Silicon light modulator based on cascaded traveling wave electrode MZI structure

Abstract

The invention discloses a silicon optical modulator based on a cascaded traveling wave electrode MZI structure. The silicon optical modulator is characterized by comprising a silicon-based substrate, and an input optical waveguide, a cascaded MZI modulation unit group, an output optical waveguide and a driving circuit which are integrated on the silicon-based substrate, the output end of the input optical waveguide is connected with the input end of the cascade MZI modulation unit group, the output end of the cascade MZI modulation unit group is connected with the input end of the output optical waveguide, and the driving circuit is electrically connected with the cascade MZI modulation unit group; the cascaded MZI modulation unit group is formed by cascading at least two MZI modulation units in sequence, and each MZI modulation unit is provided with a sectional traveling wave electrode; according to the invention, the contradictory limitation of bandwidth and driving voltage is broken through; the cascaded MZI modulation unit group design is adopted, and the traveling wave electrode length of each MZI modulation unit can be greatly shortened.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of modulators, and particularly relates to a silicon optical modulator based on a cascaded traveling wave electrode MZI structure. BACKGROUND

[0002] As a core device in an optical communication system, a silicon optical modulator undertakes the key function of converting an electrical signal into an optical signal, and its performance directly determines the transmission rate, bandwidth and power consumption of the communication system. A Mach-Zehnder interferometer (MZI) structure has the advantages of good modulation linearity and high integration, and has become one of the mainstream structures of a silicon optical modulator. The working principle of the MZI structure is to change the phase of an optical wave by applying an electrical signal to two arms of the MZI, and to realize optical intensity modulation after interference.

[0003] The existing silicon optical modulator based on the MZI structure mainly adopts a single-stage traveling wave electrode design. However, this design has many technical bottlenecks that are difficult to overcome. Firstly, there is an inherent contradiction between bandwidth and driving voltage. In order to improve the modulation bandwidth, the length of the traveling wave electrode needs to be shortened to reduce the RC delay. However, shortening the length of the electrode will result in insufficient phase modulation depth, and a high driving voltage is needed to achieve the target modulation effect. However, a high driving voltage will increase the power consumption of the system, which is contrary to the development demand of low power consumption of the optical communication system. Secondly, the phase modulation efficiency is low. The single-stage electrode has limited ability to regulate the phase of the optical wave. Especially in the high-speed modulation scene, the phase change rate is difficult to match the change speed of the electrical signal, resulting in an increase in distortion of the modulated signal. Thirdly, the signal integrity is poor. The traveling wave electrode is prone to impedance discontinuity when transmitting high-frequency electrical signals, which causes signal reflection, reduces the modulation efficiency, and also causes electromagnetic interference to adjacent circuits, affecting the stability of the system.

[0004] In order to solve the above problems, researchers have tried to use multiple electrode parallel connection or optimize electrode materials, but none of them has made a breakthrough. Although multiple electrode parallel connection can reduce the driving voltage, it will increase the parasitic capacitance between the electrodes, further limiting the bandwidth improvement. Although optimizing the electrode material can improve the signal transmission characteristics, it is difficult to realize large-scale integrated application due to the compatibility of silicon-based materials. Therefore, developing a silicon optical modulator with low driving voltage, high bandwidth and high modulation efficiency has become a key technical problem to be solved in the field of silicon-based optoelectronics. SUMMARY

[0005] In view of the problems mentioned in the background art, the purpose of the present application is to provide a silicon optical modulator based on a cascaded traveling wave electrode MZI structure to solve the problems mentioned in the background art.

[0006] The above-mentioned technical objective of the present invention is achieved through the following technical solution: a silicon optical modulator based on a cascaded traveling-wave electrode MZI structure, comprising a silicon substrate, and an input optical waveguide, a cascaded MZI modulation unit group, an output optical waveguide, and a driving circuit integrated on the silicon substrate; the output end of the input optical waveguide is connected to the input end of the cascaded MZI modulation unit group, the output end of the cascaded MZI modulation unit group is connected to the input end of the output optical waveguide, and the driving circuit is electrically connected to the cascaded MZI modulation unit group; the cascaded MZI modulation unit group is composed of at least two MZI modulation units cascaded sequentially, each MZI modulation unit is configured with a segmented traveling-wave electrode, and the segmented traveling-wave electrodes of adjacent MZI modulation units are connected through an impedance matching structure.

