Electro-optical modulator, optical chip and integrated chip

Abstract

The embodiment of the invention discloses an electro-optical modulator, an optical chip and an integrated chip, the electro-optical modulator is arranged on the surface of a substrate, and the electro-optical modulator comprises an optical waveguide layer arranged on the substrate; the modulation electrode is arranged on the optical waveguide layer; the metal electrode is arranged on the modulation electrode and is electrically connected with the modulation electrode (003); the first end of the metal electrode is coupled with the radio frequency driver; wherein the metal electrode is used for receiving a modulation signal input by the radio frequency driver, and the modulation electrode is used for performing electro-optical modulation on the optical waveguide layer based on the modulation signal; the second end of the metal electrode is coupled to a direct-current voltage end, and the direct-current voltage end is used for inputting a voltage signal and providing bias voltage for the radio frequency driver through the metal electrode. The electro-optical modulator multiplexes the metal electrode, a complex peripheral circuit does not need to be arranged, the cost is reduced, meanwhile, the size of the electro-optical modulator is reduced, and miniaturization of equipment is facilitated.

Description

[0001] This application is a divisional application. The original application was entitled "Electro-optic Modulator, Optical Chip and Integrated Chip", with application number 202080098076.6 and application date of May 30, 2020. The entire contents of the original application are incorporated herein by reference. Technical Field

[0002] This application relates to the field of electro-optic modulation, and more particularly to an electro-optic modulator, an optical chip, and an integrated chip. Background Technology

[0003] With the development of optical communication technology, the application of optical networks in communication has become widespread. For example, more and more users are using fiber optic broadband to access the internet. When using fiber optic broadband to access the internet, an electro-optic modulator needs to be deployed. The electro-optic modulator can be used to modulate electrical signals onto optical signals.

[0004] The modulation electrode design in existing electro-optic modulators uses a single-ended AC coupling method, which requires external circuits such as capacitors and inductors for signal processing. This results in a complex structure, large size, and high cost, which is not conducive to the miniaturization of the device. Summary of the Invention

[0005] This application provides an electro-optic modulator, an optical chip, and an integrated chip, which solves the problems of complex peripheral circuits, high cost, and large size of electro-optic modulators.

[0006] To achieve the above objectives, this application adopts the following technical solution: In a first aspect, an electro-optic modulator is provided, disposed on the surface of a substrate. The electro-optic modulator includes: an optical waveguide layer disposed on the substrate; a modulation electrode disposed on the optical waveguide layer; and a metal electrode disposed on and electrically connected to the modulation electrode. A first end of the metal electrode is coupled to a radio frequency (RF) driver. The metal electrode is used to receive a modulation signal input from the RF driver, and the modulation electrode is used to electro-optically modulate the optical waveguide layer based on the modulation signal. A second end of the metal electrode is coupled to a DC voltage terminal, which is used to input a voltage signal and provide a bias voltage to the RF driver through the metal electrode. Thus, the modulation electrode is electrically connected to the signal output terminal of the RF driver through the metal electrode, and can receive the voltage signal input from the DC voltage terminal through the metal electrode. Furthermore, the metal electrode is coupled to the DC voltage terminal, allowing the metal electrode to be reused to power the RF driver. The electro-optic modulator reuses the metal electrode and uses open-circuit DC coupling to power the driver of the electro-optic modulator. This eliminates the need for complex external circuits, reducing costs and decreasing the size of the electro-optic modulator, which is beneficial for device miniaturization.

[0007] In one optional implementation, the optical waveguide layer includes an electro-optic crystal layer parallel to the substrate. The electro-optic crystal layer has a modulation electrode and a ridge waveguide on its side away from the substrate. The modulation electrode is disposed on both sides of the ridge waveguide and is used to electro-optically modulate the light wave transmitted through the ridge waveguide. Thus, a capacitor is formed between the modulation electrodes, and an electric field can be generated through capacitive coupling to electro-optically modulate the light wave transmitted through the ridge waveguide.

[0008] In one optional implementation, the electro-optic modulator further includes an insulating layer disposed on the surface of the substrate, with the optical waveguide layer and the modulation electrode located within the insulating layer. An opening is provided on the insulating layer on the surface of the modulation electrode, and a metal electrode is formed at the opening. This arrangement of the modulation electrode within the insulating layer prevents short circuits in the modulation electrode.

[0009] In one optional implementation, the optical waveguide layer includes: a symmetrically arranged first branch and a second branch, with the input terminals of the first and second branches coupled together, and the output terminals of the first and second branches coupled together. A first end of a modulation electrode is coupled to the input terminals of the first and second branches, and a second end of the modulation electrode is coupled to the output terminals of the first and second branches. The first end of the modulation electrode is coupled to the signal output terminal of the RF driver, and the second end of the modulation electrode is connected to a terminating resistor and coupled to a DC voltage terminal. The optical signals output by the first and second branches are out of phase. This achieves a push-pull modulation scheme, improving modulation efficiency.

[0010] In one optional implementation, the modulation electrode includes a first electrode pair and a second electrode pair. The first electrode pair is symmetrically disposed on both sides of the first branch, and the second electrode pair is symmetrically disposed on both sides of the second branch. Thus, the first electrode pair and the second electrode pair can be modulated along with the first branch and the second branch, respectively. Furthermore, the symmetrical structure of the modulation electrode enables chirp-free modulation, ensuring signal transmission quality.

