Electro-optical modulator and optical transmitter

Abstract

The invention provides an electro-optical modulator and an optical transmitter, the electro-optical modulator comprises a first branch waveguide, a second branch waveguide and a radio frequency electrode, 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 sequentially arranged 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 a spacing area between any two adjacent electrodes in the radio frequency electrodes, and the directions of electric fields at the positions of the first branch waveguide and the second branch waveguide are opposite.

Description

Technical Field

[0001] The present disclosure relates to the field of optical waveguide technology, and in particular to an electro-optic modulator and an optical transmitter. Background Art

[0002] Electro-optic modulators are modulators made using the electro-optic effect of certain electro-optic crystals, such as lithium niobate crystals (LiNbO3), gallium arsenide crystals (GaAs) and lithium tantalate crystals (LiTaO3). The electro-optic effect means that when voltage is applied to an electro-optic crystal, the refractive index of the electro-optic crystal will change, resulting in changes in the characteristics of the light wave passing through the crystal, thereby modulating the phase, amplitude, intensity and polarization state of the optical signal.

[0003] However, the crosstalk between the electrodes of the electro-optic modulator will affect the stability of the transmitted signal and thus degrade the performance of the electro-optic modulator, which urgently needs to be improved. Summary of the invention

[0004] The embodiments of the present disclosure provide an optical modulation module and an optical modulator to improve the stability of a transmission signal, thereby improving the performance of the device.

[0005] According to one aspect of the present disclosure, an electro-optic 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 at intervals, wherein 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 in the radio frequency electrode, and the electric field directions at the positions of the first branch waveguide and the second branch waveguide are opposite.

[0006] 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 away from the first ends are connected by wires.

[0007] In some embodiments, first ends of the first ground electrode, the second ground electrode, and the third ground electrode are respectively connected by wires.

[0008] 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.

[0009] In some embodiments, the electro-optic modulator also 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 connected to the power supply voltage.

[0010] In some embodiments, the electro-optic modulator further comprises 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.

[0011] 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, respectively.

[0012] According to one aspect of the present disclosure, there is provided an optical transmitter, comprising the electro-optical modulator of the aforementioned aspect.

[0013] In some embodiments, the optical transmitter further includes an amplifier 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.

[0014] In some embodiments, the optical modulator also 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.

[0015] According to one or more embodiments of the present disclosure, a ground electrode is arranged between the first signal electrode and the second signal electrode, so that the crosstalk between adjacent electrodes can be suppressed to a certain extent. Therefore, the design scheme of the embodiment of the present disclosure can improve the stability of the transmission signal, thereby improving the performance of the device.

[0016] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present disclosure, nor is it intended to limit the scope of the present disclosure. Other features of the present disclosure will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] 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:

[0018] Figure 1 is a schematic structural diagram of an electro-optic modulator according to some exemplary embodiments of the present disclosure;

[0019] Figure 2 is a schematic structural diagram of an electro-optic modulator according to some other exemplary embodiments of the present disclosure;

[0020] Figure 3is a schematic structural diagram of an electro-optic modulator according to some further exemplary embodiments of the present disclosure;

[0021] Figure 4 is a schematic structural diagram of an optical transmitter according to some exemplary embodiments of the present disclosure.

[0022] Reference numerals:

[0023] Optical transmitter 1000;

[0024] 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, light splitting unit 151, light combining unit 152;

[0025] Amplifier 200. DETAILED DESCRIPTION

[0026] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present disclosure. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0027] Electro-optic modulators mostly use Mach-Zehnder optical waveguides, which are composed of an input waveguide for introducing light from the outside, a branching part for dividing the light introduced by the input waveguide into two paths for propagation, two parallel waveguides for propagating the branched lights in the rear section of the branching part, and an output waveguide for combining the lights propagating in the two parallel waveguides and outputting them to the outside. Mach-Zehnder optical modulators have a control electrode, which is used to control the phase change of the light wave propagating in the parallel waveguides by using the electro-optical effect by applying a voltage. The control electrode is usually composed of an RF (high frequency) signal electrode (hereinafter referred to as "signal electrode") formed on the upper part or near the parallel waveguide and a ground electrode arranged separately from the signal electrode. The multiple signal electrodes arranged in the parallel waveguide are close to each other, so when the modulation frequency is broadbanded, electrical crosstalk will be emitted between adjacent electrodes, which will cause the performance of the electro-optic modulator to deteriorate.

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

[0029] like Figure 1As shown, according to one aspect of the present disclosure, an electro-optic 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, wherein the first signal electrode 112 and the second signal electrode 114 are configured to receive driving 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 of the first branch waveguide 101 and the second branch waveguide 102 are opposite.

[0030] The electro-optic modulator 100 may be a substrate having an electro-optic effect on which a first branch waveguide 101, a second branch waveguide 102 and a radio frequency electrode are formed. The first branch waveguide 101 and the second branch waveguide 102 may be Mach-Zehnder type optical waveguides. The first branch waveguide 101 and the second branch waveguide 102 are made of electro-optical materials, and their refractive index varies with the magnitude of the applied voltage, so that a phase difference is generated when the two light signals arrive at the output end of the electro-optical modulator. The radio frequency electrode may be an electrode prepared and formed on a substrate, and the material of the radio frequency electrode may be a high-conductivity, low-resistance material such as gold, silver, copper, aluminum, graphene, etc.

