Micro-ring modulator, optical communication system and modulation method of micro-ring modulator

Abstract

The application relates to a kind of micro-ring modulators, optical communication systems and the modulation method of micro-ring modulator, the micro-ring modulator includes: transmission waveguide, ring waveguide and modulation module;Transmission waveguide is coupled with ring waveguide, the effective refractive index of ring waveguide is periodically changed in circumferential direction, the period number of effective refractive index change is integer, and period number is 2 times of the resonance mode number of the ring waveguide;Transmission waveguide, for transmitting optical signal;Ring waveguide, for guiding optical signal to propagate along clockwise direction and counterclockwise direction respectively, so that the optical signal propagating along clockwise direction and the optical signal propagating along counterclockwise direction are coupled with each other, and are distributed in the form of standing wave in ring waveguide;Modulation module, for changing the refractive index of ring waveguide in response to external control signal, to modulate the phase of optical signal distributed in the form of standing wave.By periodic refractive index change, so that micro-ring modulator no longer depends on harsh critical coupling.

Description

Technical Field

[0001] This application relates to the field of micro-ring modulator technology, and in particular to micro-ring modulators, optical communication systems, and modulation methods for micro-ring modulators. Background Technology

[0002] Microring modulators are widely used in integrated optics and optical communications, especially in high-speed optical communication systems such as optical interconnects and data centers. Silicon-based microring modulators have become an important component of on-chip optical interconnects due to their advantages such as small size, low power consumption, and compatibility with complementary metal-oxide-semiconductor (CMOS) processes.

[0003] However, to achieve a high extinction ratio, traditional microring modulators require the coupling strength between the transmission waveguide and the microring to be exactly equal to the intrinsic loss of the microring modulator. Therefore, even small changes in the coupling gap, or coupling deviations caused by process errors or temperature fluctuations, can disrupt the critical coupling state of the microring modulator, resulting in a high dependence of the microring modulator on the critical coupling state.

[0004] There is currently no effective solution to the problem of high dependence on critical coupling state in related technologies. Summary of the Invention

[0005] This embodiment provides a micro-ring modulator, an optical communication system, and a modulation method for the micro-ring modulator to address the problem of high dependence on critical coupling states in related technologies.

[0006] Firstly, this embodiment provides a micro-ring modulator, which includes: a transmission waveguide, a ring waveguide, and a modulation module; the transmission waveguide is coupled to the ring waveguide, the effective refractive index of the ring waveguide changes periodically in the circumferential direction, the number of periods of the effective refractive index change is an integer, and the number of periods is twice the number of resonant modes of the ring waveguide;

[0007] The transmission waveguide is used to transmit optical signals;

[0008] The ring waveguide is used to guide the optical signal to propagate in clockwise and counterclockwise directions respectively, so that the optical signal propagating in the clockwise direction is coupled with the optical signal propagating in the counterclockwise direction and distributed in the form of a standing wave in the ring waveguide;

[0009] The modulation module is used to change the refractive index of the ring waveguide in response to an external control signal, so as to modulate the phase of the optical signal distributed in the form of a standing wave.

[0010] In some embodiments, the boundary width of the annular waveguide varies periodically in the circumferential direction so that the effective refractive index varies accordingly.

[0011] In some embodiments, the modulation module includes a PN junction and a signal input unit; the PN junction is integrated on the ring waveguide, and the signal input unit is connected to the PN junction; wherein:

[0012] The signal input unit is used to apply an electrical signal to the PN junction in response to the external control signal;

[0013] The PN junction is used to change the refractive index of the ring waveguide in response to the electrical signal.

[0014] In some embodiments, the ring waveguide includes a modulation section and a first coupling section; wherein the modulation section is connected to the modulation module;

[0015] The first coupling segment is used for optical signal coupling with the transmission waveguide;

[0016] The modulation segment is used to perform phase modulation on the optical signal under the action of the modulation module.

[0017] In some embodiments, the ring waveguide includes multiple discontinuous modulation segments; each modulation segment is connected to the modulation module.

[0018] In some embodiments, the transmission waveguide includes an input segment, a second coupling segment, and an output segment, wherein the second coupling segment is disposed opposite to the first coupling segment; wherein:

[0019] The input segment is used to receive externally input optical signals;

[0020] The second coupling segment is used for optical signal coupling with the ring waveguide;

[0021] The output section is used to couple and output the optical signal modulated by the ring waveguide.

[0022] In some embodiments, the second coupling segment of the transmission waveguide is a curved waveguide, and the curvature of the curved waveguide is the same as the curvature of the first coupling segment of the ring waveguide.

[0023] In some embodiments, the second coupling segment of the transmission waveguide is a straight waveguide, and the straight waveguide is parallel to the tangent direction of the first coupling segment of the ring waveguide.

[0024] Secondly, this embodiment provides an optical communication system, including a light source, a photodetector, and a micro-ring modulator according to any one of the first aspects; wherein:

[0025] The light source is used to generate light signals;

[0026] The photodetector is used to receive optical signals.

