Optical Modulator and Related Apparatus

An optical modulator includes a waveguide layer, an electro-optical material layer, and electrodes. The waveguide layer includes a sub-wavelength waveguide; the electro-optical material layer is disposed on a surface of the sub-wavelength waveguide, and the sub-wavelength waveguide is configured to diffuse a light field at the waveguide layer into the electro-optical material layer; the electrodes are disposed on a surface of the electro-optical material layer, and a connection line between the electrodes is parallel to a plane on which the electro-optical material layer is located, or the electrodes are disposed on two sides of the electro-optical material layer, and a connection line between the electrodes intersects with a plane on which the electro-optical material layer is located; and the electrodes are configured to apply an electrical signal to the electro-optical material layer.

TECHNICAL FIELD

This disclosure relates to the field of optical communications technologies, and in particular, to an optical modulator and a related apparatus.

BACKGROUND

An optical modulator is one of the most important integrated devices in an optoelectronic integrated circuit. In recent years, with emergence of artificial intelligence and big data computing, people's requirements for a communications capacity, bandwidth, and a rate have increased explosively, and the optical modulator has developed rapidly. The bandwidth and modulation efficiency are two important parameters for measuring device performance of the optical modulator.

A conventional optical modulator (for example, a silicon optical modulator) is limited by an electron migration rate, and a theoretical bandwidth limit of the conventional optical modulator is less than 70 gigahertz (GHz). An electro-optical material having a high electro-optical effect (for example, an organic polymer or a lithium niobate thin film) is used, to increase bandwidth of the optical modulator.

In the conventional technology, a common solution is to fill a waveguide slot with an organic polymer or to etch a waveguide layer on a lithium niobate thin film, so that a light field is limited within an electro-optical material. However, the waveguide slot has a small size, and it is very difficult to fill the waveguide slot with the organic polymer, and a physicochemical property of the lithium niobate thin film is very stable, and it is very difficult to etch the waveguide layer on the lithium niobate thin film. In the foregoing solution, there is a complex process, high preparation costs, and low practicality.

SUMMARY

Embodiments of this disclosure provide an optical modulator and a related apparatus, to simplify a process, so as to reduce preparation costs and improve practicality of applying an electro-optical material to the optical modulator.

According to a first aspect, an embodiment of this disclosure provides an optical modulator. The optical modulator includes a waveguide layer, an electro-optical material layer, and electrodes. The waveguide layer includes a sub-wavelength waveguide, the electro-optical material layer is disposed on a surface of the sub-wavelength waveguide, and the sub-wavelength waveguide is configured to diffuse a light field at the waveguide layer into the electro-optical material layer, the electrodes are disposed on a surface of the electro-optical material layer, and a connection line between the electrodes is parallel to a plane on which the electro-optical material layer is located, or the electrodes are disposed on two sides of the electro-optical material layer, and a connection line between the electrodes intersects with a plane on which the electro-optical material layer is located, and the electrodes are configured to apply an electrical signal to the electro-optical material layer. A material of the waveguide layer includes silicon, silicon nitride, or group III-V materials. A material of the electro-optical material layer includes an organic polymer, a lithium tantalate thin film, a lithium niobate thin film, or a barium titanate thin film. A material of the electrodes includes graphene or a transparent conductive oxide.

According to a second aspect, an embodiment of this disclosure provides an optical module, including a light source, a drive apparatus, and the optical modulator according to any one of the first aspect and the specific implementations of the first aspect. The light source is configured to generate input light, and transmit the input light to a waveguide layer of the optical modulator through an optical fiber. The drive apparatus is configured to generate an electrical signal, and transmit the electrical signal to electrodes of the optical modulator through a circuit path. The optical modulator is configured to receive the input light and the electrical signal, and modulate the input light based on the electrical signal.