[0011] In one optional implementation, the first end of the first electrode pair is connected to the signal output terminal of the RF driver, the second end of the first electrode pair is connected to the first end of the second electrode pair, and the second end of the second electrode pair is connected to the DC voltage terminal. The first branch and the second branch each include a first part and a second part, the first part of the first branch and the first part of the second branch are opposite to each other, and the second part of the first branch and the second part of the second branch are opposite to each other. The first electrode pair is disposed on both sides of the first part of the first branch, and the second electrode pair is disposed on both sides of the second part of the second branch. The polarization directions of the first branch and the second branch are opposite, and the electric field direction applied by the first electrode pair to the first branch is the same as the electric field direction applied by the second electrode pair to the second branch. Thus, during operation, the RF signal is first loaded onto the first electrode pair of the electro-optic modulator through the signal output terminal of the RF driver, and then loaded onto the second electrode pair of the electro-optic modulator. The first electrode pair, the second electrode pair, and the third electrode pair are connected in series, so that the electric field direction applied by the first electrode pair and the second electrode pair to the first branch and the second branch is the same. Since the polarization directions of the first and second branches are opposite, the optical signals output by the first and second branches are in opposite phases. This eliminates the need for external circuitry, thus achieving push-pull modulation, improving modulation efficiency, and reducing the size of the electro-optic modulator.

[0012] In one optional implementation, the modulation electrode further includes: a third electrode pair, wherein a first end of the first electrode pair is connected to the signal output terminal of the RF driver, a second end of the first electrode pair is connected to the first end of the second electrode pair, a first end of the third electrode pair is connected to the second end of the second electrode pair, and a second end of the third electrode pair is connected to the DC voltage terminal; the first branch and the second branch include: a first part, a second part, and a third part arranged in an S-shape and parallel to each other, the second part being located between the first part and the third part; the first electrode pair is disposed on both sides of the first part of the first branch, the second electrode pair is disposed on both sides of the second part of the second branch, and the third electrode pair is disposed on both sides of the third part of the first branch; wherein the electric field direction applied by the first electrode pair to the first branch is opposite to the electric field direction applied by the second electrode pair to the second branch, the electric field direction applied by the third electrode pair to the third modulation arm is opposite to the electric field direction applied by the second electrode pair to the second branch, and the polarization directions of the first branch and the second branch are the same. Therefore, during operation, the radio frequency (RF) signal is first applied to the first electrode pair of the electro-optic modulator through the signal output terminal of the RF driver. The first part of the second branch is not loaded with an electric field. Then, the optical path and electric field make a 180° turn with the modulation arm, and the RF signal is applied to the second electrode pair of the electro-optic modulator. At this point, the second part of the first branch is not loaded with an electric field. Next, the optical path and electric field make another 180° turn with the modulation arm, and the RF signal is applied to the third electrode pair of the electro-optic modulator. The third part of the second branch is not loaded with an electric field. This results in the electric field directions of the first and second electrode pairs being opposite, and the electric field directions of the third electrode pair being opposite to those of the second electrode pairs. Since the polarization directions of the first and second branches are the same, the final output optical signals of the first and second branches are out of phase, thus eliminating the need for external circuitry. This achieves a push-pull modulation method, improving modulation efficiency and reducing the size of the electro-optic modulator.

[0013] In one optional implementation, the first ends of the first electrode pair and the second electrode pair are respectively connected to the signal output terminal of the RF driver, and the second ends of both the first electrode pair and the second electrode pair are connected to resistors. The first electrode pair includes a first electrode and a second electrode, and the second electrode pair includes a third electrode and a fourth electrode. The first electrode and the second electrode are located, for example, on opposite sides of the first branch and the second branch, and the third electrode and the fourth electrode are located, for example, between the first branch and the second branch. The first electrode, the second electrode, the third electrode, and the fourth electrode can adopt an input configuration of S+S-, S-S+, such that the electric field direction applied by the first electrode pair to the first branch is opposite to the electric field direction applied by the second electrode pair to the second branch, and the polarization directions of the first branch and the second branch are the same. Thus, the first electrode and the second electrode pair are connected in parallel, and the electric field direction of the first electrode pair and the second electrode pair can be changed by adjusting the positive and negative connection of the first electrode pair and the second electrode pair, so that the optical signals finally output by the first branch and the second branch are out of phase, that is, a push-pull modulation method is realized, which improves the modulation efficiency and reduces the size of the electro-optic modulator.

[0014] In one optional implementation, the first terminals of the first electrode pair and the second electrode pair are respectively connected to the signal output terminal of the RF driver, and the second terminals of both the first electrode pair and the second electrode pair are connected to resistors. The first electrode pair includes a first electrode and a second electrode, and the second electrode pair includes a third electrode and a fourth electrode. The first electrode and the second electrode are located, for example, on opposite sides of a first branch and a second branch, and the third electrode and the fourth electrode are located, for example, between the first branch and the second branch. The first electrode, the second electrode, the third electrode, and the fourth electrode can be used in an S+S- or S+S- input configuration. The electric field direction applied by the first electrode pair to the first branch is the same as the electric field direction applied by the second electrode pair to the second branch, and the polarization directions of the first branch and the second branch are opposite. Thus, the first electrode and the second electrode pair are connected in parallel, which makes the electric field direction of the point electrode pair and the second electrode pair the same, and the polarization directions of the first branch and the second branch are opposite, so that the optical signals output by the first branch and the second branch are out of phase, thereby realizing a push-pull modulation method, improving modulation efficiency, and reducing the size of the electro-optic modulator.

[0015] A second aspect of this application provides an optical chip, comprising: a substrate, and an electro-optic modulator as described above, the electro-optic modulator being disposed on the surface of the substrate. Therefore, by employing the aforementioned electro-optic modulator, the optical chip can reduce its size and facilitate encapsulation with other chips.

[0016] In one optional implementation, the optical chip further includes an input waveguide and an output waveguide, wherein the input waveguide is connected to the input terminal of the electro-optic modulator, and the output waveguide is connected to the output terminal of the electro-optic modulator. Thus, the optical signal to be modulated can be input through the input waveguide, and the modulated optical signal can be output through the output waveguide.

[0017] In one optional implementation, the optical chip further includes a photodetector connected to the output waveguide via a connecting waveguide, and the photodetector is used to detect the modulated optical signal. Thus, by incorporating a photodetector, a small-sized, low-cost optical chip with higher integration and transceiver capabilities can be achieved.