[0027] Thirdly, this embodiment provides a modulation method for a micro-ring modulator, including:

[0028] The optical signal is input to the transmission waveguide of the modulator;

[0029] In response to an external control signal, the refractive index of the modulator's ring waveguide is changed by the modulator's modulation module to obtain a modulated optical signal, and the modulated optical signal is output from the transmission waveguide;

[0030] The modulator is the micro-ring modulator described in any one of the first aspects.

[0031] Compared with related technologies, this embodiment provides a micro-ring modulator, an optical communication system, and a modulation method for the micro-ring modulator. The micro-ring modulator includes: a transmission waveguide, a ring waveguide, and a modulation module; the transmission waveguide is coupled to the ring waveguide, the effective refractive index of the ring waveguide changes periodically in the circumferential direction, the number of periods of the effective refractive index change is an integer, and the number of periods is twice the number of resonant modes of the ring waveguide; the transmission waveguide is used to transmit optical signals; the ring waveguide is used to guide the optical signals to propagate in clockwise and counterclockwise directions respectively, so that the optical signals propagating in the clockwise direction are coupled to each other and distributed in the form of standing waves in the ring waveguide; the modulation module is used to change the refractive index of the ring waveguide in response to an external control signal to modulate the phase of the optical signals distributed in the form of standing waves. By introducing a periodic refractive index change along the circumference of the ring waveguide, optical signals propagating in the clockwise and counterclockwise directions are coupled, forming a standing wave in the ring waveguide of the micro-ring modulator. This allows the micro-ring modulator to no longer rely on stringent critical coupling and maintain a high extinction ratio over a wider range of coupling strengths.

[0032] Details of one or more embodiments of this application are set forth in the following drawings and description to make other features, objects and advantages of this application more readily apparent. Attached Figure Description

[0033] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0034] Figure 1 This is a schematic diagram of the structure of a micro-ring modulator according to an embodiment of this application;

[0035] Figure 2 This is a schematic diagram of the specific structure of a micro-ring modulator according to one embodiment of this application. Figure 1 ;

[0036] Figure 3 This is a schematic diagram of the specific structure of a micro-ring modulator according to one embodiment of this application. Figure 2 ;

[0037] Figure 4 This is a curve showing the relationship between transmittance and coupling strength under different coupling idealities in one embodiment of this application;

[0038] Figure 5 This is a transmittance curve of a ring waveguide according to an embodiment of this application under different coupling strengths;

[0039] Figure 6 This is a graph showing the relationship between the extinction ratio and optical bandwidth of a micro-ring modulator under different splitting intensities in one embodiment of this application, as a function of coupling strength.

[0040] Figure 7 This is a flowchart of a micro-ring modulator modulation method according to an embodiment of this application. Detailed Implementation

[0041] To better understand the purpose, technical solution, and advantages of this application, the application is described and illustrated below in conjunction with the accompanying drawings and embodiments.

[0042] Unless otherwise defined, the technical or scientific terms used in this application shall have the general meaning understood by one of ordinary skill in the art to which this application pertains. Words such as “a,” “an,” “an,” “the,” “the,” and “these” used in this application do not indicate quantitative limitation and may be singular or plural. The terms “comprising,” “including,” “having,” and any variations thereof used in this application are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or device that comprises a series of steps or modules (units) is not limited to the listed steps or modules (units) but may include steps or modules (units) not listed, or may include other steps or modules (units) inherent to these processes, methods, products, or devices. Words such as “connected,” “linked,” and “coupled” used in this application are not limited to physical or mechanical connections but may include electrical connections, whether direct or indirect. “Multiple” used in this application refers to two or more. “And / or” describes the relationship between related objects, indicating that three relationships may exist; for example, “A and / or B” can represent: A alone, A and B simultaneously, and B alone. Normally, the character " / " indicates that the objects before and after it are in an "or" relationship. The terms "first," "second," "third," etc., used in this application are merely to distinguish similar objects and do not represent a specific order of objects.

[0043] This embodiment provides a micro-ring modulator. Figure 1 This is a schematic diagram of the structure of a micro-ring modulator according to an embodiment of this application, as shown below. Figure 1 As shown, the micro-ring modulator includes: a transmission waveguide 10, a ring waveguide 20, and a modulation module 30; the transmission waveguide 10 is coupled to the ring waveguide 20, and the effective refractive index of the ring waveguide 20 changes periodically in the circumferential direction. The number of periods of the effective refractive index change is an integer, and the number of periods is twice the number of resonant modes of the ring waveguide 20.

[0044] Transmission waveguide 10 is used to transmit optical signals. Transmission waveguide 10 is used to input optical signals to ring waveguide 20 and receive modulated optical signals output from ring waveguide 20.

[0045] The ring waveguide 20 is used to guide the optical signal to propagate in the clockwise and counterclockwise directions respectively, so that the optical signal propagating in the clockwise direction is coupled with the optical signal propagating in the counterclockwise direction and distributed in the form of a standing wave within the ring waveguide 20.