According to a third aspect, an embodiment of this disclosure provides a network device, including a wavelength division multiplexer/demultiplexer, a main board, and the optical module in the second aspect. The optical module is disposed on the main board. The wavelength division multiplexer/demultiplexer is disposed on the main board, the wavelength division multiplexer/demultiplexer is connected to the optical module through an optical fiber, and the wavelength division multiplexer/demultiplexer is configured to process wavelength division multiplexing/demultiplexing of an optical signal.

DESCRIPTION OF EMBODIMENTS

An embodiment of this disclosure provides an optical modulator. The optical modulator includes a waveguide layer, an electro-optical material layer, and electrodes. The waveguide layer includes a sub-wavelength waveguide. The electro-optical material layer is disposed on a surface of the sub-wavelength waveguide. An electro-optical material does not need to be further processed, and the sub-wavelength waveguide at the waveguide layer may be used to diffuse a light field at the waveguide layer into the electro-optical material layer. When bandwidth of the photoelectric modulator is increased, a process is simplified, preparation costs are reduced, and practicality of the optical modulator is improved.

The following describes embodiments of this disclosure with reference to the accompanying drawings. A person of ordinary skill in the art may learn that, with technology development and emergence of a new scenario, the technical solutions provided in embodiments of this disclosure are also applicable to resolving a similar technical problem.

FIG.1is a schematic diagram of an application scenario according to an embodiment of this disclosure.FIG.1shows an optical module100. An optical modulator200is provided in this embodiment of this disclosure may be applied to the optical module100. As shown inFIG.1, the optical module100further includes a light source101and a drive apparatus102. The light source101is configured to generate input light. The input light is transmitted to the optical modulator200through an optical fiber. The drive apparatus102is configured to generate an electrical signal. The electrical signal is transmitted to the optical modulator200through a circuit path. The optical modulator200is configured to receive the input light and the electrical signal, and modulate the input light based on the electrical signal. The optical modulator200is further configured to transmit output light through the optical fiber.

It should be noted that a use scenario of the optical modulator provided in this disclosure is not limited to the optical module, but may be further applied to another optical system, for example, an optical coherent system (OCS).

FIG.2is a schematic top view of a structure of an optical modulator200according to an embodiment of this disclosure. The optical modulator200includes a waveguide layer201, an electro-optical material layer202, and electrodes203. The electrodes203include three electrodes. It should be understood that a quantity of electrodes may be set based on an actual requirement. For example, in another example shown inFIG.7, there are two electrodes.

The waveguide layer201is disposed on a substrate. The substrate may be a semiconductor material such as silicon, germanium, or silicon dioxide, or may be an insulating material. This is not limited herein. The waveguide layer201is made of silicon, silicon nitride, or III-V materials. A related structure shown inFIG.2may be etched on the substrate in a manner such as a dry etching manner or a wet etching manner. The waveguide layer201includes an input end, a beam splitter, a sub-wavelength waveguide2011, a beam combiner, and an output end. Light is emitted from a light source (for example, the light source is a laser), and enters the waveguide layer201of the optical modulator200through the input end. After passing through the beam splitter, the light is transmitted through two arms, and enters the sub-wavelength waveguide2011.

The sub-wavelength waveguide2011is of a periodic structure whose size is less than a wavelength of acting light (as shown inFIG.3andFIG.4). A basic characteristic is as follows: When a light wave acts on a sub-wavelength structure, there is only zero-order reflection and projection diffraction, and a property of the sub-wavelength structure is similar to a property of a same homogeneous medium. A depth and a duty cycle of the sub-wavelength structure are adjusted, so that a related optical property such as reflectivity, a refractive index, or a transmittance of the sub-wavelength structure can be adjusted. In this embodiment of this disclosure, the waveguide layer201is etched with the sub-wavelength waveguide2011. The electro-optical material layer202is disposed on a surface of the sub-wavelength waveguide2011, and the sub-wavelength waveguide2011is used to diffuse a light field at the waveguide layer201into the electro-optical material layer202. An electro-optical material has a characteristic of a high electro-optical effect, and the light field is modulated under a joint action of the electro-optical material and the electrodes203, to increase bandwidth of the optical modulator200.

