Electro-optical modulator and electro-optical modulation module

Abstract

The present application discloses an electro-optical modulator and an electro-optical modulation module, relating to the technical field of electro-optical modulators. The electrode layer of the electro-optical modulator includes a parallel plate capacitor structure composed of a capacitor signal electrode and a capacitor ground electrode. A modulation waveguide for transmitting an optical signal is provided between the capacitor signal electrode and the capacitor ground electrode. A variable resistance line signal electrode and a variable resistance line ground electrode are provided on the side of the capacitor signal electrode facing away from the capacitor ground electrode, and one end of the variable resistance line signal electrode is connected to the capacitor signal electrode, and the other end serves as a microwave signal input interface, so that the variable resistance line signal electrode and the variable resistance line ground electrode form a quarter-wavelength converter structure. An open-circuit gap region is provided in the capacitor ground electrode to offset the imaginary part of the impedance of the parallel plate capacitor structure composed of the capacitor signal electrode and the capacitor ground electrode. The impedance of the parallel plate capacitor structure composed of the capacitor signal electrode and the capacitor ground electrode as a load is matched to the input impedance of the microwave signal, thereby improving the efficiency of microwave energy use.

Description

Technical Field

[0001] The present application relates to the technical field of electro-optical modulators, and in particular to an electro-optical modulator and an electro-optical modulation module. Background Art

[0002] An electro-optic modulator (EOM) is a device that converts information-carrying electrical signals into optical signals and is a core component in optical radio frequency communication systems. Currently, EO modulators are primarily categorized into direct modulation (also called internal modulation) and indirect modulation (also called external modulation). Indirect modulation utilizes the physical properties of specific materials, such as magneto-optical, acousto-optic, and electro-optical effects, to alter the intensity, phase, and polarization state of light waves, separating the generation of the optical carrier from the signal loading process.

[0003] Most existing electro-optical modulators are traveling wave modulators or lumped capacitance modulators. Traveling wave modulators utilize traveling wave electrode technology to transmit electrical signals in a wave-like manner through an electrode structure and interact with optical signals, thereby modulating the optical signal. Lumped capacitance modulators typically include a modulation electrode and a ground electrode, forming a parallel plate capacitor between them. When a modulating signal is applied to this capacitor, the capacitance of the capacitor changes, thereby changing the transmission characteristics of the optical signal in the modulator, thereby modulating the optical signal.

[0004] However, whether it is the existing traveling wave modulator or the existing lumped capacitor modulator, the modulator itself is not the main consumer of electrical signal energy (i.e., microwave energy); specifically, in the existing traveling wave modulator, the microwave energy is transmitted through the traveling wave electrode and ultimately consumed at the terminal load; while in the existing lumped capacitor modulator, the impedance of the lumped electrode capacitor is extremely low, typically less than 2 ohms, and therefore almost all of the microwave energy will be reflected back to the incident port. As a result, the microwave energy is not effectively and fully utilized. Summary of the Invention

[0005] To solve the above technical problems, an embodiment of the present application provides an electro-optical modulator and an electro-optical modulation module so that microwave energy can be effectively and fully utilized.

[0006] To achieve the above objectives, the present invention provides the following technical solutions:

[0007] An electro-optic modulator, comprising:

[0008] substrate;

[0009] an insulating layer located on one side of the substrate;

[0010] an electrode layer located on a side of the insulating layer facing away from the substrate;

[0011] The electrode layer includes a capacitive signal electrode and a capacitive ground electrode arranged opposite to each other along a first direction, the capacitive signal electrode extends along a second direction, the first direction and the second direction are both parallel to the plane where the substrate is located, and the first direction and the second direction are perpendicular;

[0012] A capacitance modulation gap region is provided between the capacitance signal electrode and the capacitance ground electrode, wherein a modulation waveguide extending along the second direction is provided in the capacitance modulation gap region, and the modulation waveguide is used to transmit an optical signal;

[0013] The electrode layer further includes a variable resistance line signal electrode located on a side of the capacitor signal electrode facing away from the capacitor ground electrode, the variable resistance line signal electrode extending along the first direction, one end of the variable resistance line signal electrode along the first direction being connected to the capacitor signal electrode, and the other end of the variable resistance line signal electrode along the first direction being a microwave interface for inputting microwave signals;

[0014] The electrode layer further includes a varistor line ground electrode located on at least one of two sides of the varistor line signal electrode that are opposite to each other along the second direction; a varistor line gap region is defined between the varistor line signal electrode and the varistor line ground electrode; and a capacitive isolation gap region is defined between the capacitive signal electrode and the varistor line ground electrode.

[0015] The difference between the length of the signal electrode of the variable resistance line along the first direction and an odd-number multiple of 1 / 4 wavelength of the microwave signal is smaller than a first preset range;

[0016] An open gap region extending along the second direction is provided in the capacitor ground electrode. The open gap region is arranged opposite to a non-connected portion other than a connected portion between the capacitor signal electrode and the variable resistance line signal electrode along the first direction.

[0017] Optionally, the sum of the length of the variable resistance line signal electrode along the first direction and the length from the connection point of the variable resistance line signal electrode and the capacitor signal electrode to either end of the capacitor signal electrode along the second direction, divided by the average transmission speed of the microwave signal in the variable resistance line signal electrode and the capacitor signal electrode, is less than a second preset range.

[0018] Optionally, the capacitor signal electrode is symmetrical about the axis of the variable resistance line signal electrode.

[0019] Optionally, the capacitive signal electrode includes a first electrode portion and a second electrode portion symmetrically along the axis of the variable resistance line signal electrode;

[0020] The open gap region in the capacitor ground electrode includes a first open gap region and a second open gap region that are axisymmetric along the first direction, and the first open gap region and the second open gap region are spaced apart along the second direction;

[0021] The first open gap region and the first electrode portion are disposed opposite to each other along the first direction, and the second open gap region and the second electrode portion are disposed opposite to each other along the first direction.

