Electro-optic modulator and optical emitter

Abstract

Electro-optic modulator and optical emitter including electro-optic modulator. The electro-optic modulator comprises a first branched waveguide (101), a second branched 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 spaced apart in order, wherein the first signal electrode (112) and the second signal electrode (114) are configured to receive a drive signal, and the first branched waveguide (101) and the second branched waveguide (102) are located in the spacing region between any two adjacent electrodes of the radio frequency electrodes, and the electric fields at the locations of the first branched waveguide (101) and the second branched waveguide (102) are in opposite directions.

Description

Technical Field

[0001] [Cross - Reference to Related Applications] This application claims the priority of Chinese Patent Application No. 202311172015.1, titled "ELECTRO - OPTIC MODULATOR AND OPTICAL EMITTER", filed on September 12, 2023. The disclosure of the priority claimed by this application is hereby incorporated by reference in its entirety into this specification. [Technical Field] This disclosure relates to the technical field of optical waveguides, and more particularly, to electro - optic modulators and optical emitters.

Background Art

[0002] An electro - optic modulator is a modulator fabricated by using the electro - optic effect of some electro - optic crystals such as lithium niobate (LiNbO₃) crystals, gallium arsenide (GaAs) crystals, and lithium tantalate (LiTaO₃) crystals. The electro - optic effect means that when a voltage is applied to an electro - optic crystal, the refractive index of the electro - optic crystal changes, resulting in a change in the characteristics of the light wave passing through the crystal, and thus realizing the modulation of the phase, amplitude, intensity, and polarization state of the optical signal.

[0003] However, the crosstalk between the electrodes of the electro - optic modulator affects the stability of the transmitted signal, thereby degrading the performance of the electro - optic modulator, which urgently needs to be improved.

Summary of the Invention

[0004] Embodiments of this disclosure provide an optical modulation module and an optical modulator for improving the stability of the transmitted signal and thereby improving the performance of the device.

[0005] According to one aspect of the present disclosure, an electro-optic modulator is provided. The electro-optic modulator includes a first branch waveguide, a second branch waveguide, and radio frequency electrodes. The radio frequency electrodes include a first ground electrode, a first signal electrode, a second ground electrode, a second signal electrode, and a third ground electrode, spaced apart in order, wherein the first and second signal electrodes are configured to receive a drive signal, the first and second branch waveguides are located separately in the spacing region between any two adjacent electrodes of the radio frequency electrodes, and the electric field directions at the locations of the first and second branch waveguides are opposite to each other.

[0006] In some embodiments, the first terminals of the first, second, and third ground electrodes are connected to a first ground signal line, and the second terminals of the first, second, and third ground electrodes, which are separated from these first terminals, are connected via wires.

[0007] In some embodiments, the first terminals of the first ground electrode, the second ground electrode, and the third ground electrode are connected via wires.

[0008] In some embodiments, the second terminals of the first, second, and third ground electrodes are connected to a second ground signal line, respectively.

[0009] In some embodiments, the electro-optic modulator further includes a first load resistor and a second load resistor connected in parallel, wherein the first terminal of the first load resistor is connected to a first signal electrode, the first terminal of the second load resistor is connected to a second signal electrode, and the second terminal of the first load resistor is connected to the second terminal of the second load resistor and is connected to a power supply voltage.

[0010] In some embodiments, the electro-optic modulator further includes a capacitor, where the second terminals of a first ground electrode, a second ground electrode, and a third ground electrode are connected to a first plate of the capacitor, and the second terminals of a first load resistor and a second load resistor are connected to a second plate of the capacitor.

[0011] In some embodiments, the electro-optic modulator further includes an optical splitting unit separately connected to the input terminal of a first branched waveguide and the input terminal of a second branched waveguide, and a photosynthesis unit separately connected to the output terminal of the first branched waveguide and the output terminal of the second branched waveguide.

[0012] According to one aspect of this disclosure, an optical emitter is provided. The optical emitter includes an electro-optic modulator as described above.

[0013] In some embodiments, the optical emitter further includes an amplifier, which is connected to the electro-optic modulator to provide drive signals separately to a first signal electrode and a second signal electrode of the electro-optic modulator.

[0014] In some embodiments, the optical modulator further includes a first load resistor and a second load resistor connected in parallel, the first terminal of the first load resistor being connected to a first signal electrode, the first terminal of the second load resistor being connected to a second signal electrode, and the second terminal of the first load resistor being connected to the second terminal of the second load resistor and connected to a power supply voltage, which is supplied to the amplifier to power the amplifier.