As shown inFIG.3andFIG.4, the sub-wavelength waveguide includes a plurality of trenches. A size (for example, a length, a width, and a depth of the trench) of the trench in the sub-wavelength waveguide2011and a duty cycle of the sub-wavelength waveguide2011(a ratio of a volume of the trench to a total volume of the sub-wavelength waveguide2011) are adjusted, so that a refractive index of the sub-wavelength waveguide2011can be adjusted. Further, a structural parameter of a part that is of the sub-wavelength waveguide2011and that is close to the beam splitter is adjusted, so that the light field at the waveguide layer201can be diffused into the electro-optical material layer202, and a structural parameter of a part that is of the sub-wavelength waveguide2011and that is close to the beam combiner is adjusted, so that the light field at the electro-optical material layer202can be diffused into the waveguide layer201, and light can be transmitted to the beam combiner.

The sub-wavelength waveguide2011has a circular hole structure or a polygonal hole structure, for example, a rhombic hole structure, a rectangular hole structure, or an elliptic hole structure. This is not limited herein.FIG.3is a schematic diagram of a structure of a sub-wavelength waveguide2011according to an embodiment of this disclosure.FIG.3is used as an example. When the sub-wavelength waveguide2011is applied to the optical modulator200, the electro-optical material layer202is disposed on an upper surface (namely, an upper surface in a Z-axis direction) of the sub-wavelength waveguide2011.

FIG.4is a schematic diagram of another structure of a sub-wavelength waveguide2011according to an embodiment of this disclosure. An upper half part inFIG.4is a top view of the sub-wavelength waveguide2011, and a lower half part is a cross-sectional view of the wavelength structure. The sub-wavelength waveguide2011is filled with a first material, and a refractive index of the first material is different from a refractive index of a material of the waveguide layer201. The first material may be air, silicon dioxide, or another dielectric material that matches a refractive index of the electro-optical material. This is not limited herein. Further, the refractive index of the first material is related to a refractive index of the waveguide layer201and a refractive index of the electro-optical material layer202. For example, when the refractive index of the waveguide layer201is greater than the refractive index of the electro-optical material layer202, a refractive index of a dielectric material selected as the first material is small, or when the refractive index of the waveguide layer201is less than the refractive index of the electro-optical material layer202, a refractive index of a dielectric material selected as the first material is large.

A material with a high electro-optical coefficient such as an organic polymer, a lithium tantalate thin film, a lithium niobate thin film, or a barium titanate thin film is used for the electro-optical material layer202, to increase the bandwidth of the optical modulator200. For example, the lithium niobate thin film is used for the electro-optical material layer202, and the lithium niobate thin film is tiled on the surface of the sub-wavelength waveguide2011(for example, silicon) through bonding.

The electrodes203are disposed on a surface or two sides of the electro-optical material layer202. The optical modulator200applies an electrical signal to the electro-optical material layer202through the electrodes203. In a specific implementation, a material with high electrical conductivity and a small optical absorption loss, for example, graphene or a transparent conductive oxide (TCO), is used for the electrodes203. A spacing between the electrodes203may be effectively reduced, to effectively reduce a half-wave voltage of a device, and reduce power consumption of the optical modulator200. A metal material such as gold, silver, or copper may alternatively be used for the electrodes203. This is not limited herein.

In an optional implementation, a size of the waveguide layer201is 500 nanometers to 800 nanometers, a size of the electro-optical material layer202is 1 micron to 5 microns, the sub-wavelength waveguide2011has a circular hole structure, and a size of the circular hole structure is 1 nanometer to 50 nanometers.

