Electro-optic modulator and optical emitter

Abstract

An electro-optic modulator and an optical emitter comprising same. The electro-optic modulator comprises a first branch waveguide (101), a second branch waveguide (102) and radio-frequency electrodes. The radio-frequency electrodes include a first ground electrode (111), a first signal electrode (112), a second ground electrode (113), a second signal electrode (114) and a third ground electrode (115), which are sequentially arranged at intervals, wherein the first signal electrode (112) and the second signal electrode (114) are configured to receive a drive signal, the first branch waveguide (101) and the second branch waveguide (102) are respectively located in spacing regions between any two adjacent electrodes among the radio-frequency electrodes, and electric fields at the positions of the first branch waveguide (101) and the second branch waveguide (102) are in opposite directions.

Description

Electro-optical modulators and optical transmitters

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese invention patent application No. 202311172015.1, filed on September 12, 2023, entitled “Electro-optical modulator and optical transmitter,” and the disclosure of the priority claimed in this application is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure relates to the field of optical waveguide technology, and in particular to an electro-optical modulator and an optical transmitter. Background Art

[0004] Electro-optic modulators utilize the electro-optic effect of certain electro-optic crystals, such as lithium niobate (LiNbO3), gallium arsenide (GaAs), and lithium tantalate (LiTaO3). The electro-optic effect refers to the change in the refractive index of an electro-optic crystal when a voltage is applied. This changes the properties of the light wave passing through the crystal, modulating the phase, amplitude, intensity, and polarization of the optical signal.

[0005] However, crosstalk between the electrodes of the electro-optic modulator will affect the stability of the transmitted signal, thereby degrading the performance of the electro-optic modulator, and urgently needs to be improved.

[0006] Summary of the Invention

[0007] The embodiments of the present disclosure provide an optical modulation module and an optical modulator to enhance the stability of a transmission signal, thereby improving the performance of the device.

[0008] According to one aspect of the present disclosure, an electro-optical modulator is provided, comprising: a first branch waveguide, a second branch waveguide, and a radio frequency electrode, the radio frequency electrode comprising a first ground electrode, a first signal electrode, a second ground electrode, a second signal electrode, and a third ground electrode, which are arranged in sequence and spaced apart, wherein the first signal electrode and the second signal electrode are configured to receive a drive signal, the first branch waveguide and the second branch waveguide are respectively located in a spacing region between any two adjacent electrodes in the radio frequency electrode, and the electric field directions at the positions where the first branch waveguide and the second branch waveguide are located are opposite.

[0009] In some embodiments, the first ends of the first ground electrode, the second ground electrode, and the third ground electrode are connected to the first ground signal line, and the second ends of the first ground electrode, the second ground electrode, and the third ground electrode are connected via wires.

[0010] In some embodiments, first ends of the first ground electrode, the second ground electrode, and the third ground electrode are connected by wires.

[0011] In some embodiments, the second ends of the first ground electrode, the second ground electrode, and the third ground electrode are respectively connected to the second ground signal line.

[0012] In some embodiments, the electro-optical modulator further includes a first load resistor and a second load resistor connected in parallel, the first end of the first load resistor is connected to the first signal electrode, the first end of the second load resistor is connected to the second signal electrode, and the second end of the first load resistor is connected to the second end of the second load resistor and is connected to the power supply voltage.

[0013] In some embodiments, the electro-optic modulator further includes a capacitor, wherein the second ends of the first ground electrode, the second ground electrode, and the third ground electrode are respectively connected to the first plate of the capacitor, and the second ends of the first load resistor and the second load resistor are respectively connected to the second plate of the capacitor.

[0014] In some embodiments, the electro-optic modulator further includes a light splitting unit connected to the input end of the first branch waveguide and the input end of the second branch waveguide, and a light combining unit connected to the output end of the first branch waveguide and the output end of the second branch waveguide.

