Distributed Optical Phase Modulator

Abstract

The present application discloses a distributed optical phase modulator, comprising: a substrate, and an optical waveguide arranged on the substrate; a driving electrode, arranged on the substrate, including a plurality of sub-driving electrodes arranged at intervals, and at least one shielding electrode, at least partially spaced from the sub-driving electrode; the optical waveguide sequentially passes through the sub-driving electrodes and the shielding electrodes. The length of the driving electrode of each part is much smaller than the total length of the equivalent traditional modulator, and the driving signal voltage of each part is also much smaller than the driving signal voltage of the equivalent traditional modulator. In the driving electrode of each part, the propagation of the optical signal can achieve approximately synchronous propagation or even synchronous propagation with the electrical signal. The walk-off phenomenon between the photoelectric signals is minimized, and the upper limit of the modulation bandwidth is increased. Shielding electrodes are respectively arranged between the sub-driving electrodes to shield the crosstalk between the sub-driving electrodes, which can greatly reduce the crosstalk between the sub-driving electrodes.

Description

Technical Field

[0001] The present application relates to the field of optical modulation technology, and in particular to a distributed optical phase modulator. Background Art

[0002] High-speed electro-optic modulation has very wide and important applications, such as optical communication, microwave optoelectronics, laser beam deflection, wavefront modulation, etc. Electro-optic modulators are modulators made using the electro-optic effect of certain electro-optic crystals, such as lithium niobate crystals (LiNbO3), gallium arsenide crystals (GaAs) and lithium tantalate crystals (LiTaO3). The electro-optic effect means that when a voltage is applied to an electro-optic crystal, the refractive index of the electro-optic crystal will change, resulting in changes in the characteristics of the light wave passing through the crystal, thereby achieving modulation of the phase, amplitude, intensity and polarization state of the optical signal.

[0003] However, in the light modulation process, it is difficult to achieve low driving voltage and high modulation bandwidth modulation at the same time. Summary of the invention

[0004] The main purpose of the present application is to provide a distributed optical phase modulator to achieve modulation with low driving voltage and high modulation bandwidth.

[0005] Based on this, an embodiment of the present application provides a distributed optical phase modulator, comprising: a substrate, and an optical waveguide arranged on the substrate; a driving electrode, arranged on the substrate, comprising a plurality of sub-driving electrodes arranged at intervals, and at least one shielding electrode, at least partially spaced apart from the sub-driving electrode; the optical waveguide sequentially passes through the sub-driving electrodes and the shielding electrode.

[0006] Optionally, the driving electrode is a coplanar waveguide structure.

[0007] Optionally, the same electrical signal is applied to the sub-driving electrodes.

[0008] Optionally, the electrical signals applied to the adjacent sub-driving electrodes have a delay, wherein the delay duration is the time required for the optical signal to be transmitted from the starting end of the previous sub-driving electrode to the starting end of the next adjacent sub-driving electrode.

[0009] Optionally, the optical waveguide includes a plurality of modulation sections and a plurality of bending sections connected between the modulation sections, wherein a bending direction of the bending section is toward a previous modulation section connected to the bending section.

[0010] Optionally, the modulation part includes a first sub-modulation part and a second sub-modulation part, wherein light propagation directions inside the first sub-modulation part and the second sub-modulation part are opposite.

[0011] Optionally, the first sub-modulation section is parallel to the second sub-modulation section, and optical signal propagation directions in the first sub-modulation section and the second sub-modulation section are opposite.

[0012] Optionally, the first sub-modulation part passes through the sub-driving electrode and / or the shielding electrode; the second sub-modulation part passes through the shielding electrode and / or the sub-driving electrode.

[0013] Optionally, the sub-driving electrodes include: a driving signal electrode located on one side of the optical waveguide and applied with a driving signal; and a ground electrode located on the other side of the optical waveguide.

[0014] Optionally, the shielding electrode comprises: a first grounding wire located on one side of the optical waveguide, and a second grounding wire located on the other side of the optical waveguide.

