A mach zehnder modulator chip based on serpentine traveling wave electrode

Abstract

This disclosure relates to the field of optical communication technology, and more particularly to a Mach-Zehnder modulator chip based on a serpentine traveling-wave electrode. The chip includes: a waveguide structure comprising two modulation arms, with a serpentine traveling-wave electrode disposed above at least one of the modulation arms; the serpentine traveling-wave electrode comprising a serpentine transmission line, the serpentine transmission line comprising at least one sub-transmission line, the sub-transmission line comprising an active portion, a passive portion, and a bent portion, the active portion being in contact with the modulation arm, and the passive portion and the bent portion being non-contacting with the modulation arm. Using this disclosure can improve the response bandwidth and integration density of the Mach-Zehnder modulator, and reduce the optical insertion loss, power consumption, packaging, and testing costs of the Mach-Zehnder modulator.

Description

Technical Field

[0001] This disclosure relates to the field of optical communication technology, and in particular to a Machzed modulator chip based on a serpentine traveling wave electrode. Background Technology

[0002] With the development of science and technology, the demand for optical modules is showing a rapid growth trend. Compared with traditional optical modules based on discrete components, photonic integrated chips dominate the optical module field due to their advantages such as low packaging cost, small size, and low power consumption. In optical communication technology, Mach-Zehnder modulator chips can not only achieve intensity modulation, but also form coherent modulators to achieve high-order quadrature amplitude modulation, further enhancing communication capabilities.

[0003] In related technologies, traveling wave electrodes in Mach-Zehnder modulators typically employ continuous coplanar waveguide traveling wave electrodes, capacitive traveling wave electrodes, or segmented traveling wave electrodes. However, continuous coplanar waveguide traveling wave electrodes have limited design optimization space, making it difficult to achieve optimal speed and impedance matching results, thus limiting the response bandwidth. Capacitive traveling wave electrodes waste waveguide length in the phase shift region, which is detrimental to high integration and reducing optical insertion loss, and also results in a larger half-wave voltage in the Mach-Zehnder modulator, thereby increasing power consumption. Segmented traveling wave electrodes have high packaging and testing costs, which is not conducive to large-scale production. Summary of the Invention

[0004] This disclosure provides a Machzed modulator chip based on a serpentine traveling wave electrode, with the main purpose of improving the response bandwidth and integration of the Machzed modulator, and reducing the optical insertion loss, power consumption, packaging and testing costs of the Machzed modulator.

[0005] According to one aspect of this disclosure, a Mach-Zehnder modulator chip based on a serpentine traveling-wave electrode is provided, comprising:

[0006] A waveguide structure, the waveguide structure including two modulation arms, at least one of the two modulation arms having a serpentine traveling wave electrode disposed above it;

[0007] The serpentine traveling wave electrode includes a serpentine transmission line, which includes at least one sub-transmission line. The sub-transmission line includes an active portion, a passive portion, and a curved portion. The active portion is in contact with the modulation arm, while the passive portion and the curved portion are not in contact with the modulation arm.

[0008] The Mahzell modulator chip based on the serpentine traveling-wave electrode modulates the optical signal input to the modulation arm below the serpentine traveling-wave electrode according to the electrical signal input to the serpentine traveling-wave electrode. The target electrical signal and the target optical signal generate an electro-optic effect so that the modulation arm outputs the modulated optical signal. The target electrical signal is the electrical signal that passes through the active part, and the target optical signal is the optical signal that passes through the modulation arm that is in contact with the active part.

[0009] Optionally, the electrical signal passes sequentially through each of the sub-transmission lines in the serpentine traveling wave electrode, such that the optical signal passing through the modulation arm corresponding to the serpentine traveling wave electrode sequentially generates at least one sub-phase difference, and the at least one sub-phase difference is sequentially accumulated to generate the phase difference in the optical signal, thereby obtaining the modulated optical signal.

[0010] Optionally, the waveguide structure includes an input optical waveguide, a beam combiner, a beam splitter, and an output optical waveguide, wherein the two modulation arms are a first modulation arm and a second modulation arm, respectively; wherein,

[0011] The input optical waveguide is used to receive optical carriers;

[0012] The input end of the beam splitter is connected to the input optical waveguide, and the output end of the beam splitter is connected to the input end of the first modulation arm and the input end of the second modulation arm, respectively. The beam splitter is used to split the optical carrier and input the first optical signal obtained after beam splitting to the first modulation arm and input the second optical signal obtained after beam splitting to the second modulation arm.