[0022] Optionally, a varistor line ground electrode is provided on each of two opposite sides of the varistor line signal electrode along the second direction;

[0023] A variable resistance line gap region is provided between the variable resistance line signal electrode and the variable resistance line ground electrode; and a capacitor isolation gap region is provided between the capacitor signal electrode and the variable resistance line ground electrode.

[0024] Optionally, each gap region in the electrode layer is provided with a filling medium, and the filling medium includes air, silicon dioxide or polymethyl methacrylate polymer.

[0025] Optionally, the material of the modulation waveguide is a material having nonlinear effects.

[0026] Optionally, the electro-optical modulator further includes:

[0027] A modulation residual layer is located between the insulating layer and the electrode layer, and the modulation residual layer and the modulation waveguide are integrally formed.

[0028] An electro-optical modulation module, comprising a plurality of electro-optical modulators, wherein the electro-optical modulators are any of the electro-optical modulators described above;

[0029] The modulation waveguides of the electro-optical modulators are connected in sequence.

[0030] Optionally, the microwave input interfaces of the electro-optical modulators are connected in parallel.

[0031] Compared with the existing technology, the above technical solution has the following advantages:

[0032] The electro-optical modulator provided in the embodiment of the present application includes a substrate, an insulating layer located on one side of the substrate, and an electrode layer located on the side of the insulating layer away from the substrate, the electrode layer includes a capacitor signal electrode and a capacitor ground electrode arranged opposite to each other, the capacitor signal electrode and the capacitor ground electrode constitute a parallel plate capacitor structure, a modulation waveguide is arranged between the capacitor signal electrode and the capacitor ground electrode, the modulation waveguide is used to transmit an optical signal, by arranging a variable resistance line signal electrode and a variable resistance line ground electrode on the side of the capacitor signal electrode away from the capacitor ground electrode, and one end of the variable resistance line signal electrode is connected to the capacitor signal electrode, and the other end is used as a microwave interface for inputting a microwave signal, and the length of the variable resistance line signal electrode is set to an odd multiple of 1 / 4 wavelength of the microwave signal The difference between them is less than a first preset range, so that the variable resistance line signal electrode and the variable resistance line ground electrode form a quarter-wavelength converter structure, and by setting an open-circuit gap area in the capacitor ground electrode, and the open-circuit gap area is arranged relative to the non-connected part outside the connecting part of the capacitor signal electrode and the variable resistance line signal electrode, so that the imaginary part of the impedance of the parallel plate capacitor structure formed by the capacitor signal electrode and the capacitor ground electrode is offset, thereby matching the parallel plate capacitor structure formed by the capacitor signal electrode and the capacitor ground electrode as the impedance of the load to the input impedance of the microwave signal, then the signal reflection at the microwave interface can be eliminated, so that the microwave signal has the highest efficiency during the transmission process, thereby improving the utilization efficiency of microwave energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0034] Figure 1 A schematic cross-sectional view of an electro-optic modulator provided in an embodiment of the present application;

[0035] Figure 2 A schematic diagram of a top view of an electro-optic modulator provided in an embodiment of the present application;

[0036] Figure 3 A partial impedance equivalent circuit diagram of an electro-optic modulator provided in an embodiment of the present application;

[0037] Figure 4 An impedance equivalent circuit diagram of an electro-optic modulator provided in an embodiment of the present application;

[0038] Figure 5 A schematic cross-sectional view of another electro-optical modulator provided in an embodiment of the present application;

[0039] Figure 6 A schematic diagram of the top structure of an electro-optical modulation module provided in an embodiment of the present application. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0041] In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0042] Secondly, this application is described in detail with reference to schematic diagrams. When describing the embodiments of this application, for ease of explanation, the cross-sectional and top views of the device structures may be partially enlarged and not to scale. Furthermore, the schematic diagrams are merely illustrative and should not limit the scope of protection of this application. Furthermore, in actual production, the three-dimensional dimensions of length, width, and depth should be included.

[0043] As described in the background technology section, whether it is an existing traveling wave modulator or an existing lumped capacitor modulator, the modulator is not the main consumer of electrical signal energy (i.e., microwave energy); specifically, in the existing traveling wave modulator, microwave energy is transmitted through the traveling wave electrode and ultimately consumed at the terminal load; while in the existing lumped capacitor modulator, the impedance of the lumped electrode capacitor is extremely low, typically less than 2 ohms, and therefore almost all of the microwave energy will be reflected back to the incident port, so that the microwave energy is not effectively and fully utilized.

[0044] The embodiment of the present application provides an electro-optic modulator, Figure 1 FIG. 1 shows a schematic cross-sectional structure diagram of an electro-optical modulator provided in an embodiment of the present application. Figure 1 As shown, the electro-optic modulator includes a substrate 100 , an insulating layer 200 located on one side of the substrate 100 , and an electrode layer 300 located on a side of the insulating layer 200 facing away from the substrate 100 .

[0045] Figure 2 A schematic diagram of a top view of an electro-optical modulator provided in an embodiment of the present application is shown. Figure 1 and Figure 2As shown, the electrode layer 300 includes a capacitive signal electrode 10 and a capacitive ground electrode 20 arranged opposite to each other along a first direction Y. The capacitive signal electrode 10 extends along a second direction X. Both the first direction Y and the second direction X are parallel to the plane of the substrate 100, and the first direction Y and the second direction X are perpendicular to each other. In this way, the capacitive signal electrode 10 and the capacitive ground electrode 20 arranged opposite to each other along the first direction Y form a parallel plate capacitor structure.

