CN112394447B - Ultra-wideband beam splitting and combining device - Google Patents
Ultra-wideband beam splitting and combining device Download PDFInfo
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B6/122—Basic optical elements, e.g. light-guiding paths
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B6/122—Basic optical elements, e.g. light-guiding paths
- G02B6/1228—Tapered waveguides, e.g. integrated spot-size transformers
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B2006/12035—Materials
- G02B2006/12061—Silicon
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B2006/12133—Functions
- G02B2006/12147—Coupler
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
- Y02D30/00—Reducing energy consumption in communication networks
- Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks
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Abstract
The embodiment of the application discloses an ultra-wideband beam splitter-combiner, which comprises: a substrate, a first waveguide layer and a second waveguide layer sequentially stacked on the substrate; wherein an upper surface of the first waveguide layer is in direct contact with a lower surface of the second waveguide layer; the second waveguide layer comprises an input gradual change waveguide area and an output gradual change waveguide area for coupling optical signals; a first projection of the input graded waveguide region in a direction perpendicular to the substrate, a second projection of the output graded waveguide region in a direction perpendicular to the substrate, and a third projection of the first waveguide layer in a direction perpendicular to the substrate satisfy the following relationship: the first projection and the second projection fall entirely within the scope of the third projection.
Description
Technical Field
The application relates to the field of optical communication devices, in particular to an ultra-wideband beam splitter-combiner.
Background
An ultra-wideband 3dB (decibel) beam splitter is a critical device in an optical communication system, and is widely used in optical switches, optical modulators, and multiplexing/demultiplexing devices.
However, the existing 3dB beam splitter has the defects of high preparation precision requirement, overlong waveguide length, low transmission efficiency and difficult large-scale integration.
Disclosure of Invention
Accordingly, an embodiment of the present application provides an ultra-wideband beam splitter to solve at least one of the problems in the prior art.
In order to achieve the above purpose, the technical scheme of the application is realized as follows:
in one aspect, an embodiment of the present application provides an ultra-wideband beam splitter, including: a substrate, a first waveguide layer and a second waveguide layer sequentially stacked on the substrate; wherein,,
an upper surface of the first waveguide layer is in direct contact with a lower surface of the second waveguide layer;
the second waveguide layer comprises an input gradual change waveguide area and an output gradual change waveguide area for coupling optical signals;
a first projection of the input graded waveguide region in a direction perpendicular to the substrate, a second projection of the output graded waveguide region in a direction perpendicular to the substrate, and a third projection of the first waveguide layer in a direction perpendicular to the substrate satisfy the following relationship: .
In the above scheme, a space exists between the input graded waveguide region and the output graded waveguide region, and the first waveguide layer is continuously distributed below the input graded waveguide region, the output graded waveguide region and the space.
In the above aspect, a distance between a boundary of the third projection and a boundary of the first projection and/or the second projection is greater than or equal to 2 μm.
In the above aspect, the second waveguide layer further includes a non-coupling region other than a region where the optical signal coupling is performed, and a boundary of the projection of the non-coupling region in a direction perpendicular to the substrate at least partially overlaps with a boundary of the third projection.
In the above scheme, the second waveguide layer further comprises a non-coupling region except for a region where the optical signal coupling is performed, and a projection of the non-coupling region in a direction perpendicular to the substrate falls completely within a range of the third projection.
In the above scheme, the distance between the boundary of the projection of the non-coupling region in the direction perpendicular to the substrate and the boundary of the third projection is greater than or equal to 2 μm.
In the above scheme, the material of the first waveguide layer includes silicon and/or silicon nitride.
In the above aspect, the thickness of the first waveguide layer in a direction perpendicular to the substrate is between 50nm and 200 nm.
In the above scheme, the refractive index of the first waveguide layer is greater than or equal to 2.
In the above scheme, the output graded waveguide area comprises a first output graded waveguide area and a second output graded waveguide area, and the first output graded waveguide area and the second output graded waveguide area are symmetrically distributed on two sides of the input graded waveguide area.