[0046] Specifically, in the design of the micro-ring modulator, by setting a specific periodic structure on the ring waveguide 20, the effective refractive index of the ring waveguide 20 can be made to change periodically along the circumference. The effective refractive index refers to the equivalent refractive index experienced by light propagating in the ring waveguide 20, comprehensively reflecting the influence of the refractive index of the ring waveguide 20 material and the waveguide geometry (such as width, thickness, and sidewall shape) on the light propagation speed. The effective refractive index determines the propagation speed of light in the ring waveguide 20 and the spatial phase distribution of the light wave. When light is coupled from the transmission waveguide 10 into the ring waveguide 20, the optical signal that meets the phase matching condition can propagate stably in the ring waveguide 20 and form resonance. The modulated optical signal is then coupled back from the ring waveguide 20 to the transmission waveguide 10 through the coupling region 40, completing the input and output process of the optical signal. When the geometry of the ring waveguide 20 changes periodically, the effective refractive index experienced by light at different positions in the ring waveguide 20 also changes periodically, thus forming spatial modulation of the effective refractive index.

[0047] This periodic variation can be achieved through various methods, including width modulation, aperture array modulation, or sidewall gratings. Width modulation involves alternating waveguide segments of varying widths along the circumference of the annular waveguide 20, utilizing the change in mode distribution caused by the waveguide width variation to achieve a periodic change in the effective refractive index. Aperture array modulation involves periodically arranging air holes on the annular waveguide 20, utilizing the difference in refractive index between silicon and air to create a periodic change in the effective refractive index. Sidewall gratings involve periodically creating protrusions or depressions on the inner or outer sidewalls of the annular waveguide 20, modulating the effective refractive index through changes in sidewall geometry. The core parameter for this periodic variation is the number of periods, denoted as N. This parameter is set to an integer, representing the number of effective refractive index changes completed in one revolution of the annular waveguide 20. The number of periods N must be twice the number of resonant modes m of the annular waveguide 20. The number of resonant modes m can be determined based on the operating wavelength requirements. Figure 2 This is a schematic diagram of the specific structure of a micro-ring modulator according to one embodiment of this application. Figure 1 ,like Figure 2 As shown, a periodic structure is set on the ring waveguide 20, wherein the ring waveguide 20 has a radius of 5 micrometers and a width of 380 nm. The boundary width of the ring waveguide 20 is sinusoidally modulated, with a modulation period of 124 and a modulation amplitude of 20 nm. The number of affected resonant modes is 62, and the resonant wavelength is in the O-band.

[0048] When the effective refractive index of the ring waveguide 20 changes periodically along the circumference, the periodic structure can couple the portion of the optical signal propagating in the clockwise direction to the counterclockwise direction, or vice versa. This simultaneously excites propagation modes in both clockwise and counterclockwise directions within the ring waveguide 20, corresponding to two propagation modes with positive and negative angular mode numbers, respectively. These two modes should ideally be degenerate modes with the same frequency in a uniform waveguide, propagating independently. Specifically, there is an inherent momentum difference between the clockwise and counterclockwise propagation modes, determined by the number of resonant modes. When the spatial modulation frequency provided by the periodic structure precisely matches this momentum difference, the clockwise and counterclockwise propagation modes are strongly coupled, exchanging and superimposing their energy. They no longer exist as independent traveling waves but form a stable standing wave. The characteristics of a standing wave are that the light intensity is periodically distributed along the circumference, with fixed antinodes (points of maximum light intensity) and nodes (points of near-zero light intensity), and the entire light field pattern remains stationary on the ring.

[0049] Under this strong coupling state, the energy of the micro-ring modulator can be approximately evenly distributed in the clockwise and counterclockwise output channels, and the coupling ideality of the micro-ring modulator approaches 0.5. Here, the coupling ideality is the ratio of the power of the resonant cavity fundamental mode coupled to the bus waveguide fundamental mode to the total power coupled to all modes (including higher-order modes and radiation modes) of the bus waveguide.

[0050] According to coupled-mode theory, the optical fields of clockwise and counterclockwise propagation modes in ring waveguide 20 satisfy the following relationship:

[0051] ;

[0052] ;

[0053] ;

[0054] in, For the input light field amplitude, To output the amplitude of the light field; Let be the field amplitude of the forward-propagating optical field in the ring waveguide 20. The amplitude of the optical field propagating in the reverse direction in the ring waveguide 20; This represents the total loss after coupling the ring waveguide 20 and the transmission waveguide 10. For the intrinsic loss of the ring waveguide 20, The coupling strength between the ring waveguide 20 and the transmission waveguide 10 is given. The coupling strength between the forward propagating optical field and the reverse propagating optical field; The frequency detuning between the light source and the ring waveguide 20 is given by the value of 20. The frequency of the light source, is the resonant frequency of the ring waveguide 20.

[0055] In a microring modulator, considering only the parasitic losses caused by backscattering, the coupling ideality is defined as:

[0056] ;

[0057] in, Let be the field amplitude of the forward-propagating optical field in the ring waveguide 20. The amplitude of the optical field propagating in the reverse direction in the ring waveguide 20. Let represent the coupling strength between the ring waveguide 20 and the transmission waveguide 10. According to the formula for coupling ideality, for a traditional micro-ring modulator, the ring waveguide 20 contains only the forward-propagating optical field, therefore its coupling ideality is 1; for a photonic crystal micro-ring modulator with strong coupling, the backward-propagating optical field is approximately equal to the forward-propagating optical field, and the coupling ideality is approximately 0.5.