In this embodiment of this disclosure, the sub-wavelength waveguide at the waveguide layer is used to diffuse the light field at the waveguide layer into the electro-optical material layer, so that the electrodes can be used to modulate the light field by using the electro-optical material. Further, the sub-wavelength waveguide is used to change the refractive index of the waveguide layer, so that a difference between the refractive index of the waveguide layer and the refractive index of the electro-optical material layer becomes smaller, to diffuse the light field into the electro-optical material. The sub-wavelength waveguide is obtained through etching based on a characteristic that it is convenient to etch and process a common material of the waveguide layer such as silicon or silicon nitride. The electro-optical material layer is disposed on the surface of the sub-wavelength waveguide, the electro-optical material does not need to be further processed, and the sub-wavelength waveguide at the waveguide layer may also be used to diffuse the light field at the waveguide layer into the electro-optical material layer. When the bandwidth of the photoelectric modulator is increased, a process is simplified, preparation costs are reduced, and practicality of applying the electro-optical material to the optical modulator is improved. The material with high electrical conductivity and a small optical absorption loss is used for the electrodes. The spacing between the electrodes can be effectively reduced, to effectively reduce the half-wave voltage of the device, reduce an insertion loss, reduce power consumption of the optical modulator, and improve modulation efficiency of the optical modulator.

Based on the foregoing embodiment shown inFIG.2toFIG.4, there may be two optional implementations of the optical modulator proposed in this embodiment of this disclosure, and the two optional implementations are separately described below.

FIG.5is a schematic diagram of a structure of an optical modulator according to an embodiment of this disclosure. The optical modulator provided in this embodiment of this disclosure includes a waveguide layer201, an electro-optical material layer202, and electrodes203. The waveguide layer201includes a sub-wavelength waveguide2011. A structure of the optical modulator inFIG.5is similar to the structure of the optical modulator inFIG.2. Further, the electrodes203are disposed on a surface of the electro-optical material layer202, and a connection line between the electrodes203is parallel to a plane on which the electro-optical material layer202is located.

FIG.6is a schematic diagram of another structure of an optical modulator according to an embodiment of this disclosure. The optical modulator provided in this embodiment of this disclosure includes a waveguide layer201, an electro-optical material layer202, and electrodes203. The waveguide layer201includes a sub-wavelength waveguide2011. A difference between the structure of the optical modulator inFIG.6and the structure of the optical modulator inFIG.2lies in that inFIG.6, a connection line between the electrodes203intersects a plane on which the electro-optical material layer202is located.

Based on the optical modulators shown inFIG.5andFIG.6, in an optional implementation, the waveguide layer201is a silicon waveguide etched on a silicon-on-insulator (SOI) substrate. To fit the waveguide layer201, a lithium niobate thin film may be selected for the electro-optical material layer202. The lithium niobate thin film is tiled on a surface of the waveguide layer201through bonding. Optionally, the lithium niobate thin film may cover the waveguide layer201, or may cover only the sub-wavelength waveguide2011. The optical modulator200limits a light field within the electro-optical material layer202by using the sub-wavelength waveguide2011. In this case, a transparent conductive oxide may be selected as a material of the electrodes203.

Based on the optical modulators shown inFIG.5andFIG.6, in an optional implementation, the waveguide layer201is a silicon waveguide etched on a silicon nitride substrate. An organic polymer may be selected for the electro-optical material layer202. Graphene may be selected as the material of the electrodes203.

The optical modulator provided in this disclosure may be an optical modulator with a single waveguide arm in addition to an optical modulator (for example, a waveguide layer including a beam splitter and a beam combiner) with two waveguide arms shown inFIG.2toFIG.6.FIG.7is a schematic diagram of still another structure of an optical modulator according to an embodiment of this disclosure. In an optical modulator200shown inFIG.7, a waveguide layer201does not include a beam splitter or a beam combiner, but includes only one waveguide. A structure and a composition of the optical modulator200are similar to a structure and a composition of the optical modulators shown inFIG.2toFIG.7. Details are not described herein again.

