Optical modulator, optical signal modulation method and electronic device

Abstract

An optical modulator, an optical signal modulation method and an electronic device. The optical modulator comprises: a single-mode bus waveguide (10), an input end of the single-mode bus waveguide (10) being used for receiving incident light in a first mode, and an output end being used for outputting output light in the first mode; a front resonant cavity waveguide (20) having an antisymmetric grating structure, the front resonant cavity waveguide (20) being used for exciting the incident light in the first mode into forward light in a second mode, and performing conversion processing on the forward light in the second mode and backward light in a third mode; and a rear resonant cavity waveguide (30) having an antisymmetric grating structure, the rear resonant cavity waveguide (30) being cascaded with the front resonant cavity waveguide (20) and being used for affecting, by means of adjusting the phase of an optical signal transmitted in the rear resonant cavity waveguide (30), the resonance distribution state of an optical signal transmitted in the front resonant cavity waveguide (20), thereby achieving modulation of the output light of the single-mode bus waveguide (10).

Description

Optical modulator, optical signal modulation method, and electronic device

[0001] Cross-reference to related applications

[0002] This application claims priority to the Chinese patent application No. 202411379225.2, filed on September 30, 2024, entitled “Optical modulator, optical signal modulation method, and electronic device”, the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0003] Embodiments of the present application relate to the technical field of silicon-based optoelectronic integrated chip, and particularly relate to an optical modulator, an optical signal modulation method, and an electronic device. BACKGROUND

[0004] With the advent of the big data era, there is an increasing demand for high-speed and high-capacity optical communication networks. In an optical communication system, an optical modulator, as a key device, directly determines the transmission rate and transmission distance of the entire system. Silicon-based optoelectronic integration technology is widely used in the new generation of optical communication systems due to its compatibility with complementary metal oxide semiconductor (CMOS) process, high integration, low energy consumption, and other advantages.

[0005] Silicon-based modulators play a crucial role in the new generation of optical communication systems and are key devices for realizing high-speed and high-capacity optical communication networks. Silicon-based modulators have the characteristics of small size and high integration, which are beneficial to the construction of compact optical circuit systems. With the increasing demand for interconnection within and between data centers, there is an urgent need for highly integrated optical interconnection systems, and silicon-based modulators can meet this demand. Silicon-based modulators can support transmission rates of hundreds of gigabits per second (Gbps) or even terabits per second (Tbps) through carrier injection or depletion mechanisms, which can effectively alleviate the current bandwidth bottleneck and meet the growing demand for data transmission. In addition, silicon-based modulators have low power consumption and can be highly integrated with electronic devices to construct energy-efficient optoelectronic integrated systems, which are conducive to realizing green and environmentally friendly new-generation communication networks. As a key device in optical circuits, the performance of silicon-based modulators directly determines the transmission capacity of the entire optical communication system.

[0006] In the related art, there are mainly two types of silicon-based optical modulators: Mach-Zehnder modulators and micro-ring modulators. The Mach-Zehnder modulator modulates an optical signal by changing the relative phase difference of two arm waveguides, has a large optical modulation range, but occupies a large area and is difficult to highly integrate. The micro-ring modulator modulates an optical signal by using the resonance effect of a micro-ring cavity, has a small volume and is easy to integrate, but is limited by the free spectral range of the micro-ring, and has a limited modulation bandwidth.

[0007] Therefore, how to improve the modulation bandwidth of the micro-ring modulator is a technical problem to be solved in the related art. SUMMARY

[0008] Embodiments of the present application provide an optical modulator, an optical signal modulation method and an electronic device.

[0009] In a first aspect, an optical modulator is provided, comprising: a single-mode bus waveguide, an input end of the single-mode bus waveguide being configured to receive incident light of a first mode, and an output end of the single-mode bus waveguide being configured to output output light of the first mode; a front resonant cavity waveguide having an anti-symmetric grating structure, configured to excite the incident light of the first mode into forward light of a second mode, and to perform conversion processing on the forward light of the second mode and backward light of a third mode; and a back resonant cavity waveguide having an anti-symmetric grating structure, cascaded with the front resonant cavity waveguide, configured to adjust the phase of an optical signal transmitted in the back resonant cavity waveguide to affect the resonance distribution state of an optical signal transmitted in the front resonant cavity waveguide, and thereby to realize modulation of the output light of the single-mode bus waveguide.