[0018] A third aspect of this application provides an integrated chip, comprising: an electrical chip and an optical chip as described above, wherein the electrical chip is disposed on the surface of the optical chip and is soldered to the optical chip via solder balls. Therefore, the soldering connection method simplifies the circuit, and the small size of the optical chip reduces the overall size of the integrated chip. Attached Figure Description

[0019] Figure 1 This is an equivalent circuit diagram of an electro-optic modulator; Figure 2 This is a schematic diagram of the structure of an electro-optic modulator provided in an embodiment of this application; Figure 3 An equivalent circuit diagram of an electro-optic modulator provided in an embodiment of this application; Figure 3a This is a schematic diagram of the X-section structure of an electro-optic modulator provided in an embodiment of this application; Figure 3b This is a schematic diagram of the Z-cut structure of an electro-optic modulator provided in an embodiment of this application; Figure 3c This is a schematic diagram of the Y-cut structure of an electro-optic modulator provided in an embodiment of this application; Figure 3d Hysteresis curve of a lithium niobate material provided in an embodiment of this application; Figure 4 An equivalent circuit diagram of another electro-optic modulator provided in the embodiments of this application; Figure 5 An equivalent circuit diagram of another electro-optic modulator provided in the embodiments of this application; Figure 6 An equivalent circuit diagram of another electro-optic modulator provided in the embodiments of this application; Figure 7 This is a schematic diagram of the structure of an optical chip provided in an embodiment of this application; Figure 8 This is a schematic diagram of an integrated chip structure; Figure 9 This is a schematic diagram of an integrated chip provided in an embodiment of this application. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this application clearer, the application will now be described in further detail with reference to the accompanying drawings.

[0021] In the following description, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0022] Furthermore, in this application, directional terms such as "upper" and "lower" are defined relative to the orientation of the components shown in the accompanying drawings. It should be understood that these directional terms are relative concepts, used for relative description and clarification, and can change accordingly depending on the orientation of the components in the accompanying drawings.

[0023] This application provides an electro-optic modulator that can be used as a conversion interface for switching from the electrical domain to the optical domain in an optical network, and can be used in a communication system.

[0024] It should be noted that optical networks refer to wide area networks, metropolitan area networks, or newly built large-scale local area networks that use optical fiber as the primary transmission medium.

[0025] Figure 1 This is a schematic diagram of an electro-optic modulator. It should be noted that an electro-optic modulator is typically a semiconductor device. Figure 1 The equivalent circuit diagram of the semiconductor device. (See diagram below.) Figure 1 As shown, the electro-optic modulator includes: a first branch 202 and a second branch 201 arranged symmetrically, the input terminal of the first branch 202 and the input terminal of the second branch 201 are connected, and the output terminal of the first branch 202 and the output terminal of the second branch 201 are connected.

[0026] The electro-optic modulator, for example a Mach-Zehnder modulator, splits the input light into two equal signals, which are then fed into the first branch 202 and the second branch 201, respectively. The first branch 202 and the second branch 201 are made of electro-optic materials, such as lithium niobate, whose refractive index varies with the magnitude of the externally applied electrical signal.

[0027] The first branch 202 and the second branch 201 are provided with a first metal layer 101 and a second metal layer 103 on both sides, and a third metal layer 102 is provided between the first branch 202 and the second branch 201. The first metal layer 101 and the third metal layer 102 form a first electrode pair, and the second metal layer 103 and the third metal layer 102 form a second electrode pair.

[0028] The input side of the electro-optic modulator is provided with, for example, a radio frequency input terminal 11 and a DC input terminal 12. The radio frequency input terminal 11 (which is also the driver output terminal of the electro-optic modulator) is used to input a high-frequency modulated AC signal to the first electrode pair and the second electrode pair, and the DC input terminal 12 is used to input a DC bias signal to the driver of the electro-optic modulator.

[0029] The signal output terminal 11 of the RF driver is connected to the first electrode pair and the second electrode pair via a capacitor 111, which is used to filter out DC signals. The DC voltage terminal 12 is connected to the modulation electrode of the electro-optic modulator via an inductor 121, which is used to filter out high-frequency signals.

[0030] The modulation signal input to the DC voltage terminal 12 can be coupled to the first branch 202 and the second branch 201 respectively through the capacitor 111 structure formed by the first electrode pair and the second electrode pair.

[0031] In the above embodiments, the first electrode pair and the second electrode pair are, for example, AC bias electrodes. In order to ensure that the input modulator only has a high-frequency AC signal and the input driver 11 only has a DC signal, peripheral circuits such as capacitor 111 and inductor 121 are provided between the signal output terminal 11 and DC voltage terminal 12 of the RF driver and the first electrode pair and the second electrode pair of the electro-optic modulator to obtain DC signal and high-frequency AC signal respectively. The peripheral circuit structure is complex and the device size is large, which is not conducive to the miniaturization of the device.

[0032] Figure 8 This is a schematic diagram of an integrated chip provided in this application. Figure 8 As shown, the integrated chip includes: a substrate 01, and an optical chip 01 and an electrical chip 03 disposed on the substrate. The optical chip 02, for example, employs... Figure 1 The electro-optic modulator shown is relatively large, and the optical chip 02 and the electrical chip 03 are connected by wires.

[0033] This application provides an electro-optic modulator. Figure 2 This is a schematic diagram of an electro-optic modulator provided in an embodiment of this application. Figure 3 An equivalent circuit diagram of an electro-optic modulator provided in an embodiment of this application is shown. Figure 2 , Figure 3As shown, the electro-optic modulator includes: an optical waveguide layer 002 formed on a substrate 01, a modulation electrode 003 disposed on the optical waveguide layer 002, and a metal electrode 004 disposed on the modulation electrode 003 and electrically connected to the modulation electrode 003.

