Evanescent wave coupling structure, silicon-based semiconductor laser and laser device

Abstract

The invention provides an evanescent wave coupling structure, a silicon-based semiconductor laser and a laser device.The evanescent wave coupling structure comprises a lower cladding layer, an active layer, a dielectric layer and a ridge waveguide layer, the lower cladding layer is formed below the active layer, so that light in the active layer can be limited by the lower cladding layer and can only be reflected upwards, and the light is coupled and transmitted into the dielectric layer through evanescent waves; and the light is transmitted to the ridge waveguide layer from the dielectric layer through evanescent wave coupling, and the light is output outwards by the ridge waveguide layer. According to the invention, the active layer is arranged to be in a structural form of which the width gradually changes from large to small, so that the light in the active layer is gradually restrained in a smaller area range in a transmission process, thereby improving the coupling efficiency of the light in a coupling process in a vertical direction, and reducing the optical coupling loss. According to the invention, the problems of low coupling efficiency, weak expandability, high process difficulty and the like of the silicon-based waveguide directly coupled with the III-V epitaxial material waveguide are solved.

Description

Technical Field

[0001] The present application relates to the field of semiconductor production process technology, and in particular to an evanescent wave coupling structure, a silicon-based semiconductor laser and a laser device. Background Art

[0002] Silicon-based optoelectronic integration shows great potential in rapidly growing applications such as high-speed optical interconnection, large-capacity optical communication, and high-precision optical detection. Because silicon (Si) is an indirect bandgap semiconductor material and cannot provide efficient optical gain, while III-V materials, as direct bandgap semiconductor materials, can be used to make high-efficiency on-chip lasers in the communication band. Therefore, the existing technology combines III-V materials with Si materials to obtain hybrid lasers with high gain effects.

[0003] The preparation schemes of hybrid lasers mainly include bonding scheme and direct epitaxy scheme. Bonding technology is to combine the prepared III-V optoelectronic devices or epitaxial III-V materials with silicon substrates through a bonding process, which can better solve the problem of lattice mismatch between materials. However, this technology has problems such as complex process, poor device thermal conductivity and low yield, which is not conducive to large-scale production. The technical scheme of directly epitaxying high-performance III-V materials on silicon-based substrates is considered to be the ultimate solution for making full use of CMOS technology to prepare low-power, high-integration and high-density silicon optoelectronic chips. The key to direct epitaxy of III-V materials on silicon is to achieve efficient coupling of III-V optical waveguides and Si optical waveguides. However, due to the huge material mismatch between III-V materials and Si, III-V materials grown directly on silicon substrates often have a large thickness (4-5 microns), resulting in a large height difference between the light-emitting surface of the III-V waveguide and the Si waveguide in the vertical and horizontal directions. This will also lead to problems such as low coupling efficiency between the III-V waveguide and the Si waveguide in practical applications, weak scalability and high process difficulty. Summary of the invention

[0004] The present application aims to solve one of the technical problems in the related art at least to some extent.

[0005] To this end, the purpose of this application is to propose an evanescent wave coupling structure, a silicon-based semiconductor laser and a laser device, which can improve the output gain of the semiconductor laser by improving the coupling efficiency between the III-V group optical waveguide and the Si-based waveguide, and reduce the difficulty of the preparation process of the semiconductor laser.

[0006] To achieve the above-mentioned purpose, the first embodiment of the present application proposes an evanescent wave coupling structure, including:

[0007] Lower cladding;

[0008] An active layer is formed on the lower cladding layer, wherein the active layer extends along a first direction and has a width gradually reduced in a second direction; the first direction and the second direction are orthogonal;

[0009] A dielectric layer is formed above the active layer and covers the upper surface of the active layer;

[0010] A ridge waveguide layer is formed on the dielectric layer, one end of the ridge waveguide layer is located above the active layer, and the other end thereof extends along the first direction, so that the light emitted from the active layer can be transmitted to the ridge waveguide layer through the dielectric layer by evanescent wave coupling and output by the ridge waveguide layer.

[0011] To achieve the above-mentioned purpose, a second embodiment of the present application proposes a silicon-based semiconductor laser, including the above-mentioned evanescent wave coupling structure.

[0012] To achieve the above-mentioned purpose, the third aspect of the present application provides a silicon-based semiconductor laser, comprising:

[0013] substrate;

[0014] An epitaxial structure, the epitaxial structure comprising a lower cladding layer, an upper cladding layer and an active layer therebetween, the epitaxial structure further comprising a lateral extension formed by lateral extension of the active layer, the lateral extension extending laterally along a first direction and gradually decreasing in width in a second direction; the first direction and the second direction are orthogonal, and the orthogonal plane is parallel to the substrate surface;

[0015] A silicon-based waveguide structure comprises a dielectric layer and a ridge waveguide layer; the dielectric layer is formed on the substrate, covers at least part of the sidewalls of the epitaxial structure, and covers the top surface of the lateral extension; the ridge waveguide layer is formed on the dielectric layer, and extends along the first direction to the lateral extension, so that the light emitted from the lateral extension can be transmitted to the ridge waveguide layer through the dielectric layer by evanescent wave coupling, and output by the ridge waveguide layer.

