High-power electro-optical modulator

Abstract

The invention relates to a high-power electro-optical modulator, and belongs to the technical field of lithium niobate electro-optical modulators, the high-power electro-optical modulator comprises a substrate, a waveguide, a traveling wave electrode and a matching circuit, the matching circuit comprises a matching electrode, a load resistor and a gold wire, and the traveling wave electrode and the matching electrode are of a coplanar waveguide structure. And a signal electrode of the traveling wave electrode is connected with a signal electrode of the matching electrode through a gold wire. The traveling wave electrode turns at the tail end of the waveguide, microwave loss is increased by increasing the length of the traveling wave electrode, microwave energy reaching a microwave matching resistor at the output end of the traveling wave electrode is reduced, and the microwave energy is reduced under the conditions that the length of an electro-optical interaction area of the electrode and the waveguide is kept unchanged and the bandwidth performance of the device is not affected. And the length of the electrode on the chip is greatly increased, so that the bearing capacity of the modulator on high-power microwave input is greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of lithium niobate electro-optic modulator technology, and specifically relates to a high-power electro-optic modulator. Background Technology

[0002] Research on integrated optical devices based on lithium niobate, such as electro-optic intensity modulators, electro-optic phase modulators, IQ modulators, electric field sensors, and magnetic field sensors, has attracted much attention. High-speed lithium niobate electro-optic modulators have advantages such as wide spectral operating range, low driving voltage, low insertion loss, high extinction ratio, zero or adjustable chirp, high reliability, and ease of mass production, making them the mainstream modulators currently used in microwave photonics, laser communication, and other fields.

[0003] The lithium niobate electro-optic modulator mainly consists of two electrodes: a traveling wave electrode and a DC bias electrode. The traveling wave electrode employs a coplanar waveguide (CPW) transmission line structure, composed of three metal lines: a signal electrode in the middle and ground electrodes on either side. The microwave propagation direction is the same as the optical wave propagation direction, generating equal but opposite electric fields in the two waveguide branches of the photoelectric interaction region, thus modulating the two optical waves. Due to the electro-optic effect of the lithium niobate crystal, the two optical waves will have an equal but opposite phase difference. When the two optical waves interfere, the microwave signal can be loaded onto the optical waves. The microwave signal transmitted to the end of the coplanar waveguide enters the output matching circuit and is consumed by the matching load.

[0004] The matching load on the output matching circuit is a thin-film resistor. The microwave signal is converted into heat on the thin-film resistor. Since the thickness of the thin-film resistor is only a few micrometers, when the microwave power is high, the temperature of the thin-film resistor will rise, which will affect the lithium niobate chip inside the device, or even burn it out directly.

[0005] Due to microwave transmission loss, extending the length of the traveling wave electrode can increase microwave transmission loss, thereby reducing the microwave power transmitted to the load resistor. However, simply extending the length of the traveling wave electrode first increases microwave transmission loss, reducing the device's key performance indicator—bandwidth. Secondly, it increases the overlap area between the traveling wave electrode and the waveguide, increasing the mismatch between microwaves and optical waves, further reducing bandwidth. Summary of the Invention

[0006] The purpose of this invention is to provide a high-power electro-optic modulator that bends the traveling wave electrode at the end of the waveguide, increases the microwave transmission loss by increasing the length of the traveling wave electrode, reduces the microwave energy reaching the microwave matching resistor at the output end of the traveling wave electrode, and improves the modulator's ability to handle high-power microwave input.

[0007] The above-mentioned objectives of the present invention are mainly achieved through the following technical solutions:

[0008] A high-power electro-optic modulator includes a substrate, a waveguide, a traveling-wave electrode, and a matching circuit. The matching circuit includes a matching electrode, a load resistor, and gold wires. The waveguide, traveling-wave electrode, and matching circuit are disposed on the substrate. The traveling-wave electrode and the matching electrode have a coplanar waveguide structure. The signal electrode of the traveling-wave electrode is connected to the signal electrode of the matching electrode through gold wires. The two ground electrodes of the matching electrode are respectively connected to the two ground electrodes of the traveling-wave electrode through gold wires. The signal electrode of the matching electrode is connected to the load resistor.

[0009] Microwaves enter from the input port of the traveling wave electrode, propagate along the signal electrode of the traveling wave electrode, and modulate the light wave in the waveguide during propagation. After modulation, the signal electrode of the traveling wave electrode turns, and the microwaves continue to propagate in the opposite direction and eventually enter the matching circuit.

[0010] The substrate is a lithium niobate substrate.

[0011] The cross-sectional diameters at both ends of the signal electrode of the traveling wave electrode are larger than the cross-sectional diameters at the other positions.