In the above scheme, the widths of the input graded waveguide region, the first output graded waveguide region and the second output graded waveguide region in the direction perpendicular to the light transmission direction are graded, the variation trend of the widths of the first output graded waveguide region and the second output graded waveguide region is the same, and the variation trend of the widths of the input graded waveguide region is opposite to the variation trend of the widths of the first output graded waveguide region and the second output graded waveguide region.
In the above scheme, the input graded waveguide region, the first output graded waveguide region and the second output graded waveguide region respectively comprise a terminal at one side with smaller width, and the width of the terminal is between 50nm and 200 nm.
In the above scheme, the interval width between the input graded waveguide region and the first output graded waveguide region is the same as the interval width between the input graded waveguide region and the second output graded waveguide region.
In the above scheme, a space exists between the input graded waveguide region and the output graded waveguide region; the width of the space remains unchanged along the direction of light transmission.
In the above scheme, the second waveguide layer further includes an optical input region, and the optical input region and the input graded waveguide region are sequentially connected to form an optical input waveguide.
In the above scheme, the second waveguide layer further includes a curved waveguide region and an optical output region, and the output graded waveguide region, the curved waveguide region and the optical output region are sequentially connected to form an optical output waveguide.
The ultra-wideband beam splitter and combiner provided by the embodiment of the application comprises: a substrate, a first waveguide layer and a second waveguide layer sequentially stacked on the substrate; wherein an upper surface of the first waveguide layer is in direct contact with a lower surface of the second waveguide layer; the second waveguide layer comprises an input gradual change waveguide area and an output gradual change waveguide area for coupling optical signals; a first projection of the input graded waveguide region in a direction perpendicular to the substrate, a second projection of the output graded waveguide region in a direction perpendicular to the substrate, and a third projection of the first waveguide layer in a direction perpendicular to the substrate satisfy the following relationship: the first projection and the second projection fall entirely within the scope of the third projection. In this way, in the coupling region of the beam splitter-combiner, the second waveguide layer and the first waveguide layer below the second waveguide layer form a ridge waveguide structure. The ridge waveguide structure can reduce the limiting effect of the waveguide on the optical mode field, quicken the coupling rate of the input optical signal from the input gradual change waveguide area to the output gradual change waveguide area, reduce the coupling length of the device and reduce the size of the device, thereby improving the integration level of the device. Meanwhile, the ridge waveguide structure can also reduce the refractive index difference between the terminal with the smallest size in the input graded waveguide region and/or the output graded waveguide region and the waveguide below the terminal, thereby reducing the reflection of the input optical signal and improving the transmission efficiency. The ridge waveguide structure can improve transmission efficiency, so that the size of the terminal with the smallest size in the input gradual change waveguide area and/or the output gradual change waveguide area of the coupling area is not critical any more, and the ridge waveguide structure can also reduce the preparation difficulty of the beam splitter-combiner.
Drawings
Fig. 1a and 1b are a top view and a cross-sectional view, respectively, of a 3dB beam splitter provided by the related art;
fig. 2a and fig. 2b are a top view and a cross-sectional view, respectively, of an ultra-wideband beam splitter and combiner according to an embodiment of the present application;
FIGS. 3a and 3b are top views of an ultra wideband beam splitter/combiner according to another embodiment;
FIG. 4 is a graph showing a relationship between a wavelength and a transmission rate of an ultra-wideband beam splitter having first waveguide layers with different thicknesses according to an embodiment of the present application;
FIG. 5 is a schematic flow chart of a method for manufacturing an ultra-wideband beam splitter-combiner according to an embodiment of the present application;
FIGS. 6a-6c are schematic cross-sectional views of a device structure in the preparation process of an ultra wideband beam splitter/combiner according to an embodiment of the present application;
fig. 7 is a top view of an ultra wideband beam splitter and combiner according to an embodiment of the present application.
Detailed Description
The application will be described in further detail with reference to the accompanying drawings and specific examples.
Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the application are shown in the drawings, it should be understood that the application may be embodied in various forms and should not be limited to the specific embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present application. It will be apparent, however, to one skilled in the art that the application may be practiced without one or more of these details. In other instances, well-known features have not been described in detail so as not to obscure the application; that is, not all features of an actual implementation are described in detail herein, and well-known functions and constructions are not described in detail.