[0013] The serpentine traveling wave electrode is used to modulate the first optical signal and / or the second optical signal to cause a phase shift in the first optical signal and / or the second optical signal, thereby obtaining the modulated first optical signal and / or the modulated second optical signal.

[0014] The input end of the beam combiner is connected to the output end of the first modulation arm and the output end of the second modulation arm, respectively, for combining the first beam-splitting optical signal input by the first modulation arm and the second beam-splitting optical signal input by the second modulation arm, converting the phase difference between the first beam-splitting optical signal and the second beam-splitting optical signal into amplitude modulation to obtain a modulated optical carrier, wherein the first beam-splitting optical signal is the modulated first optical signal or the first optical signal, and the second beam-splitting optical signal is the modulated second optical signal or the second optical signal;

[0015] The input end of the output optical waveguide is connected to the output end of the beam combiner, and is used to output the modulated optical carrier.

[0016] Optionally, the waveguide structure further includes a substrate, a first doped layer, an undoped layer, and a second doped layer, wherein the undoped layer includes a multiple quantum well layer, a first spacer layer, and a second spacer layer; wherein,

[0017] The first doped layer is disposed above the substrate, the undoped layer is disposed above the first doped layer, and the second doped layer is disposed above the undoped layer;

[0018] In the undoped layer, the multiple quantum well layer is disposed above the first spacer layer, and the second spacer layer is disposed above the multiple quantum well layer.

[0019] Optionally, the waveguide structure can be any of the following structures:

[0020] pin-type epitaxial waveguide structure;

[0021] Nin-type epitaxial waveguide structure;

[0022] npin type epitaxial waveguide structure;

[0023] nipn type epitaxial waveguide structure.

[0024] Optionally, the waveguide structure is the pin-type epitaxial waveguide structure, the substrate is made of n-type doped indium phosphide, the first doped layer is made of n-type doped indium phosphide, the second doped layer is made of p-type doped indium phosphide, the multiple quantum well layer is made of undoped indium gallium arsenide phosphide quaternary compound material or aluminum gallium indium arsenide quaternary compound material, and both the first spacer layer and the second spacer layer are made of undoped indium phosphide or indium gallium arsenide phosphide quaternary compound material or aluminum gallium indium arsenide quaternary compound material.

[0025] Optionally, it also includes an N-contact electrode layer; wherein,

[0026] The N-contact electrode layer is disposed beneath the substrate.

[0027] Optionally, the substrate, the first doped layer, the undoped layer, and the second doped layer together constitute an isolation mesa and ridge structure; wherein,

[0028] The isolation platform is located below the ridge structure;

[0029] The ridge structure and part of the isolation platform together form the input optical waveguide, the beam combiner, the beam splitter, the first modulation arm, the second modulation arm, and the output optical waveguide.

[0030] Optionally, a planarization layer may also be included; wherein,

[0031] The planarization layer is disposed above the waveguide structure, and the upper surface of the planarization layer and the upper surface of the ridge structure together constitute the planarized upper surface;

[0032] The serpentine traveling wave electrode is disposed above the planarized upper surface, and the lower surface of the active portion of the serpentine transmission line contacts the upper surface of the ridge structure, so that the active portion is in contact with the modulation arm.

[0033] Optionally, the serpentine traveling-wave electrode further includes a pad and a terminating resistor; wherein,

[0034] The first end of the pad is connected to the substrate through a metal via, and the second end of the pad is connected to the input end of the serpentine transmission line.

[0035] The first end of the terminating resistor is connected to the output end of the serpentine transmission line, and the second end of the terminating resistor is connected to the substrate through a metal via.

[0036] In one or more embodiments of this disclosure, the Mach-Zehnder modulator chip based on a serpentine traveling-wave electrode includes a waveguide structure with two modulation arms. A serpentine traveling-wave electrode is disposed above at least one of the modulation arms. The serpentine traveling-wave electrode includes a serpentine transmission line, which includes at least one sub-transmission line. The sub-transmission line includes an active portion, a passive portion, and a curved portion. The active portion is in contact with the modulation arm, while the passive portion and the curved portion are not in contact with the modulation arm. The Mach-Zehnder modulator chip modulates an optical signal input to the modulation arm below the serpentine traveling-wave electrode according to an electrical signal input to the serpentine traveling-wave electrode. The target electrical signal and the target optical signal generate an electro-optic effect, causing the modulation arm to output a modulated optical signal. The target electrical signal is the electrical signal passing through the active portion, and the target optical signal is the optical signal passing through the modulation arm in contact with the active portion. Therefore, the response bandwidth and integration density of the Mach-Zehnder modulator can be improved, while the optical insertion loss, power consumption, packaging, and testing costs of the Mach-Zehnder modulator can be reduced.