[0015] According to one or more embodiments of the present disclosure, a ground electrode is positioned between a first signal electrode and a second signal electrode, thereby suppressing crosstalk between adjacent electrodes to a certain extent. Thus, the solution of this design in the embodiments of the present disclosure can improve the stability of the transmitted signal, thereby improving the performance of the device.

[0016] It should be understood that the contents of this section are not intended to identify any defining or essential features of the embodiments of the Disclosure, nor are they intended to limit the scope of the Disclosure. Other features of the Disclosure will be readily apparent from the following description.

[0017] Further details, features, and advantages of this disclosure are disclosed in the following description of exemplary embodiments with reference to the accompanying drawings. [Brief explanation of the drawing]

[0018] [Figure 1] Figure 1 is a schematic diagram of an electro-optic modulator according to some exemplary embodiments of the present disclosure. [Figure 2] Figure 2 is a schematic diagram of an electro-optic modulator according to some other exemplary embodiments of the present disclosure. [Figure 3] Figure 3 is a schematic diagram of an electro-optic modulator according to some other exemplary embodiments of the present disclosure. [Figure 4] Figure 4 is a schematic diagram of an optical emitter according to some exemplary embodiments of the present disclosure. [Explanation of Symbols]

[0019] List of reference symbols: Optical emitter 1000, electro-optic 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, optical splitting unit 151, photosynthesis unit 152, amplifier 200. [Modes for carrying out the invention]

[0020] Hereinafter, only some exemplary embodiments will be briefly described. As will be understood by those skilled in the art, the described embodiments can be modified in various ways without departing from the spirit or scope of the present disclosure. Therefore, the accompanying drawings and description are considered to be illustrative in nature and not restrictive.

[0021] Mach-Zehnder optical waveguide is widely used in electro-optic modulators. The Mach-Zehnder optical waveguide includes an incident waveguide for guiding external light, a branching section for splitting the light guided by the incident waveguide into two propagation paths, two parallel waveguides for propagating the split light in the rear section of the branching section, and an output waveguide for combining the light propagating in the two parallel waveguides and outputting it to the outside. The Mach-Zehnder optical modulator includes a control electrode for controlling the phase change of the light wave propagating in the parallel waveguides by applying a voltage and utilizing the electro-optic effect. The control electrode usually includes an RF (radio frequency) signal electrode (hereinafter referred to as the "signal electrode") formed on or near the upper part of the above-mentioned parallel waveguide, and a ground electrode arranged separately from the signal electrode. A plurality of signal electrodes arranged on the parallel waveguide are close to each other. Therefore, when the modulation frequency is widened, electrical crosstalk may occur between adjacent electrodes, which in turn causes a performance degradation of the electro-optic modulator.

[0022] Embodiments of the present disclosure provide an electro-optic modulator and an optical emitter to reduce crosstalk between their electrodes, thereby improving the performance of the device.

[0023] As shown in FIG. 1, according to one aspect of the present disclosure, an electro-optical modulator 100 is provided. The electro-optical modulator 100 includes a first branched waveguide 101, a second branched 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 arranged at intervals in order. Here, the first signal electrode 112 and the second signal electrode 114 are configured to receive drive signals S1 and S2. The first branched waveguide 101 and the second branched waveguide 102 are separately located in the interval region between any two adjacent electrodes of the radio frequency electrode, and the electric field directions at the positions where the first branched waveguide 101 and the second branched waveguide 102 are located are opposite to each other.

[0024] The electro-optical modulator 100 can be formed by forming the first branched waveguide 101, the second branched waveguide 102, and the radio frequency electrode on a substrate having an electro-optical effect. The first branched waveguide 101 and the second branched waveguide 102 can be Mach-Zehnder optical waveguides. The first branched waveguide 101 and the second branched waveguide 102 are each made of an electro-optical material whose refractive index changes with an applied voltage. Thereby, when the optical signals for the two beams reach the output terminals of the electro-optical modulator, they have a phase difference therebetween. The radio frequency electrode can be an electrode prepared and formed on the substrate, and the material of the radio frequency electrode can be a highly conductive and low-resistance material such as gold, silver, copper, aluminum, or graphene.

[0025] The radio frequency electrode includes two signal electrodes and three ground electrodes. These signal electrodes are arranged sequentially at intervals from the ground electrodes such that each 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 electrodes of the radio frequency electrode form four spacing regions, each of which is located between the signal electrodes and the ground electrodes. The first branch waveguide 101 and the second branch waveguide 102 can be located in two of the four spacing regions, respectively.