[0034] The first end of the metal electrode 004 is coupled to the signal output terminal 11 of the radio frequency driver.

[0035] The metal electrode 004 is used to receive the modulation signal input by the radio frequency driver, and the modulation electrode is used to perform electro-optic modulation on the optical waveguide layer based on the modulation signal.

[0036] The second end of the metal electrode 004 is coupled to the DC voltage terminal 12, which is used to input voltage signals and provides bias voltage to the RF driver through the metal electrode 004.

[0037] It should be noted that the RF driver includes at least an RF signal output terminal and a bias voltage terminal. The RF signal output terminal is coupled to the modulation electrode 003, for example, through the metal electrode 004. The RF signal output terminal can output an RF signal to the metal electrode 004, and the modulation electrode 003 is used to perform electro-optic modulation on the optical waveguide layer based on the modulation signal. The bias voltage input terminal can be coupled to the metal electrode 004 to receive the bias voltage output from the DC voltage terminal through the metal electrode 004, thereby powering the RF driver.

[0038] The specific configuration of the radio frequency signal output terminal and the bias voltage input terminal is existing technology for those skilled in the art and will not be described in detail here.

[0039] like Figure 3 As shown, the metal electrodes 004 are continuously arranged, while the different modulation electrodes 003 are discontinuous. Therefore, the high-frequency modulation signal input to the RF driver can be loaded onto the waveguide through the modulation electrodes 003 and terminated at the terminating resistor 104. The DC voltage signal transmitted at the DC voltage terminal 12 can pass through the metal electrodes 004 to provide the bias voltage required for the operation of the RF driver.

[0040] During operation, the DC voltage terminal 12 supplies power to the RF driver through the metal electrode, causing the RF driver to start working. Then, the RF driver outputs a modulation signal, and the metal electrode 004 receives the modulation signal input by the RF driver. The modulation electrode 003 performs electro-optic modulation on the optical waveguide layer based on the modulation signal.

[0041] The electro-optic modulator provided in this application embodiment has a modulation electrode electrically connected to the signal output terminal of an RF driver via a metal electrode. The metal electrode can receive a voltage signal input from a DC voltage terminal, and the metal electrode is coupled to the DC voltage terminal, allowing the metal electrode to be reused to power the RF driver. This electro-optic modulator reuses the metal electrode and uses open-circuit DC coupling to power the driver, eliminating the need for complex external circuitry, reducing costs, and decreasing the size of the electro-optic modulator, thus facilitating device miniaturization.

[0042] like Figure 2 As shown, the optical waveguide layer 002 includes: an electro-optic crystal layer 005 parallel to the substrate, and a ridge waveguide 006 disposed on the side of the electro-optic crystal layer 005 away from the substrate. Modulation electrodes 003 are disposed on both sides of the ridge waveguide 006, and are used to electro-optically modulate the light waves transmitted through the ridge waveguide 006. Thus, the modulation electrodes 003 form a capacitor, and an electric field can be formed between the modulation electrodes 003 through capacitive coupling to electro-optically modulate the light waves transmitted through the ridge waveguide 006.

[0043] It should be noted that the electro-optic crystal layer 005 and the ridge waveguide 006 can be integrally formed. The materials of the electro-optic crystal layer 005 and the ridge waveguide 006 are, for example, electro-optic materials, specifically lithium niobate, whose refractive index varies with the magnitude of the externally applied electrical signal.

[0044] The substrate 01 is made of silicon (Si) for example, and an insulating layer 02 is provided on the surface of the substrate 01. The insulating layer 02 is made of silicon dioxide for example, and the optical waveguide layer 002 and the modulation electrode 003 are disposed in the insulating layer 02.

[0045] In other embodiments of this application, reference is then made to... Figure 2 An opening is provided on the insulating layer on the surface of the modulation electrode, and a metal electrode 004 is formed at the opening.

[0046] Therefore, by placing the modulation electrode 003 inside the insulating layer, short circuits can be avoided when the modulation electrode 003 is in operation. like Figure 3 As shown, the optical waveguide layer includes: a first branch 202 and a second branch 201 symmetrically arranged (i.e., Figure 2 In the ridge waveguide 006, modulation electrodes are provided on both sides of the first branch 202 and the second branch 201. Figure 3 (10, 20).

[0047] The input terminal of the first branch 202 is connected to the input terminal of the second branch 201, and the output terminal of the first branch 202 is connected to the output terminal of the second branch 201.

[0048] The modulation electrodes are respectively disposed on both sides of the first branch 202 and the second branch 201, and are used to modulate the electric field around the first branch 202 and the second branch 201, so that the optical signals output by the first branch 202 and the second branch 201 are out of phase. The first end of the modulation electrode is coupled to the input terminal 21 of the first branch 202 and the second branch 201, and the second end of the modulation electrode is coupled to the output terminal 22 of the first branch 202 and the second branch 201. The second end of the modulation electrode is connected to a terminating resistor 104.

[0049] The terminating resistor 104 can be two resistors connected in series, with a resistance value of, for example, 32.5 ohms.

[0050] The phase directions of the first branch 202 and the second branch 201 being opposite include: the polarization directions of the first branch 202 and the second branch 201 being the same, and the direction of the electric field applied to the first branch 202 and the second branch 201 by the modulation electrode can be adjusted so that the electric field directions of the first branch 202 and the second branch 201 are opposite, so that the phase directions of the first branch 202 and the second branch 201 are opposite.

[0051] Alternatively, the modulation electrodes have the same direction of the external electric field applied to the first branch 202 and the second branch 201, and the polarization directions of the first branch 202 and the second branch 201 are opposite, so that the phase directions of the first branch 202 and the second branch 201 are opposite.

[0052] The first branch 202 and the second branch 201 are made of electro-optic materials, specifically lithium niobate, whose refractive index varies with the magnitude of the externally applied electrical signal.

