A hybrid waveguide-integrated graphene mid-infrared all-optical modulator

Abstract

The present invention discloses a hybrid waveguide-integrated graphene mid-infrared all-optical modulator. The modulator comprises a sapphire substrate, a silicon waveguide transmission layer formed on the sapphire substrate; a graphene layer or a chalcogenide strip waveguide positioned on the silicon waveguide transmission layer, with the graphene layer positioned on the upper or lower surface of the chalcogenide strip waveguide; a chalcogenide strip waveguide formed on the graphene layer; and a chalcogenide material layer formed on the sapphire substrate or the silicon waveguide transmission layer, encapsulating the silicon waveguide transmission layer, the graphene layer, and the chalcogenide strip waveguide. The present invention utilizes a low-loss mid-infrared sapphire-silicon-chalcogenide hybrid waveguide structure and flexibly integrates graphene, significantly enhancing light-matter interaction while also utilizing graphene's ultrafast saturable absorption effect.

Description

Technical Field

[0001] The present invention belongs to the field of optical communication technology and is a light intensity modulation device, in particular to a hybrid waveguide integrated mid-infrared all-optical modulator of a sapphire-silicon-chalcogenide material-graphene system. Background Art

[0002] The mid-infrared band (2-20μm) is an optical band with great engineering application value. First, it contains the absorption fingerprints of most chemical molecules and biological molecules (7μm-20μm), which can be used for chemical gas sensing and bio-information sensing. It contains atmospheric windows (3-5μm and 8-14μm), which can be used for thermal imaging, infrared countermeasures, and free-space communication. It has strong water absorption in the 2μm band and low penetration into human tissue, which can be used for wind direction tracking and precision surgery. Among them, free-space communication is a technology for point-to-point bidirectional information transmission without optical fiber. It is of great significance and has broad application prospects in bandwidth access, wide area network and metropolitan area network expansion, local area network interconnection, deep space communication, etc. In these applications, mid-infrared lasers, amplifiers, optical switches, optical modulators, detectors, wavelength division multiplexers, power dividers and other functional devices are indispensable. Chip-level mid-infrared devices provide an important foundation for greatly improving the performance of mid-infrared application systems and reducing system size. In particular, the research on mid-infrared chip integrated modulators provides key support for building compact, high-speed, low-power 3-5μm band space optical communication systems. Summary of the Invention

[0003] To increase the modulation speed of current 3-5 μm mid-infrared modulators and reduce modulation power consumption, the purpose of the embodiments of the present invention is to provide a hybrid waveguide-integrated mid-infrared modulator with strong light-matter interaction based on a sapphire-silicon-chalcogenide glass-graphene system. This modulator achieves low-power modulation through the strong interaction between graphene and TE0 and TM0, and realizes ultra-high-speed all-optical modulation by utilizing the saturable absorption effect of graphene.

[0004] To achieve the above-mentioned purpose, the technical solution adopted by the present invention includes:

[0005] The device structure includes:

[0006] including a sapphire substrate;

[0007] The silicon waveguide transmission layer is formed on a sapphire substrate and is integrated with the sapphire substrate using a bonding process;

[0008] It includes a graphene layer or a chalcogenide strip waveguide, which is located on a silicon waveguide transmission layer; the graphene layer is located on the upper surface or lower surface of the chalcogenide strip waveguide; the chalcogenide strip waveguide is formed on the graphene layer, specifically, grown on the graphene layer using a thermal evaporation process.

[0009] It includes a chalcogenide material layer formed on a sapphire substrate or a silicon waveguide transmission layer, specifically prepared by thermal evaporation growth, and is used to cover the silicon waveguide transmission layer, the graphene layer, and the chalcogenide strip waveguide to provide waveguide protection.

[0010] A silicon waveguide transmission layer, a graphene layer, and a chalcogenide strip waveguide are provided. The silicon waveguide transmission layer is formed entirely on a sapphire substrate. The chalcogenide strip waveguide is located in the middle of the silicon waveguide transmission layer. The graphene layer is located between the lower surface of the chalcogenide strip waveguide and the silicon waveguide transmission layer.