In this embodiment of this disclosure, a sub-wavelength waveguide is disposed at the waveguide layer, to change a refractive index of the waveguide layer, so as to diffuse a light field at the waveguide layer into a lithium niobate thin film material, and improve modulation efficiency.FIG.8is a schematic diagram of a simulation of a light field distribution according to an embodiment of this disclosure.FIG.9is a schematic diagram of a simulation of another light field distribution according to an embodiment of this disclosure. For example, as shown inFIG.8, the light field distribution of the optical modulator provided in this embodiment of this disclosure is only in a white dashed frame region, and the white dashed frame region is a region in which a cross section of a waveguide layer201(not a sub-wavelength waveguide2011) is located. A light field distribution of the sub-wavelength waveguide2011is shown inFIG.9. In this case, a region in which a light field is located is at the electro-optical material layer202. The sub-wavelength waveguide2011is used to diffuse the light field into the electro-optical material layer202, to improve modulation efficiency of the optical modulator. Compared with modulation efficiency of a conventional optical modulator, modulation efficiency of the optical modulator provided in this embodiment of this disclosure is improved from 13.8 Vcm to 2.3 Vcm. Because the light field is limited within the electro-optical material layer, a device loss is further reduced, and a transmission loss is less than 0.5 decibels per centimeter (dB/cm). When a TCO material is used for the electrodes203of the optical modulator, the modulation efficiency is further increased to 0.7 Vcm. It should be noted that, this is only a possible simulation experiment result, and another simulation experiment result may also exist based on different arrangements of actual devices. This is not limited herein. The sub-wavelength waveguide is disposed in the waveguide layer, to change an equivalent refractive index of a material, so that the light field fully interacts with the electro-optical material layer. A material with a high electro-optical effect is used for the electro-optical material layer, to improve the modulation efficiency. For different electro-optical materials, different waveguide structures can be designed to match a refractive index of a material, so that the different waveguide structures can be compatible with the electro-optical materials with different refractive indices. The sub-wavelength waveguide is etched on the substrate, to be compatible with an existing etching process of the waveguide layer, to reduce process difficulty.

An optical module100provided in an embodiment of this disclosure includes a light source101, a drive apparatus102, and an optical modulator200. The optical modulator200includes the optical modulator200shown in any one of the foregoing embodiments. A structure of the optical module is similar to a structure of the optical module shown inFIG.1. Details are not described herein again.

As shown inFIG.10, this embodiment further provides a network device1000, including an optical module100, a wavelength division multiplexer/demultiplexer1001, and a main board1002. The optical module100includes the optical modulator200shown in any one of the foregoing embodiments. The optical module100is disposed on the main board1002. The wavelength division multiplexer/demultiplexer1001is disposed on the main board1002. The optical modulator200in the optical module100is connected to the wavelength division multiplexer/demultiplexer1001through an optical fiber, and the optical fiber and the wavelength division multiplexer/demultiplexer1001are configured to process wavelength division multiplexing (WDM)/demultiplexing of optical signals with different wavelengths.

It should be noted that, for a specific structure and function of the optical modulator200included in the network device in this embodiment, refer to related content disclosed in the related embodiments related to the optical modulator200. Details are not described herein again.

It should be understood that “an embodiment” or “one embodiment” mentioned in the entire specification means that particular features, structures, or characteristics related to the embodiment are included in at least one embodiment of this disclosure. Therefore, “in an embodiment” or “in one embodiment” appearing throughout the specification does not necessarily refer to a same embodiment. In addition, these particular features, structures, or characteristics may be combined in one or more embodiments by using any appropriate manner. It should be understood that sequence numbers of the foregoing processes do not mean execution sequences in various embodiments of this disclosure. The execution sequences of the processes should be determined based on functions and internal logic of the processes, and should not be construed as any limitation on the implementation processes of embodiments of this disclosure.

In summary, the foregoing descriptions are merely example embodiments of the technical solutions of this disclosure, but are not intended to limit the protection scope of this disclosure. Any modification, equivalent replacement, or improvement made without departing from the spirit and principle of this disclosure shall fall within the protection scope of this disclosure.