[0010] In a second aspect, an optical signal modulation method is provided, applied to the optical modulator of the first aspect, and comprising: receiving incident light of a first mode through an input end of a single-mode bus waveguide; exciting the incident light of the first mode into forward light of a second mode through a front resonant cavity waveguide, and performing conversion processing on the forward light of the second mode and backward light of a third mode; and adjusting the phase of an optical signal transmitted in the back resonant cavity waveguide through the back resonant cavity waveguide to affect the phase resonance distribution state of an optical signal transmitted in the front resonant cavity waveguide, so as to realize modulation of the output light of the single-mode bus waveguide.

[0011] In a third aspect, an electronic device is provided, comprising the optical modulator of the first aspect.

[0012] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present application. BRIEF DESCRIPTION OF DRAWINGS

[0013] The accompanying drawings, which are incorporated into and form part of the specification, illustrate embodiments consistent with the present application and, together with the specification, serve to explain the principles of the application.

[0014] FIG. 1 shows a structural diagram of an optical modulator according to an example embodiment of the present application;

[0015] FIG. 2 shows a structural diagram of an optical modulator according to another example embodiment of the present application;

[0016] FIG. 3 shows a structural diagram of an optical modulator according to yet another example embodiment of the present application;

[0017] FIG. 4a shows a diagram of simulation results of carrier concentration distribution of a horizontal PN junction under 0V bias;

[0018] FIG. 4b shows a diagram of simulation results of a horizontal PN junction;

[0019] FIG. 4c shows a diagram of simulation results of carrier concentration distribution of an S-shaped PN junction under 0V bias;

[0020] FIG. 4d shows a diagram of simulation results of an S-shaped PN junction;

[0021] FIG. 5a shows a diagram of an antisymmetric grating structure according to an example embodiment;

[0022] FIG. 5b shows a diagram of simulation results of transmission and reflection spectrum of the antisymmetric grating structure according to an example embodiment;

[0023] FIG. 5c shows a diagram of input TE0 mode optical signal of the antisymmetric grating structure according to an example embodiment;

[0024] FIG. 5d shows a diagram of reflected output TE1 mode optical signal of the antisymmetric grating structure according to an example embodiment;

[0025] FIG. 6a shows a diagram of output transmission spectrum of the optical modulator according to an example embodiment;

[0026] FIG. 6b shows a diagram of electro-optical modulation response of the optical modulator according to an example embodiment;

[0027] FIG. 7 shows a flowchart of an optical modulation method according to an example embodiment of the present application. DETAILED DESCRIPTION

[0028] The example embodiments will be described in detail herein with reference to the accompanying drawings. In the following description, unless otherwise indicated, like numbers in the different drawings represent similar or analogous elements. The following description of example embodiments is not representative of all embodiments consistent with the present application. Rather, it is merely an example of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0029] Figure 1 shows a schematic diagram of an optical modulator according to an example embodiment of the present application. As shown in Figure 1, the optical modulator mainly comprises a single-mode bus waveguide 10, a front resonant cavity waveguide 20 and a back resonant cavity waveguide 30. The input end of the single-mode bus waveguide 10 is configured to receive incident light of a first mode, and the output end of the single-mode bus waveguide 10 is configured to output output light of the first mode. The front resonant cavity waveguide 20 has an anti-symmetrical grating structure, and is configured to excite the incident light of the first mode into forward light of a second mode, and to convert the forward light of the second mode and backward light of a third mode. The back resonant cavity waveguide 30 also has an anti-symmetrical grating structure, and is cascaded with the front resonant cavity waveguide 20. The back resonant cavity waveguide 30 is configured to affect the resonance distribution state of the light signal transmitted in the front resonant cavity waveguide 20 by adjusting the phase of the light signal transmitted in the back resonant cavity waveguide 30, thereby achieving modulation of the output light of the single-mode bus waveguide 10.

[0030] The above optical modulator according to the example embodiments of the present application is composed of a single-mode bus waveguide and two cascaded resonant cavity waveguides with anti-symmetrical grating structures. By using the anti-symmetrical grating structure, a resonant cavity with high quality factor can be formed, thereby obtaining a modulator with high extinction ratio. In addition, by using the cascaded double-cavity structure, the effective trade-off between wide bandwidth and high extinction ratio can be achieved by adjusting the coupling strength and phase relationship, thereby expanding the modulation bandwidth.