[0011] The chalcogenide material layer includes a chalcogenide cap layer, which is formed on the silicon waveguide transmission layer and covers the graphene layer and the chalcogenide strip waveguide.

[0012] The silicon waveguide transmission layer and the chalcogenide strip waveguide form a hybrid ridge waveguide, and the TE0 mode optical signal propagates from the hybrid ridge waveguide formed by the silicon waveguide transmission layer and the chalcogenide strip waveguide, and strongly interacts with the graphene layer.

[0013] The optical signal of the TM0 mode is input from one end of the hybrid ridge waveguide and output from the other end of the hybrid ridge waveguide. The graphene layer directly interacts with the optical signal of the TE0 mode to realize all-optical modulation.

[0014] A silicon waveguide transmission layer, a graphene layer, and a chalcogenide strip waveguide are provided. The silicon waveguide transmission layer is formed entirely on a sapphire substrate. The chalcogenide strip waveguide is located in the middle of the silicon waveguide transmission layer. The graphene layer is located on the upper surface of the chalcogenide strip waveguide.

[0015] The chalcogenide material layer includes a chalcogenide planarization layer and a chalcogenide capping layer. The chalcogenide planarization layer is formed on the silicon waveguide transmission layer and covers the chalcogenide strip waveguide. The chalcogenide capping layer is formed on the chalcogenide planarization layer and covers the graphene layer.

[0016] The optical signal of the TM0 mode is input from one end of the whole formed by the silicon waveguide and the chalcogenide strip waveguide, and is output from the other end of the whole formed by the silicon waveguide and the chalcogenide strip waveguide. The optical signal of the TM0 mode propagates from the chalcogenide strip waveguide and interacts with the graphene layer to realize all-optical modulation.

[0017] A silicon waveguide transmission layer and a graphene layer are provided, wherein the silicon waveguide transmission layer is formed in the middle of the sapphire substrate, and the graphene layer is located on the silicon waveguide transmission layer;

[0018] The chalcogenide material layer includes a chalcogenide planarization layer and a chalcogenide capping layer. The chalcogenide planarization layer is formed on the sapphire substrate and covers the silicon waveguide transmission layer. The chalcogenide capping layer is formed on the chalcogenide planarization layer and covers the graphene layer.

[0019] The TM0 mode optical signal is input from one end of the silicon waveguide and output from the other end of the silicon waveguide. The TM0 mode optical signal propagates through the silicon waveguide and interacts with the graphene layer to achieve all-optical modulation.

[0020] The sapphire substrate is made of sapphire material.

[0021] The graphene layer is made of graphene material.

[0022] The silicon waveguide transmission layer is made of silicon material.

[0023] The chalcogenide strip waveguide, chalcogenide planarization layer and chalcogenide cap layer are made of chalcogenide glass materials including but not limited to Ge23Sb7S70 and Ge2Sb2Se5 components.

[0024] The material system has the characteristics of a wide infrared window and high optical nonlinearity, so the device can operate in the mid-infrared band with low loss.

[0025] The waveguide structure may be a silicon slab / chalcogenide strip waveguide structure or a silicon strip waveguide structure.

[0026] For a silicon slab / chalcogenide strip waveguide structure, the graphene can be transferred to the upper and lower surfaces of the chalcogenide strip waveguide structure; for a silicon strip waveguide structure, the graphene is transferred to the upper surface of the silicon strip waveguide structure.

[0027] The present invention uses, but is not limited to, two waveguide structures, wherein a silicon slab layer and a chalcogenide strip waveguide constitute a hybrid ridge waveguide structure, supporting the transmission and modulation of TE0 and TM0 mode optical signals; wherein a sapphire substrate and a silicon strip waveguide structure support the transmission and modulation of TM0 mode signals; in these two types of waveguide structures, the graphene layer can be integrated at the maxima of the TE0 mode and TM0 mode field strengths, respectively.

[0028] The modulator of the present invention uses graphene, uses one beam of modulated light to modulate another beam of communication light, and can directly use the saturable absorption effect of graphene to perform ultra-high-speed all-optical modulation.

[0029] Beneficial effects of the present invention:

[0030] The substrate and waveguide structure of the present invention support low-loss transmission of signal light in the 3-5 μm band. At the same time, graphene can be absorbed by the mid-infrared band, thereby modulating the signal light.