[0058] Based on the above formula, the transmittance of the output of waveguide 10 can be obtained as follows:

[0059] ;

[0060] in, For the input light field amplitude, To output the amplitude of the light field; This represents the total loss after coupling the ring waveguide 20 and the transmission waveguide 10. For the intrinsic loss of the ring waveguide 20, The coupling strength between the ring waveguide 20 and the transmission waveguide 10 is given. The coupling strength between the forward propagating optical field and the reverse propagating optical field.

[0061] The modulation module 30 is used to change the refractive index of the ring waveguide 20 in response to an external control signal, so as to modulate the phase of the optical signal distributed in the form of a standing wave.

[0062] Specifically, the modulation module 30 is integrated into the ring waveguide 20. By applying an external control signal, it induces a dynamic change in the refractive index of the ring waveguide 20 material using plasma dispersion or electro-optic effects. When the modulation module 30 changes the refractive index of the ring waveguide 20, the optical path length of light propagating in the ring waveguide 20 changes, causing a change in the resonant wavelength of the ring cavity. Since the wavelength of the input light source is fixed, the shift in the resonant wavelength causes a change in the power coupled from the input waveguide to the ring waveguide 20 (as can be seen from the transmittance formula of the transmission waveguide 10), thereby realizing the function of converting the external control signal into a light intensity modulation signal.

[0063] Traditional micro-ring modulators only support a single-direction (clockwise or counterclockwise) light propagation mode, with a coupling ideality close to 1. To achieve a high extinction ratio, traditional micro-ring modulators need to operate precisely in a critical coupling state, meaning the coupling strength between the transmission waveguide 10 and the ring waveguide 20 must be strictly equal to the intrinsic loss of the ring waveguide 20 itself. However, such stringent operating conditions can lead to minute variations in the coupling gap, or coupling deviations caused by process errors or temperature fluctuations, all of which can disrupt the critical coupling state, resulting in a significant decrease in the extinction ratio. For existing silicon photonics fabrication processes, the geometric parameters such as the spacing between the transmission waveguide 10 and the ring waveguide 20, and the waveguide width, inevitably deviate from the design values; even with well-controlled process parameters, the accuracy limitations of the simulation software itself can introduce design errors. These factors collectively contribute to the high dependence of traditional micro-ring modulators on the critical coupling state.

[0064] The aforementioned micro-ring modulator, by introducing a periodic refractive index change in the circumferential direction on the ring waveguide 20, couples the optical signals propagating in the clockwise and counterclockwise directions, forming a standing wave within the ring waveguide 20 of the micro-ring modulator. Its coupling ideality becomes 0.5, thereby enabling the micro-ring modulator to no longer rely on stringent critical coupling and maintain a high extinction ratio over a wider range of coupling strengths.

[0065] Alternatively, in one embodiment, the boundary width of the ring waveguide 20 varies periodically in the circumferential direction so that the effective refractive index varies accordingly.

[0066] The boundary refers to the sidewall boundary of the ring waveguide 20. In the cross-section of the ring waveguide 20, it has an inner sidewall and an outer sidewall, with the inner sidewall facing the center of the ring and the outer sidewall facing away from the center. The periodic variation of the boundary width can be achieved by periodically alternating the vertical distance between the inner and outer sidewalls along the circumference of the ring waveguide 20. Specifically, when the boundary expands outward, the local width of the ring waveguide 20 increases, the optical field is more tightly confined to the waveguide core, resulting in an increase in the effective refractive index; when the boundary contracts inward, the local width of the ring waveguide 20 decreases, the optical field extends towards the cladding, resulting in a decrease in the effective refractive index. This periodic alternation of width causes the effective refractive index experienced by the optical signal at different locations in the ring waveguide 20 to exhibit a periodic distribution of alternating high and low values, thus forming spatial modulation of the effective refractive index. The number of periods of boundary width variation is denoted as N, an integer representing the number of effective refractive index changes completed around the circumference of the ring waveguide 20.

[0067] Spatial modulation of the effective refractive index is achieved through periodic changes in the boundary width, providing a structural basis for the formation of standing waves, thereby enabling high extinction ratios without the need for precise critical coupling.

[0068] In one embodiment, the modulation module 30 includes a PN junction and a signal input unit; the PN junction is integrated on the ring waveguide 20, and the signal input unit is connected to the PN junction; wherein: the signal input unit is used to apply an electrical signal to the PN junction in response to an external control signal; the PN junction is used to change the refractive index of the ring waveguide 20 in response to the electrical signal.

[0069] Specifically, a vertical PN junction structure can be used, where the upper half of the ring waveguide 20 is an N-type doped region and the lower half is a P-type doped region. Alternatively, a horizontal PN junction structure can be used, where the inner part of the ring waveguide 20 is an N-type doped region and the outer part is a P-type doped region. For example... Figure 2 As shown, the pink area on the inner side of the ring waveguide 20 is an N-type doped region, and the green area on the outer side is a P-type doped region. The signal input unit is connected to the P-type and N-type doped regions of the PN junction, respectively, to apply reverse or forward bias voltage.