[0053] This application embodiment does not limit the polarization direction of the first branch 202 and the second branch 201. In one implementation of this application, the first branch 202 and the second branch 201 can be as follows: Figure 2 As shown, a structure for transmitting light along the Y direction is fabricated on a Z-cut lithium niobate substrate.

[0054] In another implementation of this application, the first branch 202 and the second branch 201 can also be as follows: Figure 3a As shown, a structure for transmitting light along the Z direction is fabricated on an X-cut lithium niobate substrate.

[0055] In another implementation of this application, the first branch 202 and the second branch 201 can also be as follows: Figure 3b As shown, a structure for transmitting light along the X direction is fabricated on a Z-cut lithium niobate substrate.

[0056] In another implementation of this application, the first branch 202 and the second branch 201 can also be as follows: Figure 3c As shown, a structure for transmitting light along the Z direction is fabricated on a Y-cut lithium niobate substrate.

[0057] It should be noted that lithium niobate is also a good ferroelectric material, exhibiting both spontaneous polarization and applied electric field polarization. Figure 3d The figure shows the hysteresis curve of lithium niobate. The horizontal axis represents the applied electric field strength E, and the vertical axis represents the polarization intensity P. Ps is the polarization direction of lithium niobate at the corresponding polarization intensity. When a reverse electric field is applied to lithium niobate, the spontaneous polarization direction tends to reverse. If the applied electric field is strong enough, ions will overcome the potential barrier and jump from one equilibrium position to another, causing the polarization direction to reverse. The trajectory of this change is along curve 1. At this time, reducing the electric field strength causes the polarization intensity to change along another curve 2, called the hysteresis loop. When the electric field is reduced to zero, spontaneous polarization still exists. At this time, the polarization direction changes from point A to point B, that is, the polarization direction is reversed. Continuing to apply a reverse voltage, the polarization intensity will become zero only when the field strength reaches a certain value. This voltage value is called the coercive field strength Ec.

[0058] In this embodiment, the second branch 201 of the electro-optic modulator can be polarized by applying a pulsed voltage, so that the polarization directions of the first branch 202 and the second branch 201 are opposite. For example, a radio frequency signal can be first applied to the first branch 202 of the modulator, with the applied electric field direction as follows: Figure 2 As shown by the arrow, the direction of the applied electric field is opposite to the "+Z" direction. After being applied to 1 / 2 of the equivalent modulation region length, the electric field is transferred to the second branch 201. The polarized "+Z" direction is downward as shown by the arrow, and the electric field direction remains unchanged, so that the polarization directions of the first branch 202 and the second branch 201 are opposite.

[0059] Furthermore, the electro-optic modulator also includes, for example, a signal output terminal 11 of a radio frequency driver (i.e., the driver output terminal of the electro-optic modulator) and a DC voltage terminal 12. The signal output terminal 11 of the radio frequency driver is connected to the first terminal of the modulation electrode and is used to input a modulation signal. The DC voltage terminal 12 is connected to the second terminal of the modulation electrode through the terminating resistor 104 and is used to input a DC bias signal to the driver of the electro-optic modulator.

[0060] During operation, the input light wave is split into two equal beams at a Y branch after passing through the input end of the electro-optic modulator. The beams are transmitted through the first branch 202 and the second branch 201, respectively. Since the first branch 202 and the second branch 201 are made of electro-optic materials, their refractive index varies with the magnitude of the applied electric field, thereby causing a phase difference between the two light signals when they reach the second Y branch.

[0061] The radio frequency (RF) signal input to the signal output terminal 11 of the RF driver is directly coupled to the modulation electrode for electro-optic modulation. By adjusting the electric field strength, the phase difference of the optical signal can be changed, thus achieving modulation of the optical signal. Finally, the RF signal terminates at the series terminating resistor 104. Simultaneously, a DC bias voltage can be applied to the terminating resistor 104 to power the driver of the electro-optic modulator.

[0062] The electro-optic modulator provided in this embodiment has its signal output terminal 11 and DC voltage terminal 12 of the RF driver located at both ends of the modulation electrode. The modulation electrode adopts open-collector DC coupling, which, compared with traditional single-terminal AC coupling, eliminates the need for filtering components such as capacitor 111 and inductor 121, greatly simplifying the peripheral circuit. While ensuring the performance of the electro-optic modulator remains unaffected, it can further improve the integration of the electro-optic modulator, effectively reducing the difficulty of high-sealing packaging layout and wiring pressure, and facilitating chip packaging. Furthermore, the modulation electrode adopts a symmetrical structure, enabling chirp-free modulation and ensuring signal transmission quality.

[0063] In addition, the electro-optic modulator uses a push-pull modulation method, which makes the phase directions of the first branch 202 and the second branch 201 opposite, thus improving the modulation efficiency.

[0064] This application does not limit the specific structure of the modulation electrode in its embodiments. In one implementation of this application, such as... Figure 2 As shown, the modulation electrode includes a first electrode pair 20 and a second electrode pair 10. The first electrode pair 20 is disposed on both sides of the first branch 202, and the second electrode pair 10 is disposed on both sides of the second branch 201.

[0065] In one implementation of this application, the polarization directions of the first branch 202 and the second branch 201 are opposite, and the electric field direction applied by the first electrode pair 20 to the first branch 202 is the same as the electric field direction applied by the second electrode pair 10 to the second branch 201. This electro-optic modulator employs a push-pull method for modulator driving.

[0066] For example, such as Figure 2As shown, the first electrode pair 20 and the second electrode pair 10 are connected in series. The first end of the first electrode pair 20 is connected to the signal output terminal 11 of the RF driver, the second end of the first electrode pair 20 is connected to the first end of the second electrode pair 10, a resistor is connected to the second end of the second electrode pair 10, and the second end of the second electrode pair 10 is connected to the DC voltage terminal 12.

[0067] Next, refer to Figure 2 The first branch 202 and the second branch 201 each include a first part and a second part, the first part of the first branch 202 and the first part of the second branch 201 are opposite to each other, and the second part of the first branch 202 and the second part of the second branch 201 are opposite to each other.