[0031] Based on this material system, the present invention can fabricate a silicon slab / chalcogenide strip waveguide structure supporting TE0 and TM0 mode transmission, as well as a sapphire substrate / silicon strip waveguide structure supporting TM0 mode transmission. Because of the hybrid material system, in both waveguide structures, graphene can be flexibly transferred to the maximum value of the mode light field, greatly enhancing the interaction between graphene and signal light, thereby reducing optical power consumption.

[0032] The present invention is based on a mid-infrared low-loss sapphire-silicon-chalcogenide material hybrid waveguide structure and flexibly integrates graphene, which greatly enhances the interaction between light and matter. At the same time, it utilizes the ultra-fast saturable absorption effect of graphene to propose a new solution for realizing an ultra-fast, ultra-low power all-optical modulator in the mid-infrared band. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0034] Figure 1 It is a schematic diagram of the sapphire substrate / silicon slab waveguide layer / chalcogenide strip waveguide / chalcogenide dielectric layer and cap layer structure shown in Example 1.

[0035] Figure 2 It is a schematic diagram of the sapphire substrate / silicon slab waveguide layer / chalcogenide strip waveguide / chalcogenide dielectric layer and cap layer structure shown in Example 2.

[0036] Figure 3 This is a schematic diagram of the sapphire substrate / silicon strip waveguide / chalcogenide dielectric layer and cap layer structure shown in Example 3.

[0037] Figure 4 yes Figure 1 The TE0 mode field distribution diagram of the sapphire substrate / silicon slab waveguide layer / chalcogenide strip waveguide structure shown.

[0038] Figure 5 yes Figure 2 The TM0 mode field distribution diagram of the sapphire substrate / silicon slab waveguide layer / chalcogenide strip waveguide structure shown.

[0039] Figure 6 yes Figure 3 The TM0 mode field distribution diagram of the sapphire substrate / silicon strip waveguide structure shown.

[0040] Figure 7 This is the basic modulation process of all-optical modulation.

[0041] Figure 8Schematic diagram of a straight waveguide device of an all-optical modulator, (a) shows a top view of the straight waveguide device of Example 1, and (b) shows a top view of the straight waveguide device of Example 2 or 3.

[0042] Figure 9 Schematic diagram of a micro-ring waveguide form of an all-optical modulator, (a) a top view of the micro-ring form device of Example 1, (b) a top view of the micro-ring form device of Example 2 or 3.

[0043] In the figure: sapphire substrate (1), silicon waveguide transmission layer (2), graphene layer (3), sulfide strip waveguide (4), sulfide planarization layer (5), sulfide cap layer (6). DETAILED DESCRIPTION

[0044] Exemplary embodiments will be described in detail herein, examples of which are illustrated in the accompanying drawings. In the following description, when referring to the drawings, like numbers in different figures represent like or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments are not intended to represent all possible embodiments consistent with the present invention. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present invention, as detailed in the appended claims.

[0045] The terms used in this invention are for the purpose of describing specific embodiments only and are not intended to limit the invention. The singular forms "a," "the," and "the" used in this invention and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0046] The embodiments of the present invention are as follows:

[0047] Example 1

[0048] like Figure 1 As shown, in this embodiment, a silicon waveguide transmission layer 2, a graphene layer 3, and a chalcogenide strip waveguide 4 are provided on a sapphire substrate 1. The silicon waveguide transmission layer 2 is formed entirely on the sapphire substrate 1. The chalcogenide strip waveguide 4 is located in the middle of the silicon waveguide transmission layer 2. The graphene layer 3 is located between the lower surface of the chalcogenide strip waveguide 4 and the silicon waveguide transmission layer 2. The width of the graphene layer 3 is greater than the width of the chalcogenide strip waveguide 4. The graphene layer 3 is transferred and prepared on the silicon waveguide transmission layer 2.

[0049] The chalcogenide material layer includes a chalcogenide capping layer 6 , which is formed on the silicon waveguide transmission layer 2 . Specifically, the chalcogenide capping layer 6 is grown on the silicon waveguide transmission layer 2 using a thermal evaporation process, and covers the graphene layer 3 and the chalcogenide strip waveguide 4 .