[0070] In one embodiment, the ring waveguide 20 is made of silicon. When the signal input unit applies a reverse bias voltage to the PN junction in response to an external control signal, the depletion region of the PN junction widens, and free carriers in the P-type and N-type regions are further depleted, resulting in a decrease in the free carrier concentration in the ring waveguide 20 material. According to the plasma dispersion effect, the decrease in the free carrier concentration in the material will cause an increase in the refractive index of the material. Conversely, when a forward bias voltage is applied, carrier injection causes the depletion region to narrow, the free carrier concentration to increase, and the refractive index of the material to decrease.

[0071] The dynamic change in the refractive index of the ring waveguide 20 material directly alters the optical path length of light propagating within the ring waveguide 20, causing an overall shift in the spatial phase of the standing wave formed by the clockwise and counterclockwise coupling modes. Since the coupling position between the transmission waveguide 10 and the ring waveguide 20 is fixed, the shift in the standing wave phase will cause a change in the light intensity at this fixed coupling point, thereby converting the external control signal into an intensity modulation signal output.

[0072] The modulation module 30 achieves efficient modulation of optical signals based on the standing wave operation established by the periodic structure. The PN junction has a simple structure, fast response speed, and compatibility with existing processes, which is conducive to the large-scale integration and low-cost manufacturing of micro-ring modulators. At the same time, since the standing wave mode has reduced the dependence on critical coupling, the modulation process of the PN junction is not affected by the fluctuation of coupling strength.

[0073] The modulation module 30 achieves efficient electro-optic modulation based on standing wave operation through the coordinated cooperation of the PN junction and the signal input unit. It has the advantages of simple structure, fast response speed and good process compatibility. Moreover, the modulation process is not affected by the fluctuation of coupling strength, which further enhances the overall robustness of the micro-ring modulator.

[0074] In one embodiment, the ring waveguide 20 includes a modulation section and a first coupling section; wherein the modulation section is connected to the modulation module 30; the first coupling section is used for optical signal coupling with the transmission waveguide 10; and the modulation section is used for phase modulation of the optical signal under the action of the modulation module 30.

[0075] Specifically, the modulation segment extends along the circumference of the ring waveguide 20, covering the region on the ring waveguide 20 that overlaps with the PN junction of the modulation module 30. Within this region, the PN junction is integrated inside the ring waveguide 20. When the modulation module 30 applies an electrical signal, the refractive index of the material in the PN junction region changes, thereby applying phase modulation to the optical signal passing through this region.

[0076] The first coupling segment is adjacent to the modulation segment along the circumferential direction of the ring waveguide 20 and is located near the transmission waveguide 10. Within this region, optical signals are coupled between the ring waveguide 20 and the transmission waveguide 10 through the coupling region 40, enabling the optical signal to be input from the transmission waveguide 10 to the ring waveguide 20 and output from the ring waveguide 20 to the transmission waveguide 10. Figure 2As shown, the coupling region 40 is located in the adjacent area between the first coupling segment and the transmission waveguide 10, and is the core functional unit for optical signal exchange between the two. This coupling region 40 is formed by arranging the first coupling segment and the second coupling segment of the transmission waveguide 10 parallel and adjacent to each other, maintaining a specific coupling distance between them, so that their evanescent fields overlap, thereby achieving mutual exchange of optical energy. The geometric range of the coupling region 40 covers the entire area adjacent to the first and second coupling segments; its length is the coupling length, and its width is determined by the coupling distance. The length of the first coupling segment and its distance from the transmission waveguide 10 (i.e., the coupling distance) can be designed according to the required coupling strength. The coupling strength increases with the increase of the coupling length and decreases with the decrease of the coupling distance. By precisely designing these two geometric parameters, the coupling strength can be adjusted to the target value.

[0077] By dividing the ring waveguide 20 into a modulation segment and a first coupling segment, the modulation function and the coupling function are spatially separated, allowing the modulation segment and the coupling segment to be independently optimized according to their respective functional requirements.

[0078] In one embodiment, the ring waveguide 20 includes multiple discontinuous modulation segments; each modulation segment is connected to the modulation module 30.

[0079] The length of the modulation segment can be designed according to the required modulation efficiency and the electrical bandwidth requirements of the modulator, and can occupy one-half to three-quarters of the circumference of the ring waveguide 20 to ensure sufficient modulation depth. Furthermore, the ring waveguide 20 may include multiple discontinuous modulation segments, each spaced apart along the circumference of the ring waveguide 20 and connected to each other via waveguide segments without modulation structures, and each connected to the modulation module 30. Specifically, the distribution of the multiple modulation segments can be periodic or aperiodic, depending on actual needs. Each modulation segment covers an area overlapping with the PN junction of the modulation module 30, used to apply phase modulation to the optical signal passing through the modulation segment. The waveguide segments between adjacent modulation segments do not have modulation structures and only serve as transmission channels for the optical signal, maintaining the continuity of the ring waveguide 20.