In the drawings, the size of layers, regions, elements and their relative sizes may be exaggerated for clarity. Like numbers refer to like elements throughout.
It will be understood that when an element or layer is referred to as being "on" … …, "" adjacent to "… …," "connected to" or "coupled to" another element or layer, it can be directly on, adjacent to, connected to or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on" … …, "" directly adjacent to "… …," "directly connected to" or "directly coupled to" another element or layer, there are no intervening elements or layers present. It will be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present application. When a second element, component, region, layer or section is discussed, it does not necessarily mean that the first element, component, region, layer or section is present.
Spatially relative terms, such as "under … …," "under … …," "below," "under … …," "above … …," "above," and the like, may be used herein for ease of description to describe one element or feature's relationship to another element or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use and operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements or features described as "under" or "beneath" other elements would then be oriented "on" the other elements or features. Thus, the exemplary terms "under … …" and "under … …" may include both an upper and a lower orientation. The device may be otherwise oriented (rotated 90 degrees or other orientations) and the spatially relative descriptors used herein interpreted accordingly.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term "and/or" includes any and all combinations of the associated listed items.
In order to provide a thorough understanding of the present application, detailed steps and detailed structures will be presented in the following description in order to explain the technical solution of the present application. Preferred embodiments of the present application are described in detail below, however, the present application may have other embodiments in addition to these detailed descriptions.
A 3dB beam splitter, which can split and combine the incident light. In the related art, a thermally insulated graded waveguide structure is often adopted to realize a 3dB beam splitter with low loss and uniform beam splitting. Fig. 1a is a top view of a 3dB beam splitter in the related art, referring to fig. 1a, the 3dB beam splitter includes a waveguide layer 3, the waveguide layer 3 including an optical input waveguide, a first optical output waveguide, and a second optical output waveguide; wherein the optical input waveguide comprises an optical input area 31 and an input graded waveguide area 32 which are sequentially connected; the first light output waveguide includes a first output graded waveguide region 33, a first curved waveguide region 35, and a first light output region 37, which are sequentially connected; the second light output waveguide includes a second output graded waveguide section 34, a second curved waveguide section 36, and a second light output section 38, which are connected in sequence. Fig. 1b is a cross-sectional view of a 3dB beam splitter provided in the related art, specifically, a cross-sectional view of the 3dB beam splitter along a line A-A shown in fig. 1a, and fig. 1b shows a substrate 1, and an intermediate layer 2, a waveguide layer 3, a cladding layer 4, and the like sequentially stacked on the substrate 1.
The light beam is incident via the light input region 31, enters the input graded waveguide region 32, and is then coupled to the first output graded waveguide region 33 and the second output graded waveguide region 34.
When the lengths of the input graded waveguide region 32, the first output graded waveguide region 33, and the second output graded waveguide region 34 are sufficiently long, the coupling process is adiabatic, i.e., ultra-wideband coupling covering the optical communication O-waveguide to the U-band is achieved. Thus, in order to increase the bandwidth of the 3dB combiner, the length of the adiabatic graded waveguide needs to be increased, but this leads to an increase in the device size, reducing the device integration.
On the other hand, at the tip of the input graded waveguide region and/or the output graded waveguide region, due to abrupt change of refractive index, mode mismatch is caused, which increases the reflection of the 3dB beam splitter and reduces transmission efficiency. Thus, in order to improve the transmission efficiency, it is necessary to use a tip structure having an ultra-small size, which increases the difficulty in manufacturing the device.
Based on this, the following technical solutions of the present embodiment are proposed.
An embodiment of the present application provides an ultra-bandwidth beam splitter, including: a substrate, a first waveguide layer and a second waveguide layer sequentially stacked on the substrate; wherein an upper surface of the first waveguide layer is in direct contact with a lower surface of the second waveguide layer; the second waveguide layer comprises an input gradual change waveguide area and an output gradual change waveguide area for coupling optical signals; a first projection of the input graded waveguide region in a direction perpendicular to the substrate, a second projection of the output graded waveguide region in a direction perpendicular to the substrate, and a third projection of the first waveguide layer in a direction perpendicular to the substrate satisfy the following relationship: the first projection and the second projection fall entirely within the scope of the third projection.