[0012] The signal electrode of the traveling wave electrode has a smooth, arc-shaped transition at the turning point.

[0013] The microwave propagation path of the traveling wave electrode after the signal electrode turns is parallel to the microwave propagation path before the turn.

[0014] The two ground electrodes of the traveling wave electrode are located on both sides of the signal electrode of the traveling wave electrode. The sidewalls of the two ground electrodes of the traveling wave electrode and the sidewalls of the signal electrode of the traveling wave electrode are conformal, forming two channels with a constant diameter.

[0015] The two ground electrodes of the matching electrode are an integral structure.

[0016] The ground electrode of the matching electrode is U-shaped, and the signal electrode of the matching electrode is set in the U-shaped groove.

[0017] The load resistor is disposed on the bottom surface of the groove of the ground electrode.

[0018] The waveguide is positioned between the signal electrode and the ground electrode of the traveling wave electrode or below the signal electrode.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects:

[0020] This invention bends the traveling-wave electrode at the end of the waveguide. While keeping the length of the optical-electric interaction region between the electrode and the waveguide unchanged and the bandwidth performance of the device unaffected, the increased length of the traveling-wave electrode increases microwave transmission loss, reduces microwave energy reaching the microwave matching resistor at the output end of the traveling-wave electrode, and improves the modulator's ability to handle high-power microwave input. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the high-power electro-optic modulator structure of the present invention. Detailed Implementation

[0022] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments:

[0023] like Figure 1 As shown, a high-power electro-optic modulator includes a lithium niobate substrate 1, a waveguide 2, a traveling wave electrode 3, and a matching circuit 4; the matching circuit 4 includes a matching electrode 5, a load resistor 6, and a gold wire 7.

[0024] Waveguide 2, traveling wave electrode 3 and matching circuit 4 are disposed on substrate 1. Traveling wave electrode 3 and matching electrode 5 are coplanar waveguide structures. The signal electrode of traveling wave electrode 3 and the signal electrode of matching electrode 5 are connected by gold wire 7. The two ground electrodes of matching electrode 5 and the two ground electrodes of traveling wave electrode 3 are respectively connected by gold wire 7. The signal electrode of matching electrode 5 is connected to load resistor 6.

[0025] Microwaves enter from the input port 8 of traveling wave electrode 3, propagate along the signal electrode of traveling wave electrode 3, and modulate the light wave in waveguide 2 during propagation. After modulation, the signal electrode of traveling wave electrode 3 turns, and microwaves continue to propagate in the opposite direction and eventually enter matching circuit 4.

[0026] The substrate 1 is a lithium niobate substrate.

[0027] The cross-sectional diameters at both ends of the signal electrode of the traveling wave electrode 3 are larger than the cross-sectional diameters at the other positions.

[0028] The signal electrode turning point of the traveling wave electrode 3 has a smooth, arc-shaped transition.

[0029] The microwave propagation path of the traveling wave electrode 3 after the signal electrode turns is parallel to the microwave propagation path before the turn.

[0030] The two ground electrodes of the traveling wave electrode 3 are located on both sides of the signal electrode of the traveling wave electrode 3. The sidewalls of the two ground electrodes of the traveling wave electrode 3 and the sidewalls of the signal electrode of the traveling wave electrode 3 are conformal, forming two channels with a constant diameter.

[0031] The two ground electrodes of the matching electrode 5 are an integral structure.

[0032] The ground electrode of the matching electrode 5 is U-shaped, and the signal electrode of the matching electrode 5 is disposed in the U-shaped groove.

[0033] The load resistor 6 is disposed on the bottom surface of the groove of the ground electrode.

[0034] The waveguide 2 is positioned between or below the signal electrode and the ground electrode of the traveling wave electrode 3.

[0035] Waveguide 2, traveling wave electrode 3 and matching circuit 4 are disposed on the upper surface of lithium niobate substrate 1. Traveling wave electrode 3 is a coplanar waveguide structure consisting of 3 metal strips. The central metal strip is the signal electrode and the metal strips on both sides are the ground electrodes. Waveguide 2 is located between or below the signal electrode and the ground electrode of traveling wave electrode 3.

[0036] The matching electrode 5 is a coplanar waveguide structure, including a central signal electrode and a ground electrode. The signal electrode in the matching electrode 5 is connected to the load resistor 6. The signal electrode in the matching electrode 5 is connected to the signal electrode of the traveling wave electrode 3 through a gold wire 7. The two ground electrodes in the matching electrode 5 are respectively connected to the two ground electrodes of the traveling wave electrode 3 through gold wires 7.