[0015] According to one aspect of the present disclosure, there is provided an optical transmitter comprising the electro-optical modulator of the aforementioned aspect.

[0016] In some embodiments, the optical transmitter further includes an amplifier connected to the electro-optical modulator to provide driving signals to the first signal electrode and the second signal electrode of the electro-optical modulator respectively.

[0017] In some embodiments, the optical modulator further includes a first load resistor and a second load resistor connected in parallel, the first end of the first load resistor is connected to the first signal electrode, the first end of the second load resistor is connected to the second signal electrode, the second end of the first load resistor is connected to the second end of the second load resistor and is connected to a power supply voltage, and the power supply voltage is provided to the amplifier to power the amplifier.

[0018] According to one or more embodiments of the present disclosure, a ground electrode is placed between the first and second signal electrodes, thereby suppressing crosstalk between adjacent electrodes to a certain extent. Therefore, the design scheme of the embodiments of the present disclosure can improve the stability of the transmitted signal, thereby improving the performance of the device.

[0019] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present disclosure, nor are they intended to limit the scope of the present disclosure. Other features of the present disclosure will become readily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Further details, features and advantages of the present disclosure are disclosed in the following description of exemplary embodiments in conjunction with the accompanying drawings, in which:

[0021] FIG1 is a schematic structural diagram of an electro-optical modulator according to some exemplary embodiments of the present disclosure;

[0022] FIG2 is a schematic structural diagram of an electro-optical modulator according to some other exemplary embodiments of the present disclosure;

[0023] FIG3 is a schematic structural diagram of an electro-optical modulator according to some further exemplary embodiments of the present disclosure;

[0024] FIG4 is a schematic structural diagram of an optical transmitter according to some exemplary embodiments of the present disclosure.

[0025] Explanation of the accompanying drawings: Optical transmitter 1000; electro-optical modulator 100, first branch waveguide 101, second branch waveguide 102, first ground electrode 111, first signal electrode 112, second ground electrode 113, second signal electrode 114, third ground electrode 115; first ground signal line 121, second ground signal line 122, first load resistor 131, second load resistor 132, capacitor 140, splitting unit 151, combining unit 152; amplifier 200. DETAILED DESCRIPTION

[0026] Hereinafter, only certain exemplary embodiments are briefly described. As will be appreciated by those skilled in the art, the described embodiments may be modified in various ways without departing from the spirit or scope of the present disclosure. Therefore, the drawings and description are to be considered as illustrative in nature and not restrictive.

[0027] Electro-optical modulators often use Mach-Zehnder optical waveguides. These consist of an input waveguide for introducing light from the outside, a branching section for splitting the light introduced by the input waveguide into two propagation paths, two parallel waveguides in the rear section of the branching section for propagating the branched light, and an output waveguide for combining the light propagating in the two parallel waveguides and outputting it externally. Mach-Zehnder optical modulators include control electrodes that control the phase of the light waves propagating in the parallel waveguides by applying a voltage and utilizing the electro-optic effect. These control electrodes typically consist of an RF (high-frequency) signal electrode (hereinafter referred to as the "signal electrode") formed above or near the parallel waveguides and a ground electrode disposed separately from the signal electrode. Because the multiple signal electrodes arranged in the parallel waveguides are close to each other, electrical crosstalk is emitted between adjacent electrodes when the modulation frequency is widened, causing performance degradation of the electro-optical modulator.

[0028] The embodiments of the present disclosure provide an electro-optic modulator and an optical transmitter to alleviate crosstalk between electrodes thereof, thereby improving device performance.

[0029] As shown in Figure 1, according to one aspect of the present disclosure, an electro-optical modulator 100 is provided, which includes a first branch waveguide 101, a second branch waveguide 102 and a radio frequency electrode. The radio frequency electrode includes a first ground electrode 111, a first signal electrode 112, a second ground electrode 113, a second signal electrode 114 and a third ground electrode 115, which are arranged in sequence. The first signal electrode 112 and the second signal electrode 114 are configured to receive drive signals S1 and S2. The first branch waveguide 101 and the second branch waveguide 102 are respectively located in the interval area between any two adjacent electrodes in the radio frequency electrode, and the electric field directions at the positions of the first branch waveguide 101 and the second branch waveguide 102 are opposite.