[0046] Combine Figure 1 and Figure 2 As shown, a capacitance modulation gap region K1 is provided between the capacitance signal electrode 10 and the capacitance ground electrode 20 . The capacitance modulation gap region K1 is provided with a modulation waveguide 30 extending along the second direction X. The modulation waveguide 30 is used to transmit an optical signal.

[0047] It can be understood that during the modulation process, the modulation waveguide 30 transmits the optical signal, the microwave signal (i.e., the radio frequency signal) is loaded on the capacitive signal electrode 10, and the capacitive ground electrode 20 is connected to the ground signal. Since the modulation waveguide 30 is located in the capacitive modulation gap region K1 between the capacitive signal electrode 10 and the capacitive ground electrode 20, the change in the microwave signal can cause specific changes in the physical properties (such as the refractive index) of the modulation waveguide 30 through the capacitive signal electrode 10, thereby changing the characteristic parameters of the optical signal transmitted by the modulation waveguide 30, such as intensity, phase or polarization state, so that the optical signal contains information of the microwave signal, thereby realizing electro-optical modulation.

[0048] Optionally, the material of the substrate 100 may include silicon, silicon nitride, lithium niobate, aluminum oxide or sapphire. The thickness of the substrate 100 may be several hundred microns. The substrate 100 is located at the bottom of the electro-optic modulator and supports the entire device structure.

[0049] Optionally, the insulating layer 200 may be made of a low-refractive-index insulating material, or an insulating transparent material such as an organic polymer, silicon oxide, or aluminum oxide. The thickness of the insulating layer 200 may be several microns. The insulating layer 200 is used to prevent optical signals from propagating toward the substrate 100 .

[0050] Optionally, the material of the modulation waveguide 30 can be a material with nonlinear effects such as silicon and lithium niobate. In this way, when the microwave signal loaded on the capacitive signal electrode 10 changes, the physical properties of the modulation waveguide 30 (such as the refractive index) undergo specific changes, so that the characteristic parameters of the optical signal transmitted by the modulation waveguide 30 change, so that the optical signal transmitted by the modulation waveguide 30 contains information of the microwave signal.

[0051] Optionally, the width of the capacitance modulation gap region K1 between the capacitance signal electrode 10 and the capacitance ground electrode 20 along the first direction Y can be in the range of several microns to tens of microns, the width of the modulation waveguide 30 along the second direction X can be several hundred nanometers to several microns, the thickness of the modulation waveguide 30 along the direction perpendicular to the plane of the substrate 100 can be several hundred nanometers to about one micron, the thickness of the modulation waveguide 30 along the direction perpendicular to the plane of the substrate 100 is less than the thickness of the electrode layer 300 along the direction perpendicular to the plane of the substrate 100, and the thickness of the electrode layer 300 along the direction perpendicular to the plane of the substrate 100 can be several hundred nanometers to several microns.

[0052] Specifically, when the microwave signal loaded on the capacitive signal electrode 10 changes, the electric field strength of the capacitive modulation gap region K1 between the capacitive signal electrode 10 and the capacitive ground electrode 20 changes. This can cause the refractive index of the modulation waveguide 30 to change, thereby causing the phase of the optical signal transmitted by the modulation waveguide 30 to change, thereby realizing the phase modulation function.

[0053] As described in the background technology section, in existing traveling wave modulators, microwave energy is transmitted through the traveling wave electrode and eventually consumed at the terminal load; whereas in existing lumped capacitive modulators, the impedance of the lumped electrode capacitor is extremely low, typically less than 2 ohms, and thus almost all of the microwave energy is reflected back to the incident port; for ease of understanding, refer to Figure 2 As shown, in the existing traveling wave modulator, the microwave signal is input from one end of the capacitor signal electrode 10 along the second direction X, outputted along the other end of the second direction X, and then consumed by the terminal load; while in the existing lumped capacitor modulator, the microwave signal is loaded on the capacitor signal electrode 10 and then reflected back to the incident port. It can be seen that the modulator itself is not the main body of microwave energy consumption, and the microwave energy is not effectively and fully utilized.

[0054] In view of this, in the electro-optical modulator provided in the embodiment of the present application, Figure 2 As shown, the electrode layer 300 also includes a variable resistance line signal electrode 40 located on the side of the capacitor signal electrode 10 away from the capacitor ground electrode 20. The variable resistance line signal electrode 40 extends along the first direction Y. One end of the variable resistance line signal electrode 40 along the first direction Y is connected to the capacitor signal electrode 10, and the other end of the variable resistance line signal electrode 40 along the first direction Y is a microwave interface In for inputting microwave signals (i.e., radio frequency signals).

[0055] It can be understood that the microwave interface In can connect the variable resistance line signal electrode 40 to other conductors by microstrip lines, heterogeneous integration or wire bonding, so as to input the external microwave signal into the variable resistance line signal electrode 40, and then load the microwave signal onto the capacitive signal electrode 10 through the variable resistance line signal electrode 40.

[0056] According to transmission line theory, if the transmission line matches the load impedance, the signal reflection on the transmission line can be eliminated, so that the energy loss during transmission is minimized or the efficiency is maximized. Figure 3 As shown, the microwave signal is also transmitted on the transmission line before being input to the microwave interface In. The characteristic impedance of the transmission line outside the microwave interface In is Z0. That is, the input impedance of the microwave signal is Z0. The parallel plate capacitor structure composed of the capacitor signal electrode 10 and the capacitor ground electrode 20 is equivalent to the load, and the impedance of the load is Z L , if the impedance Z of the parallel plate capacitor structure as a load can be L By matching the input impedance Z0 of the microwave signal, signal reflection at the microwave interface In can be eliminated, making the microwave signal most efficient during transmission, thereby improving the efficiency of microwave energy use.