[0026] 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, which are provided from outside the modulator, may be two differential signals having the same amplitude and opposite phase. Using differential signals can further improve the interference immunity of the modulator. In the modulator, the potential applied to the optical waveguide is the potential difference between adjacent signal electrodes and the ground electrode. Since the drive signals are differential signals, the electric field directions at the locations where the first branch waveguide 101 and the second branch waveguide 102 are located may be the same, which results in the same potential applied to the optical waveguide, making it impossible to achieve phase modulation of the optical signal at different branches. In this embodiment, the first branch waveguide 101 and the second branch waveguide 102 are located in two spaced regions, respectively, with opposite electric field directions. For example, the first branch waveguide 101 is located between the first signal electrode 112 and the second ground electrode 113, and the second branch waveguide 102 is located 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 dispersed to other suitable locations, as long as the electric field directions at their respective locations are opposite.

[0027] The potentials at the first ground electrode 111, the second ground electrode 113, and the third ground electrode 115 are the ground potential, and these electrodes can be grounded, for example, by being connected to a grounding wire. The first signal electrode 112 and the second signal electrode 114 are configured to receive their respective drive signals, thereby forming an electric field which is the potential difference between the signal electrode and its adjacent ground electrode and is applied to both sides of each optical waveguide.

[0028] By designing the radio frequency electrode structure such that two signal electrodes are sandwiched between three ground electrodes, electrical crosstalk between the signal electrodes can be effectively suppressed. This makes the electric field applied to the optical waveguide in the modulator more stable, thereby improving the stability of signal transmission and achieving higher modulation efficiency.

[0029] In some embodiments, the first terminals 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 terminals of the first ground electrode 111, the second ground electrode 113, and the third ground electrode 115, which are separated from these first terminals, are connected via wires.

[0030] Radio frequency electrodes can be electrodes that extend in the direction of extension of the optical waveguide in the electro-optic modulator 100. In some examples, the first ground electrode 111, the second ground electrode 113, the third ground electrode 115, the first signal electrode 112, and the second signal electrode 114 all extend in the same direction. When designing electrodes, one terminal of each of the multiple ground electrodes is usually grounded. For example, as shown in Figure 1, the first terminals 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 electrodes have a specific length in the direction of extension, the second terminals of the multiple ground electrodes that are far from their ground terminals (first terminals) are free terminals, and it is difficult for the potential at the free terminals to be constant. In particular, under interference from electrical signals from surrounding electrodes, the potential at the second terminal of the ground electrode may fluctuate to a certain extent, which can cause the potential difference between the signal electrode and the ground electrode at their second terminals to fluctuate relative to the potential difference at their first terminals, thereby affecting the modulation of the optical waveguide. The first and second terminals referred to in this embodiment may be any two opposing terminals of the ground electrode in the direction of extension of the optical waveguide, but it should be understood that they do not necessarily correspond to the signal input and signal output terminals of the modulator. In some embodiments, the first terminal of the ground electrode may also be the terminal on which the signal output terminal of the modulator is located, and the second terminal of the ground electrode may be the terminal on which the signal input terminal of the modulator is located.

[0031] The first ground signal line 121 may be a single ground line or a plurality of distributed ground lines. The first ground electrode 111, the second ground electrode 113, and the third ground electrode 115 may each be connected to their respective first ground signal line 121, or some or all of these electrodes may be connected to a single first ground signal line 121.

[0032] In this embodiment, the second terminals of the three ground electrodes are connected via wires, so that the potential at the second terminals of the ground electrodes remains the same. This improves the stability of the potential difference between the signal electrode and the ground electrode along the direction of extension of the optical waveguide, thereby suppressing the reduction of modulation effects caused by variations in the potential difference at different locations.

[0033] In some embodiments, as shown in Figure 1, the first terminals of the first grounding electrode 111, the second grounding electrode 113, and the third grounding electrode 115 are connected via wires.

[0034] The first grounding electrode 111, the second grounding electrode 113, and the third grounding electrode 115 need to be grounded separately in order to maintain their potentials at ground potential. However, grounding multiple electrodes can lead to complex circuit connections and the potential risk of unreliable grounding connections. The first terminals of the multiple grounding electrodes are connected via wires. In this way, even if some of the grounding wires of the grounding electrodes fail, the consistency of the potential of the grounding electrodes can be maintained through this connection method, thereby improving the stability of the modulated signal.

[0035] In some embodiments, as shown in Figure 2, the second terminals of the first ground electrode 111, the second ground electrode 113, and the third ground electrode 115 are each connected to the second ground signal line 122.