[0080] Furthermore, each modulation segment can be controlled independently or work collaboratively. When controlled independently, the standing wave phase can be adjusted by selectively activating modulation segments at different positions, making it suitable for applications requiring high-precision modulation. When working collaboratively, all modulation segments respond to external control signals simultaneously, achieving a stronger cumulative phase modulation effect, suitable for applications requiring modulation depth.

[0081] The arrangement of multiple discontinuous modulation segments can further increase the effective length of the interaction between the modulation structure and the optical signal without changing the overall perimeter of the ring waveguide 20, thereby reducing the length of a single modulation segment and the required driving voltage, and thus reducing the power consumption and thermal effect of the micro-ring modulator.

[0082] In one embodiment, the transmission waveguide 10 includes an input segment, a second coupling segment, and an output segment, with the second coupling segment disposed opposite to the first coupling segment. The input segment is used to receive externally input optical signals; it is located at the first end of the transmission waveguide 10 and is used to receive optical signals from an external light source. The optical signals from the input segment propagate through the transmission waveguide 10 to the second coupling segment.

[0083] The second coupling segment is used for optical signal coupling with the ring waveguide 20. Located between the input and output segments, it is adjacent to and parallel to the first coupling segment of the ring waveguide 20, together forming the coupling region 40. Within this region, the optical signal in the transmission waveguide 10 enters the first coupling segment of the ring waveguide 20 through the coupling region 40, exciting clockwise and counterclockwise propagation modes within the ring waveguide 20. Simultaneously, the modulated optical signal within the ring waveguide 20 is also coupled back from the first coupling segment to the second coupling segment of the transmission waveguide 10 through the same coupling region 40. The spacing between the second and first coupling segments and the length of the coupling region 40 (i.e., the coupling length) are designed according to the target coupling strength.

[0084] The output section is used to couple the modulated optical signal from the output ring waveguide 20. The output section is located at the second end of the transmission waveguide 10 and is used to receive the modulated optical signal from the second coupling section and output it to subsequent photodetectors or other optical processing units.

[0085] By dividing the transmission waveguide 10 into an input segment, a second coupling segment, and an output segment, a clear spatial division of labor is achieved for the three functions of optical signal input, coupled transmission, and modulation output. This segmented design allows each segment to be independently optimized for its specific function, improving design flexibility and manufacturability.

[0086] In one embodiment, the second coupling segment of the transmission waveguide 10 is a curved waveguide, and the curvature of the curved waveguide is the same as the curvature of the first coupling segment of the ring waveguide 20.

[0087] like Figure 2As shown, in one embodiment, the transmission waveguide 10 is a curved waveguide. The second coupling segment of the transmission waveguide 10 has a curvature that matches the first coupling segment of the ring waveguide 20, maintaining an approximately parallel relative position between the two within the coupling region 40. This curved design can significantly increase the length of the coupling region 40, extending the interaction distance between the transmission waveguide 10 and the ring waveguide 20, thereby improving coupling efficiency. Curved waveguides are suitable for applications requiring strong coupling or with limited layout space. In practical designs, the radius of curvature of the curved waveguide should be chosen to be consistent with or approximately the radius of curvature of the ring waveguide 20 to avoid excessive radiation loss caused by an excessively small curvature radius, while ensuring the uniformity of spacing within the coupling region 40.

[0088] In one embodiment, the second coupling segment of the transmission waveguide 10 is a straight waveguide, and the straight waveguide is parallel to the tangent direction of the first coupling segment of the ring waveguide 20.

[0089] Figure 3 This is a schematic diagram of the specific structure of a micro-ring modulator according to one embodiment of this application. Figure 2 ,like Figure 3 As shown, in another embodiment, the transmission waveguide 10 is a straight waveguide. In this case, the second coupling segment of the transmission waveguide 10 is a straight waveguide, positioned along the tangent direction of the ring waveguide 20, parallel and adjacent to the first coupling segment of the ring waveguide 20. The straight waveguide structure is simple, easy to design and manufacture, and the length of the coupling region 40 can be precisely controlled by adjusting the length of the parallel segment. The straight waveguide scheme is suitable for applications requiring high coupling accuracy and with ample layout space.

[0090] By selecting straight or curved waveguides, coupling efficiency, layout, and process complexity can be flexibly optimized according to specific application requirements, thereby improving the adaptability and manufacturability of the design while ensuring the core performance of the micro-ring modulator.