[0057] However, the impedance Z of the parallel plate capacitor structure composed of the capacitive signal electrode 10 and the capacitive ground electrode 20 is L It is impossible to match the input impedance Z0 of the microwave signal. Therefore, in the electro-optic modulator provided in the embodiment of the present application, Figure 2 As shown, a variable resistance line signal electrode 40 is provided on a side of the capacitor signal electrode 10 away from the capacitor ground electrode 20. The variable resistance line signal electrode 40 extends along a first direction Y. One end of the variable resistance line signal electrode 40 along the first direction Y is connected to the capacitor signal electrode 10. The other end of the variable resistance line signal electrode 40 along the first direction Y is a microwave interface In for inputting a microwave signal (i.e., a radio frequency signal). In addition, the electrode layer 300 further includes a variable resistance line ground electrode 50 located on at least one of two opposite sides of the variable resistance line signal electrode 40 along a second direction X. A variable resistance line gap region K2 is defined between the variable resistance line signal electrode 40 and the variable resistance line ground electrode 50. A capacitive isolation gap region K3 is defined between the capacitor signal electrode 10 and the variable resistance line ground electrode 50. With this configuration, the variable resistance line signal electrode 40 and the variable resistance line ground electrode 50 form a quarter-wavelength transformer structure, which serves as an impedance matching network between the microwave interface In and the parallel plate capacitor formed by the capacitor signal electrode 10 and the capacitor ground electrode 20.

[0058] For ease of understanding, Figure 4 As shown, the parallel plate capacitor structure composed of the capacitor signal electrode 10 and the capacitor ground electrode 20 is used as a load, and the impedance is Z L, the input impedance of the microwave signal is Z0, the quarter-wavelength transformer structure composed of the variable resistance line signal electrode 40 and the variable resistance line ground electrode 50 serves as an impedance matching network, and the impedance is Z1. Moreover, in the quarter-wavelength transformer structure composed of the variable resistance line signal electrode 40 and the variable resistance line ground electrode 50, the equivalent length of the transmission line is an odd multiple of λ / 4, where λ is the wavelength of the microwave signal; thus, according to the characteristics of the quarter-wavelength transformer, in order to achieve impedance matching, the input impedance of the microwave interface In is Z in =Z0, then That is, it is only necessary to make the impedance of the quarter-wavelength transformer structure composed of the variable resistance line signal electrode 40 and the variable resistance line ground electrode 50 , that is, the parallel plate capacitor structure composed of the capacitor signal electrode 10 and the capacitor ground electrode 20 can be realized as the impedance Z of the load L Matched to the input impedance Z0 of the microwave signal.

[0059] Theoretically, in order for the varistor line signal electrode 40 and the varistor line ground electrode 50 to form a quarter-wavelength converter structure, the length of the varistor line signal electrode 40 along the first direction Y is equal to an odd-numbered multiple of 1 / 4 wavelength of the microwave signal. However, in actual applications, the difference between the length of the varistor line signal electrode 40 along the first direction Y and the odd-numbered multiple of 1 / 4 wavelength of the microwave signal can be less than a first preset range. In other words, the length of the varistor line signal electrode 40 along the first direction Y can be in the vicinity of an odd-numbered multiple of 1 / 4 wavelength of the microwave signal.

[0060] Furthermore, considering that the quarter-wavelength transformer can only match real impedance to the transmission line, and the parallel plate capacitor structure composed of the capacitive signal electrode 10 and the capacitive ground electrode 20 is a complex impedance, in the electro-optical modulator provided in the embodiment of the present application, Figure 2 As shown, an open gap area K4 extending along the second direction X is provided in the capacitor ground electrode 20 , and the open gap area K4 is arranged opposite to the non-connected portion other than the connected portion between the capacitor signal electrode 10 and the variable resistance line signal electrode 40 along the first direction Y.

[0061] Optional, such as Figure 2 As shown, the capacitor signal electrode 10 is axially symmetrical about the variable resistance line signal electrode 40, that is, the connection position between the capacitor signal electrode 10 and the variable resistance line signal electrode 40 is located in the middle position of the capacitor signal electrode 10 along the second direction X. In this way, the microwave signal can be transmitted from the microwave interface In along the variable resistance line signal electrode 40 to one end of the capacitor signal electrode 10 along the second direction X, and can also be transmitted from the microwave interface In along the variable resistance line signal electrode 40 to the other end of the capacitor signal electrode 10 along the second direction X.

[0062] On this basis, if Figure 2As shown, the capacitor signal electrode 10 includes a first electrode portion 11 and a second electrode portion 12 that are symmetrical along the axis of the variable resistance line signal electrode 40; the open gap area K4 in the capacitor ground electrode 20 includes a first open gap area K41 and a second open gap area K42 that are symmetrical along the first direction Y, and the first open gap area K41 and the second open gap area K42 are arranged at intervals along the second direction X; the first open gap area K41 and the first electrode portion 11 are arranged opposite to each other along the first direction Y, and the second open gap area K42 and the second electrode portion 12 are arranged opposite to each other along the first direction Y.