[0050] The silicon waveguide transmission layer 2 and the chalcogenide strip waveguide 4 form a hybrid ridge waveguide. The optical signal in the TE0 mode propagates through the hybrid ridge waveguide formed by the silicon waveguide transmission layer 2 and the chalcogenide strip waveguide 4 and interacts strongly with the graphene layer 3.

[0051] In this embodiment, Figure 4 This is the simulation result of the field distribution of the TE0 mode of the waveguide structure. The sub-figures from left to right are the total field strength E, the x component E x , y component E y , z component E z The direction of the electric field component is shown in the figure, where the z direction is perpendicular to the cross section and is the direction of light propagation.

[0052] Specifically, the graphene layer 3 is at the maximum value of the total field strength E, which is also the E x The maximum value E xmax The x component of the electric field E x The polarization direction is parallel to the graphene plane and can strongly interact with the graphene. By utilizing the saturable absorption effect of the graphene layer 3, ultra-high-speed all-optical modulation can be achieved.

[0053] As can be seen, in this structure of the present invention, the silicon waveguide transmission layer 2, graphene layer 3, and chalcogenide strip waveguide 4 are arranged sequentially from bottom to top. The graphene layer 3 is located where the optical field is strongest, interacting with the optical field, enhancing the optical field interaction and resulting in enhanced modulation performance. The present invention utilizes the chalcogenide waveguide-silicon slab transmission layer structure to achieve the characteristic of concentrating the optical field maximum at the interface between the chalcogenide waveguide and the silicon slab waveguide. This enhances light-matter interaction, reduces device size, reduces optical power consumption, and increases modulation depth.

[0054] Example 2

[0055] like Figure 2 As shown, in this embodiment, a silicon waveguide transmission layer 2, a graphene layer 3, and a chalcogenide strip waveguide 4 are provided on a sapphire substrate 1. The silicon waveguide transmission layer 2 is formed entirely on the sapphire substrate 1. The chalcogenide strip waveguide 4 is located in the middle of the silicon waveguide transmission layer 2. The graphene layer 3 is located on the upper surface of the chalcogenide strip waveguide 4. The width of the graphene layer 3 is greater than the width of the chalcogenide strip waveguide 4. The graphene layer 3 is transferred and prepared on the chalcogenide strip waveguide 4.

[0056] The chalcogenide material layer includes a chalcogenide planarization layer 5 and a chalcogenide capping layer 6. The chalcogenide planarization layer 5 is formed on the silicon waveguide transmission layer 2 and covers the chalcogenide strip waveguide 4. The chalcogenide capping layer 6 is formed on the chalcogenide planarization layer 5 and covers the graphene layer 3. Specifically, it is grown and prepared using a thermal evaporation process.

[0057] In this case, the graphene layer 3 is transferred onto the chalcogenide strip waveguide 4. Before the transfer and preparation of the graphene layer 3, a chalcogenide planarization layer 5 is grown and a planarization process is performed.

[0058] In this embodiment, Figure 5 This is the field distribution simulation result of the TM0 mode of the waveguide structure. The sub-figures from left to right are the total field strength E, the x component E x , y component E y , z component E z Specifically, the z component of the electric field E z The polarization direction is parallel to the graphene plane, which can strongly interact with graphene. By utilizing the saturable absorption effect of graphene, ultra-high-speed all-optical modulation can be achieved.

[0059] As can be seen, in this structure of the present invention, the silicon waveguide transmission layer 2, the chalcogenide strip waveguide 4, and the graphene layer 3 are arranged sequentially from bottom to top. Because the TM0 light field is concentrated on the upper and lower surfaces of the waveguide, and the graphene layer 3 is also located at the point where the light field is strongest, the interaction between the graphene layer 3 and the light field is enhanced, resulting in enhanced modulation performance. The present invention utilizes a chalcogenide waveguide-silicon slab transmission layer structure and uses the TM0 mode for propagation, resulting in the optical field maximum being concentrated at the interface between the chalcogenide waveguide and the silicon slab waveguide. This enhances light-matter interaction, reduces device size, reduces optical power consumption, and increases modulation depth.