[0037] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of this disclosure, nor is it intended to limit the scope of this disclosure. Other features of this disclosure will become readily apparent from the following description. Attached Figure Description

[0038] The accompanying drawings are provided to better understand this solution and do not constitute a limitation of this disclosure. Wherein:

[0039] Figure 1 This is a schematic diagram of the structure of a Mach-Zehnder modulator chip based on a serpentine traveling wave electrode, provided in an embodiment of this disclosure.

[0040] Figure 2 This is a top view schematic diagram of a Machzed modulator chip based on a serpentine traveling wave electrode provided in an embodiment of this disclosure. Detailed Implementation

[0041] The exemplary embodiments of this disclosure are described below with reference to the accompanying drawings, including various details of the embodiments to aid understanding, and should be considered merely exemplary. Therefore, those skilled in the art will recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of this disclosure. Similarly, for clarity and brevity, descriptions of well-known functions and structures are omitted in the following description.

[0042] With the development of science and technology, internet data applications have played a crucial role in driving the evolution of communication technologies. As can be seen from the development roadmap of Ethernet communication standards, with the development of high technologies such as hyperscale data centers, the demand for data transmission bandwidth is increasing. Against the backdrop of exponential growth in global traffic, the demand for optical modules is showing a rapid growth trend. Compared with traditional optical modules based on discrete components, photonic integrated chips dominate the optical module field due to their advantages such as low packaging cost, small size, and low power consumption. In optical communication technology, Mach-Zehnder modulator chips can not only achieve intensity modulation but also form coherent modulators to achieve high-order quadrature amplitude modulation, further enhancing communication capabilities. High-performance Mach-Zehnder modulators should meet the performance requirements of high response bandwidth, low half-wave voltage, and low optical insertion loss. The quality of electrode design directly affects the high-frequency performance of the modulator, and the electrode length also affects the half-wave voltage and optical insertion loss.

[0043] In related technologies, Mach-Zehnder modulator chips can be broadly categorized by waveguide material into III-V compound materials, silicon materials, and lithium niobate thin films. III-V compound materials are direct bandgap semiconductors and can be used to fabricate semiconductor laser chips; while silicon is an indirect bandgap semiconductor and cannot be used to fabricate laser sources. Mach-Zehnder modulator chips, represented by indium phosphide, can be monolithically integrated with lasers, improving integration density and reducing packaging costs, making them a mainstream solution in the field of optical communication.

[0044] In terms of electrode structure, modulators are divided into lumped electrodes and traveling-wave electrodes. The bandwidth of a lumped electrode modulator is mainly limited by the parasitic capacitance of the electrode. Increasing the length of the lumped electrode can reduce the half-wave voltage. However, as the electrode length increases, the parasitic capacitance also increases, leading to a decrease in modulation speed. Typically, the speed of a lumped electrode modulator is less than 10 Gb / s. To further improve the modulation speed, the more complex traveling-wave electrode structure has become the main research direction.

[0045] In traveling-wave electrode modulators, the propagation direction of light is the same as that of the high-frequency electrical signal. The electrical signal propagates along the transmission line. When the speeds of the electrical and optical signals are equal (the refractive index of microwaves equals the refractive index of optical groups), their phases are aligned, resulting in the highest modulation efficiency and a theoretically infinite modulation bandwidth (i.e., speed matching). Using a traveling-wave electrode structure avoids the influence of parasitic capacitance on the modulation speed and reduces the half-wave voltage by increasing the length of the high-frequency transmission line. To prevent reflection of the high-frequency electrical signal, an external load is usually required, the value of which is determined by the characteristic impedance of the high-frequency transmission line (i.e., impedance matching). The following are some mainstream design schemes for traveling-wave electrodes:

[0046] The first approach uses a continuous coplanar waveguide traveling wave electrode. In this structure, the high-frequency electrical signal is input into the thinner central electrode, while the two wider electrodes are grounded. The drawback of this approach is its limited design optimization space, making it difficult to achieve optimal speed and impedance matching, and resulting in a limited response bandwidth.