[0031] The radio frequency electrode includes two signal electrodes and three ground electrodes, and the signal electrodes and the ground electrodes are arranged in sequence and spaced apart, so that the signal electrode is sandwiched between the two ground electrodes. Figure 1 As shown, 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 RF electrode form four spacing regions, each of which is between the signal electrode and the ground electrode, and 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 may be two differential signals with the same amplitude and opposite phases. The use of differential signals can further improve the anti-interference ability of the modulator. The potential applied to the optical waveguide in the modulator is the potential difference between the adjacent signal electrode 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, so that the potential applied to the optical waveguide is also the same, so that phase modulation of different branch optical signals cannot be achieved. 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 on the first ground electrode 111, the second ground electrode 113, and the third ground electrode 115 are ground potentials, for example, they can be grounded by connecting to a ground line. The first signal electrode 112 and the second signal electrode 114 are used to receive corresponding driving 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 such that two signal electrodes are respectively 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 away from the first ends are connected by wires.

[0036] The RF electrode may be an electrode extending along the extension direction 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 the electrodes, one end of the plurality of ground electrodes is usually grounded, for example Figure 1As shown, the first end of each of the first ground electrode 111, the second ground electrode 113 and the third ground electrode 115 is connected to the first ground signal line 121 to achieve grounding, but because the electrode has a certain length along the extension direction, the second end of the multiple ground electrodes far away from the ground end (first end) is a free end, and its potential is difficult to remain unchanged. In particular, under the interference of the electrical signal of the surrounding electrodes, the potential of the second end of the ground electrode will fluctuate to a certain extent, which will cause the potential difference between the signal electrode at the second end and the ground electrode to fluctuate relative to the first end, thereby affecting the modulation of the optical waveguide. It can be understood that the first end and the second end referred to in this embodiment can be any two opposite ends of the ground electrode along the extension direction of the optical waveguide, but do not necessarily correspond to the signal input end and the signal output end of the modulator. In some embodiments, the first end of the ground electrode can also be the end where the signal output end of the modulator is located, and the second end of the ground electrode is the end where the signal input end of the modulator is located.

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

[0038] In this embodiment, the second ends of the three ground electrodes are connected by wires, so that the potential of the second ends of the ground electrodes can be maintained 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, Figure 1 As shown, first ends of the first ground electrode 111 , the second ground electrode 113 , and the third ground electrode 115 are connected by wires.

[0040] The first ground electrode 111, the second ground electrode 113 and the third ground electrode 115 need to be grounded respectively 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. Even if the grounding lines of some ground electrodes fail, the potential of the ground electrodes can be kept consistent through this connection method, thereby improving the stability of the modulated signal.

[0041] In some embodiments, Figure 2 As shown, 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 may be a plurality of distributed ground lines, respectively connected to the second ends of one or more corresponding ground electrodes, or may be a ground line simultaneously connected to the second ends of a plurality of ground electrodes. In some examples, the second ground signal line 122 may be multiplexed from other ground lines, for example, multiplexed from the first ground signal line 121, that is, the first end and the second end of the ground electrode 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 grounded respectively 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, Figure 1 and Figure 2 As shown, 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 V cc .

[0045] The first load resistor 131 and the second load resistor 132 can be used to perform differential impedance matching on the high-speed driving signal. The first load resistor 131 and the second load resistor 132 are respectively connected to the first signal electrode 112 and the second signal electrode 114, and then connected in parallel to the power supply voltage V cc , which can stabilize the voltage at the second end of the signal electrode and improve the driving signal quality of the modulator.

[0046] In some embodiments, Figure 2 As shown, the electro-optic modulator 100 also includes a capacitor 140, and 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] Arranging a capacitor between the second end of the ground electrode and the second end of the load resistor can effectively isolate the influence of the DC signal, especially the interference of the DC signal on the non-grounded end of the ground electrode on the signal electrode. At the same time, the capacitor enables the signal of the signal electrode to use the ground potential next to it as a reference, thereby improving the stability of the RF transmission signal. In addition, arranging a capacitor at the second end of the load resistor connected to the power supply can stabilize the voltage of the signal electrode at the second end, reduce the loss of the electrical signal, and thus improve the modulation efficiency.

[0048] In some embodiments, Figure 2 and Figure 3 As shown, the electro-optic modulator 100 further includes a light splitting unit 151 and a light combining unit 152. The light 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 light 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 light splitting unit 151 may adopt a Y-branch beam splitting optical waveguide, and the light combining element 30 may adopt a Y-branch beam combining optical waveguide. In one example, the light splitting unit 151 is specifically a half-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, and the light combining unit 152 is specifically a two-in-one light 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, Figure 4 As shown, an optical transmitter 1000 is provided, comprising the electro-optic modulator 100 of the aforementioned aspect.

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

[0052] For a modulator with a relatively large driving voltage, it is necessary to add an amplifier 200 in front of the modulator. The amplifier 200 can be connected to the electro-optic modulator 100 in a direct coupling manner. The amplifier 200 is used to generate a driving signal and provide it to the first signal electrode 112 and the second signal electrode 114 of the electro-optic modulator. In some examples, the driving signals S1 and S2 can be high-speed differential driving 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 is connected to a power supply voltage V cc Supplied 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 the power supply voltage, for example, by connecting the amplifier to the power supply voltage V through a transmission line of a modulator. cc The access end connection can realize reverse power supply, 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 stability of signal transmission 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 that are 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 referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the scope of protection of the present disclosure.

[0057] In addition, the terms "first", "second", "third", etc. are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first", "second", "third" may explicitly or implicitly include one or more of the feature. In the description of the present disclosure, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0058] In the present disclosure, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or a communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present disclosure can be understood according to specific circumstances.

[0059] In the present disclosure, unless otherwise expressly specified and limited, a first feature being “above” or “below” a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being “above”, “above”, and “above” a second feature includes that the first feature is 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 that the first feature is 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 present specification, which should all be included in 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 attached 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 4, 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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