[0031] In some embodiments, as shown in Figure 2, the front resonant cavity waveguide is composed of a front cavity mirror 21, a first phase shift waveguide 22 and a first part of an inter-cavity coupler 40. The front cavity mirror 21 has an anti-symmetrical grating structure, and is configured to reflect the backward light of the third mode into forward light of the second mode. The first phase shift waveguide 22 is connected in series with the front cavity mirror 21, and is configured to excite the input light of the first mode into forward light of the second mode. The inter-cavity coupler 40 is configured to couple the front resonant cavity waveguide 20 and the back resonant cavity waveguide 30. The inter-cavity coupler 40 is configured to forward transmit a part of the forward light of the second mode to the back resonant cavity waveguide 30, and to convert another part of the forward light of the second mode into backward light of the third mode, which is transmitted to the front cavity mirror 21 through the first phase shift waveguide 22. The first phase shift waveguide 22 is also configured to couple the forward light of the second mode into the output light of the first mode output from the output end of the single-mode bus waveguide 10.

[0032] In some embodiments, as shown in FIG. 2, the back resonant cavity waveguide 30 is composed of the second part of the inter-cavity coupler 40, the second phase shift waveguide 31 and the back cavity mirror 32, wherein the second phase shift waveguide 31 is configured to adjust the phase of the forward light of the second mode and transmit the adjusted forward light of the second mode to the back cavity mirror 32; and the back cavity mirror 32 is a reverse-symmetry grating structure configured to reflect the forward light of the second mode as backward light of the third mode, and transmit the backward light of the third mode to the front cavity mirror 21 through the second phase shift waveguide 31 and the inter-cavity coupler 40.

[0033] In some embodiments, as shown in FIG. 1 and FIG. 2, the inter-cavity coupler 40 can be a waveguide with a reverse-symmetry grating structure. In these embodiments, the coupling strength between the two resonant cavities can be controlled by adjusting the number of periods of the inter-cavity coupler 40. Alternatively, the transmissivity of the inter-cavity coupler 40 can be determined based on the coupling strength between the front resonant cavity waveguide 20 and the back resonant cavity waveguide 30, that is, the coupling strength between the front resonant cavity waveguide 20 and the back resonant cavity waveguide 30 is controlled by the reflectivity of the inter-cavity coupler 40. In these embodiments, by setting the inter-cavity coupler 40 as a reverse-symmetry grating structure, the coupling strength between the two resonant cavities can be controlled by controlling the reflectivity of the inter-cavity coupler 40.

[0034] In the above embodiments, a phase shift waveguide is added between the two resonant cavities, and the phase relationship between the two resonant cavities can be adjusted through the phase shift waveguide, so as to control the extinction ratio of the optical modulator.

[0035] By using the optical modulator in the above embodiments, the reflectivity, the coupling strength and the phase relationship can be precisely controlled by optimizing the parameters (such as the period, the side wall corrugation width, etc.) of the reverse-symmetry grating structure, the length of the coupling region and the length of the phase shift waveguide, so as to obtain the performance of the modulator with high quality factor, high extinction ratio and wide bandwidth.

[0036] In some embodiments, in order to avoid the optical signal of the third mode being coupled back into the bus waveguide, the absolute value of the difference between the refractive index of the optical signal of the second mode and the refractive index of the optical signal of the third mode can be greater than a second threshold value. The second threshold value can be set according to actual application.

[0037] In some embodiments of the present application, the first mode can be TE b0 mode, the second mode can be TE g1 mode, and the third mode can be TE g0 mode. In these embodiments, the single-mode bus waveguide 10 supports TE b0 mode, the first phase shift waveguide 22 and the second phase shift waveguide 31 support TE g0 and TE g1 mode; wherein TE b0 and TEg1 The effective refractive indices of the modes are equal; the anti-symmetrical grating structure has a mode conversion function, and the input TE g0 Mode light is reflected as TE g1 Mode light.