[0068] The first electrode pair 20 is disposed on both sides of the first part of the first branch 202, and the second electrode pair 10 is disposed on both sides of the second part of the second branch 201. The polarization directions of the first branch 202 and the second branch 201 are opposite. The electric field direction applied by the first electrode pair 20 to the first branch 202 is the same as the electric field direction applied by the second electrode pair 10 to the second branch 201.

[0069] During operation, the radio frequency (RF) signal is applied to the first electrode pair 20 of the electro-optic modulator through the signal output terminal 11 of the RF driver. The electric field applied by the first electrode pair 20 to the first portion of the first branch 202 is directed downwards, as shown by the arrow. At this time, the first portion of the second branch 201 is not loaded with an electric field. Next, the RF signal is applied to the second electrode pair 10 of the electro-optic modulator. The electric field applied by the second electrode pair 10 to the second portion of the second branch 201 is directed in the same direction as the electric field applied by the first electrode pair 20 to the first branch 202. At this time, the second portion of the first branch 202 is not loaded with an electric field. Since the polarization directions of the first branch 202 and the second branch 201 are opposite, the optical signals output from the first branch 202 and the second branch 201 are out of phase, achieving a push-pull modulation method and improving modulation efficiency.

[0070] For example, such as Figure 4 As shown, the first electrode pair 20 and the second electrode pair 10 are connected in parallel. The first end of the first electrode pair 20 and the first end of the second electrode pair 10 are both connected to the signal output terminal 11 of the RF driver. A resistor is connected to the second end of the first electrode pair 20 and the second end of the second electrode pair 10. The second ends of the first electrode pair 20 and the second end of the second electrode pair 10 are connected to the DC voltage terminal 12. The polarization directions of the first branch 202 and the second branch 201 are opposite.

[0071] The signal output terminal 11 of the RF driver is increased with a set of differential inputs. The first electrode pair 20 and the second electrode pair 10 respectively include a first electrode and a second electrode. The first electrode of the first electrode pair 20 is located on the upper side of the first branch 202, and the second electrode of the first electrode pair 20 is located on the lower side of the first branch 202. The first electrode of the second electrode pair 10 is located on the upper side of the second branch 201, and the first electrode of the second electrode pair 10 is located on the lower side of the second branch 201.

[0072] The first electrode of the first electrode pair 20 is connected to the positive terminal of the signal output terminal 11 of the RF driver, and the second electrode of the first electrode pair 20 is connected to the negative terminal of the signal output terminal 11 of the RF driver. The first electrode of the second electrode pair 10 is connected to the positive terminal of the signal output terminal 11 of the RF driver, and the second electrode of the second electrode pair 10 is connected to the negative terminal of the signal output terminal 11 of the RF driver. The electric field direction applied by the first electrode pair 20 to the first branch 202 is the same as the electric field direction applied by the second electrode pair 10 to the second branch 201.

[0073] During operation, the radio frequency (RF) signal is simultaneously applied to the first electrode pair 20 and the second electrode pair 10 of the electro-optic modulator through the signal output terminal 11 of the RF driver. The electric field applied by the first electrode pair 20 to the first branch 202 is directed downwards, as shown by the arrow. The electric field applied by the second electrode pair 10 to the second branch 201 is also directed downwards, as shown by the arrow. Since the polarization directions of the first branch 202 and the second branch 201 are opposite, the optical signals output from the first branch 202 and the second branch 201 are out of phase. Finally, the RF signal is terminated at the terminating resistor 104.

[0074] In another implementation of this application, the polarization directions of the first branch 202 and the second branch 201 are the same, and the electric field direction applied by the first electrode pair 20 to the first branch 202 is opposite to the electric field direction applied by the second electrode pair 10 to the second branch 201. This electro-optic modulator employs a push-pull method to drive the modulator.

[0075] like Figure 5 As shown, the electro-optic modulator includes a first electrode pair 20, a second electrode pair 10, and a third electrode pair 30, wherein the first electrode pair 20, the second electrode pair 10, and the third electrode pair 30 are connected in series. The first end of the first electrode pair 20 is connected to the signal output terminal 11 of the RF driver, the second end of the first electrode pair 20 is connected to the first end of the second electrode pair 10, the first end of the third electrode pair 30 is connected to the second end of the second electrode pair 10, a resistor is connected to the second end of the third electrode pair 30, and the second end of the second electrode pair 10 is connected to the DC voltage terminal 12.

[0076] Both the first branch 202 and the second branch 201 are S-shaped. The first branch 202 and the second branch 201 include a first part, a second part and a third part that are parallel to each other. The second part is located between the first part and the third part. The first electrode pair 20 is disposed on both sides of the first part of the first branch 202, the second electrode pair 10 is disposed on both sides of the second part of the second branch 201, and the third electrode pair 30 is disposed on both sides of the third part of the first branch 202. The electric field direction applied by the first electrode pair 20 to the first branch 202 is opposite to the electric field direction applied by the second electrode pair 10 to the second branch 201. The electric field direction applied by the third electrode pair 30 to the third modulation arm is opposite to the electric field direction applied by the second electrode pair 10 to the second branch 201. The polarization directions of the first branch 202 and the second branch 201 are the same.

[0077] During operation, the radio frequency (RF) signal is applied to the first electrode pair 20 of the electro-optic modulator through the signal output terminal 11 of the RF driver. The first electrode pair 20 applies an electric field to the first part of the first branch 202 in the direction of downwards, as shown by the arrow. At this time, the first part of the second branch 201 is not loaded with an electric field. Then, after a 180° optical path and electric field turn, as the waveguide and electrodes turn, the RF signal is applied to the second electrode pair 10 of the electro-optic modulator. The second electrode pair 10 applies an electric field to the second part of the second branch 201 in the direction of upwards, as shown by the arrow. At this time, the second part of the first branch 202 is not loaded with an electric field. Next, after another 180° optical path and electric field turn, as the waveguide and electrodes turn, the RF signal is applied to the third electrode pair 30 of the electro-optic modulator. The third electrode pair 30 applies an electric field to the third part of the first branch 202 in the direction of downwards, as shown by the arrow. At this time, the third part of the second branch 201 is not loaded with an electric field. Finally, the RF signal terminates at the terminating resistor 104.

