals; the smaller the preset distance L1, the weaker the coupling strength between the surface plasmon resonator 20 and the straight waveguide 10, and the lower the modulation efficiency of the surface plasmon resonator 20 for optical signals.

[0108] Step 1205: A second dielectric layer is formed on the surface of the second waveguide layer, and the second horizontal waveguide around the micro-ring waveguide is connected to the third electrical signal through a conductive via passing through the second dielectric layer.

[0109] See Figure 22 As shown in Figures (2a) and (2b), a second dielectric layer 211 is formed on the surface of the second waveguide layer 210, and a second horizontal waveguide 210A surrounding the microring waveguide 210B is connected to a third electrical signal through conductive vias passing through the second dielectric layer 211. The second dielectric layer 211 can be, for example, silicon dioxide or hafnium dioxide (HFO2). The thickness of the second dielectric layer 211 can be greater than or equal to 5 nanometers, or less than or equal to 15 nanometers. This range ensures that the surface plasmon resonance microring resonator 20 has sufficient modulation bandwidth while also maintaining its modulation efficiency. Figure 7 and Figure 8 Conductive vias are not shown.

[0110] Step 1206: A second surface plasmon active layer is formed on the surface of the second dielectric layer on the side away from the micro-ring waveguide. The second surface plasmon active layer is used to connect the fourth electrical signal, and the interface between the second active layer and the second dielectric layer is used to generate surface plasmons for modulating optical signals.

[0111] See Figure 22 In Figures (3a) and (3b), a second surface plasmon active layer 212 is formed on the surface of the second dielectric layer 211 on the side away from the micro-ring waveguide 210B. The second surface plasmon active layer 212 is used to connect a fourth electrical signal, and the contact surface between the second surface plasmon active layer 212 and the second dielectric layer 212 is used to generate surface plasmons for modulating the optical signal. The second surface plasmon active layer 212 can generate plasmons under the action of the electrical signal, and can be exemplarily a material with a near-zero dielectric constant. When the optical signal is in a resonant state, it can propagate at the interface between the second surface plasmon active layer 212 and the second dielectric layer 211, and the propagation medium is surface plasmons. Furthermore, the second surface plasmon active layer 212 has a good ion dispersion effect. That is, under the action of an electrical signal, the second surface plasmon active layer 212 can generate charge carriers to change the effective refractive index at the interface between the second surface plasmon active layer 212 and the second dielectric layer 211, thereby modulating the intensity of the optical signal.

[0112] like Figure 9As shown, multiple pads 20B can also be formed in the surface plasmonic microring resonator 20, with each conductive via corresponding to a pad 20B. The conductive vias acquire corresponding electrical signals through the pads 20B. The second horizontal waveguide 210A, located around the microring waveguide 210B, includes two conductive vias passing through the second dielectric layer 211, symmetrically arranged with respect to the surface plasmonic resonator 20. Therefore, the corresponding pads 20B are symmetrically arranged with respect to the surface plasmonic resonator 20. Optionally, the surface plasmonic microring resonator 20 further includes an active connection layer 20C. The active connection layer 20C is made of the same material as the second surface plasmonic active layer 212 and is partially located on the second surface plasmonic active layer 212. The second surface plasmonic active layer 212 is connected to the fourth electrical signal through the pads 20B on the active connection layer 20C. To avoid direct electrical connection between the second surface plasmon active layer 212 on the micro-ring waveguide 210B and the pad 20B, which would damage the second surface plasmon active layer 212 and affect the modulation efficiency of the surface plasmon micro-ring resonator 20 for optical signals.

[0113] Optionally, the third electrical signal can be a positive power supply signal, and the fourth electrical signal can be a negative power supply signal. By controlling the difference between the third and fourth electrical signals, the concentration of charge carriers in the second surface plasmon active layer 212 is changed, thereby changing the effective refractive index at the interface between the second surface plasmon active layer 212 and the second dielectric layer 211, and thus modulating the intensity of the optical signal.