[0038] In the optical modulator shown in FIG. 2, the input TE b0 Mode light is first coupled into the first phase-shifted waveguide 22 of the front resonant cavity waveguide 20, exciting the TE g1 Mode forward light (i.e., forward-transmitted optical signal), the TE g1 Mode forward light continues to propagate forward, passes through the inter-cavity coupler 40 (i.e., the second segment of the anti-symmetrical grating), and a portion of the reflected mode is converted into the TE g0 Mode backward light (i.e., backward-transmitted optical signal), and the other portion of the transmitted TE g1 Mode forward light enters the rear resonant cavity waveguide 30; the above-mentioned transmitted TE g1 Mode forward light propagates forward and encounters the rear cavity mirror 32 (i.e., the third segment of the anti-symmetrical grating), and a portion of the reflected mode is converted into the TE g0 Mode backward light propagates backward and possibly transmits out of the rear resonant cavity waveguide 30; the above-mentioned reflected TE g0 Mode backward light propagates backward and encounters the front cavity mirror 21 (i.e., the first segment of the anti-symmetrical grating), and a portion of the reflected mode is converted into the TE g1 Mode forward light propagates forward and possibly transmits out of the front resonant cavity waveguide 20. As can be seen, in this structure, the TE g1 Mode optical signal always propagates forward, and the TE g0 Mode optical signal always propagates backward, and both modes exist in the two resonant cavity waveguides simultaneously, constituting a resonance; because the effective refractive indices of the TE g0 and TE g1 Modes are quite different, the backward-propagating light will not be coupled into the bus waveguide in the reverse direction.

[0039] Light field may leak in the first and third segments of the anti-symmetrical grating structure, and therefore, in some embodiments, the absolute value of the difference between the reflectivity of the front cavity mirror 21 and the rear cavity mirror 32 and 1 is less than a first threshold, that is, the reflectivity of the front cavity mirror 21 and the rear cavity mirror 32 is designed to approach 1.

[0040] In some embodiments, as shown in FIG. 3, a PN junction 33 can also be integrated in the second phase-shifted waveguide 31. In these embodiments, the adjustment of the transmitted optical signal in the rear resonant cavity waveguide is achieved through the carrier dispersion effect, thereby achieving modulation of the output light intensity.

[0041] In the above embodiment, the phase modulation of light can be achieved by adding a PN junction 33 in the second phase-shifted waveguide 31 and applying a reverse bias voltage to the PN junction 33 using the plasma dispersion effect. When different reverse bias voltages are applied, the carrier concentration in the silicon waveguide changes, which in turn changes the effective refractive index of the waveguide, thereby causing a change in the phase of light propagating in the waveguide, and achieving phase modulation of light.

[0042] Optionally, the PN junction 33 can be a horizontal PN junction or an S-shaped PN junction. FIGS. 4a and 4b show simulation results of the carrier concentration distribution of a horizontal PN junction under a 0V bias. For a horizontal PN junction, as the reverse bias increases, the junction capacitance gradually decreases, and the corresponding electrical bandwidth gradually increases.

[0043] FIGS. 4c and 4d show simulation results of the carrier concentration distribution of an S-shaped PN junction under a 0V bias. Unlike a horizontal PN junction, the P region and the N region of an S-shaped PN junction are not parallelly distributed in the lateral direction, but are S-shaped. This structure design increases the junction interface area between the P region and the N region, thereby enhancing the interaction between the optical field and the carriers and improving the modulation efficiency. The junction capacitance of an S-shaped PN junction is generally higher than that of a horizontal PN junction, and decreases more significantly as the bias increases, but the corresponding electrical bandwidth also has more room for improvement. Therefore, when designing a modulator, the balance between the junction capacitance (which determines the electrical bandwidth) and the modulation efficiency can be considered. An S-shaped PN junction can achieve higher modulation efficiency at the cost of sacrificing some electrical bandwidth, while a horizontal PN junction has relatively high electrical bandwidth but relatively low modulation efficiency.