Reference is now made in particular to figures 2a to 2b. As shown, the ultra-wideband 3dB beam splitter includes: the substrate 1 may be a simple substance semiconductor material substrate (e.g., a silicon (Si) substrate, a germanium (Ge) substrate, etc.), a compound semiconductor material substrate (e.g., a silicon germanium (SiGe) substrate, etc.), or a silicon-on-insulator (SOI) substrate, a germanium-on-insulator (GeOI) substrate, etc. The embodiment of the application is described by taking the substrate as a Si substrate as an example.
It should be understood that, in order to clearly show each layer structure in the drawings, dimensional proportion relation of each layer structure may be different from that of the actual structure.
In the embodiment of the present application, an intermediate layer 2 is further formed on the substrate 1, and the intermediate layer 2 can prevent light in the waveguide layer from leaking to the substrate. The refractive index of the intermediate layer 2 is preferably less than or equal to 1.8; the material of the intermediate layer 2 may be silica, but is not limited thereto, and may be other materials.
The first waveguide layer 5 and the second waveguide layer 3 are sequentially stacked on the intermediate layer 2, and the second waveguide layer 3 is in direct contact with the first waveguide layer 5. The first and second waveguide layers 5 and 3 are formed of a material having a high refractive index, preferably 2 or more.
The first and second waveguide layers 5, 3 may be composed of the same material or may be composed of different materials, and preferably, the materials of the first and second waveguide layers 5, 3 include silicon and/or silicon nitride.
The thickness of the second waveguide layer 3 in the direction perpendicular to the substrate is between 100nm and 500nm and the thickness of the first waveguide layer 5 in the direction perpendicular to the substrate is between 50nm and 200 nm.
The second waveguide layer 3 includes an input graded waveguide region and an output graded waveguide region for coupling optical signals.
In a specific embodiment, the output graded waveguide region includes a first output graded waveguide region and a second output graded waveguide region.
A first projection of the input graded waveguide region in a direction perpendicular to the substrate, a second projection of the output graded waveguide region in a direction perpendicular to the substrate, and a third projection of the first waveguide layer in a direction perpendicular to the substrate satisfy the following relationship: the first projection and the second projection fall entirely within the scope of the third projection.
Referring specifically to fig. 2a, the projection of the input graded waveguide region 32 in the direction perpendicular to the substrate falls entirely within the projection region of the first waveguide layer 5 in the direction perpendicular to the substrate, said input graded waveguide region 32 and the first waveguide layer 5 therebelow forming a ridge waveguide. The ridge waveguide can reduce the limiting effect of the waveguide on the optical mode field, quicken the coupling of input light to the output waveguide, reduce the refractive index difference between the tip with the minimum width of the input gradual change waveguide and/or the output gradual change waveguide and the waveguide below the tip, and improve the transmission efficiency.
Similarly, the projection of the first output graded waveguide region 33 perpendicular to the direction perpendicular to the substrate falls completely within the projection region of the first waveguide layer 5 perpendicular to the substrate, and the first output graded waveguide region 33 and the first waveguide layer 5 therebelow form a ridge waveguide; the projection of the second output graded waveguide region 34 in the direction perpendicular to the substrate falls completely into the projection region of the first waveguide layer 5 in the direction perpendicular to the substrate, and the second output graded waveguide region 34 and the first waveguide layer 5 below the second output graded waveguide region form a ridge waveguide.
In an embodiment, the second waveguide layer 3 further includes an optical input region 32, and the optical input region and the graded waveguide region 33 are sequentially connected to form an optical input waveguide.
In an embodiment, the second waveguide layer 3 further includes a curved waveguide region and a light output region, where the output graded waveguide region and the light output region are sequentially connected to form a light output waveguide. In a specific embodiment, the curved waveguide region includes a first curved waveguide region 35 and a second curved waveguide region 36, the light output region includes a first light output region 37 and a second light output region 38, the first output graded waveguide region 33, the first curved waveguide region 35 and the first output region 37 are sequentially connected to form a first light output waveguide, and the second output graded waveguide region 34, the second curved waveguide region 36 and the second output region 38 are sequentially connected to form a second light output waveguide.