[0030] The electro-optic modulator 100 may comprise a first branch waveguide 101, a second branch waveguide 102, and a radio frequency electrode formed on a substrate exhibiting an electro-optic effect. The first branch waveguide 101 and the second branch waveguide 102 may be Mach-Zehnder waveguides. The first branch waveguide 101 and the second branch waveguide 102 are made of an electro-optic material whose refractive index varies with the magnitude of an applied voltage, thereby causing a phase difference between the two optical signals at the output of the electro-optic modulator. The radio frequency electrode may be an electrode formed on the substrate and may be made of a highly conductive, low-resistance material such as gold, silver, copper, aluminum, or graphene.

[0031] The RF electrode includes two signal electrodes and three ground electrodes, which are spaced apart from each other so that the signal electrode is sandwiched between the two ground electrodes. As shown in Figure 1, the first signal electrode 112 is sandwiched between the first ground electrode 111 and the second ground electrode 113, and the second signal electrode 114 is sandwiched between the second ground electrode 113 and the third ground electrode 115. The five RF electrodes form four spacing regions, each of which is between a signal electrode and a ground electrode. The first branch waveguide 101 and the second branch waveguide 102 can be arranged in two of the four spacing regions.

[0032] In some examples, the drive signal S1 provided to the first signal electrode 112 and the drive signal S2 provided to the second signal electrode 114 outside the modulator can be two differential signals with the same amplitude and opposite phases. The use of differential signals can further improve the anti-interference capability of the modulator. The potential applied to the optical waveguide in the modulator is the potential difference between the adjacent signal electrodes and the ground electrode. Since the drive signal is a differential signal, the electric field direction at the location of the first branch waveguide 101 and the second branch waveguide 102 may be the same, resulting in the same potential applied to the optical waveguide, making it impossible to achieve phase modulation of the different branch optical signals. In this embodiment, the first branch waveguide 101 and the second branch waveguide 102 are arranged in two interval areas with opposite electric field directions. For example, the first branch waveguide 101 is arranged between the first signal electrode 112 and the second ground electrode 113, and the second branch waveguide 102 is arranged between the second signal electrode 114 and the third ground electrode 115. It can be understood that the first branch waveguide 101 and the second branch waveguide 102 can be distributed in other suitable positions as long as the electric field directions at the positions are opposite.

[0033] The potentials at the first ground electrode 111, the second ground electrode 113, and the third ground electrode 115 are ground potential, which can be achieved, for example, by connecting to a ground line. The first signal electrode 112 and the second signal electrode 114 are used to receive corresponding drive signals, thereby forming an electric field that applies a potential difference between the signal electrodes and the ground electrodes on both sides of the optical waveguide.

[0034] By designing the structure of the RF electrode so that two signal electrodes are sandwiched between three ground electrodes, the electrical crosstalk between the signal electrodes can be effectively suppressed, making the electric field applied to the optical waveguide in the modulator more stable, improving the stability of signal transmission, and achieving higher modulation efficiency.

[0035] In some embodiments, the first ends of the first ground electrode 111, the second ground electrode 113 and the third ground electrode 115 are connected to the first ground signal line 121, and the second ends of the first ground electrode 111, the second ground electrode 113 and the third ground electrode 115 are connected by wires away from the first ends.