[0044] In some embodiments, the waveguide with the anti-symmetric grating structure has sawtooth-shaped protrusions that are anti-symmetrically distributed on both sides of the waveguide, and the distribution period of the anti-symmetrically distributed sawtooth-shaped protrusions satisfies the Bragg reflection condition. Optionally, the waveguide with the anti-symmetric grating structure is periodically arranged by at least two waveguides with different widths, and can support two different modes. By designing the period of the grating and the width of the sidewall corrugation, effective coupling between the two modes can be achieved, so that one mode is strongly Bragg reflected when propagating in the grating, while the other mode can be freely transmitted. Using this characteristic, the anti-symmetric grating can be used as a high-reflectivity resonant cavity mirror to form a high-quality-factor resonant cavity.

[0045] Figure 5a shows a schematic diagram of a structure of an antisymmetric grating in an example embodiment of the present application, Figure 5b shows a curve diagram of transmission and reflection spectra of the antisymmetric grating in the example embodiment, Figure 5c is a schematic diagram of an input optical signal of TE0 mode in the antisymmetric grating structure, and Figure 5d is a schematic diagram of an output optical signal of TE1 mode after the antisymmetric grating structure reflects the optical signal of TE0 mode. As shown in Figures 5a to 5d, grooves can be periodically etched on both sides of a silicon waveguide to form corrugated sidewall structures, and the period of the sidewall corrugated structure is designed to satisfy the Bragg condition near the working wavelength, thereby forming an antisymmetric grating. When the wavelength of the incident light satisfies the phase matching condition, an orthogonal mode is excited in the waveguide of the antisymmetric grating structure. The input is TE0 mode, and the optical field is symmetrically distributed in the center of the waveguide. After reflection by the grating, the TE1 mode with antisymmetric distribution is excited. By optimizing the parameters such as the waveguide width, the corrugated width and the period, the coupling strength of the two modes can be adjusted. The transmission spectrum and the reflection spectrum of the antisymmetric grating obtained by the Finite Difference Time Domain (FDTD) simulation can be seen that the transmittance is close to 0 at the center wavelength of 1549.63 nm, and the reflectance reaches the maximum value.

[0046] In some embodiments, the front resonant cavity waveguide 20, the single-mode bus waveguide 10 and the back resonant cavity waveguide 30 can be silicon waveguides.

[0047] Optionally, the width of the front cavity mirror 21, the back cavity mirror 32, the first phase shift waveguide 22 and the second phase shift waveguide 31 can range from 0.6 to 0.8 microns, and the height can be 0.22 microns.

[0048] Figures 6a and 6b respectively show the simulation results of the transmission spectrum and the electro-optical bandwidth of the optical modulator in an example embodiment of the present application. The 3dB modulation electro-optical bandwidth can exceed 60GHz under a 5V reverse bias. The reason why such a high electro-optical bandwidth can be achieved is mainly due to the following two factors: the double-cavity coupling reduces the photon lifetime in the cavity, thereby increasing the optical bandwidth of the modulator; and the resonant cavity based on the antisymmetric grating has a small mode volume, which reduces the PN junction capacitance and improves the electrical bandwidth. In addition, since the PN junction is short, the driving power consumption can also be greatly reduced. By adjusting the resonant wavelength of the two resonant cavities and the coupling strength before them, the resonant extinction ratio can be flexibly adjusted, so that a relatively large modulation depth can be obtained.

[0049] As can be seen, the optical modulator provided in the embodiments of the present application combines the antisymmetric grating and the cascaded double cavity, and takes into account the electro-optical bandwidth, the driving power consumption and the modulation depth, and can achieve a high-performance optical modulation.

[0050] FIG. 7 shows a flowchart of a method for modulating an optical signal according to an example embodiment of the present application. The method can be applied to the optical modulator described above. As shown in FIG. 7, the method mainly includes the following steps.

[0051] S701, receiving incident light of a first mode through an input end of a single-mode bus waveguide;

[0052] S702, exciting the incident light of the first mode into forward light of a second mode through a front resonant cavity waveguide, and performing conversion processing on the forward light of the second mode and backward light of a third mode;

[0053] S703, adjusting a phase of light transmitted in the back resonant cavity waveguide to affect a resonance distribution state of light transmitted in the front resonant cavity waveguide through the back resonant cavity waveguide, so as to realize modulation of output light of the single-mode bus waveguide.

[0054] According to the above method provided by the example embodiments of the present application, the optical modulator with the resonant cavity waveguide having an anti-symmetrical grating structure can be used to modulate light, so as to realize effective trade-off between wide bandwidth and high extinction ratio, and expand the modulation bandwidth.