[0091] Figure 4 This is a graph showing the relationship between transmittance and coupling strength under different coupling idealities in one embodiment of this application. Figure 4 As shown, the horizontal axis represents the coupling strength between the transmission waveguide and the ring waveguide, and the vertical axis represents the extinction ratio. Figure 4 The figure shows the relationship between the extinction ratio and the coupling strength when the coupling ideality I is 1, 0.8, 0.5, and 0.2, respectively. From... Figure 4As can be seen, for a traditional micro-ring modulator (with ideal coupling I=1), its extinction ratio reaches its maximum value only at the critical coupling point where the coupling strength between the transmission waveguide and the ring waveguide is strictly equal to the intrinsic loss of the ring waveguide. The region with an extinction ratio greater than 20dB is limited to a very narrow range near the critical point. This steep response characteristic means that to maintain a high extinction ratio, a traditional micro-ring modulator requires precise design and control of the coupling strength. Any slight deviation caused by process errors or temperature fluctuations will lead to a sharp drop in the extinction ratio. More importantly, to increase the modulation bandwidth, a traditional micro-ring modulator needs to increase the coupling strength, but this will cause the micro-ring modulator to deviate from the critical coupling point, resulting in a sharp deterioration in the extinction ratio. Conversely, if the critical coupling point is adhered to in order to maintain a high extinction ratio, the bandwidth will be limited, making it difficult to meet the requirements of high-speed modulation. This trade-off makes it impossible for a traditional micro-ring modulator to simultaneously achieve both a high extinction ratio and a large bandwidth.

[0092] When the coupling ideality is reduced to 0.8, the region with an extinction ratio greater than 20 dB widens compared to when the coupling ideality is 1, indicating that the micro-ring modulator's tolerance to coupling strength fluctuations begins to improve. When the coupling ideality reaches 0.5, the region with an extinction ratio greater than 20 dB significantly expands to the entire range where the coupling strength is greater than or equal to 4.5 times the intrinsic loss. This means that as long as the coupling strength between the transmission waveguide and the ring waveguide is greater than 4.5 times the intrinsic loss, a high extinction ratio of over 20 dB can be guaranteed, reducing the requirements for coupling accuracy and effectively supporting the large-scale mass production needs of micro-ring modulators. Further reducing the coupling ideality to 0.2, although the high extinction ratio region is still relatively wide, the maximum extinction ratio decreases, failing to meet the requirements of high-performance micro-ring modulators. Therefore, maintaining the coupling ideality at around 0.5 is crucial for maintaining the robustness of high extinction ratios. Furthermore, as... Figure 4 As shown, when the coupling ideality is between 0.5 and 1, compared with the traditional micro-ring modulator (coupling ideality is 1), the high extinction ratio region still has a certain degree of broadening, which can achieve synergistic optimization of extinction ratio and bandwidth to a certain extent.

[0093] Figure 5 This is a transmittance curve of a ring waveguide according to an embodiment of this application under different coupling strengths. Figure 5 As shown, Figure 5 The coupling state coefficient K is shown in the figure. ex The evolution of the transmission spectrum as / γ increases from 0.1 to 16, where K ex Let γ be the coupling strength between the transmission waveguide and the ring waveguide, and γ be the intrinsic loss rate of the ring waveguide. The transmittance data shows that as the coupling state coefficient increases, the extinction ratio at the resonant wavelength (i.e., the depth of the transmittance dip) also increases. This indicates that in standing wave mode, increasing the coupling strength of the ring waveguide not only does not degrade the modulation performance but can actually improve the extinction ratio.

[0094] Figure 6 This is a graph showing the relationship between the extinction ratio and optical bandwidth of a micro-ring modulator at different splitting intensities under different modes, as a function of coupling strength, in one embodiment of this application. Figure 6 As shown, the horizontal axis represents the coupling strength between the transmission waveguide and the ring waveguide, the left vertical axis represents the extinction ratio, and the right vertical axis represents the optical bandwidth. The orange line in the figure indicates that increasing the coupling strength linearly increases the optical bandwidth. The family of blue curves shows the change in extinction ratio under different mode splitting intensities: the normalized mode splitting intensity of 0 corresponds to a traditional micro-ring modulator, whose extinction ratio only has sharp peaks at extremely low coupling intensities. When the coupling strength is increased to pursue bandwidth, the extinction ratio drops sharply. As the normalized mode splitting intensity increases, the extinction ratio curve changes significantly. When the normalized mode splitting intensity is 15, the coupling strength shifts to the right into the high bandwidth region, and the sharp peaks are reshaped into gentle plateaus, allowing the micro-ring modulator to maintain both high extinction ratio and high bandwidth over a wide coupling strength range.

[0095] This application provides an optical communication system, including a light source, a photodetector, and a micro-ring modulator; wherein: the light source is used to generate optical signals; the photodetector is used to receive optical signals; the specific structure and function of the micro-ring modulator have been described in detail in the above embodiments.

[0096] Figure 7 This is a flowchart of a micro-ring modulator modulation method according to an embodiment of this application. Figure 7 As shown, the modulation method of this micro-ring modulator includes the following steps:

[0097] In step S710, the optical signal is input to the transmission waveguide of the modulator. The optical signal generated by the external light source enters the modulator through the input section of the transmission waveguide and is transmitted to the ring waveguide through the coupling region between the transmission waveguide and the ring waveguide.