[0036] The second ground signal line 122 may be a plurality of distributed ground lines, each connected to the second terminal of one or more corresponding ground electrodes, or it may be a single ground line simultaneously connected to the second terminals of a plurality of ground electrodes. In some examples, the second ground signal line 122 may be reused from another ground line, for example, from the first ground signal line 121, meaning that both the first and second terminals of the ground electrode are connected to the same ground signal line.

[0037] The second terminals of the first ground electrode 111, the second ground electrode 113, and the third ground electrode 115 are each grounded through the second ground signal line 122, thereby ensuring that the distal ends of the ground electrodes are also stably maintained at ground potential. This maintains potential balance at both terminals of the ground electrodes and consistency of potential at the second terminals of the multiple ground electrodes, thereby improving the stability of the radio frequency transmission signal.

[0038] 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, where the first terminal of the first load resistor 131 is connected to a first signal electrode 112, the first terminal of the second load resistor 132 is connected to a second signal electrode 114, and the second terminal of the first load resistor 131 is connected to the second terminal of the second load resistor 132 and is connected to the power supply voltage Vcc.

[0039] The first load resistor 131 and the second load resistor 132 may be configured to perform differential mode impedance matching for high-speed drive signals. 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, and then connecting these load resistors in parallel to the power supply voltage Vcc, can stabilize the voltage at the second terminal of the signal electrode, thereby improving the quality of the modulator drive signal.

[0040] In some embodiments, as shown in Figure 2, the electro-optic modulator 100 further includes a capacitor 140, where the second terminals of a first ground electrode 111, a second ground electrode 113, and a third ground electrode 115 are connected to a first plate of the capacitor 140, and the second terminals of a first load resistor 131 and a second load resistor 132 are connected to a second plate of the capacitor 140.

[0041] Placing a capacitor between the second terminal of the ground electrode and the second terminal of the load resistor can effectively isolate the effects of DC signals, particularly interference from DC signals on the signal electrode to the ungrounded terminal of the ground electrode. At the same time, the capacitor allows the signal on the signal electrode to use the nearby ground potential as a reference, thereby improving the stability of the radio frequency transmission signal. In addition, placing a capacitor at the second terminal of the load resistor connected to the power supply can stabilize the voltage at the second terminal of the signal electrode, which reduces electrical signal loss and thereby improves modulation efficiency.

[0042] In some embodiments, as shown in Figures 2 and 3, the electro-optic modulator 100 further includes an optical splitting unit 151 and a photosynthesis unit 152. The optical splitting unit 151 is separately connected to the input terminal of the first branched waveguide 101 and the input terminal of the second branched waveguide 102. The photosynthesis unit 152 is separately connected to the output terminal of the first branched waveguide 101 and the output terminal of the second branched waveguide 102.

[0043] The optical splitting unit 151 may use a Y-branch beam splitting optical waveguide, and the photosynthesis element 30 may use a Y-branch beam combining optical waveguide. In one example, the optical splitting unit 151 is specifically a 1:2 optical splitter, which is configured to equally split an optical signal into two branched optical signals with a 1:1 splitting ratio and output these signals to the input terminals of the first branched waveguide 101 and the second branched waveguide 102, respectively. The photosynthesis unit 152 is specifically a 2:1 optical combiner, which is configured to combine two modulated branched optical signals received from the output terminals of the first branched waveguide 101 and the second branched waveguide 102 into a single modulated optical signal and output this signal.

[0044] According to one aspect of this disclosure, an optical emitter 1000 is provided, as shown in Figure 4. The optical emitter includes an electro-optic modulator 100 in the aforementioned aspect.

[0045] In some embodiments, the optical emitter 1000 further includes an amplifier 200, which is connected to an electro-optic modulator 100 to provide drive signals separately to a first signal electrode 112 and a second signal electrode 114.

[0046] For modulators with high drive voltages, an amplifier 200 must be added before the modulator. The amplifier 200 may be connected to the electro-optic modulator 100 via direct coupling. The amplifier 200 is configured to generate drive signals and provide these signals to the first signal electrode 112 and the second signal electrode 114 of the electro-optic modulator. In some examples, the drive signals S1 and S2 may be high-speed differential drive signals.

[0047] In some embodiments, the second terminal of the first load resistor 131 is connected to the second terminal of the second load resistor 132 and is connected to a power supply voltage Vcc, which is supplied to the amplifier to power it.

[0048] The second terminal of the load resistor may be connected to a power supply voltage that is the same as the amplifier's operating voltage. In one example, the amplifier may be powered by the power supply voltage. For example, reverse power supply may be achieved by connecting the amplifier to the power supply voltage Vcc terminal through the modulator's transmission line, which can simplify the internal wiring of the optical emitter.