The first light output waveguide and the second light output waveguide are symmetrically distributed on two sides of the light input waveguide. In a specific embodiment, the first light output waveguide and the second light output waveguide are mirror images.
With continued reference to fig. 2a, the widths of the input graded waveguide region 32, the first output graded waveguide region 33 and the second output graded waveguide region 34 in the direction perpendicular to the light transmission direction are graded, the variation trend of the widths of the first output graded waveguide region 33 and the second output graded waveguide region 34 is the same, and the variation trend of the widths of the input graded waveguide region 32 is opposite to the variation trend of the widths of the first output graded waveguide region 33 and the second output graded waveguide region 34.
The input graded waveguide region 32, the first output graded waveguide region 33, and the second output graded waveguide region 34 each include a terminal on a side where the respective widths become smaller, the terminal having a width between 50nm and 200 nm.
A first interval and a second interval are respectively arranged between the input graded waveguide region 32 and the first output graded waveguide region 33 and between the input graded waveguide region 32 and the second output graded waveguide region 34, the widths of the first interval and the second interval are the same, and the interval width is between 50nm and 250 nm. And the width of the space is constant along the direction of light transmission.
In an embodiment, the input graded waveguide region 32, the first output graded waveguide region 33, the second output graded waveguide region 34, and the first waveguide layer 5 below the coupling region formed by the first interval and the second interval are continuously distributed. In a specific embodiment, the distance between the projected boundary of the coupling region in the direction perpendicular to the substrate and the projected boundary of the first waveguide layer 5 in the direction perpendicular to the substrate is greater than or equal to 2 μm.
In an embodiment, the first waveguide layer 5 also extends to a non-coupling region of the second waveguide layer 3 other than the coupling region, the boundary of the projection of the non-coupling region in the direction perpendicular to the substrate at least partially overlapping the boundary of the projection of the first waveguide layer 5 in the direction perpendicular to the substrate. Preferably, the projection of the uncoupled region in the direction perpendicular to the substrate falls completely within the area of the projection of the first waveguide layer 5 in the direction perpendicular to the substrate. More preferably, the boundary distance of the projection of the non-coupling region in the direction perpendicular to the substrate is greater than or equal to 2 μm from the boundary of the projection of the first waveguide layer 5 in the direction perpendicular to the substrate.
In a specific embodiment, the first waveguide layer 5 covers the entire intermediate layer 2, being shaped like a plate, as shown in fig. 2 a.
In other alternative embodiments, the first waveguide layer 5 may also partially cover part of the intermediate layer 2. As shown in fig. 3a, 3 b.
Fig. 4 shows the transmission rate versus wavelength of an ultra-wideband beam splitter having a first waveguide layer 5 of different thickness. As can be seen from the figure, the thickness of the first waveguide layer 5 affects the transmission rate of the beam splitter.
It is noted that, in the present embodiment, in order to prevent the optical modes between the first and second light output regions 37 and 38 from being coupled to each other, the pitch width between the first and second light output regions 37 and 38 is greater than or equal to 4 μm.
The first curved waveguide section 35 and the second curved waveguide section 36 are used to couple the light waves in the first output graded waveguide section 33 and the second output graded waveguide section 34 to the first light output section 37 and the second light output section 38, respectively, and in order to reduce the curved loss, the curved radius of the first curved waveguide section 35 and the second curved waveguide section 36 is greater than or equal to 20 μm.
In one embodiment, the ultra wideband beam splitter further includes a cover layer 4, where the cover layer 4 is formed on the waveguide layer 3, and the material may be silica, but is not limited thereto, and may also be other materials.
The embodiment of the application can realize 3dB beam splitting and combining of 1.2-2 um, and has the advantages of ultra-wide optical bandwidth, low preparation difficulty and cost, small structure size, easiness in large-scale integration and the like.