[0015] This application has the following beneficial effects:

[0016] The driving electrode is set as a distributed driving electrode. Since the driving electrode is distributed, the length of the driving electrode of each part is much smaller than the total length of the equivalent traditional modulator, and the driving signal voltage of each part is also much smaller than the driving signal voltage of the equivalent traditional modulator. In the driving electrode of each part, the propagation of the optical signal can achieve approximately synchronous propagation or even synchronous propagation with the electrical signal. The walk-off phenomenon between the photoelectric signals is minimized, and the upper limit of the modulation bandwidth is increased. At the same time, since the driving electrode is changed from a traditional one-segment driving electrode to a distributed multi-segment driving electrode, the driving voltage required to be applied to each electrode is also greatly reduced. Shielding electrodes are respectively set between the sub-driving electrodes to shield the crosstalk between the sub-driving electrodes, which can greatly reduce the crosstalk between the sub-driving electrodes.

[0017] The electrical signals applied to each sub-driving electrode are the same. The same electrical signal is applied to each part of the driving electrode, which is equivalent to resetting the electrical signal when the electrical signal propagates along each part of the driving electrode, greatly reducing the loss of the electrical signal and significantly improving the modulation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings constituting a part of this application are used to provide a further understanding of this application, so that other features, purposes and advantages of this application become more obvious. The schematic embodiment drawings and their descriptions of this application are used to explain this application and do not constitute an improper limitation on this application. In the drawings:

[0019] Figure 1 is a schematic diagram of a distributed optical phase modulator according to an embodiment of the present application;

[0020] Figure 2 It is a partial cross-sectional schematic diagram of a distributed optical phase modulator according to an embodiment of the present application. DETAILED DESCRIPTION

[0021] In order to enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions.

[0022] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0023] As described in the background technology, there is often a trade-off between the driving voltage and the modulation bandwidth. The electro-optic effect is usually weak in the electro-optic medium, so a low modulation voltage requires a sufficiently long waveguide to accumulate sufficient electro-optic effect. However, the inventors have found through research that there is a group velocity mismatch between the light wave and the driving electrical signal, and a serious light wave-driving point signal walk-off phenomenon will occur after long-distance transmission, which seriously limits the modulation bandwidth. In addition, a long optical waveguide also requires a long driving electrode. Due to the resistance loss of the electrode material, a large microwave driving signal propagation loss is caused, which ultimately limits the possibility of further reducing the driving voltage. Moreover, as the modulation bandwidth increases, the crosstalk problem between multiple signals becomes more and more significant. Ultimately, it will make it difficult to continue to reduce the driving voltage. This serious design trade-off problem exists in almost all traveling-wave-based optoelectronic modulators, which seriously limits the performance of the device.

[0024] Based on the inventor's research, the present invention provides a distributed optical phase modulator. Figure 1As shown, the optical modulator includes: a substrate 10, and an optical waveguide 20 arranged on the substrate 10; a driving electrode 30, which is arranged on the substrate 10, including a plurality of sub-driving electrodes 31 arranged at intervals, and at least one shielding electrode 40, which is at least partially arranged at intervals from the sub-driving electrode 31; in this embodiment, the shielding electrode 40 and the sub-driving electrode 31 can be arranged at intervals in sequence, or can be arranged at intervals in sequence, for example, a sub-driving electrode 31 can be arranged every two or more shielding electrodes 40. The optical waveguide 20 sequentially passes through the sub-driving electrode 31 and the shielding electrode 40. Due to the group velocity mismatch between the optical wave and the driving electrical signal, a serious optical wave-driving point signal walk-off phenomenon will occur after long-distance transmission, which seriously limits the reduction of the driving voltage and the improvement of the modulation bandwidth. Therefore, in this embodiment, the driving electrode 30 is set as a distributed driving electrode. Since the driving electrode 30 is distributed, the length of each part of the driving electrode 30 is much smaller than the total length of the modulator. In each part of the driving electrode 30, the propagation of the optical signal can achieve approximately synchronous propagation or even synchronous propagation with the electrical signal. The walk-off phenomenon between the photoelectric signals is minimized, and the upper limit of the modulation bandwidth is increased. As the bandwidth increases, the crosstalk problem between multiple signals becomes more and more significant. Multiple shielding electrodes 40 are respectively arranged between multiple sub-driving electrodes 31 to shield the crosstalk between the sub-driving electrodes 31, which can greatly reduce the crosstalk between the sub-driving electrodes. The driving voltage is further reduced while the bandwidth is increased.