[0047] The second approach is a capacitive traveling-wave electrode: This structure connects a load capacitor with a certain duty cycle to a microstrip transmission line. By adjusting the duty cycle of the load capacitor, the total capacitance of the transmission line is changed, thereby optimizing the microwave refractive index and characteristic impedance with higher matching degree. This approach is widely used, but its disadvantage is that the low duty cycle of the load capacitor means a reduction in the effective length of the phase shift region of the Mach-Zehnder modulator, resulting in wasted waveguide length in the phase shift region. This is not conducive to high integration or reducing optical insertion loss, and it also leads to a larger half-wave voltage of the Mach-Zehnder modulator, thus increasing power consumption.

[0048] The third approach: Segmented traveling-wave electrode: This approach uses multiple lumped electrodes to form a segmented electrode array. A high-frequency multi-claw probe simultaneously drives the electrode array at high frequency, achieving an effect similar to a traveling-wave electrode. The biggest drawback of this approach is the high cost of packaging and testing, mainly due to the need for customized high-frequency multi-claw probes and a high-frequency electrical signal driver with strictly controlled timing.

[0049] The present disclosure will now be described in detail with reference to specific embodiments.

[0050] This disclosure provides a Mach-Zehnder modulator chip based on a serpentine traveling-wave electrode. Specifically, the Mach-Zehnder modulator chip based on the serpentine traveling-wave electrode includes:

[0051] The waveguide structure (WG) includes two modulation arms, and a traveling wave electrode (TWE) is disposed above at least one of the modulation arms.

[0052] Traveling Wave Electrode (TWE) includes a serpentine transmission line, which includes at least one sub-transmission line, and the sub-transmission line includes an active portion (L). a ), passive part (L) p ) and curved section (L s ), active part (L a The passive part (L) is set to contact the modulation arm. p ) and curved section (L s () and the modulation arm are set in a non-contact manner.

[0053] According to some embodiments, a Mach-Zehnder modulator chip based on a serpentine traveling-wave electrode modulates an optical signal input to a modulation arm below the serpentine traveling-wave electrode based on an electrical signal input to the serpentine traveling-wave electrode. Specifically, the target electrical signal and the target optical signal generate an electro-optic effect to cause the modulation arm to output a modulated optical signal.

[0054] In some embodiments, the target electrical signal is obtained through the active portion (L a ) electrical signals.

[0055] In some embodiments, the target optical signal is transmitted through the active portion (L a The optical signal of the modulation arm is contacted.

[0056] In some embodiments, due to the passive portion (L) p ) and curved section (L s The electrical signal and the passive part (L) p ) and the curved portion (L s The optical signal of the corresponding modulation arm does not undergo electro-optic effect, and it does not affect the transmission phase of the optical signal.

[0057] In some embodiments, the electrical signal passes sequentially through each sub-transmission line in the serpentine traveling wave electrode, causing the optical signal passing through the modulation arm corresponding to the serpentine traveling wave electrode to generate at least one sub-phase difference in sequence. The at least one sub-phase difference is accumulated in sequence to generate a phase difference in the optical signal, thereby obtaining a modulated optical signal.

[0058] In some embodiments, the number of traveling wave electrodes (TWE) can be one or two. When there is one traveling wave electrode (TWE), it is disposed above one of the two modulation arms. When there are two traveling wave electrodes (TWE), one traveling wave electrode (TWE) is disposed above each of the two modulation arms.

[0059] According to some embodiments, the waveguide structure includes an input optical waveguide, a beam combiner, a beam splitter, and an output optical waveguide, with two modulation arms, namely a first modulation arm and a second modulation arm; wherein...

[0060] The input waveguide is used to receive optical carrier waves;

[0061] The input end of the beam splitter is connected to the input optical waveguide, and the output end of the beam splitter is connected to the input end of the first modulation arm and the input end of the second modulation arm, respectively. The beam splitter is used to split the optical carrier and input the first optical signal obtained after beam splitting to the first modulation arm and input the second optical signal obtained after beam splitting to the second modulation arm.

[0062] The serpentine traveling wave electrode is used to modulate the first optical signal and / or the second optical signal to cause a phase shift in the first optical signal and / or the second optical signal, thereby obtaining the modulated first optical signal and / or the modulated second optical signal.