The embodiment of the application also provides a preparation method of the ultra-wideband beam splitter-combiner, and particularly relates to fig. 5. As shown, it includes the following steps:
step 501, providing a substrate;
step 502, forming a first waveguide layer on the substrate;
step 503, directly forming a second waveguide layer on the first waveguide layer, wherein the second waveguide layer comprises an input graded waveguide region and an output graded waveguide region for optical signal coupling;
wherein a first projection of the input graded waveguide region in a direction perpendicular to the substrate, a second projection of the output graded waveguide region in a direction perpendicular to the substrate, and a third projection of the first waveguide layer in a direction perpendicular to the substrate satisfy the following relationship: the first projection and the second projection fall entirely within the scope of the third projection.
The method for preparing the ultra wideband beam splitter provided by the embodiment of the application is further described in detail below with reference to the cross-sectional views of the device in the preparation process of the ultra wideband beam splitter in fig. 6a-6 c.
First, step 501 is performed to provide a substrate;
referring to fig. 6a, a substrate 1 is provided; the substrate may be an elemental semiconductor material substrate (e.g., a silicon (Si) substrate, a germanium (Ge) substrate, etc.), a composite semiconductor material substrate (e.g., a silicon germanium (SiGe) substrate, etc.), or a silicon-on-insulator (SOI) substrate, a germanium-on-insulator (GeOI) substrate, etc.
The embodiment of the application is described by taking the substrate as a silicon substrate as an example.
Next, step 502 is performed to form a first waveguide layer on the substrate.
Referring to fig. 6b, a first waveguide layer 5 is formed on the substrate 1, and an intermediate layer 2 may be formed on the substrate before the first waveguide layer 5 is formed, where the intermediate layer 2 may prevent light of the first waveguide layer from leaking into the substrate 1. The refractive index of the intermediate layer 2 may be less than or equal to 1.8; the material of the intermediate layer 2 may be silica, but is not limited thereto, and it may be other materials.
Next, step 503 is performed to form a second waveguide layer directly on the first waveguide layer.
Referring to fig. 6c, the second waveguide layer 3 is formed on the first waveguide layer 5, and the first waveguide layer 5 and the second waveguide layer 3 may be made of the same material or different materials, preferably, the materials of the first waveguide layer 5 and the second waveguide layer 3 include silicon and/or silicon nitride.
In a practical process, a waveguide layer may be formed first, and then the second waveguide layer 3 may be formed by etching.
In an embodiment, the thickness of the second waveguide layer 3 in the direction perpendicular to the substrate is between 100nm and 500nm, and the thickness of the first waveguide layer 5 in the direction perpendicular to the substrate is between 50nm and 200 nm.
The second waveguide layer 3 includes an input graded waveguide region and an output graded waveguide region for coupling optical signals.
In a specific embodiment, the output graded waveguide region includes a first output graded waveguide region and a second output graded waveguide region.
A first projection of the input graded waveguide region in a direction perpendicular to the substrate, a second projection of the output graded waveguide region in a direction perpendicular to the substrate, and a third projection of the first waveguide layer in a direction perpendicular to the substrate satisfy the following relationship: the first projection and the second projection fall entirely within the scope of the third projection.
Fig. 7 is a top view of an ultra wideband beam splitter and combiner according to an embodiment of the present application. As can be seen from the figure, the projection of the input graded waveguide region 32 in the direction perpendicular to the substrate falls completely within the projection region of the first waveguide layer 5 in the direction perpendicular to the substrate, said input graded waveguide region 32 and the first waveguide layer 5 therebelow forming a ridge waveguide. The ridge waveguide can reduce the limiting effect of the waveguide on the optical mode field, quicken the coupling of input light to the output waveguide, reduce the refractive index difference between the tip with the minimum width of the input gradual change waveguide and/or the output gradual change waveguide and the waveguide below the tip, and improve the transmission efficiency.
Similarly, the projection of the first output graded waveguide region 33 perpendicular to the direction perpendicular to the substrate falls completely within the projection region of the first waveguide layer 5 perpendicular to the substrate, and the first output graded waveguide region 33 and the first waveguide layer 5 therebelow form a ridge waveguide; the projection of the second output graded waveguide region 34 in the direction perpendicular to the substrate falls completely into the projection region of the first waveguide layer 5 in the direction perpendicular to the substrate, and the second output graded waveguide region 34 and the first waveguide layer 5 below the second output graded waveguide region form a ridge waveguide.