[0078] In another implementation of this application, such as Figure 6 As shown, in another implementation of this application, the first electrode pair and the second electrode pair 10 are connected in parallel. A set of differential inputs is added to the signal output terminal 11 of the RF driver, using an S+S-, S+S- input method. The first ends of the first electrode pair 20 and the second electrode pair 10 are respectively connected to the signal output terminal 11 of the RF driver. Resistors are connected to the second ends of both the first electrode pair 20 and the second electrode pair 10, and the second ends of both are respectively connected to the DC voltage terminal 12. The polarization directions of the first branch 202 and the second branch 201 are the same.

[0079] The first electrode pair 20 and the second electrode pair 10 each include a first electrode and a second electrode. The first electrode of the first electrode pair 20 is located on the upper side of the first branch 202, and the second electrode of the first electrode pair 20 is located on the lower side of the first branch 202. The first electrode of the second electrode pair 10 is located on the upper side of the second branch 201, and the first electrode of the second electrode pair 10 is located on the lower side of the second branch 201.

[0080] The first electrode of the first electrode pair 20 is connected to the positive terminal of the signal output terminal 11 of the RF driver, and the second electrode of the first electrode pair 20 is connected to the negative terminal of the signal output terminal 11 of the RF driver. The first electrode of the second electrode pair 10 is connected to the negative terminal of the signal output terminal 11 of the RF driver, and the second electrode of the second electrode pair 10 is connected to the positive terminal of the signal output terminal 11 of the RF driver. The direction of the electric field applied by the first electrode pair 20 to the first branch 202 is opposite to the direction of the electric field applied by the second electrode pair 10 to the second branch 201.

[0081] During operation, the radio frequency (RF) signal is simultaneously applied to the first electrode pair 20 and the second electrode pair 10 of the electro-optic modulator through the signal output terminal 11 of the RF driver. The electric field applied by the first electrode pair 20 to the first branch 202 is directed downwards, as shown by the arrow, while the electric field applied by the second electrode pair 10 to the second branch 201 is directed upwards, as shown by the arrow. Since the polarization directions of the first branch 202 and the second branch 201 are the same, the optical signals output from the first branch 202 and the second branch 201 are out of phase. Finally, the RF signal is terminated at the terminating resistor 104.

[0082] In the above embodiments, a comparison reveals that the electro-optic modulator has the characteristics of small size, no external circuitry, and suitability for encapsulation.

[0083] This application also provides an optical chip, which may include: a substrate 01, and an electro-optic modulator and other devices disposed on the substrate, wherein the other devices may be connected to the electro-optic modulator via a connecting waveguide.

[0084] Other devices can be at least one of laser diodes, semiconductor optical amplifiers, and photodetectors. It is understood that there can be multiple devices on the same substrate, and the devices can be connected in any desired connection order.

[0085] Figure 7 This is a schematic diagram of the structure of the optical chip provided in an embodiment of this application. Figure 7 As shown, the optical chip includes: a substrate 01, and an electro-optic modulator, an input waveguide 010, and an output waveguide 011 disposed on the substrate 01.

[0086] The embodiments of this application do not limit the material of the modulation electrode. In one implementation of this application, the material of the modulation electrode 003 is a metal material such as copper (Cu) or zinc (Zn).

[0087] In another implementation of this application, the modulation electrode 003 is made of transparent conductive oxide (TCO). TCO has high conductivity and low light absorption. Replacing Au as the lower electrode can further reduce the electrode distance, thereby increasing the electric field intensity in the optical field region and improving the modulation efficiency of the electro-optic modulator. Compared with conventional modulation electrodes, the chip length corresponding to the same phase modulation is shorter, which is beneficial to reducing the chip size.

[0088] The optical chip may also include, for example, a light source 014 and a photodetector 012. The light source 014 is disposed on the surface of the substrate 01, for example, in parallel with the silicon dioxide layer. The photodetector 012 is disposed on the surface of the silicon dioxide layer. The light source 014 is used to emit light, and the input waveguide 010 is used to transmit the light emitted by the light source 014 to the electro-optic modulator. The electro-optic modulator is used to modulate the light emitted by the light source 014. The photodetector 012 can be connected to the input terminal 011 of the electro-optic modulator 001 through the connecting waveguide 013. The photodetector 012 can detect the optical signal modulated by the electro-optic modulator.

[0089] This application also provides an integrated chip, including: an electrical chip, and an optical chip as described above.

[0090] The electro-optic modulator in this optical chip can be used as follows: Figure 2 , Figure 4 , Figure 5 or Figure 6 The structure shown indicates that the optical chip is small in size and can be encapsulated with the electrical chip by soldering.

[0091] like Figure 9 As shown, the electrical chip is disposed on the surface of the optical chip, and the electrical chip is soldered to the optical chip via solder balls.

[0092] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An electro-optic modulator, characterized in that, The system includes an optical waveguide layer, a modulation electrode, and a metal electrode. The optical waveguide layer is disposed on the substrate, the modulation electrode is disposed on the optical waveguide layer, and the metal electrode is disposed on the modulation electrode and electrically connected to the modulation electrode. The first end of the metal electrode is coupled to the radio frequency driver, and the second end of the metal electrode is coupled to the DC voltage terminal. The DC voltage terminal is used to input a voltage signal and to provide a bias voltage to the radio frequency driver through the metal electrode. The metal electrode is used to receive the modulation signal input by the radio frequency driver, and the modulation electrode is used to perform electro-optic modulation on the optical waveguide layer based on the modulation signal.