[0025] As an exemplary embodiment, the optical modulator may be a lithium niobate crystal (LiNbO3) optical modulator, a gallium arsenide crystal (GaAs) optical modulator, or a lithium tantalate crystal (LiTaO3) optical modulator. In this embodiment, the lithium niobate crystal optical modulator is taken as an example for description. Figure 2 As shown in the partial cross-sectional view of the optical modulator, the optical waveguide 20 and the driving electrode 30 are located on the surface of the substrate 10 , and a bonding layer 50 may be provided between the substrate 10 and the optical waveguide 20 and the driving electrode 30 .

[0026] As an exemplary embodiment, the driving electrode 30 includes a signal electrode S and a ground electrode G to which an electrical signal is applied. An optical waveguide is located between the signal electrode S and the ground electrode G. In this embodiment, the signal electrode S and the ground electrode G of the driving electrode can be arranged in parallel with the optical waveguide. In this embodiment, the optical waveguide is made of an electro-optical material, and its refractive index varies with the magnitude of an applied voltage, and the accumulated phase of the input light passing through the optical waveguide varies with the voltage applied to the optical waveguide. Optical phase modulation is achieved by applying an electrical signal to the driving electrode to change the phase of the optical signal in the optical waveguide.

[0027] As an exemplary embodiment, the driving electrode 30 includes N sub-driving electrodes 31 arranged at intervals along the optical waveguide 20, wherein N ≥ 2. Figure 1 As shown. The driving electrode 30 is divided into N parts, each part has a shorter length L, and the final effective driving length is N*L. In this embodiment, the electrical signals applied to each sub-driving electrode 31 are the same, and the same electrical signal is applied to each part of the sub-driving electrode 31, which is equivalent to resetting the electrical signal when the electrical signal propagates along each part of the sub-driving electrode 31, greatly reducing the loss of the electrical signal and greatly improving the modulation efficiency.

[0028] In order to better match the electrical signals on each sub-driving electrode 31, so that the modulation of the optical signal on each sub-driving electrode 31 is as similar as possible, in this embodiment, the electrical signals applied to the adjacent sub-driving electrodes 31 are delayed, wherein the delay time is the time required for the optical signal to be transmitted from the end of the previous sub-driving electrode 31 to the starting end of the next adjacent sub-driving electrode 31. As an exemplary embodiment, assuming that the electrical signal applied to the first sub-driving electrode 31 is V1(t), the time required for the optical signal to be transmitted from the end of the nth sub-driving electrode 31 to the starting end of the n+1th sub-driving electrode 31 is T n , where n=1, 2, ..., N-1 represents the number of sub-driving electrodes 31. The electric signal applied to each sub-driving electrode 31 is expressed as follows:

[0029]

[0030] Due to the delay in the propagation of the electrical and optical signals applied to the adjacent sub-driving electrodes 31 before the distributed driving electrodes 30, each part of the sub-driving electrodes 31 has the same electrical signal, which is equivalent to resetting the electrical signal when the electrical signal propagates along each part of the sub-driving electrodes 31, greatly reducing the loss of the electrical signal and significantly improving the modulation efficiency.

[0031] In the present embodiment, the driving electrode 30 is a coplanar waveguide structure, which can be exemplarily a GS coplanar waveguide wire (the coplanar waveguide structure can also use other phase modulation units). The unmodulated constant light source is input from the entrance end and passes through the N sub-driving electrode 31 areas in sequence. The left end of the sub-driving electrode 31 is the input area of ​​the electrical signal, and the right end is coupled to an external microwave terminal blocker (RF terminator) or a microwave terminal blocker circuit (on-chip circuit). The input optical signal is output after passing through multiple sections of sub-driving electrodes 31. As an exemplary embodiment, the impedance of the sub-driving electrode 31 is the same or similar to the impedance of the electrical signal input end, for example, it can be 50Ω; the propagation speed of the electrical signal in the driving electrode 30 is the same or similar to the speed of light in the optical waveguide 20; the resistance loss of the electrical signal transmitted in the driving electrode 30 is as low as possible. In the present embodiment, the material of the driving electrode 30 can be a high-conductivity and low-resistance material such as gold, silver, and graphene.