[0036] The RF electrode can be an electrode extending along the extension direction of the optical waveguide in the electro-optical modulator 100. In some examples, the first ground electrode 111, the second ground electrode 113, the third ground electrode 115, and the first signal electrode 112 and the second signal electrode 114 all extend in the same direction. When designing the electrodes, one end of the multiple ground electrodes is usually grounded. For example, as shown in FIG1 , the first end of the first ground electrode 111, the second ground electrode 113, and the third ground electrode 115 are each connected to the first ground signal line 121 to achieve grounding. However, since the electrodes have a certain length along the extension direction, the second ends of the multiple ground electrodes, which are far away from the ground end (the first end), are free ends. It is difficult for their potential to remain constant. In particular, under the interference of electrical signals from surrounding electrodes, the potential of the second end of the ground electrode will fluctuate to a certain extent. This will cause the potential difference between the second end signal electrode and the ground electrode to fluctuate relative to the first end, thereby affecting the modulation of the optical waveguide. It is understandable that the first end and the second end referred to in this embodiment can be any opposite ends of the ground electrode along the extension direction of the optical waveguide, but do not necessarily correspond to the signal input and signal output of the modulator. In some embodiments, the first end of the ground electrode may also be the end where the signal output end of the modulator is located, and the second end of the ground electrode may be the end where the signal input end of the modulator is located.

[0037] The first ground signal line 121 can be a single ground line or multiple distributed ground lines. The first ground electrode 111, the second ground electrode 113, and the third ground electrode 115 can each be connected to a corresponding first ground signal line 121, or can be partially or fully connected to a single first ground signal line 121.

[0038] In this embodiment, the second ends of the three ground electrodes are connected through wires, so that the potential of the second ends of the ground electrodes can be maintained at the same, thereby improving the stability of the potential difference between the signal electrode and the ground electrode along the extension direction of the optical waveguide, thereby suppressing the degradation of the modulation effect caused by the fluctuation of the potential difference at different positions.

[0039] In some embodiments, as shown in FIG1 , first ends of the first ground electrode 111 , the second ground electrode 113 , and the third ground electrode 115 are connected via wires.

[0040] The first ground electrode 111, the second ground electrode 113 and the third ground electrode 115 need to be grounded separately so that the potential remains at the ground potential. However, the grounding of multiple electrodes will make the circuit connection complicated, and there is also a potential risk of unreliable grounding connection. The first ends of multiple ground electrodes are connected by wires. In this way, even if the grounding lines of some ground electrodes fail, the potential consistency of the ground electrodes can be maintained through this connection method, thereby improving the stability of the modulated signal.

[0041] In some embodiments, as shown in FIG. 2 , the second ends of the first ground electrode 111 , the second ground electrode 113 , and the third ground electrode 115 are respectively connected to the second ground signal line 122 .

[0042] The second ground signal line 122 can be a plurality of distributed ground lines, each connected to the second end of one or more corresponding ground electrodes, or a ground line simultaneously connected to the second ends of multiple ground electrodes. In some examples, the second ground signal line 122 can be reused from other ground lines, for example, reused from the first ground signal line 121, i.e., the first and second ends of the ground electrodes are both connected to the same ground signal line.

[0043] The second ends of the first ground electrode 111, the second ground electrode 113, and the third ground electrode 115 are respectively grounded through the second ground signal line 122, so that the far ends of the ground electrodes can also be stably maintained at the ground potential, and the potential balance at both ends of the ground electrodes and the consistency of the potential of the second ends of multiple ground electrodes can be maintained, thereby improving the stability of the RF transmission signal.

[0044] In some embodiments, as shown in Figures 1 and 2, the electro-optic modulator 100 further includes a first load resistor 131 and a second load resistor 132 connected in parallel, wherein a first end of the first load resistor 131 is connected to the first signal electrode 112, a first end of the second load resistor 132 is connected to the second signal electrode 114, and a second end of the first load resistor 131 is connected to a second end of the second load resistor 132 and is connected to a power supply voltage Vcc.

[0045] The first load resistor 131 and the second load resistor 132 can be used to perform differential-mode impedance matching on the high-speed drive signal. By connecting the first load resistor 131 and the second load resistor 132 to the first signal electrode 112 and the second signal electrode 114 respectively, connecting them in parallel and then connecting them to the power supply voltage Vcc, the voltage at the second end of the signal electrode can be stabilized, thereby improving the drive signal quality of the modulator.