[0049] Based on the above design and beneficial effects of the electro-optic modulation module 100, the optical emitter 1000 has improved device performance, along with better signal transmission stability and higher modulation efficiency.

[0050] In this specification, orientations, positional relationships, or dimensions indicated by terms such as “center,” “longitudinal,” “transverse,” “length,” “width,” “thickness,” “top,” “bottom,” “front,” “rear,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inside,” “outside,” “clockwise,” “counterclockwise,” “axial,” “radial,” and “circumferential” are orientations, positional relationships, or dimensions shown in the accompanying drawings. These terms are used merely to facilitate explanation and do not indicate or imply that the device or element referred to must have a particular orientation, or must be configured and operated in that particular orientation, and should therefore not be construed as limiting the scope of protection of this disclosure.

[0051] In addition, terms such as “first,” “second,” and “third” are for descriptive purposes only and should not be interpreted as indicating or implying relative importance, or as implicitly indicating the number of technical features described. Accordingly, features defined as “first,” “second,” and “third” may explicitly or implicitly include one or more features. In this disclosure, the term “multiple” means two or more unless specifically and explicitly defined otherwise.

[0052] In this disclosure, unless otherwise specified or defined, terms such as “attach,” “connect,” “connected,” and “fixed” should be interpreted broadly, for example, and could be a fixed connection, a detachable connection, or an integrated connection; a mechanical connection, or an electrical connection, or a communication; a direct connection or an indirect connection via an intermediate medium; internal communication between two elements, or interaction between two elements. A person skilled in the art will be able to understand the specific meaning of the above terms in this disclosure depending on the specific context.

[0053] In this disclosure, unless otherwise specified or defined, the expression that a first feature is "above" or "below" a second feature may include cases where the first feature is in direct contact with the second feature, or where the first and second features are not in direct contact but are in contact with each other through another feature. Furthermore, "over," "above," or "on" a first feature includes the first feature being directly above or diagonally above the second feature, or simply indicating that the first feature is at a higher level than the second feature. "Below," "under," or "beneath" a first feature includes the first feature being directly below or diagonally below the second feature, or simply indicating that the first feature is at a lower level than the second feature.

[0054] This description provides many different implementations or examples that may be used to carry out the disclosure. It should be understood that these different implementations or examples are purely illustrative and are not intended in any way to limit the scope of protection of the disclosure. Based on the disclosure as described in this description, a person skilled in the art may come up with various modifications or substitutions. All such modifications or substitutions shall fall within the scope of protection of the disclosure. Therefore, the scope of protection of the disclosure shall be subject to the scope of protection of the claims.

Claims

1. A first branched waveguide and a second branched waveguide, A 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 arranged in sequence at intervals, An electro-optic modulator comprising, The first signal electrode and the second signal electrode are configured to receive a drive signal. The first branched waveguide and the second branched waveguide are located separately in the spacing region between any two adjacent electrodes of the radio frequency electrodes, and the electric field directions at the locations where the first branched waveguide and the second branched waveguide are located are opposite to each other. Electro-optic modulator.

2. The electro-optic modulator according to claim 1, wherein the first terminals of the first ground electrode, the second ground electrode, and the third ground electrode are connected to a first ground signal line, and the second terminals of the first ground electrode, the second ground electrode, and the third ground electrode, which are separated from the respective first terminals, are connected via wires.

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

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

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

6. The electro-optic modulator further comprises a capacitor The second terminals of the first ground electrode, the second ground electrode, and the third ground electrode are connected to the first plate of the capacitor. The electro-optic modulator according to claim 5, wherein the second terminals of the first load resistor and the second load resistor are connected to the second plate of the capacitor.

7. The electro-optic modulator is Optical splitting units are separately connected to the input terminal of the first branched waveguide and the input terminal of the second branched waveguide, A photosynthesis unit is separately connected to the output terminal of the first branched waveguide and the output terminal of the second branched waveguide, An electro-optic modulator according to any one of claims 1 to 6, further comprising the above.

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

9. The aforementioned optical emitter further comprises an amplifier The optical emitter according to claim 8, wherein the amplifier is connected to the electro-optic modulator to separately provide drive signals to the first signal electrode and the second signal electrode of the electro-optic modulator.

10. The electro-optic modulator further comprises a first load resistor and a second load resistor connected in parallel. The first terminal of the first load resistor is connected to the first signal electrode, the first terminal of the second load resistor is connected to the second signal electrode, the second terminal of the first load resistor is connected to the second terminal of the second load resistor, and is also connected to the power supply voltage. The optical emitter according to claim 9, wherein the power supply voltage is supplied to the amplifier in order to supply power to the amplifier.

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