[0032] As an exemplary embodiment, Figure 1 As shown, the optical waveguide includes a plurality of modulation sections 21 and a plurality of bends 22 connected between the modulation sections 21, wherein the bending direction of the bends 22 is toward the previous modulation section 21 connected to the bends 22. Exemplarily, the optical waveguide starts from the first modulation section 21, and the bending direction of the first bend 22 connected to the first modulation section 21 is toward the first modulation section 21, so that the extension direction of the second modulation section 21 connected to the first bend 22 is toward the first modulation section 21, and after the plurality of modulation sections 21 are connected to the plurality of bends 22, the shape formed is roughly "S"-shaped or a "snake" extending back and forth. As an exemplary embodiment, the modulation section 21 includes a first sub-modulation section and a second sub-modulation section, wherein the light propagation directions inside the first sub-modulation section and the second sub-modulation section are different. Exemplarily, the extension direction of the first sub-modulation section can be the "forward" direction of the optical waveguide, and the extension direction of the second sub-modulation section can be the "reciprocal" direction of the optical waveguide.

[0033] As an exemplary embodiment, the first sub-modulation part passes through the sub-driving electrode, and the second sub-modulation part passes through the shielding electrode. Those skilled in the art should understand that the first sub-modulation part may also pass through the shielding electrode 40, and the second sub-modulation part may also pass through the sub-driving electrode 41. In this embodiment, the arrangement positions of the shielding electrode 40 and the sub-driving electrode 41 are not limited. Figure 1As shown, the first sub-modulation part and the second sub-modulation part are arranged at intervals along the Y direction of the substrate surface, and the sub-driving electrode and the shielding electrode are arranged at intervals. The signal electrode is located on one side of the first sub-modulation part, and the grounding electrode is located on the other side of the first sub-modulation part. At the same time, the first grounding line G1 of the shielding electrode is located on one side of the second sub-modulation part, and the second grounding line G2 of the shielding electrode is located on the other side of the second sub-modulation part. Since there is crosstalk between the sub-driving electrodes while synchronizing low driving voltage and high modulation bandwidth, the shielding electrodes are arranged at intervals between the sub-driving electrodes along the Y direction of the substrate surface, which can reduce the crosstalk problem between the sub-driving electrodes while synchronously reducing the driving voltage and increasing the modulation bandwidth, and further reduce the driving voltage, thereby greatly improving the modulation performance of the optical modulator.

[0034] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A distributed optical phase modulator, characterized in that: include: A substrate, and an optical waveguide disposed on the substrate; The driving electrode is arranged on the substrate and includes a plurality of sub-driving electrodes arranged at intervals. A plurality of shielding electrodes are respectively arranged between the plurality of sub-driving electrodes; The optical waveguide sequentially passes through the sub-driving electrodes and the plurality of shielding electrodes; The optical waveguide includes a plurality of modulation sections and a plurality of bending sections connected between the modulation sections; The bending direction of the bending portion is toward the previous modulation portion connected to the bending portion; The modulation unit includes a first sub-modulation unit and a second sub-modulation unit; The light propagation directions inside the first sub-modulation part and the second sub-modulation part are opposite; The same electrical signal is applied to the sub-driving electrodes; The sub-driving electrode comprises: The signal electrode is located on one side of the optical waveguide and is applied with a driving signal; and a ground electrode located on the other side of the optical waveguide.

2. The distributed optical phase modulator according to claim 1, characterized in that: The driving electrode is a coplanar waveguide structure.

3. The distributed optical phase modulator according to claim 2, characterized in that: The electrical signals applied to the adjacent sub-driving electrodes have a delay, wherein the delay duration is the time required for the optical signal to be transmitted from the starting end of the previous sub-driving electrode to the starting end of the next adjacent sub-driving electrode.

4. The distributed optical phase modulator according to claim 1, wherein: The first sub-modulation section is parallel to the second sub-modulation section, and optical signals in the first sub-modulation section and the second sub-modulation section propagate in opposite directions.

5. The distributed optical phase modulator according to claim 1 or 4, characterized in that: The first sub-modulation part passes through the sub-driving electrode; The second sub-modulation portion passes through the shielding electrode.

6. The distributed optical phase modulator according to claim 1, characterized in that: The shielding electrode comprises: A first grounding wire is located at one side of the optical waveguide, and a second grounding wire is located at the other side of the optical waveguide.

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