[0063] It can be understood that since the capacitor signal electrode 10 is axially symmetrical about the variable resistance line signal electrode 40, the capacitor signal electrode 10 includes a first electrode portion 11 and a second electrode portion 12 that are axially symmetrical along the variable resistance line signal electrode 40, and the microwave signal can be transmitted from the microwave interface In along the variable resistance line signal electrode 40 to one end of the capacitor signal electrode 10 along the second direction X, and can also be transmitted from the microwave interface In along the variable resistance line signal electrode 40 to the other end of the capacitor signal electrode 10 along the second direction X. Therefore, it is equivalent to the first electrode portion 11 and the capacitor ground electrode 20 forming a parallel plate capacitor, and the second electrode portion 12 and the capacitor ground electrode 20 also forming a parallel plate capacitor, and a first open gap area K41 and a second open gap area K42 are set in the capacitor ground electrode 20, and the first open gap area K41 is opposite to the first electrode portion 11 along the first direction Y. The second open gap area K42 is arranged relative to the second electrode portion 12 along the first direction Y, which is equivalent to connecting a short stub with an open terminal in parallel to the parallel plate capacitor formed by the first electrode portion 11 and the capacitor ground electrode 20. Similarly, it is also equivalent to connecting a short stub with an open terminal in parallel to the parallel plate capacitor formed by the second electrode portion 12 and the capacitor ground electrode 20. The short stub with an open terminal is equivalent to having a load with infinite impedance connected to the terminal, and its input impedance is a pure imaginary number. By taking a suitable length for the short stub, that is, by setting the length of the first open gap area K41 along the second direction X, and setting the length of the second open gap area K42 along the second direction X, the imaginary part of the impedance of the parallel plate capacitor structure formed by the capacitor signal electrode 10 and the capacitor ground electrode 20 can always be offset, thereby realizing the conversion of the complex impedance of the load into a real impedance.

[0064] Since the capacitive signal electrode 10 is axially symmetrical about the varistor line signal electrode 40, a varistor line ground electrode 50 can be provided on each of two opposite sides of the varistor line signal electrode 40 along the second direction X, and a varistor line gap region K2 is provided between the varistor line signal electrode 40 and the varistor line ground electrode 50; and a capacitive isolation gap region K3 is provided between the capacitive signal electrode 10 and the varistor line ground electrode 50.

[0065] It should be noted that the varistor line ground electrode 50 is connected to the ground signal for isolating the signal and helping the impedance of the quarter-wavelength transformer structure formed by the varistor line signal electrode 40 and the varistor line ground electrode 50 to reach the target impedance.

[0066] The open gap region K4 (including the first open gap region K41 and the second open gap region K42) within the capacitor ground electrode 20 can not only adjust the impedance of the parallel plate capacitor structure formed by the capacitor signal electrode 10 and the capacitor ground electrode 20, but also modify the electric field distribution near the parallel plate capacitor structure formed by the capacitor signal electrode 10 and the capacitor ground electrode 20.

[0067] The capacitive isolation gap region K3 between the capacitive signal electrode 10 and the varistor line ground electrode 50 can prevent the quarter-wavelength transformer structure formed by the varistor line signal electrode 40 and the varistor line ground electrode 50 from interfering with the impedance of the parallel plate capacitor structure formed by the capacitive signal electrode 10 and the capacitive ground electrode 20.

[0068] It can be understood that by adjusting the distance between the capacitive signal electrode 10 and the capacitive ground electrode 20, that is, adjusting the width of the capacitance modulation gap region K1 between the capacitive signal electrode 10 and the capacitive ground electrode 20 along the first direction Y, the capacitance value of the parallel plate capacitor structure formed by the capacitive signal electrode 10 and the capacitive ground electrode 20 can be adjusted, thereby adjusting the impedance of the parallel plate capacitor structure formed by the capacitive signal electrode 10 and the capacitive ground electrode 20.

[0069] By adjusting the distance between the varistor line signal electrode 40 and the varistor line ground electrode 50, that is, adjusting the width of the varistor line gap region K2 between the varistor line signal electrode 40 and the varistor line ground electrode 50 along the second direction X, the impedance of the quarter-wavelength transformer structure formed by the varistor line signal electrode 40 and the varistor line ground electrode 50 can be adjusted.

[0070] In addition, by adjusting the thickness of the electrode layer 300, the capacitance value of the parallel plate capacitor structure formed by the capacitor signal electrode 10 and the capacitor ground electrode 20 can also be adjusted, thereby adjusting the impedance of the parallel plate capacitor structure formed by the capacitor signal electrode 10 and the capacitor ground electrode 20, and the impedance of the quarter-wavelength converter structure formed by the variable resistance line signal electrode 40 and the variable resistance line ground electrode 50 can also be adjusted.

[0071] like Figure 2 As shown, when the capacitor signal electrode 10 is axially symmetrical with respect to the variable resistance line signal electrode 40 , the capacitor signal electrode 10 and the variable resistance line signal electrode 40 form a T-shaped structure.

[0072] Alternatively, the capacitive signal electrode 10 may be asymmetric with respect to the variable resistance line signal electrode 40 , that is, the connection position between the capacitive signal electrode 10 and the variable resistance line signal electrode 40 is located on one side of the middle position of the capacitive signal electrode 10 along the second direction X.

[0073] For example, the capacitive signal electrode 10 and the varistor signal electrode 40 form an L-shaped structure. In this case, a single open gap region K4 extending along the second direction X can be provided within the capacitive ground electrode 20. This open gap region K4 is disposed opposite the non-connected portion of the capacitive signal electrode 10 and the varistor signal electrode 40, excluding the connected portion, along the first direction Y. The length of the open gap region K4 along the second direction X can be set to offset the imaginary part of the impedance of the parallel plate capacitor structure formed by the capacitive signal electrode 10 and the capacitive ground electrode 20, thereby converting the complex impedance of the load into a real impedance. Accordingly, a varistor ground electrode 50 can be provided on one side of the varistor signal electrode 40 along the second direction X.

[0074] It should be noted that if Figure 2 As shown, a portion of the capacitor ground electrode 20 is still present between the open gap region K4 and the capacitance modulation gap region K1 , so as to form an electric field between the capacitor ground electrode 20 and the capacitor signal electrode 10 .