[0007] Preferably, each MZI modulation unit includes two parallel phase modulation arms, an input 3dB coupler, and an output 3dB coupler; the input of the input 3dB coupler is the input of the MZI modulation unit, and the two outputs of the input 3dB coupler are respectively connected to the inputs of the two phase modulation arms; the two inputs of the output 3dB coupler are respectively connected to the outputs of the two phase modulation arms, and the output of the output 3dB coupler is the output of the MZI modulation unit.

[0008] Preferably, the segmented traveling wave electrode includes a signal electrode and a ground electrode, the signal electrode and the ground electrode are located on both sides of the phase modulation arm, and a silicon oxide insulating layer is provided between the signal electrode and the silicon substrate.

[0009] Preferably, the impedance matching structure is a tapered transmission line, wherein the characteristic impedance of the tapered transmission line smoothly transitions from the characteristic impedance of the segmented traveling-wave electrode of the front-end MZI modulation unit to the characteristic impedance of the segmented traveling-wave electrode of the rear-end MZI modulation unit along the optical signal transmission direction.

[0010] Preferably, the driving circuit includes at least two sub-driving modules, each sub-driving module being electrically connected to a segmented traveling wave electrode of an MZI modulation unit in a one-to-one correspondence; the output signal delay time of adjacent sub-driving modules is equal to the transmission time of the optical signal from the output end of the previous MZI modulation unit to the input end of the next MZI modulation unit.

[0011] Preferably, the sub-driving module includes a differential amplifier and a phase adjuster. The phase adjuster is used to adjust the phase of the electrical signal output to the segmented traveling wave electrode so that the phase of the electrical signal matches the phase modulation requirements of the corresponding MZI modulation unit.

[0012] Preferably, the phase modulation arm is a silicon-based ridge waveguide, and the core layer doping concentration of the ridge waveguide is [missing value]. The ridge width is 400-600nm and the ridge height is 200-300nm.

[0013] Preferably, in the cascaded MZI modulation unit group, the number of MZI modulation units is 2-4, and the length of the connecting optical waveguide between adjacent MZI modulation units is 50-200μm.

[0014] Preferably, the signal electrode is a gold-titanium composite electrode, with a titanium layer thickness of 20-50 nm and a gold layer thickness of 200-500 nm; the ground electrode has the same material and structure as the signal electrode.

[0015] In summary, the present invention has the following advantages: The present invention overcomes the contradiction between bandwidth and driving voltage: The present invention adopts a cascaded MZI modulation unit group design, which can significantly shorten the traveling wave electrode length of each MZI modulation unit, effectively reducing RC delay and improving modulation bandwidth; at the same time, the phase modulation effect of multiple modulation units is superimposed, and the target modulation depth can be achieved without increasing the driving voltage. Experimental verification shows that at a modulation rate of 100Gbps, the driving voltage can be reduced to below 1.2V, and the bandwidth exceeds 80GHz. Compared with the existing single-stage structure, the driving voltage is reduced by more than 40%, and the bandwidth is increased by more than 30%.

[0016] This invention significantly improves phase modulation efficiency: each MZI modulation unit is equipped with an independent segmented traveling-wave electrode and a sub-drive module. The phase and delay time of the output signal of the sub-drive module are precisely matched with the optical signal transmission characteristics, realizing segmented and precise control of the optical wave phase, achieving a phase modulation efficiency of up to [percentage missing]. Compared to existing technologies, this technology offers a 50% improvement and effectively reduces signal distortion. In 100Gbps QPSK signal transmission, the bit error rate can be reduced to [missing value]. the following.

[0017] This invention optimizes signal transmission integrity: the impedance matching structure between adjacent MZI modulation units adopts a gradient transmission line design with a smooth transition of characteristic impedance, which can reduce the signal reflection coefficient to below -35dB, significantly reducing signal reflection and electromagnetic interference; at the same time, the insulating layer design of the segmented traveling wave electrode reduces the parasitic capacitance between the electrode and the substrate, further improving the stability of electrical signal transmission and ensuring signal quality under high-speed modulation. This invention features high integration and compatibility: all structures are integrated on silicon substrates, compatible with existing CMOS processes, and can achieve large-scale mass production; the modular design of the cascaded structure makes it easy to adjust the number of MZI modulation units according to modulation requirements, flexibly adapting to different transmission rate scenarios and having a wide range of applications. Attached Figure Description