[0098] In step S720, in response to an external control signal, the refractive index of the modulator's ring waveguide is changed through the modulation module to obtain a modulated optical signal, which is then output from the transmission waveguide. Specifically, an electrical signal is applied to the PN junction integrated on the ring waveguide according to the external control signal. The PN junction responds to the electrical signal by changing the refractive index of the ring waveguide material through plasma dispersion or electro-optic effects. The change in refractive index causes an overall shift in the phase of the standing wave within the ring waveguide, thereby changing the light intensity at the fixed coupling point and achieving modulation of the light intensity of the external control signal. The modulated optical signal is transmitted back to the transmission waveguide through the coupling region between the ring waveguide and the transmission waveguide, and then output from the output section of the transmission waveguide to subsequent optoelectronic devices.

[0099] The modulator is any of the micro-ring modulators in the above embodiments, and its specific structure and working principle have been described in detail in the above embodiments, and will not be repeated here.

[0100] The above steps S710 and S720 directly modulate the standing wave phase to achieve optical signal modulation through external control signals. This can simultaneously obtain high extinction ratio and large modulation bandwidth without the need for precise critical coupling, and has the advantages of strong process robustness and high modulation efficiency.

[0101] It should be understood that the specific embodiments described herein are merely illustrative of the application and not intended to limit it. All other embodiments derived by those skilled in the art based on the embodiments provided in this application without inventive effort are within the scope of protection of this application.

[0102] Obviously, the accompanying drawings are merely some examples or embodiments of this application. Those skilled in the art can apply this application to other similar situations based on these drawings without any creative effort. Furthermore, it is understood that although the work done in this development process may be complex and lengthy, for those skilled in the art, certain design, manufacturing, or production modifications made based on the technical content disclosed in this application are merely conventional technical means and should not be considered as insufficient disclosure of this application.

[0103] The term "embodiment" in this application refers to a specific feature, structure, or characteristic described in connection with an embodiment that may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily imply the same embodiment, nor does it imply that it is mutually exclusive with or independent of other embodiments. It will be clearly or implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments without conflict.

[0104] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of patent protection. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the appended claims.

Claims

1. A micro-ring modulator, characterized in that, The micro-ring modulator includes: a transmission waveguide, a ring waveguide, and a modulation module; the transmission waveguide is coupled to the ring waveguide, the effective refractive index of the ring waveguide changes periodically in the circumferential direction, the number of periods of the effective refractive index change is an integer, and the number of periods is twice the number of resonant modes of the ring waveguide; The transmission waveguide is used to transmit optical signals; The ring waveguide is used to guide the optical signal to propagate in clockwise and counterclockwise directions respectively, so that the optical signal propagating in the clockwise direction is coupled with the optical signal propagating in the counterclockwise direction and distributed in the form of a standing wave in the ring waveguide; The modulation module is used to change the refractive index of the ring waveguide in response to an external control signal, so as to modulate the phase of the optical signal distributed in the form of a standing wave.

2. The micro-ring modulator according to claim 1, characterized in that, The boundary width of the ring waveguide varies periodically in the circumferential direction, so that the effective refractive index varies accordingly.

3. The micro-ring modulator according to claim 1, characterized in that, The modulation module includes a PN junction and a signal input unit; the PN junction is integrated on the ring waveguide, and the signal input unit is connected to the PN junction; wherein: The signal input unit is used to apply an electrical signal to the PN junction in response to the external control signal; The PN junction is used to change the refractive index of the ring waveguide in response to the electrical signal.

4. The micro-ring modulator according to claim 1, characterized in that, The ring waveguide includes a modulation section and a first coupling section; wherein the modulation section is connected to the modulation module; The first coupling segment is used for optical signal coupling with the transmission waveguide; The modulation segment is used to perform phase modulation on the optical signal under the action of the modulation module.

5. The micro-ring modulator according to claim 4, characterized in that, The ring waveguide includes multiple discontinuous modulation segments; each modulation segment is connected to the modulation module.

6. The micro-ring modulator according to claim 4, characterized in that, The transmission waveguide includes an input segment, a second coupling segment, and an output segment, wherein the second coupling segment is disposed opposite to the first coupling segment; wherein: The input segment is used to receive externally input optical signals; The second coupling segment is used for optical signal coupling with the ring waveguide; The output section is used to couple and output the optical signal modulated by the ring waveguide.

7. The micro-ring modulator according to claim 6, characterized in that, The second coupling segment of the transmission waveguide is a curved waveguide, and the curvature of the curved waveguide is the same as the curvature of the first coupling segment of the ring waveguide.

8. The micro-ring modulator according to claim 6, characterized in that, The second coupling segment of the transmission waveguide is a straight waveguide, and the straight waveguide is parallel to the tangent direction of the first coupling segment of the ring waveguide.

9. An optical communication system, characterized in that, It includes a light source, a photodetector, and a micro-ring modulator according to any one of claims 1 to 8; wherein: The light source is used to generate light signals; The photodetector is used to receive optical signals.

10. A modulation method for a micro-ring modulator, characterized in that, include: The optical signal is input to the transmission waveguide of the modulator; In response to an external control signal, the refractive index of the modulator's ring waveguide is changed by the modulator's modulation module to obtain a modulated optical signal, and the modulated optical signal is output from the transmission waveguide; The modulator is the micro-ring modulator according to any one of claims 1 to 8.

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