[0063] The input end of the beam combiner is connected to the output end of the first modulation arm and the output end of the second modulation arm, respectively, for combining the first beam-splitting optical signal input from the first modulation arm and the second beam-splitting optical signal input from the second modulation arm, converting the phase difference between the first beam-splitting optical signal and the second beam-splitting optical signal into amplitude modulation, to obtain a modulated optical carrier. The first beam-splitting optical signal is the modulated first optical signal or the first optical signal, and the second beam-splitting optical signal is the modulated second optical signal or the second optical signal.

[0064] The input end of the output optical waveguide is connected to the output end of the beam combiner to output the modulated optical carrier.

[0065] In some embodiments, at least one of the first and second beam-splitting optical signals is a modulated optical signal. For example, when the first beam-splitting optical signal is a first optical signal, the second beam-splitting optical signal is a modulated second optical signal; when the first beam-splitting optical signal is a modulated first optical signal, the second beam-splitting optical signal is a modulated second optical signal or a second optical signal.

[0066] In some embodiments, Figure 1 This is a schematic diagram of the structure of a Machzed modulator chip based on a serpentine traveling wave electrode, provided in an embodiment of this disclosure. Figure 2 This is a top view schematic diagram of a Mach-Zehnder modulator chip based on a serpentine traveling-wave electrode, provided as an embodiment of this disclosure. Figure 1 and Figure 2 As shown, the first modulation arm is the upper modulation arm, and the second modulation arm is the lower modulation arm. An upper serpentine traveling wave electrode is disposed above the upper modulation arm, and a lower serpentine traveling wave electrode is disposed above the lower modulation arm. The upper and lower modulation arms are structurally symmetrical, as are the upper and lower serpentine traveling wave electrodes.

[0067] At this point, the optical carrier is input from the optical waveguide at the input end, and split into two uniform optical signals (the first optical signal and the second optical signal) by the beam splitter. They enter the upper modulation arm and the lower modulation arm respectively. After being modulated by a high-speed electrical signal, the phase difference between the two optical signals changes. They are then combined into one beam by the beam combiner. Due to the interference principle, the optical signals are constructive and destructive, achieving intensity modulation. Finally, the light is output from the optical waveguide at the output end.

[0068] In some embodiments, the beam combiner and beam splitter include, but are not limited to, multimode interference couplers and Y-branch structures. Figure 1 and Figure 2 Both the beam combiner and beam splitter in the design are multimode interference couplers.

[0069] Optionally, in one embodiment of this disclosure, the waveguide structure (WG) further includes a substrate, a first doped layer, an undoped layer, and a second doped layer, wherein the undoped layer includes a multiple quantum well (MQW) layer, a first spacer layer, and a second spacer layer; wherein,

[0070] The first doped layer is disposed above the substrate, the undoped layer is disposed above the first doped layer, and the second doped layer is disposed above the undoped layer;

[0071] In the undoped layer, a multiple quantum well (MQW) layer is disposed above the first spacer layer, and a second spacer layer is disposed above the multiple quantum well layer.

[0072] In some embodiments, the waveguide structure (WG) includes, but is not limited to, pin-type epitaxial waveguide structure, nin-type epitaxial waveguide structure, npin-type epitaxial waveguide structure, nipn-type epitaxial waveguide structure, etc.

[0073] In some embodiments, such as Figure 1 and Figure 2 As shown, the waveguide structure (WG) is a pin-type epitaxial waveguide structure; wherein,

[0074] Both the substrate and the first doped layer are made of n-type doped indium phosphide (N-InP), which can be used to form the n-type doped region in the pin junction.

[0075] The second doped layer uses p-type doped indium phosphide material P-InP, which can be used to form the p-type doped region in the pin junction.

[0076] The undoped layer is used to form the i-type intrinsic region in the pin junction, together with N-InP and P-InP to form the pin junction, and an electric field is formed in the i-type intrinsic region.

[0077] The multi-quantum well layer uses undoped indium gallium arsenide phosphide quaternary compound material or aluminum gallium indium arsenide quaternary compound material, which belongs to the region where the Machzed modulator generates electro-optic modulation.

[0078] Both the first and second spacer layers are made of undoped indium phosphide, indium gallium arsenide phosphide, or aluminum gallium indium arsenide quaternary compound materials. This is used to reduce the coverage of optical modes and doped regions in the optical waveguide, thereby reducing optical insertion loss.

[0079] According to some embodiments, such as Figure 1 As shown, when the waveguide structure (WG) is a pin-type epitaxial waveguide structure, the Mach-Zehnder modulator chip based on the serpentine traveling wave electrode also includes an N-contact electrode layer (DC bias); wherein,

[0080] The N-contact electrode layer (DC bias) is disposed below the substrate.