In an embodiment, the second waveguide layer 3 further includes an optical input region 32, and the optical input region and the graded waveguide region 33 are sequentially connected to form an optical input waveguide.
In an embodiment, the second waveguide layer 3 further includes a curved waveguide region and a light output region, where the output graded waveguide region and the light output region are sequentially connected to form a light output waveguide. In a specific embodiment, the curved waveguide region includes a first curved waveguide region 35 and a second curved waveguide region 36, the light output region includes a first light output region 37 and a second light output region 38, the first output graded waveguide region 33, the first curved waveguide region 35 and the first output region 37 are sequentially connected to form a first light output waveguide, and the second output graded waveguide region 34, the second curved waveguide region 36 and the second output region 38 are sequentially connected to form a second light output waveguide.
The first light output waveguide and the second light output waveguide are symmetrically distributed on two sides of the light input waveguide. In a specific embodiment, the first light output waveguide and the second light output waveguide are mirror images.
With continued reference to fig. 7, the widths of the input graded waveguide region 32, the first output graded waveguide region 33 and the second output graded waveguide region 34 in the direction perpendicular to the light transmission direction are graded, the variation trend of the widths of the first output graded waveguide region 33 and the second output graded waveguide region 34 is the same, and the variation trend of the widths of the input graded waveguide region 32 is opposite to the variation trend of the widths of the first output graded waveguide region 33 and the second output graded waveguide region 34.
The input graded waveguide region 32, the first output graded waveguide region 33, and the second output graded waveguide region 34 each include a terminal on a side where the respective widths become smaller, the terminal having a width between 50nm and 200 nm.
A first interval and a second interval are respectively arranged between the input graded waveguide region 32 and the first output graded waveguide region 33 and between the input graded waveguide region 32 and the second output graded waveguide region 34, the widths of the first interval and the second interval are the same, and the interval width is between 50nm and 250 nm. And the width of the space is constant along the direction of light transmission.
In an embodiment, the input graded waveguide region 32, the first output graded waveguide region 33, the second output graded waveguide region 34, and the first waveguide layer 5 below the coupling region formed by the first interval and the second interval are continuously distributed. In a specific embodiment, the distance between the projected boundary of the coupling region in the direction perpendicular to the substrate and the projected boundary of the first waveguide layer 5 in the direction perpendicular to the substrate is greater than or equal to 2 μm.
In an embodiment, the first waveguide layer 5 also extends to a non-coupling region of the second waveguide layer 3 other than the coupling region, the boundary of the projection of the non-coupling region in the direction perpendicular to the substrate at least partially overlapping the boundary of the projection of the first waveguide layer 5 in the direction perpendicular to the substrate. Preferably, the projection of the uncoupled region in the direction perpendicular to the substrate falls completely within the area of the projection of the first waveguide layer 5 in the direction perpendicular to the substrate. More preferably, the boundary distance of the projection of the non-coupling region in the direction perpendicular to the substrate is greater than or equal to 2 μm from the boundary of the projection of the first waveguide layer 5 in the direction perpendicular to the substrate.
In a specific embodiment, the first waveguide layer 5 covers the entire intermediate layer 2, being shaped like a plate, as shown in fig. 2 a.
In other alternative embodiments, the first waveguide layer 5 may also partially cover part of the intermediate layer 2. As shown in fig. 3a, 3 b.
With continued reference to fig. 6c, a cover layer 4 is further formed on the second waveguide layer 3, and the material of the cover layer may be, but not limited to, silicon dioxide, but may also be other materials.
The embodiment of the application can realize 3dB beam splitting and combining of 1.2-2 um, and has the advantages of ultra-wide optical bandwidth, low preparation difficulty and cost, small structure size, easiness in large-scale integration and the like.
It should be appreciated that reference throughout this specification to "one embodiment," "some embodiments," "other embodiments," "alternative embodiments," or "a particular embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present application. Thus, the appearances of the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in alternative embodiments," or "in a specific embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. It should be understood that, in various embodiments of the present application, the sequence numbers of the foregoing processes do not mean the order of execution, and the order of execution of the processes should be determined by the functions and internal logic thereof, and should not constitute any limitation on the implementation process of the embodiments of the present application. The foregoing embodiment numbers of the present application are merely for the purpose of description, and do not represent the advantages or disadvantages of the embodiments.