[0114] In order to reduce the contact resistance between the conductive via and the second horizontal waveguide 210A surrounding the micro-ring waveguide 210B, the embodiment of the present invention performs the following steps before forming the second dielectric layer on the surface of the second waveguide layer in step 1205: an N-type doped region or a P-type doped region is formed on the surface of the second horizontal waveguide 210A and the micro-ring waveguide 210B adjacent to the second dielectric layer 211.

[0115] Specifically, N-type or P-type doped regions are provided on the surfaces of the second horizontal waveguide 210A and the micro-ring waveguide 210B adjacent to the second dielectric layer 211 to reduce the contact resistance between the pad 20B and the second horizontal waveguide 210A surrounding the micro-ring waveguide 210B, further reducing the series resistance of the surface plasmon resonator 20. Optionally, the contact resistance between the conductive via and the second horizontal waveguide 210A surrounding the micro-ring waveguide 210B can be controlled by controlling the concentration of dopant ions. A higher dopant ion concentration results in a lower contact resistance between the pad 20B and the second horizontal waveguide 210A surrounding the micro-ring waveguide 210B, and vice versa. For example, the doping concentration is typically 10¹⁹-10²⁰ cm⁻¹. -3 The thickness of the doped layer is typically 30-70 nm. Within this concentration range, N-type or P-type heavily doped regions are formed to further reduce the contact resistance between the pad 20B and the second horizontal waveguide 210A surrounding the microring waveguide 210B. For example, N-type heavily doped regions are formed on the surface of the second horizontal waveguide 210A and the microring waveguide 210B adjacent to the second dielectric layer 211, with boron as the dopant and a doping concentration of 1 × 10⁻⁶. 20 cm -3 Approximately, the dosage is 1×10 15 ions / cm 2 The energy is around 25keV, which reduces the series resistance to 700Ω / cm. 2 The thickness of the doped layer is approximately 40 nm.

[0116] Those skilled in the art will understand that all or some of the steps in the methods disclosed above, as well as the functional modules / units in the systems and devices, can be implemented as software, firmware, hardware, or suitable combinations thereof.

[0117] In hardware implementations, the division between functional modules / units mentioned in the above description does not necessarily correspond to the division of physical components; for example, a physical component may have multiple functions, or a function or step may be performed collaboratively by several physical components. Some or all physical components may be implemented as software executed by a processor, such as a central processing unit, digital signal processor, or microprocessor, or as hardware, or as an integrated circuit, such as an application-specific integrated circuit. Such software may be distributed on a computer-readable medium, which may include computer storage media (or non-transitory media) and communication media (or transient media). As is known to those skilled in the art, the term computer storage media includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information (such as computer-readable instructions, data structures, program modules, or other data). Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technologies, CD-ROM, digital versatile disc (DVD) or other optical disc storage, magnetic cartridges, magnetic tape, disk storage or other magnetic storage devices, or any other medium that can be used to store desired information and is accessible to a computer. Furthermore, as is known to those skilled in the art, communication media typically contain computer-readable instructions, data structures, program modules, or other data in modulated data signals such as carrier waves or other transmission mechanisms, and may include any information delivery medium.

[0118] The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but this does not limit the scope of the invention. Any modifications, equivalent substitutions, and improvements made by those skilled in the art without departing from the scope and spirit of the present invention should be within the scope of the present invention.