[0081] In some embodiments, the material of the N-contact electrode layer (DC bias) includes, but is not limited to, gold, aluminum, copper, etc., and can be used to apply a reverse bias voltage to the mach-zead modulator.

[0082] According to some embodiments, such as Figure 2 As shown, the substrate, the first doped layer, the undoped layer, and the second doped layer together constitute the isolation mesa and ridge structure; wherein,

[0083] The isolation platform (Mesa) is located below the ridge structure;

[0084] The ridge structure and the partial isolation platform (Mesa) together form the input optical waveguide, beam combiner, beam splitter, first modulation arm, second modulation arm and output optical waveguide.

[0085] In some embodiments, the isolation mesa can be used to reduce the capacitance of the passive region and bends of the serpentine transmission line, reduce microwave loss, and improve the high-frequency response bandwidth of the Machzed modulator.

[0086] According to some embodiments, such as Figure 1 and Figure 2 As shown, the Mach-Zehnder modulator chip based on serpentine traveling-wave electrodes also includes a planarization layer; wherein,

[0087] The planarization layer is placed above the waveguide structure, and the upper surface of the planarization layer and the upper surface of the ridge structure together form the planarized upper surface;

[0088] The serpentine traveling wave electrode is positioned above the planarized upper surface, and the lower surface of the active portion of the serpentine transmission line contacts the upper surface of the ridge structure, so that the active portion is positioned in contact with the modulation arm.

[0089] In some embodiments, the planarization layer can be used to achieve chip surface planarization. The planarization layer can be made of benzocyclobutene (BCB) material, such as... Figure 1 As shown. The planarization layer can also be made of polyimide.

[0090] According to some embodiments, the serpentine traveling wave electrode also includes a pad and a terminating resistor;

[0091] The first end of the pad is connected to the substrate through a metal via, and the second end of the pad is connected to the input end of the serpentine transmission line.

[0092] The first end of the terminating resistor is connected to the output end of the serpentine transmission line, and the second end of the terminating resistor is connected to the substrate through a metal via.

[0093] In some embodiments, the materials of the serpentine traveling wave electrode include, but are not limited to, gold, aluminum, copper, etc.

[0094] In some embodiments, the number of first ends of the pad can be multiple. For example, when the pad is a GSG pad, the Ground (G) end of the GSG pad is the first end of the pad, the Signal (S) end of the GSG pad is the second end of the pad, and the number of Ground (G) ends of the GSG pad is two.

[0095] At this time, when the waveguide structure (WG) is a pin-type epitaxial waveguide structure, the two Ground (G) ends of the GSG pad are in contact with N-InP through corresponding metal vias (Via), and the Signal (S) end is in contact with P-InP through a serpentine transmission line.

[0096] In some embodiments, such as Figure 2 As shown, the first GSG pad (GSG1) and the first terminating resistor (R1) are present. The lower serpentine traveling wave electrode includes a second GSG pad (GSG2) and a second terminating resistor (R2). GSG1 or GSG2 can be driven individually with a high-frequency voltage to achieve single-arm drive; alternatively, two differential high-frequency voltages (RF1, RF2) can be used to drive the upper and lower arms respectively to achieve dual-arm push-pull drive, further reducing the drive voltage and power consumption.

[0097] Taking one scenario as an example, when the substrate is made of n-type doped indium phosphide (N-InP) and the waveguide structure (WG) is a pin-type epitaxial waveguide structure, the microwave refractive index (n) of a traditional continuous coplanar waveguide traveling-wave electrode is typically about 5, which is greater than the group refractive index of 3.7 for optical signal transmission. The serpentine traveling-wave electrode proposed in this disclosure, based on the structure of a coplanar waveguide electrode, modifies the active region (L) where the electrical signal propagation speed is slower (n≈5) by changing the electrical signal propagation path. a The passive region (L) with relatively fast propagation speed (n≈2) p ) and curved section (L s The length ratio of n can achieve speed matching of electro-optical signals (n≈3.7).

[0098] Meanwhile, the characteristic impedance (Z) of the transmission line of a traditional continuous coplanar waveguide traveling wave electrode is typically below 25 ohms, far below the standard impedance value of 50 ohms. The serpentine traveling wave electrode proposed in this disclosure, based on the structure of a coplanar waveguide electrode, adjusts the low-impedance (Z≈20 ohms) active region (L) in the serpentine traveling wave electrode structure by changing the transmission path of the electrical signal. a ), high impedance (Z≈75 ohms) passive region (L) p ) and curved section (L s The length ratio of the transmission line can be adjusted to optimize the characteristic impedance (typically 50 ohms).