2. The electro-optic modulator according to claim 1, characterized in that, It also includes an insulating layer disposed on the surface of the substrate, the optical waveguide layer and the modulation electrode being located within the insulating layer, and an opening being provided on the insulating layer on the surface of the modulation electrode, with the metal electrode formed at the opening.

3. The electro-optic modulator according to claim 1 or 2, characterized in that, The optical waveguide layer includes an electro-optic crystal layer and a ridge waveguide. The ridge waveguide is located on the side of the electro-optic crystal layer away from the substrate. The modulation electrodes are respectively disposed on both sides of the ridge waveguide. The modulation electrodes are used to electro-optically modulate the optical waves transmitted in the ridge waveguide.

4. The electro-optic modulator according to claim 3, characterized in that, The ridge waveguide includes: a first branch and a second branch arranged symmetrically, the input terminals of the first branch and the second branch being coupled, the output terminals of the first branch and the second branch being coupled, the first end of the modulation electrode being coupled to the input terminals of the first branch and the second branch, and the second end of the modulation electrode being coupled to the output terminals of the first branch and the second branch; the first end of the modulation electrode is coupled to the signal output terminal of the RF driver, and the second end of the modulation electrode is connected to a terminating resistor, wherein the optical signals output by the first branch and the second branch are out of phase.

5. The electro-optic modulator according to claim 4, characterized in that, The modulation electrode includes a first electrode pair and a second electrode pair, wherein the first electrode pair is symmetrically disposed on both sides of the first branch, and the second electrode pair is symmetrically disposed on both sides of the second branch.

6. The electro-optic modulator according to claim 5, characterized in that, The optical waveguide layer is made of an electro-optic material. The electric field direction applied by the first electrode pair to the first branch is the same as the electric field direction applied by the second electrode pair to the second branch. The polarization directions of the first branch and the second branch are opposite.

7. The electro-optic modulator according to claim 6, characterized in that, The first end of the first electrode pair is connected to the signal output terminal of the radio frequency driver, the second end of the first electrode pair is connected to the first end of the second electrode pair, and the second end of the second electrode pair is connected to a terminating resistor. The first branch and the second branch each include: a first part and a second part, wherein the first part of the first branch and the first part of the second branch are opposite to each other, and the second part of the first branch and the second part of the second branch are opposite to each other; The first electrode pair is disposed on both sides of the first part of the first branch, and the second electrode pair is disposed on both sides of the second part of the second branch.

8. The electro-optic modulator according to claim 6, characterized in that, The first electrode pair and the first electrode pair are respectively connected to the signal output terminal of the radio frequency driver, and the second electrode pair and the second electrode pair are connected to a terminating resistor. The first electrode pair includes a first electrode and a second electrode, and the second electrode pair includes a third electrode and a fourth electrode. The first electrode and the second electrode are located on both sides of the first branch and the second branch, and the third electrode and the fourth electrode are located between the first branch and the second branch. The first electrode and the third electrode are connected to the positive terminal of the signal output terminal of the RF driver, and the second electrode and the fourth electrode are connected to the negative terminal of the signal output terminal of the RF driver.

9. The electro-optic modulator according to claim 5, characterized in that, The electric field applied by the first electrode pair to the first branch is in the opposite direction to the electric field applied by the second electrode pair to the second branch, and the polarization directions of the first branch and the second branch are the same.

10. The electro-optic modulator according to claim 9, characterized in that, The modulation electrode further includes: a third electrode pair, wherein a first end of the first electrode pair is connected to the signal output terminal of the radio frequency driver, a second end of the first electrode pair is connected to the first end of the second electrode pair, a first end of the third electrode pair is connected to the second end of the second electrode pair, and a terminating resistor is connected to the second end of the third electrode pair; The first branch and the second branch each include: a first part, a second part, and a third part that are S-shaped and parallel to each other, with the second part located between the first part and the third part; the first electrode pair is disposed on both sides of the first part of the first branch, the second electrode pair is disposed on both sides of the second part of the second branch, and the third electrode pair is disposed on both sides of the third part of the first branch; The electric field applied by the third electrode pair to the first branch is in the opposite direction to the electric field applied by the second electrode pair to the second branch.

11. The electro-optic modulator according to claim 9, characterized in that, The first ends of the first electrode pair and the second electrode pair are respectively connected to the signal output terminal of the radio frequency driver, and the second ends of the first electrode pair and the second electrode pair are each connected to a terminating resistor; The first electrode pair includes a first electrode and a second electrode, and the second electrode pair includes a third electrode and a fourth electrode. The first electrode and the second electrode are located on both sides of the first branch and the second branch, and the third electrode and the fourth electrode are located between the first branch and the second branch. The first electrode and the fourth electrode are connected to the positive terminal of the signal output terminal of the RF driver, and the second electrode and the third electrode are connected to the negative terminal of the signal output terminal of the RF driver.

12. The electro-optic modulator according to any one of claims 1-11, characterized in that, The modulation electrode is made of copper, zinc, or a transparent conductive oxide.

13. An optical chip, characterized in that, include: The substrate, and the electro-optic modulator as claimed in any one of claims 1-12, wherein the electro-optic modulator is disposed on the surface of the substrate.

14. The optical chip according to claim 13, characterized in that, It also includes an input waveguide and an output waveguide, wherein the input waveguide is connected to the input end of the optical waveguide layer, and the output waveguide is connected to the output end of the optical waveguide layer.

15. The optical chip according to claim 14, characterized in that, Also includes: A photodetector is connected to the output waveguide via a connecting waveguide, and the photodetector is used to detect modulated optical signals.

16. An integrated chip, characterized in that, include: An electrical chip, and an optical chip as described in any one of claims 13-15, wherein the electrical chip is disposed on the surface of the optical chip and is soldered to the optical chip via solder balls.

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