[0018] Figure 1 This is a system block diagram of the present invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example

[0020] refer to Figure 1 A silicon optical modulator based on a cascaded traveling-wave electrode MZI structure includes a silicon substrate, and an input optical waveguide, a cascaded MZI modulation unit group, an output optical waveguide, and a driving circuit integrated on the silicon substrate. The output end of the input optical waveguide is connected to the input end of the cascaded MZI modulation unit group, and the output end of the cascaded MZI modulation unit group is connected to the input end of the output optical waveguide. The driving circuit is electrically connected to the cascaded MZI modulation unit group. The cascaded MZI modulation unit group is composed of at least two MZI modulation units cascaded in sequence. Each MZI modulation unit is equipped with a segmented traveling-wave electrode, and the segmented traveling-wave electrodes of adjacent MZI modulation units are connected through an impedance matching structure.

[0021] Each MZI modulation unit includes two parallel phase modulation arms, an input 3dB coupler, and an output 3dB coupler. The input of the input 3dB coupler is the input of the MZI modulation unit, and the two outputs of the input 3dB coupler are respectively connected to the inputs of the two phase modulation arms. The two inputs of the output 3dB coupler are respectively connected to the outputs of the two phase modulation arms, and the output of the output 3dB coupler is the output of the MZI modulation unit. The segmented traveling wave electrode includes a signal electrode and a ground electrode, which are located on opposite sides of the phase modulation arm, and a silicon oxide insulating layer is provided between the signal electrode and the silicon substrate. The impedance matching structure is a gradient transmission line, in which the characteristic impedance of the gradient transmission line smoothly transitions from the characteristic impedance of the segmented traveling wave electrode of the front-end MZI modulation unit to the characteristic impedance of the segmented traveling wave electrode of the rear-end MZI modulation unit along the optical signal transmission direction. The driving circuit includes at least two sub-driving modules, each of which is electrically connected to a segmented traveling wave electrode of an MZI modulation unit. The output signal delay time of adjacent sub-driving modules is equal to the transmission time of the optical signal from the output of the previous MZI modulation unit to the input of the next MZI modulation unit.

[0022] The sub-driving module includes a differential amplifier and a phase adjuster. The phase adjuster is used to adjust the phase of the electrical signal output to the segmented traveling wave electrode so that the phase of the electrical signal matches the phase modulation requirements of the corresponding MZI modulation unit.

[0023] The phase modulation arm is a silicon-based ridge waveguide, and the core layer doping concentration of the ridge waveguide is [missing information]. The ridge width is 400-600nm and the ridge height is 200-300nm.

[0024] In the cascaded MZI modulation unit group, the number of MZI modulation units is 2-4, and the length of the connecting optical waveguide between adjacent MZI modulation units is 50-200μm.

[0025] The signal electrode is a gold-titanium composite electrode with a titanium layer thickness of 20-50 nm and a gold layer thickness of 200-500 nm; the ground electrode has the same material and structure as the signal electrode.

[0026] This invention overcomes the contradiction between bandwidth and driving voltage: it adopts a cascaded MZI modulation unit group design, which can significantly shorten the traveling wave electrode length of each MZI modulation unit, effectively reducing RC delay and improving modulation bandwidth; at the same time, the phase modulation effects of multiple modulation units are superimposed, and the target modulation depth can be achieved without increasing the driving voltage. Experimental verification shows that at a modulation rate of 100Gbps, the driving voltage can be reduced to below 1.2V, and the bandwidth exceeds 80GHz. Compared with the existing single-stage structure, the driving voltage is reduced by more than 40%, and the bandwidth is increased by more than 30%. This invention significantly improves phase modulation efficiency: each MZI modulation unit is equipped with an independent segmented traveling-wave electrode and a sub-drive module. The phase and delay time of the output signal of the sub-drive module are precisely matched with the optical signal transmission characteristics, realizing segmented and precise control of the optical wave phase, achieving a phase modulation efficiency of up to [percentage missing]. Compared to existing technologies, this technology offers a 50% improvement and effectively reduces signal distortion. In 100Gbps QPSK signal transmission, the bit error rate can be reduced to [missing value]. the following. This invention optimizes signal transmission integrity: the impedance matching structure between adjacent MZI modulation units adopts a gradient transmission line design with a smooth transition of characteristic impedance, which can reduce the signal reflection coefficient to below -35dB, significantly reducing signal reflection and electromagnetic interference; at the same time, the insulating layer design of the segmented traveling wave electrode reduces the parasitic capacitance between the electrode and the substrate, further improving the stability of electrical signal transmission and ensuring signal quality under high-speed modulation. This invention features high integration and compatibility: all structures are integrated on silicon substrates, compatible with existing CMOS processes, and can achieve large-scale mass production; the modular design of the cascaded structure makes it easy to adjust the number of MZI modulation units according to modulation requirements, flexibly adapting to different transmission rate scenarios and having a wide range of applications.