[0060] Example 3

[0061] like Figure 3 As shown, in this embodiment, a silicon waveguide transmission layer 2 and a graphene layer 3 are provided on a sapphire substrate 1. The silicon waveguide transmission layer 2 is formed in the middle of the sapphire substrate 1, and the graphene layer 3 is located on the silicon waveguide transmission layer 2. The width of the graphene layer 3 is greater than that of the silicon waveguide transmission layer 2. The graphene layer 3 is transferred and prepared on the silicon waveguide transmission layer 2.

[0062] The chalcogenide material layer includes a chalcogenide planarization layer 5 and a chalcogenide capping layer 6. The chalcogenide planarization layer 5 is formed on a sapphire substrate 1 and covers a silicon waveguide transmission layer 2. The chalcogenide capping layer 6 is formed on the chalcogenide planarization layer 5 and covers a graphene layer 3. Specifically, the chalcogenide material layer is grown and prepared using a thermal evaporation process.

[0063] In this case, the chalcogenide waveguide 4 is omitted, and the silicon waveguide transmission layer 2 is used to prepare a silicon waveguide for light transmission, and the graphene layer 3 is transferred on top of the silicon waveguide. Before transferring and preparing the graphene layer 3, a chalcogenide planarization layer 5 is grown and a planarization process is performed.

[0064] In this embodiment, Figure 6 This is the field distribution simulation result of the TM0 mode of the waveguide structure. The sub-figures from left to right are the total field strength E, the x component Ex , y component E y , z component E z Specifically, the graphene layer 3 is at E z The maximum value E zmax The z component of the electric field E z The polarization direction is parallel to the graphene plane and can strongly interact with the graphene. By utilizing the saturable absorption effect of the graphene layer 3, ultra-high-speed all-optical modulation can be achieved.

[0065] As can be seen in the present invention's structure, the silicon waveguide transmission layer 2 and graphene layer 3 are arranged sequentially from bottom to top. Due to the TM0 mode characteristics, its light field is distributed on the upper and lower surfaces of the waveguide. The graphene layer 3 is also located at the point where the light field is strongest. The interaction between the graphene layer 3 and the light field is enhanced, resulting in enhanced modulation performance. The present invention utilizes a single-layer silicon waveguide structure and the TM0 mode to achieve the characteristic that the light field maximum is concentrated on the upper and lower surfaces of the silicon waveguide, thereby achieving enhanced light-matter interaction, reducing device size, lowering optical power consumption, and increasing modulation depth.

[0066] In addition, the device of the specific embodiment of the present invention can be in the form of a straight waveguide or a microring resonator, and the graphene can be transferred below or above the strip waveguide, such as Figure 8 or Figure 9 shown.

[0067] Example 4

[0068] Construct an electro-optic modulator in the form of a straight waveguide, such as Figure 8 shown.

[0069] The silicon waveguide transmission layer 2 and the chalcogenide strip waveguide 4 form a straight waveguide arranged in a straight line along the direction of optical signal propagation. The graphene layer 3 is arranged in a straight line along the desired waveguide segment, either above or below the chalcogenide strip waveguide 4, forming the structure of the present invention. This embodiment uses modulated light to adjust the absorptivity of the graphene, thereby modulating the transmittance of the signal light, ultimately achieving all-optical modulation of the signal light. Figure 7 This is the basic modulation process of all-optical modulation. Figure 7 As shown, the modulated light to be encoded and the continuous signal light enter the graphene device in the above embodiment through the beam combining optical path. In the graphene device, the modulated light interacts with the graphene, exciting the low-energy electrons in the graphene to a high-energy state, thereby changing its carrier concentration and modulating its absorptivity. Ultimately, the loss of the graphene to the signal light is changed, achieving full optical modulation of the modulated light on the signal light. After passing through the graphene device, the signal light and the modulated light are physically separated through the beam splitting optical path to obtain the modulated signal light.

[0070] Example 5

[0071] Constructing an electro-optic modulator in the form of a microring, such as Figure 9 shown.