Claims

1. A micro-ring modulator, characterized in that, include: At least one straight waveguide and at least one surface plasmon resonator coupled to the straight waveguide; The straight waveguide is used to transmit optical signals; The surface plasmon resonator is used to modulate the intensity of an optical signal with a wavelength corresponding to the surface plasmon resonator. The surface plasmon microring resonator and the straight waveguide are perpendicularly coupled to each other. The surface plasmon microring resonator includes a conductive microring with grooves, a first dielectric layer and a first surface plasmon active layer. The grooved conductive microring includes a conductive inner ring, an annular groove, and a conductive outer ring arranged sequentially from the inside to the outside. A first dielectric layer is located on the surface of the conductive inner ring, the sidewalls and bottom of the annular groove, and the surface of the conductive outer ring. The conductive inner ring and the conductive outer ring are connected to a first electrical signal through conductive vias passing through the first dielectric layer. The first surface plasmon active layer is located on the surface of the first dielectric layer away from the annular groove within the annular groove. The first surface plasmon active layer is used to connect to the second electrical signal, and the contact surface between the first surface plasmon active layer and the first dielectric layer is used to generate surface plasmons that modulate the optical signal.

2. The micro-ring modulator according to claim 1, characterized in that, The straight waveguide includes: a substrate; The lower cladding layer is located on the surface of the substrate; A first waveguide layer is located on the surface of the lower cladding layer away from the substrate, wherein the first waveguide layer includes a first planar waveguide and a ridge waveguide located on the surface of the first planar waveguide; The upper cladding is located on the surface of the first waveguide layer away from the lower cladding, and the surface of the upper cladding away from the first waveguide layer is planar.

3. The method for fabricating the micro-ring modulator according to claim 2, characterized in that, The thickness of the portion of the upper cladding covering the ridge waveguide is greater than or equal to 50 nanometers and less than or equal to 70 nanometers.

4. The method for fabricating a micro-ring modulator according to claim 1, characterized in that, The diameter of the conductive inner ring is greater than or equal to 1.8 micrometers and less than or equal to 2.4 micrometers; and / or, The diameter of the conductive outer ring is greater than or equal to 2.8 micrometers and less than or equal to 3.2 micrometers; and / or, The width of the annular groove is greater than or equal to 80 nanometers and less than or equal to 100 nanometers.

5. A method for fabricating a micro-ring modulator, characterized in that, include: At least one straight waveguide is fabricated for transmitting optical signals; At least one surface plasmon resonance (SPR) microring resonator coupled to the straight waveguide is fabricated, and the SPR is used to modulate the intensity of an optical signal with a wavelength corresponding to the SPR. Fabricating a surface plasmonic microring resonator perpendicularly coupled to the straight waveguide includes: A conductive microring with grooves is formed, wherein the conductive microring with grooves includes a conductive inner ring, an annular groove and a conductive outer ring arranged sequentially from the inside to the outside; A first dielectric layer is formed on the surface of the conductive inner ring, the sidewalls and bottom of the annular groove, and the surface of the conductive outer ring. The conductive inner ring and the conductive outer ring are connected to a first electrical signal through conductive vias passing through the first dielectric layer. A first surface plasmon active layer is formed on the surface of the first dielectric layer in the annular groove away from the annular groove. The first surface plasmon active layer is used to connect to the second electrical signal. The contact surface between the first surface plasmon active layer and the first dielectric layer is used to generate surface plasmons that modulate the optical signal.

6. The method for fabricating a micro-ring modulator according to claim 5, characterized in that, Fabrication of a straight waveguide includes: providing a substrate; A lower cladding layer is formed on the surface of the substrate; A first waveguide layer is formed on the surface of the lower cladding layer away from the substrate, wherein the first waveguide layer includes a first planar waveguide and a ridge waveguide located on the surface of the first planar waveguide; An upper cladding is formed on the surface of the first waveguide layer away from the lower cladding, and the surface of the upper cladding away from the first waveguide layer is planar.

7. The method for fabricating a micro-ring modulator according to claim 5, characterized in that, The conductive microring is made of one or more of gold, silver, or copper.

8. The method for fabricating a micro-ring modulator according to claim 5, characterized in that, The first surface plasmon active layer comprises a material with a near-zero dielectric constant.

9. The method for fabricating a micro-ring modulator according to claim 8, characterized in that, The near-zero dielectric constant material includes a transparent conductive oxide thin film.

Images