The above description is not intended to limit the scope of the application, but is intended to cover any modifications, equivalents, and improvements within the spirit and principles of the application.
Claims (11)
1. An ultra-wideband beam splitter, comprising: a substrate, a first waveguide layer and a second waveguide layer sequentially stacked on the substrate; wherein,,
an upper surface of the first waveguide layer is in direct contact with a lower surface of the second waveguide layer; the first waveguide layer has a thickness in a direction perpendicular to the substrate between 50nm and 200 nm;
the second waveguide layer comprises an input gradual change waveguide area and an output gradual change waveguide area for coupling optical signals; the second waveguide layer has a thickness in a direction perpendicular to the substrate between 100nm and 500 nm; the refractive index of the first waveguide layer and the second waveguide layer is greater than or equal to 2;
a first projection of the input graded waveguide region in a direction perpendicular to the substrate, a second projection of the output graded waveguide region in a direction perpendicular to the substrate, and a third projection of the first waveguide layer in a direction perpendicular to the substrate satisfy the following relationship: the first projection and the second projection fall entirely within the scope of the third projection;
the second waveguide layer further comprises a bending waveguide area and a light output area, and the output gradual change waveguide area, the bending waveguide area and the light output area are sequentially connected to form a light output waveguide; the projection of the curved waveguide region in a direction perpendicular to the substrate falls entirely within the scope of the third projection;
the output graded waveguide area comprises a first output graded waveguide area and a second output graded waveguide area, and the first output graded waveguide area and the second output graded waveguide area are symmetrically distributed on two sides of the input graded waveguide area; the input graded waveguide region, the first output graded waveguide region and the second output graded waveguide region respectively comprise a terminal on one side of each smaller width, and the width of the terminal is between 50nm and 200 nm.
2. The ultra-wideband beam splitter of claim 1, wherein a space exists between the input graded waveguide region and the output graded waveguide region, and a first waveguide layer is continuously distributed below the input graded waveguide region, the output graded waveguide region, and the space.
3. The ultra-wideband beam splitter of claim 1, wherein a distance between a boundary of the third projection and a boundary of the first projection and/or the second projection is greater than or equal to 2 μιη.
4. The ultra-wideband beam splitter of claim 1, wherein the second waveguide layer further comprises a non-coupling region other than the region where the optical signal coupling occurs, the boundary of the projection of the non-coupling region in a direction perpendicular to the substrate at least partially overlapping the boundary of the third projection.
5. The ultra-wideband beam splitter of claim 1, wherein the second waveguide layer further comprises a non-coupling region other than the region where the optical signal coupling occurs, a projection of the non-coupling region in a direction perpendicular to the substrate falling entirely within the third projection.
6. The ultra-wideband beam splitter of claim 5, wherein a boundary of the projection of the uncoupled region in a direction perpendicular to the substrate is greater than or equal to 2 μιη from a boundary of the third projection.
7. The ultra-wideband beam splitter of claim 1, wherein the material of the first waveguide layer comprises silicon and/or silicon nitride.
8. The ultra-wideband beam splitter of claim 1, wherein the widths of the input graded waveguide region, the first output graded waveguide region, and the second output graded waveguide region in a direction perpendicular to the light transmission direction are graded, the variation trend of the widths of the first output graded waveguide region and the second output graded waveguide region is the same, and the variation trend of the widths of the input graded waveguide region is opposite to the variation trend of the widths of the first output graded waveguide region and the second output graded waveguide region.
9. The ultra-wideband beam splitter of claim 8, wherein a width of a separation between the input graded waveguide section and the first output graded waveguide section is the same as a width of a separation between the input graded waveguide section and the second output graded waveguide section.
10. The ultra-wideband beam splitter/combiner of claim 1, wherein there is a gap between the input graded waveguide region and the output graded waveguide region; the width of the space remains unchanged along the direction of light transmission.
11. The ultra-wideband beam splitter and combiner of claim 1, wherein the second waveguide layer further comprises an optical input region, the optical input region and the input graded waveguide region being sequentially connected to form an optical input waveguide.
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