[0072] The silicon waveguide transmission layer 2 and the chalcogenide strip waveguide 4 comprise a straight waveguide arranged in a straight line along the optical signal propagation direction and a microring waveguide coupled to the straight waveguide. The graphene layer 3 is arranged in a straight line along the optical signal propagation direction on one side of the microring waveguide, either above or below the chalcogenide strip waveguide 4, forming the structure of the present invention. In this embodiment, after the modulated light is coupled into the microring, the absorptivity of the graphene is adjusted, thereby modulating its optical absorptivity, changing the coupling conditions of the microring, and thus changing the transmittance of the signal light's resonant wavelength, thereby producing an all-optical modulation effect.

[0073] In Example 1, Example 2 and Example 3, Figure 8 and Figure 9 Schematic diagram of the device form.

[0074] Other embodiments of the present invention will readily occur to those skilled in the art after considering the specification and practicing the disclosure herein. The present invention is intended to cover any variations, uses, or adaptations of the present invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The description and examples are to be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following claims.

[0075] It should be understood that the present invention is not limited to the exact construction described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A hybrid waveguide-integrated graphene mid-infrared all-optical modulator, characterized by: comprising a sapphire substrate (1); It includes a silicon waveguide transmission layer (2) formed on a sapphire substrate (1); It comprises a graphene layer (3) and a sulfide strip waveguide (4), which are located on a silicon waveguide transmission layer (2); the graphene layer (3) is located on the upper surface or the lower surface of the sulfide strip waveguide (4); It comprises a sulfur-based material layer formed on a silicon waveguide transmission layer (2) and used for covering the silicon waveguide transmission layer (2), a graphene layer (3), and a sulfur-based strip waveguide (4).

2. The hybrid waveguide-integrated graphene mid-infrared all-optical modulator according to claim 1, characterized in that: A silicon waveguide transmission layer (2), a graphene layer (3) and a sulfide strip waveguide (4) are provided, wherein the silicon waveguide transmission layer (2) is formed as a whole on a sapphire substrate (1), the sulfide strip waveguide (4) is located in the middle of the silicon waveguide transmission layer (2), and the graphene layer (3) is located between the lower surface of the sulfide strip waveguide (4) and the silicon waveguide transmission layer (2); The sulfide material layer includes a sulfide cover layer (6), which is formed on the silicon waveguide transmission layer (2) and covers the graphene layer (3) and the sulfide strip waveguide (4).

3. The hybrid waveguide-integrated graphene mid-infrared all-optical modulator according to claim 2, characterized in that: The silicon waveguide transmission layer (2) and the sulfur-based strip waveguide (4) form a hybrid ridge waveguide, and a TE0 mode optical signal propagates through the hybrid ridge waveguide formed by the silicon waveguide transmission layer (2) and the sulfur-based strip waveguide (4), and strongly interacts with the graphene layer (3).

4. The hybrid waveguide-integrated graphene mid-infrared all-optical modulator according to claim 1, characterized in that: A silicon waveguide transmission layer (2), a graphene layer (3), and a sulfide strip waveguide (4) are provided, wherein the silicon waveguide transmission layer (2) is formed as a whole on a sapphire substrate (1), the sulfide strip waveguide (4) is located in the middle of the silicon waveguide transmission layer (2), and the graphene layer (3) is located on the upper surface of the sulfide strip waveguide (4); The sulfide material layer includes a sulfide planarization layer (5) and a sulfide cap layer (6), wherein the sulfide planarization layer (5) is formed on the silicon waveguide transmission layer (2) and covers the sulfide strip waveguide (4), and the sulfide cap layer (6) is formed on the sulfide planarization layer (5) and covers the graphene layer (3).

5. The hybrid waveguide-integrated graphene mid-infrared all-optical modulator according to claim 4, characterized in that: The optical signal of the TM0 mode is transmitted from one end of the whole formed by the silicon waveguide (2) and the sulfur-based strip waveguide (4), and is transmitted from the other end of the whole formed by the silicon waveguide (2) and the sulfur-based strip waveguide (4). The optical signal of the TM0 mode propagates from the sulfur-based strip waveguide (4), interacts with the graphene layer (3), and realizes all-optical modulation.

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