[0046] In some embodiments, as shown in Figure 2, the electro-optical modulator 100 also includes a capacitor 140, the second ends of the first ground electrode 111, the second ground electrode 113 and the third ground electrode 115 are respectively connected to the first plate of the capacitor 140, and the second ends of the first load resistor 131 and the second load resistor 132 are respectively connected to the second plate of the capacitor 140.

[0047] Placing a capacitor between the second end of the ground electrode and the second end of the load resistor effectively isolates the effects of DC signals, particularly interference from the DC signal on the signal electrode's non-grounded end. Furthermore, the capacitor allows the signal on the signal electrode to use the adjacent ground potential as a reference, thereby improving the stability of the RF transmission signal. Furthermore, placing a capacitor at the second end of the load resistor, which is connected to the power supply, stabilizes the voltage at the second end of the signal electrode, reducing electrical signal loss and thereby improving modulation efficiency.

[0048] In some embodiments, as shown in Figures 2 and 3, the electro-optical modulator 100 further includes a splitting unit 151 and a combining unit 152. The splitting unit 151 is respectively connected to the input end of the first branch waveguide 101 and the input end of the second branch waveguide 102, and the combining unit 152 is respectively connected to the output end of the first branch waveguide 101 and the output end of the second branch waveguide 102.

[0049] The optical splitting unit 151 can be a Y-branch beam splitting optical waveguide, and the optical combining element 30 can be a Y-branch beam combining optical waveguide. In one example, the optical splitting unit 151 is specifically a 1 / 2 optical splitter, which is used to split the optical signal into two branch optical signals at a splitting ratio of 1:1 and output them to the input end of the first branch waveguide 101 and the input end of the second branch waveguide 102 respectively. The optical combining unit 152 is specifically a 2-in-1 optical combiner, which is used to combine the two modulated branch optical signals received from the output end of the first branch waveguide 101 and the output end of the second branch waveguide 102 into one modulated optical signal and output it.

[0050] According to one aspect of the present disclosure, as shown in FIG4 , there is provided an optical transmitter 1000 including the electro-optical modulator 100 according to the aforementioned aspect.

[0051] In some embodiments, the optical transmitter 1000 further includes an amplifier 200 , which is connected to the electro-optical modulator 100 to provide driving signals to the first signal electrode 112 and the second signal electrode 114 .

[0052] For modulators with relatively high drive voltages, it is necessary to add an amplifier 200 before the modulator. Amplifier 200 can be directly coupled to electro-optical modulator 100 to generate drive signals and provide them to first signal electrode 112 and second signal electrode 114 of the electro-optical modulator. In some examples, drive signals S1 and S2 can be high-speed differential drive signals.

[0053] In some embodiments, the second end of the first load resistor 131 is connected to the second end of the second load resistor 132 and the power supply voltage Vcc is provided to the amplifier to power the amplifier.

[0054] The second end of the load resistor can be connected to a power supply voltage that is the same as the operating voltage of the amplifier. In one example, the amplifier can be powered by this power supply voltage. For example, reverse power supply can be achieved by connecting the amplifier to the access end of the power supply voltage Vcc through the transmission line of the modulator, which can simplify the circuit layout inside the optical transmitter.

[0055] Based on the above design of the electro-optical modulation module 100 and the beneficial effects obtained, the device performance of the optical transmitter 1000 is correspondingly improved, the signal transmission stability is better, and the modulation efficiency is higher.

[0056] It should be understood that in this specification, the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships or dimensions based on the orientations or positional relationships or dimensions shown in the accompanying drawings, and these terms are used only for the convenience of description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the scope of protection of the present disclosure.

[0057] Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature identified as "first," "second," or "third" may explicitly or implicitly include one or more of the features. Throughout the present disclosure, "plurality" means two or more, unless otherwise specifically defined.