[0055] In some embodiments, exciting the incident light of the first mode into forward light of a second mode through a front resonant cavity waveguide, and performing conversion processing on the forward light of the second mode and backward light of a third mode can include the following steps:

[0056] Step 1, exciting input light of a first mode into forward light of a second mode through a first phase shift waveguide;

[0057] Step 2, transmitting a part of the forward light of the second mode forward to the back resonant cavity waveguide through an inter-cavity coupler, converting another part of the forward light of the second mode into backward light of a third mode, and transmitting the backward light of the third mode to a front cavity mirror through the first phase shift waveguide;

[0058] Step 3, reflecting the backward light of the third mode into forward light of the second mode through the front cavity mirror;

[0059] Step 4, coupling the forward light of the second mode into output light of the first mode output from the output end through the first phase shift waveguide.

[0060] In some embodiments, adjusting the phase of light transmitted in the back resonant cavity waveguide to affect the phase of light transmitted in the front resonant cavity waveguide through the back resonant cavity waveguide includes:

[0061] Step 1, adjusting the phase of forward light of a second mode through a second phase shift waveguide, and transmitting the adjusted forward light of the second mode to a back cavity mirror;

[0062] Step 2, reflecting the forward light of the second mode into backward light of the third mode by the back cavity mirror, transmitting the backward light of the second mode to the front cavity mirror through the second phase shift waveguide and the inter-cavity coupler.

[0063] Through the technical scheme provided by the embodiments of the present application, high-efficiency light modulation can be realized by accurately controlling the phase, and the modulation depth and extinction ratio of the device are improved. Through the flexible phase adjustment capability of the first phase shifter and the second phase shifter, the modulator can be adjusted under different working conditions, thereby adapting to different application requirements. Moreover, by optimizing the design of the phase shifter, the phase error between the resonant cavities can be reduced, the Q value of the resonant cavity is improved, and thus the performance of the entire modulator is improved.

[0064] The embodiments of the present application also provide an electronic device, which can include the above-mentioned light modulator. The electronic device can be used as a light signal transmission device, and is applied in scenarios such as data centers.

[0065] Other embodiments of the present application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The specification and examples given are exemplary only and the true scope and spirit of the application are indicated by the claims. The specification and examples are to be regarded as illustrative only, the true scope and spirit of the application being indicated by the following claims.

[0066] It should be understood that the present application is not limited to the precise construction that has been described above and illustrated in the accompanying drawings, and that various modifications and changes can be made by those skilled in the art without departing from the scope of the present application. The scope of the present application is limited only by the appended claims.

Claims

1. An optical modulator, comprising: a single-mode bus waveguide, an input end of the single-mode bus waveguide configured to receive incident light of a first mode, an output end of the single-mode bus waveguide configured to output output light of the first mode; a front resonant cavity waveguide having an anti-symmetrical grating structure, configured to excite the incident light of the first mode into forward light of a second mode, and to convert the forward light of the second mode and backward light of a third mode; a back resonant cavity waveguide having an anti-symmetrical grating structure, cascaded with the front resonant cavity waveguide, configured to affect a resonance distribution state of the light signal transmitted in the front resonant cavity waveguide by adjusting a phase of the light signal transmitted in the back resonant cavity waveguide, thereby to realize modulation of the output light of the single-mode bus waveguide.

2. The optical modulator of claim 1, wherein, the front resonant cavity waveguide is composed of a front cavity mirror, a first phase shift waveguide, and a first part of an inter-cavity coupler, wherein the front cavity mirror is an anti-symmetrical grating structure, configured to reflect the backward light of the third mode into the forward light of the second mode; the first phase shift waveguide is in series with the front cavity mirror, and the first phase shift waveguide is configured to excite the input light of the first mode into the forward light of the second mode; the inter-cavity coupler is configured to couple the front resonant cavity waveguide and the back resonant cavity waveguide, and the inter-cavity coupler is configured to forward transmit a part of the forward light of the second mode to the back resonant cavity waveguide, to convert another part of the forward light of the second mode into the backward light of the third mode, to transmit the backward light of the third mode to the front cavity mirror through the first phase shift waveguide, and to couple the forward light of the second mode into the output light of the first mode output from the output end. the back resonant cavity waveguide is composed of a second part of the inter-cavity coupler, a second phase shift waveguide, and a back cavity mirror, wherein 3. The optical modulator of claim 2, wherein, the second phase shift waveguide is configured to adjust the phase of the forward light of the second mode, and to transmit the adjusted forward light of the second mode to the back cavity mirror; the back cavity mirror is an anti-symmetrical grating structure, configured to reflect the forward light of the second mode into the backward light of the third mode, and to transmit the backward light of the third mode to the front cavity mirror through the second phase shift waveguide and the inter-cavity coupler. the inter-cavity coupler is a waveguide having an anti-symmetrical grating structure.