[0099] In summary, the Mahzell modulator chip based on serpentine traveling-wave electrodes provided by the embodiments of this disclosure offers at least the following advantages:

[0100] Beneficial effects:

[0101] Unlike traditional continuous coplanar waveguide traveling wave electrode structures, this disclosure employs a serpentine traveling wave electrode structure, by designing an active section (L) in the serpentine transmission line. a ), passive part (L) p ) and the curved portion (L s The length of the traveling wave electrode can be optimized to improve the microwave refractive index and characteristic impedance, thereby increasing the response bandwidth of the Machzed modulator and achieving a high response speed.

[0102] Compared to the currently mainstream capacitive traveling wave electrode (CL-TWE) structure, which often wastes approximately 50% of the phase-shift region waveguide length when designing the load capacitance, the serpentine traveling wave electrode (TWE) scheme proposed in this disclosure can increase the proportion of the phase-shift region optical waveguide participating in the electro-optic effect, thereby improving the modulation efficiency (VL) of the Mach-Zehnder modulator chip. ΠL), that is, reducing the half-wave voltage of a Mach-Zehnder modulator with the same phase shift region length. Similarly, under a given half-wave voltage condition, this disclosure also helps to reduce the waveguide length of the Mach-Zehnder modulator, thereby reducing optical insertion loss, while also reducing chip size and increasing integration density.

[0103] Furthermore, compared to the CL-TWE scheme, which can only design the duty cycle of the load capacitor in the electrode structure, this disclosure improves upon the design of the active part (L... a ), passive part (L) p ) and the curved portion (L s Optimizing the length of the transmission line to achieve speed and impedance matching can increase the design freedom of the Mach-Zehnder modulator electrode structure, expand the range of microwave refractive index and characteristic impedance that can be achieved by the traveling wave electrode transmission line, and improve the compatibility of the Mach-Zehnder modulator chip in actual packaging and testing.

[0104] Compared with segmented traveling wave electrodes, this disclosure only requires the use of GSG high-frequency probes in practical applications, eliminating the need for multi-claw probes and custom high-frequency signal drivers, thus reducing the packaging and testing costs of Machzed modulator chips.

[0105] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this disclosure. In this specification, the illustrative expressions of the above terms may refer to different embodiments or examples. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0106] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this disclosure, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0107] Although embodiments of this disclosure have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this disclosure, the scope of which is defined by the claims and their equivalents.

Claims

1. A Mach-Zehnder modulator chip based on a serpentine traveling-wave electrode, characterized in that, include: A waveguide structure, the waveguide structure including two modulation arms, at least one of the two modulation arms having a serpentine traveling wave electrode disposed above it; The serpentine traveling wave electrode includes a serpentine transmission line, which includes at least one sub-transmission line. The sub-transmission line includes an active portion, a passive portion, and a curved portion. The active portion is in contact with the modulation arm, while the passive portion and the curved portion are not in contact with the modulation arm. The Mahzell modulator chip based on the serpentine traveling-wave electrode modulates the optical signal input to the modulation arm below the serpentine traveling-wave electrode according to the electrical signal input to the serpentine traveling-wave electrode. The target electrical signal and the target optical signal generate an electro-optic effect so that the modulation arm outputs the modulated optical signal. The target electrical signal is the electrical signal that passes through the active part, and the target optical signal is the optical signal that passes through the modulation arm that is in contact with the active part.

2. The Mach-Zehnder modulator chip based on a serpentine traveling-wave electrode according to claim 1, characterized in that, The electrical signal passes sequentially through each of the sub-transmission lines in the serpentine traveling wave electrode, causing the optical signal passing through the modulation arm corresponding to the serpentine traveling wave electrode to sequentially generate at least one sub-phase difference. The at least one sub-phase difference is accumulated sequentially to generate the phase difference in the optical signal, thus obtaining the modulated optical signal.