[0037] The traveling wave electrode 3 is a coplanar waveguide structure. After the microwave enters from the input port 8, it begins to modulate the light wave in the waveguide 2. The traveling wave electrode 3 extends to the designed length. That is, after completing the modulation of the light wave in the waveguide 2, it turns 180° and continues to extend in the opposite direction. The traveling wave electrode 3 moves away from the waveguide 2 and no longer modulates the light wave in the waveguide.

[0038] Work process:

[0039] The light wave enters from the left end of the lithium niobate substrate 1, enters the waveguide 2, and exits from the right end of the lithium niobate substrate 1 after passing through the entire waveguide 2. The traveling wave electrode 3 is disposed between the waveguides 2, with the signal electrode in the middle and the ground electrodes at the top and bottom.

[0040] After entering the traveling wave electrode 3 through the input port 8, the microwave propagates along the traveling wave electrode 3. At the same time, the microwave modulates the light wave in the waveguide 2. After turning 180° at the right end of the traveling wave electrode 3, the microwave continues to propagate in the opposite direction and finally enters the matching circuit 4. The traveling wave electrode 3 is interconnected with the matching electrode 5 on the matching circuit 4 through the gold wire 7. After entering the matching electrode 5, the microwave is finally converted into heat and dissipated on the load resistor 6. The entire microwave signal modulation process is completed.

[0041] Before the traveling wave electrode 3 is turned, the microwave modulates the light wave in waveguide 2. After the 180° turn, the traveling wave electrode 3 is moved away from waveguide 2 and no longer has a modulation effect. The microwave transmission loss generated by this part of the electrode does not reduce the bandwidth of the device, but it does reduce the microwave power transmitted to the load resistor 6. Simulation calculations of the above modulator structure show that the 6cm long electrode can reduce the microwave power by more than 10dB at a frequency of 20GHz. This improves the microwave power handling capability of the device.

[0042] The above description is only the best specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the protection scope of the present invention.

[0043] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A high-power electro-optic modulator, characterized in that: The system includes a substrate (1), a waveguide (2), a traveling wave electrode (3), and a matching circuit (4). The matching circuit (4) includes a matching electrode (5), a load resistor (6), and a gold wire (7). The waveguide (2), the traveling wave electrode (3), and the matching circuit (4) are disposed on the substrate (1). The traveling wave electrode (3) and the matching electrode (5) are coplanar waveguide structures. The signal electrode of the traveling wave electrode (3) is connected to the signal electrode of the matching electrode (5) through the gold wire (7). The two ground electrodes of the matching electrode (5) are connected to the two ground electrodes of the traveling wave electrode (3) through the gold wire (7). The signal electrode of the matching electrode (5) is connected to the load resistor (6). Microwaves enter from the input port (8) of the traveling wave electrode (3), propagate along the signal electrode of the traveling wave electrode (3), and modulate the light wave in the waveguide (2) during the propagation process. After the modulation is completed, the signal electrode of the traveling wave electrode (3) turns, and the microwaves continue to propagate in the opposite direction and eventually enter the matching circuit (4).

2. The high-power electro-optic modulator according to claim 1, characterized in that: The substrate (1) is a lithium niobate substrate.

3. A high-power electro-optic modulator according to claim 1, characterized in that: The diameter of the cross-section at both ends of the signal electrode of the traveling wave electrode (3) is larger than the diameter of the cross-section at other positions.

4. A high-power electro-optic modulator according to claim 1, characterized in that: The signal electrode turning point of the traveling wave electrode (3) is a smooth arc-shaped transition.

5. A high-power electro-optic modulator according to claim 1, characterized in that: The microwave propagation path of the traveling wave electrode (3) after the signal electrode turns is parallel to the microwave propagation path before the turn.

6. A high-power electro-optic modulator according to claim 1, characterized in that: The two ground electrodes of the traveling wave electrode (3) are located on both sides of the signal electrode of the traveling wave electrode (3). The sidewalls of the two ground electrodes of the traveling wave electrode (3) and the sidewalls of the signal electrode of the traveling wave electrode (3) are shaped to form two channels with constant diameters.

7. A high-power electro-optic modulator according to claim 1, characterized in that: The two ground electrodes of the matching electrode (5) are an integral structure.

8. A high-power electro-optic modulator according to claim 7, characterized in that: The ground electrode of the matching electrode (5) is concave, and the signal electrode of the matching electrode (5) is set in the concave groove.

9. A high-power electro-optic modulator according to claim 8, characterized in that: The load resistor (6) is disposed on the bottom surface of the groove of the ground electrode.

10. A high-power electro-optic modulator according to claim 1, characterized in that: The waveguide (2) is positioned between the signal electrode and the ground electrode of the traveling wave electrode (3) or below the signal electrode.

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