[0027] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A silicon photonic modulator based on a cascaded traveling-wave electrode MZI structure, characterized in that: The system includes a silicon substrate, and an input optical waveguide, a cascaded MZI modulation unit group, an output optical waveguide, and a driving circuit integrated on the silicon substrate. The output end of the input optical waveguide is connected to the input end of the cascaded MZI modulation unit group, and the output end of the cascaded MZI modulation unit group is connected to the input end of the output optical waveguide. The driving circuit is electrically connected to the cascaded MZI modulation unit group. The cascaded MZI modulation unit group is composed of at least two MZI modulation units cascaded in sequence. Each MZI modulation unit is equipped with a segmented traveling wave electrode, and the segmented traveling wave electrodes of adjacent MZI modulation units are connected through an impedance matching structure.

2. The silicon photonic modulator based on a cascaded traveling-wave electrode MZI structure according to claim 1, characterized in that, Each MZI modulation unit includes two parallel phase modulation arms, an input 3dB coupler, and an output 3dB coupler. The input of the input 3dB coupler is the input of the MZI modulation unit, and the two outputs of the input 3dB coupler are respectively connected to the inputs of the two phase modulation arms. The two inputs of the output 3dB coupler are respectively connected to the outputs of the two phase modulation arms, and the output of the output 3dB coupler is the output of the MZI modulation unit.

3. A silicon photonic modulator based on a cascaded traveling-wave electrode MZI structure according to claim 1, characterized in that, The segmented traveling wave electrode includes a signal electrode and a ground electrode, which are located on opposite sides of the phase modulation arm, and a silicon oxide insulating layer is provided between the signal electrode and the silicon substrate.

4. A silicon photonic modulator based on a cascaded traveling-wave electrode MZI structure according to claim 1, characterized in that, The impedance matching structure is a gradient transmission line, in which the characteristic impedance of the gradient transmission line smoothly transitions from the characteristic impedance of the segmented traveling-wave electrode of the front-end MZI modulation unit to the characteristic impedance of the segmented traveling-wave electrode of the rear-end MZI modulation unit along the optical signal transmission direction.

5. A silicon photonic modulator based on a cascaded traveling-wave electrode MZI structure according to claim 1, characterized in that, The driving circuit includes at least two sub-driving modules, each of which is electrically connected to a segmented traveling wave electrode of an MZI modulation unit. The output signal delay time of adjacent sub-driving modules is equal to the transmission time of the optical signal from the output of the previous MZI modulation unit to the input of the next MZI modulation unit.

6. A silicon photonic modulator based on a cascaded traveling-wave electrode MZI structure according to claim 5, characterized in that, The sub-driving module includes a differential amplifier and a phase adjuster. The phase adjuster is used to adjust the phase of the electrical signal output to the segmented traveling wave electrode so that the phase of the electrical signal matches the phase modulation requirements of the corresponding MZI modulation unit.

7. A silicon photonic modulator based on a cascaded traveling-wave electrode MZI structure according to claim 2, characterized in that: The phase modulation arm is a silicon-based ridge waveguide, and the core layer doping concentration of the ridge waveguide is [missing information]. The ridge width is 400-600nm and the ridge height is 200-300nm.

8. A silicon photonic modulator based on a cascaded traveling-wave electrode MZI structure according to claim 1, characterized in that: In the cascaded MZI modulation unit group, the number of MZI modulation units is 2-4, and the length of the connecting optical waveguide between adjacent MZI modulation units is 50-200μm.

9. A silicon photonic modulator based on a cascaded traveling-wave electrode MZI structure according to claim 1, characterized in that: The signal electrode is a gold-titanium composite electrode with a titanium layer thickness of 20-50 nm and a gold layer thickness of 200-500 nm; the ground electrode has the same material and structure as the signal electrode.

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