[0075] It can be seen that the electro-optical modulator provided in the embodiment of the present application is configured such that an open gap region K4 extending along the second direction X is provided in the capacitor ground electrode 20, and the open gap region K4 is arranged relative to the non-connected portion other than the connected portion of the capacitor signal electrode 10 and the variable resistance line signal electrode 40 along the first direction Y, so that the imaginary part of the impedance of the parallel plate capacitor structure formed by the capacitor signal electrode 10 and the capacitor ground electrode 20 is offset, and the impedance of the parallel plate capacitor structure formed by the capacitor signal electrode 10 and the capacitor ground electrode 20 as a load is transformed into a real impedance; and, by providing a quarter-wavelength converter structure formed by the variable resistance line signal electrode 40 and the variable resistance line ground electrode 50, the impedance Z of the parallel plate capacitor structure formed by the capacitor signal electrode 10 and the capacitor ground electrode 20 as a load is transformed into a real impedance. L By matching the input impedance Z0 of the microwave signal, the signal reflection at the microwave interface In can be eliminated, making the microwave signal most efficient during transmission, thereby improving the utilization efficiency of microwave energy.

[0076] It should be noted that the parallel plate capacitor structure composed of the capacitor signal electrode 10 and the capacitor ground electrode 20 acts as the impedance Z of the load. L The matching with the input impedance Z0 of the microwave signal is the matching under a certain frequency of the microwave signal.

[0077] Further optionally, the sum of the length of the variable resistance line signal electrode 40 along the first direction Y and the length from the connection point of the variable resistance line signal electrode 40 and the capacitor signal electrode 10 to either end of the capacitor signal electrode 10 along the second direction X, that is, the total path of the microwave signal transmitted from the microwave interface In through the variable resistance line signal electrode 40 to either end of the capacitor signal electrode 10 along the second direction X, divided by the average transmission speed of the microwave signal in the variable resistance line signal electrode 40 and the capacitor signal electrode 10, the resulting value is the total time for the microwave signal to be transmitted from the microwave interface In through the variable resistance line signal electrode 40 to either end of the capacitor signal electrode 10 along the second direction X. If the resulting value is approximately equal to an odd multiple of 1 / 2 cycle of the microwave signal, that is, the difference between the resulting value and the odd multiple of 1 / 2 cycle of the microwave signal is less than the second preset range, then the microwave signal at the microwave interface In is The phase is different from the phase of the microwave signal when it is transmitted to either end of the capacitor signal electrode 10 along the second direction X by π. Furthermore, when the microwave signal is reflected back to the microwave interface In from either end of the capacitor signal electrode 10 along the second direction X, it has the same phase as the microwave signal at the microwave interface In. In this way, the microwave signal can resonate within the overall signal electrode composed of the variable resistance line signal electrode 40 and the capacitor signal electrode 10. That is, the electro-optical modulator provided in the embodiment of the present application can operate near the resonant frequency, so that the microwave energy can be fully utilized in the generation of the electric field in the capacitor modulation gap area K1 between the capacitor signal electrode 10 and the capacitor ground electrode 20, thereby enhancing the electric field strength of the capacitor modulation gap area K1 between the capacitor signal electrode 10 and the capacitor ground electrode 20, and thereby improving the modulation depth of the electro-optical modulator, so that the optical signal transmitted by the modulation waveguide 30 is more effectively modulated.

[0078] It should be noted that the average transmission speed of the microwave signal in the variable resistance line signal electrode 40 and the capacitor signal electrode 10 can be obtained by testing or theoretical calculation. As we know, a microwave transmission line is also called a microstrip line, which usually includes a center conductor line and a ground line. The variable resistance line signal electrode portion and the capacitor signal electrode portion in this application are coplanar waveguide microstrip transmission lines in the microstrip line. The portion of the variable resistance line signal electrode portion and the capacitor signal electrode portion that transmits the signal is the center strip, and the portions on both sides that are grounded are the ground strips. During theoretical calculation, a cross section of the microwave signal during transmission in the variable resistance line signal electrode portion (including the variable resistance line signal electrode 40 and the variable resistance line ground electrode 50) can be selected. According to the dielectric constant of the medium at each location in the cross section, combined with boundary conditions such as the metal electrode, the propagation constant γ at the cross section can be calculated by the finite element difference method based on Maxwell's equations. Since the cross sections of the microstrip line are consistent at each location, the propagation constant of the microstrip line from beginning to end is also the same. Therefore, calculating the propagation constant of a certain cross section will give the propagation constant γ of the entire microstrip line, that is, the propagation constant γ of the variable resistance line signal electrode portion can be obtained. Therefore, according to the microwave propagation constant γ, which is a characteristic parameter describing microwave propagation, it is generally expressed as γ=α+iβ. Where α is the attenuation constant and β is the phase shift constant. The phase shift constant β can be calculated, and the phase shift constant β in the microwave propagation constant determines the effective refractive index n of the microwave in the transmission line. Furthermore, according to the definition of the effective refractive index n, the transmission speed of microwaves of a certain wavelength in the transmission line is c / n, and the transmission speed of the microwave signal in the signal electrode part of the variable resistance line is calculated. Similarly, the transmission speed of the microwave signal in the capacitor signal electrode part (including the capacitor signal electrode and the capacitor ground electrode) can be calculated. Furthermore, the transmission speed of the microwave signal in the signal electrode part of the variable resistance line and the transmission speed of the microwave signal in the capacitor signal electrode part are weighted averaged to obtain the average transmission speed of the microwave signal in the signal electrode 40 of the variable resistance line and the capacitor signal electrode 10.

[0079] It should also be noted that by adjusting the length of the capacitive signal electrode 10 along the second direction X, the length of the variable resistance line signal electrode 40 along the first direction Y, and the connection structure between the capacitive signal electrode 10 and the variable resistance line signal electrode 40, the resonant frequency of the electro-optical modulator can be adjusted so that the resonant frequency of the electro-optical modulator is close to the frequency of the microwave signal, thereby allowing the microwave signal to resonate within the overall signal electrode formed by the variable resistance line signal electrode 40 and the capacitive signal electrode 10.