4. The optical modulator of claim 3, wherein, a transmittance of the inter-cavity coupler is determined based on a coupling strength between the front resonant cavity and the back resonant cavity.

5. The optical modulator of claim 4, wherein, a PN junction is integrated in the second phase shift waveguide.

6. The optical modulator of claim 3, wherein, the PN junction includes a horizontal PN junction or an S-shaped PN junction.

7. The optical modulator of claim 6, wherein, the waveguide having the anti-symmetrical grating structure has sawtooth-shaped protrusions in anti-symmetrical distribution on two sides of the waveguide, and a distribution period of the sawtooth-shaped protrusions in anti-symmetrical distribution satisfies a Bragg reflection condition.

8. The optical modulator of any one of claims 1 to 7, wherein, the waveguide having the anti-symmetrical grating structure is composed of at least two waveguide structures having different widths arranged periodically.

9. The optical modulator of claim 8, wherein, an absolute value of a difference between a reflectivity of the front cavity mirror and a reflectivity of the back cavity mirror and 1 is less than a first threshold value.

10. The optical modulator of claim 3, wherein, the front resonant cavity waveguide, the single-mode bus waveguide, and the back resonant cavity waveguide include silicon waveguides.

11. The optical modulator of any one of claims 1 to 7, wherein, ​ 12. The optical modulator of claim 3, wherein, The front cavity mirror, the back cavity mirror, the first phase shift waveguide and the second phase shift waveguide have a width ranging from 0.6 to 0.8 microns and a height of 0.22 microns.

13. The optical modulator of claim 2 or 3, wherein, An absolute value of a difference between the refractive index of the second mode of light signal and the third mode of light signal is greater than a second threshold value.

14. A method for modulating a light signal, applied to the light modulator of any one of claims 1 to 13, the method comprising: receiving, by an input end of a single-mode bus waveguide, a first mode of incident light; exciting, by a front resonant cavity waveguide, the first mode of incident light into a second mode of forward light and converting the second mode of forward light and a third mode of backward light; adjusting, by the back resonant cavity waveguide, a phase of light signals transmitted in the back resonant cavity waveguide to affect a resonance distribution state of light signals transmitted in the front resonant cavity waveguide to achieve modulation of output light of the single-mode bus waveguide.

15. The method of claim 14, wherein, exciting, by a front resonant cavity waveguide, the first mode of incident light into a second mode of forward light and converting the second mode of forward light and a third mode of backward light, comprising: exciting, by a first phase shift waveguide, the first mode of input light into the second mode of forward light; transmitting, by an inter-cavity coupler, a portion of the second mode of forward light forwardly to the back resonant cavity waveguide and converting another portion of the second mode of forward light into the third mode of backward light, transmitting, by the first phase shift waveguide, the third mode of backward light to a front cavity mirror; reflecting, by the front cavity mirror, the third mode of backward light into the second mode of forward light; coupling, by the first phase shift waveguide, the second mode of forward light into the first mode of output light output from the output end.

16. The method of claim 15, wherein, adjusting, by the back resonant cavity waveguide, a phase of light signals transmitted in the back resonant cavity waveguide to affect a phase of light signals transmitted in the front resonant cavity waveguide, comprising: adjusting, by a second phase shift waveguide, a phase of the second mode of forward light and transmitting the adjusted second mode of forward light to a back cavity mirror; reflecting, by the back cavity mirror, the second mode of forward light into the third mode of backward light and transmitting the second mode of backward light to the front cavity mirror via the second phase shift waveguide and the inter-cavity coupler.

17. An electronic device comprising the light modulator of any one of claims 1 to 13.

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