[0058] In this disclosure, unless otherwise expressly specified or limited, terms such as "mounted," "connected," "connect," and "fixed" should be understood broadly. For example, they may refer to fixed connections, detachable connections, or integration; mechanical connections, electrical connections, or communication; direct connections or indirect connections through an intermediate medium; and internal connections between two components or interactions between two components. Those skilled in the art will understand the specific meanings of these terms in this disclosure based on specific circumstances.

[0059] In the present disclosure, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Moreover, a first feature being "above," "above," and "above" a second feature includes the first feature being directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature includes the first feature being directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0060] This specification provides many different embodiments or examples that can be used to implement the present disclosure. It should be understood that these different embodiments or examples are purely exemplary and are not intended to limit the scope of protection of the present disclosure in any way. Those skilled in the art can conceive of various changes or replacements based on the disclosure of the specification of the present disclosure, all of which should be included within the scope of protection of the present disclosure. Therefore, the scope of protection of the present disclosure should be based on the scope of protection defined by the appended claims.

Claims

1. An electro-optic modulator, comprising: a first branch waveguide and a second branch waveguide; as well as The radio frequency electrode comprises a first ground electrode, a first signal electrode, a second ground electrode, a second signal electrode and a third ground electrode which are arranged in sequence and at intervals. The first signal electrode and the second signal electrode are configured to receive a driving signal. The first branch waveguide and the second branch waveguide are respectively located in an interval area between any two adjacent electrodes of the radio frequency electrodes, and the electric field directions of the first branch waveguide and the second branch waveguide are opposite to each other.

2. The electro-optic modulator according to claim 1, wherein: The first ends of the first ground electrode, the second ground electrode and the third ground electrode are respectively connected to a first ground signal line, and the second ends of the first ground electrode, the second ground electrode and the third ground electrode, which are respectively away from the first end, are connected via a wire.

3. The electro-optic modulator according to claim 2, wherein: The first ends of the first ground electrode, the second ground electrode and the third ground electrode are respectively connected by a wire.

4. The electro-optic modulator according to claim 2, wherein: The second ends of the first ground electrode, the second ground electrode and the third ground electrode are respectively connected to the second ground signal line.

5. The electro-optic modulator according to any one of claims 2 to 4, wherein: The optical modulator further includes a first load resistor and a second load resistor connected in parallel. The first end of the first load resistor is connected to the first signal electrode, the first end of the second load resistor is connected to the second signal electrode, and the second end of the first load resistor is connected to the second end of the second load resistor and is connected to a power supply voltage.

6. The electro-optic modulator according to claim 5, wherein: The electro-optic modulator further comprises a capacitor, The second ends of the first ground electrode, the second ground electrode and the third ground electrode are respectively connected to the first plate of the capacitor, A second end of each of the first load resistor and the second load resistor is connected to the second plate of the capacitor.

7. The electro-optic modulator according to any one of claims 1 to 6, wherein: The electro-optic modulator further comprises: a light splitting unit connected to the input end of the first branch waveguide and the input end of the second branch waveguide respectively; and The light combining unit is connected to the output end of the first branch waveguide and the output end of the second branch waveguide respectively.

8. An optical transmitter comprising the electro-optic modulator according to any one of claims 1 to 7.

9. The optical transmitter according to claim 8, wherein: The optical transmitter further comprises an amplifier, The amplifier is connected to the electro-optic modulator to provide driving signals to the first signal electrode and the second signal electrode of the electro-optic modulator respectively.

10. The optical transmitter according to claim 9, wherein: The optical modulator further includes a first load resistor and a second load resistor connected in parallel. The first end of the first load resistor is connected to the first signal electrode, the first end of the second load resistor is connected to the second signal electrode, the second end of the first load resistor is connected to the second end of the second load resistor and is connected to a power supply voltage, The supply voltage is provided to the amplifier to power the amplifier.

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