[0080] As known from the foregoing, when the capacitive signal electrode 10 is axially symmetrical about the variable resistance line signal electrode 40, the microwave signal can be transmitted from the microwave interface In along the variable resistance line signal electrode 40 to one end of the capacitive signal electrode 10 along the second direction X, and can also be transmitted from the microwave interface In along the variable resistance line signal electrode 40 to the other end of the capacitive signal electrode 10 along the second direction X. This is equivalent to the microwave signal being able to resonate under both paths, thereby further enhancing the electric field strength of the capacitive modulation gap region K1 between the capacitive signal electrode 10 and the capacitive ground electrode 20, thereby improving the modulation depth of the electro-optical modulator; and, this also increases the length of the capacitive modulation gap region K1 along the second direction X, thereby increasing the length of the modulation waveguide 40 along the second direction X, which can further improve the modulation depth of the electro-optical modulator.

[0081] In other words, since the modulation depth of the electro-optical modulator is proportional to the electric field strength of the capacitive modulation gap region K1 between the capacitive signal electrode 10 and the capacitive ground electrode 20 and the length of the modulation waveguide 40 along the second direction X, when the microwave signal resonates within the overall signal electrode formed by the variable resistance line signal electrode 40 and the capacitive signal electrode 10, thereby enhancing the electric field strength of the capacitive modulation gap region K1 between the capacitive signal electrode 10 and the capacitive ground electrode 20, the length of the modulation waveguide 40 along the second direction X can be appropriately shortened to achieve the same modulation depth.

[0082] As is known from the above, when the capacitance signal electrode 10 is symmetrical about the variable resistance line signal electrode 40, as shown in FIG. Figure 2 As shown, the capacitive signal electrode 10 includes a first electrode portion 11 and a second electrode portion 12 that are symmetrical along the axis of the variable resistance line signal electrode 40; the open gap area K4 in the capacitive ground electrode 20 includes a first open gap area K41 and a second open gap area K42 that are symmetrical along the first direction Y, and the first open gap area K41 and the second open gap area K42 are spaced apart along the second direction X; the first open gap area K41 is arranged opposite to the first electrode portion 11 along the first direction Y, and the second open gap area K42 is arranged opposite to the second electrode portion 12 along the first direction Y; a variable resistance line ground electrode 50 is arranged on each of the two opposite sides of the variable resistance line signal electrode 40 along the second direction X, and a variable resistance line gap area K2 is provided between the variable resistance line signal electrode 40 and the variable resistance line ground electrode 50; and a capacitive isolation gap area K3 is provided between the capacitive signal electrode 10 and the variable resistance line ground electrode 50.

[0083] Optionally, the electrode layer 300 is a metal layer, and each gap area in the electrode layer 300 (including the capacitor modulation gap area K1, the variable resistance line gap area K2, the capacitor isolation gap area K3 and the open circuit gap area K4) is provided with a filling medium, which can be air, silicon dioxide or polymethyl methacrylate PMMA polymer.

[0084] Optional, such as Figure 5 As shown, the electro-optic modulator may further include a modulation residual layer 400 located between the insulating layer 200 and the electrode layer 300 , and the modulation residual layer 400 and the modulation waveguide 40 are integrally formed.

[0085] It can be understood that when preparing the modulation waveguide 40, a modulation layer is first formed, and then the modulation layer is completely etched or partially etched. Part of the modulation layer may remain, that is, there is a modulation residual layer 400 between the insulating layer 200 and the electrode layer 300. Of course, there may be no modulation residual layer 400, and only the modulation waveguide 40 may be formed.

[0086] Specifically, the electrode layer 300 has Figure 2 On the basis of the structure shown, the dimensions of each structure in the electrode layer 300 are designed, and the dimensions of each structure in the electrode layer 300 are required to meet the resonance condition at the design frequency (that is, the phase of the microwave signal at the microwave interface In differs by π from the phase when the microwave signal is transmitted to either end of the capacitive signal electrode 10 along the second direction X) and the impedance condition at the design frequency (that is, impedance matching).

[0087] For example, the resonant frequency is designed to be 7.5 GHz, and the input impedance is designed to be 100 ohms; the material of the electrode layer 300 is aluminum, and the thickness of the electrode layer 300 is 2 microns; the material of the modulation waveguide 30 is lithium niobate, and the thickness of the modulation waveguide 30 is 400 nanometers; the material of the insulating layer 200 is silicon oxide, and the thickness of the insulating layer 200 is 5 microns; the material of the substrate 100 is silicon, and the thickness of the substrate 100 is 675 microns; the width of the variable resistance line signal electrode 40 along the second direction X is 30 microns, and the distance between the variable resistance line signal electrode 40 and the variable resistance line ground electrode 50 is 100 microns. The gap K2 is 80 microns, that is, the width of the variable resistance line gap region K2 along the second direction X is 80 microns, the length of the variable resistance line signal electrode 40 along the first direction Y is 2 millimeters, the length of the capacitor signal electrode 10 along the second direction X is 2.2 millimeters, the width of the capacitor modulation gap region K1 along the first direction Y is 12 microns, the width of the capacitor signal electrode 10 along the first direction Y is 20 microns, the distance between the open gap K4 in the capacitor ground electrode 20 and the capacitor modulation gap region K1 is 20 microns, and the width of the capacitor isolation gap region K3 along the first direction Y is 150 microns. In this way, the microwave signal can generate a resonance with a quality factor Q≈10 near the designed resonant frequency, which can effectively improve the signal strength near the resonant frequency, enhance the electric field strength of the capacitor modulation gap region K2, and improve the modulation effect.