3. The Mach-Zehnder modulator chip based on a serpentine traveling-wave electrode according to claim 1, characterized in that, The waveguide structure includes an input optical waveguide, a beam combiner, a beam splitter, and an output optical waveguide; the two modulation arms are a first modulation arm and a second modulation arm, respectively. The input optical waveguide is used to receive optical carriers; The input end of the beam splitter is connected to the input optical waveguide, and the output end of the beam splitter is connected to the input end of the first modulation arm and the input end of the second modulation arm, respectively. The beam splitter is used to split the optical carrier and input the first optical signal obtained after beam splitting to the first modulation arm and input the second optical signal obtained after beam splitting to the second modulation arm. The serpentine traveling wave electrode is used to modulate the first optical signal and / or the second optical signal to cause a phase shift in the first optical signal and / or the second optical signal, thereby obtaining the modulated first optical signal and / or the modulated second optical signal. The input end of the beam combiner is connected to the output end of the first modulation arm and the output end of the second modulation arm, respectively, for combining the first beam-splitting optical signal input by the first modulation arm and the second beam-splitting optical signal input by the second modulation arm, converting the phase difference between the first beam-splitting optical signal and the second beam-splitting optical signal into amplitude modulation to obtain a modulated optical carrier, wherein the first beam-splitting optical signal is the modulated first optical signal or the first optical signal, and the second beam-splitting optical signal is the modulated second optical signal or the second optical signal; The input end of the output optical waveguide is connected to the output end of the beam combiner, and is used to output the modulated optical carrier.

4. The Mach-Zehnder modulator chip based on a serpentine traveling-wave electrode according to claim 3, characterized in that, The waveguide structure further includes a substrate, a first doped layer, an undoped layer, and a second doped layer. The undoped layer includes a multiple quantum well layer, a first spacer layer, and a second spacer layer. The first doped layer is disposed above the substrate, the undoped layer is disposed above the first doped layer, and the second doped layer is disposed above the undoped layer; In the undoped layer, the multiple quantum well layer is disposed above the first spacer layer, and the second spacer layer is disposed above the multiple quantum well layer.

5. The Mach-Zehnder modulator chip based on a serpentine traveling-wave electrode according to claim 4, characterized in that, The waveguide structure is any of the following structures: pin-type epitaxial waveguide structure; Nin-type epitaxial waveguide structure; npin type epitaxial waveguide structure; nipn type epitaxial waveguide structure.

6. The Mach-Zehnder modulator chip based on a serpentine traveling-wave electrode according to claim 5, characterized in that, The waveguide structure is a pin-type epitaxial waveguide structure. The substrate is made of n-type doped indium phosphide. The first doped layer is made of n-type doped indium phosphide. The second doped layer is made of p-type doped indium phosphide. The multiple quantum well layer is made of undoped indium gallium arsenide phosphide quaternary compound material or aluminum gallium indium arsenide quaternary compound material. The first spacer layer and the second spacer layer are both made of undoped indium phosphide or indium gallium arsenide phosphide quaternary compound material or aluminum gallium indium arsenide quaternary compound material.

7. The Mach-Zehnder modulator chip based on a serpentine traveling-wave electrode according to claim 6, characterized in that, It also includes an N-contact electrode layer; wherein, The N-contact electrode layer is disposed beneath the substrate.

8. The Mach-Zehnder modulator chip based on a serpentine traveling-wave electrode according to claim 4, characterized in that, The substrate, the first doped layer, the undoped layer, and the second doped layer together constitute an isolation mesa and ridge structure; wherein... The isolation platform is located below the ridge structure; The ridge structure and part of the isolation platform together form the input optical waveguide, the beam combiner, the beam splitter, the first modulation arm, the second modulation arm, and the output optical waveguide.

9. The Mach-Zehnder modulator chip based on a serpentine traveling-wave electrode according to claim 8, characterized in that, It also includes a planarization layer; among which, The planarization layer is disposed above the waveguide structure, and the upper surface of the planarization layer and the upper surface of the ridge structure together constitute the planarized upper surface; The serpentine traveling wave electrode is disposed above the planarized upper surface, and the lower surface of the active portion of the serpentine transmission line contacts the upper surface of the ridge structure, so that the active portion is in contact with the modulation arm.

10. The Mach-Zehnder modulator chip based on a serpentine traveling-wave electrode according to claim 9, characterized in that, The serpentine traveling wave electrode also includes pads and terminating resistors; wherein... The first end of the pad is connected to the substrate through a metal via, and the second end of the pad is connected to the input end of the serpentine transmission line. The first end of the terminating resistor is connected to the output end of the serpentine transmission line, and the second end of the terminating resistor is connected to the substrate through a metal via.

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