[0088] Accordingly, the embodiment of the present application further provides an electro-optical modulation module 200, such as Figure 6As shown, the electro-optical modulation module includes a plurality of electro-optical modulators 100, and the electro-optical modulator 100 is the electro-optical modulator provided by any of the above embodiments, wherein the modulation waveguides 40 of each electro-optical modulator 100 can be connected sequentially to increase the overall length of the modulation waveguide 40 along the second direction X, thereby further improving the modulation depth.

[0089] Optionally, the microwave input interfaces In of the electro-optical modulators 100 in the electro-optical modulation module 200 are connected in parallel. Figure 6 As shown, the microwave signal can be transmitted in a one-to-many manner through the first transmission line 201 to each second transmission line 202, and then input to the microwave input interface In of each electro-optical modulator 100 through the second transmission line 202. The electro-optical modulation module 200 includes N electro-optical modulators 100, and the impedance of the second transmission line 202 is set to be N times the impedance of the first transmission line 201. In this case, each electro-optical modulator 100 as a whole acts as a load, and the overall impedance of the electro-optical modulator 100 is also set to N times the impedance of the first transmission line 201. This ensures that the microwave signals transmitted to the microwave input interface In of each electro-optical modulator 100 are the same, avoids reflection during microwave transmission, and ensures that all energy is consumed by the load rather than being reflected back to the input end. Figure 6 The example shows that the electro-optical modulation module 200 includes two electro-optical modulators 100 .

[0090] The various parts in this manual are described in a combination of parallel and progressive manners. Each part focuses on the differences from other parts, and the same or similar parts between the various parts can be referenced to each other.

[0091] With respect to the above description of the disclosed embodiments, the features described in the various embodiments in this specification may be interchanged or combined with one another to enable those skilled in the art to implement or use the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An electro-optic modulator, characterized in that: include: substrate; an insulating layer located on one side of the substrate; an electrode layer located on a side of the insulating layer facing away from the substrate; The electrode layer includes a capacitive signal electrode and a capacitive ground electrode arranged opposite to each other along a first direction, the capacitive signal electrode extends along a second direction, the first direction and the second direction are both parallel to the plane where the substrate is located, and the first direction and the second direction are perpendicular; A capacitance modulation gap region is provided between the capacitance signal electrode and the capacitance ground electrode, wherein a modulation waveguide extending along the second direction is provided in the capacitance modulation gap region, and the modulation waveguide is used to transmit an optical signal; The electrode layer further includes a variable resistance line signal electrode located on a side of the capacitor signal electrode facing away from the capacitor ground electrode, the variable resistance line signal electrode extending along the first direction, one end of the variable resistance line signal electrode along the first direction being connected to the capacitor signal electrode, and the other end of the variable resistance line signal electrode along the first direction being a microwave interface for inputting microwave signals; The electrode layer further includes a varistor line ground electrode located on at least one of two sides of the varistor line signal electrode that are opposite to each other along the second direction; a varistor line gap region is defined between the varistor line signal electrode and the varistor line ground electrode; and a capacitive isolation gap region is defined between the capacitive signal electrode and the varistor line ground electrode. The difference between the length of the signal electrode of the variable resistance line along the first direction and an odd-number multiple of 1 / 4 wavelength of the microwave signal is smaller than a first preset range; An open gap region extending along the second direction is provided in the capacitor ground electrode. The open gap region is arranged opposite to a non-connected portion other than a connected portion between the capacitor signal electrode and the variable resistance line signal electrode along the first direction.

2. The electro-optic modulator according to claim 1, wherein The difference between the sum of the length of the variable resistance line signal electrode along the first direction and the length from the connection point of the variable resistance line signal electrode and the capacitor signal electrode to either end of the capacitor signal electrode along the second direction, divided by the average transmission speed of the microwave signal in the variable resistance line signal electrode and the capacitor signal electrode, and an odd number of times 1 / 2 period of the microwave signal is less than a second preset range.

3. The electro-optic modulator according to claim 1 or 2, characterized in that The capacitor signal electrode is symmetrical with respect to the variable resistance line signal electrode.

4. The electro-optic modulator according to claim 3, wherein: The capacitor signal electrode includes a first electrode portion and a second electrode portion symmetrically along the axis of the variable resistance line signal electrode; The open gap region in the capacitor ground electrode includes a first open gap region and a second open gap region that are axisymmetric along the first direction, and the first open gap region and the second open gap region are spaced apart along the second direction; The first open gap region and the first electrode portion are disposed opposite to each other along the first direction, and the second open gap region and the second electrode portion are disposed opposite to each other along the first direction.

5. The electro-optic modulator according to claim 4, wherein: A varistor line ground electrode is provided on each of two opposite sides of the varistor line signal electrode along the second direction; A variable resistance line gap region is provided between the variable resistance line signal electrode and the variable resistance line ground electrode; and a capacitor isolation gap region is provided between the capacitor signal electrode and the variable resistance line ground electrode.

6. The electro-optic modulator according to claim 1 or 2, characterized in that Each gap region in the electrode layer is provided with a filling medium, and the filling medium includes air, silicon dioxide or polymethyl methacrylate polymer.

7. The electro-optic modulator according to claim 1 or 2, characterized in that: The material of the modulation waveguide is a material having nonlinear effect.

8. The electro-optic modulator according to claim 1 or 2, characterized in that The electro-optic modulator further comprises: A modulation residual layer is located between the insulating layer and the electrode layer, and the modulation residual layer and the modulation waveguide are integrally formed.

9. An electro-optical modulation module, characterized in that: comprising a plurality of electro-optical modulators, wherein the electro-optical modulator is the electro-optical modulator according to any one of claims 1 to 8; The modulation waveguides of the electro-optical modulators are connected in sequence.

10. The electro-optical modulation module according to claim 9, characterized in that: The microwave input interfaces of the electro-optical modulators are connected in parallel.

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