[0016] Optionally, the ridge waveguide layer includes an extension portion with a constant width in the second direction and a coupling portion with a gradually changing width, one end of the coupling portion is integrally connected to one end of the extension portion, and the other opposite end extends to above the lateral extension portion; wherein the width of the coupling portion in the second direction first increases and then decreases from a side close to the extension portion along the first direction to a side away from the extension portion.

[0017] Optionally, a vertical projection of the coupling portion on the substrate is a rhombus-shaped projection, and two vertex angles of the rhombus-shaped projection along the first direction are acute angles.

[0018] Optionally, one acute vertex angle of the rhombus projection is located in a vertical projection plane of the extension end, and the other acute vertex angle opposite is located in a vertical projection plane of the lateral extension portion.

[0019] Optionally, the vertical projection of the lateral extension portion is a triangular projection, and the vertex angle of the triangular projection is located within the vertical shadow plane of the ridge waveguide layer.

[0020] Optionally, the upper cladding is a ridge-shaped layer formed on the active layer and extending along the first direction, the width of the upper cladding in the second direction is equal to the maximum width of the lateral extension portion, and the projection boundary of the upper cladding close to the lateral extension portion coincides with the bottom edge boundary of the triangular projection.

[0021] Optionally, the epitaxial structure further includes a buffer layer, wherein the buffer layer is formed between the substrate and the lower cladding layer, and the thickness of the buffer layer ranges from 0 to 10 μm.

[0022] Optionally, the ridge waveguide layer is made of a silicon-based material, and the thickness of the ridge waveguide layer ranges from 0.05 μm to 1 μm.

[0023] Optionally, the epitaxial structure is composed of III-V materials, including at least one of binary, ternary and quaternary compounds.

[0024] Optionally, the dielectric layer at least covers side walls of the lower cladding layer and the active layer, and part of the side wall of the upper cladding layer; and the upper surface of the dielectric layer is between the upper surface of the active layer and the upper surface of the upper cladding layer.

[0025] Optionally, the semiconductor laser further comprises a grating layer, and the grating ruler is formed on the active layer and is located on two opposite sides of the upper cladding layer along the second direction.

[0026] Optionally, the semiconductor laser further comprises a Bragg reflection layer, wherein the Bragg reflection layer is formed on the active layer and connected to an end of the upper cladding layer away from the lateral extension portion.

[0027] To achieve the above-mentioned purpose, a fourth aspect of the present application proposes a laser device, comprising a semiconductor laser as described in any one of the above items.

[0028] The evanescent wave coupling structure, silicon-based semiconductor laser and laser device provided by the present application have at least the following beneficial effects:

[0029] The present application provides an evanescent wave coupling structure, a silicon-based semiconductor laser and a laser device, including a lower cladding, an active layer, a dielectric layer and a ridge waveguide layer. The lower cladding is formed below the active layer, so that the light in the active layer will be restricted by the lower cladding and can only be reflected upward, and transmitted to the dielectric layer through evanescent wave coupling, and then the light is transmitted from the dielectric layer to the ridge waveguide layer through evanescent wave coupling, and the ridge waveguide layer outputs the light outward. By setting the active layer to a structure with a gradually changing width from large to small, the light in the active layer is gradually constrained to a smaller area during the transmission process, thereby improving the coupling efficiency of the light in the vertical direction coupling process and reducing the optical coupling loss. The present application solves the problems of low coupling efficiency, weak scalability and high process difficulty of silicon-based waveguides directly coupling with III-V epitaxial material waveguides.

[0030] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0032] Figure 1 It is a schematic diagram of the cross-sectional structure of an evanescent wave coupling structure according to an embodiment of the present application.

[0033] Figure 2 It is a schematic diagram of the longitudinal cross-section structure of an evanescent wave coupling structure according to an embodiment of the present application.

[0034] Figure 3 It is a schematic diagram of the cross-sectional structure of a silicon-based semiconductor laser according to an embodiment of the present application.

[0035] Figure 4 It is a schematic diagram of the longitudinal cross-sectional structure of a silicon-based semiconductor laser according to an embodiment of the present application.

[0036] Figure 5 It is a schematic diagram of the cross-sectional structure of another silicon-based semiconductor laser according to an embodiment of the present application.

[0037] 10 substrate; 110 lower cladding; 120 active layer; 130 upper cladding; 140 grating layer; 150 Bragg reflection layer; 210 dielectric layer; 220 ridge waveguide layer. DETAILED DESCRIPTION

[0038] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0039] In a first aspect of an embodiment of the present application, an evanescent wave coupling structure is provided, such as Figure 1 and Figure 2 As shown, Figure 2 for Figure 1 Schematic diagram of a longitudinal section taken along the cutting line AA. The coupling structure includes a lower cladding layer 110, an active layer 120, a dielectric layer 210 and a ridge waveguide layer 220 stacked in sequence from bottom to top. Here, for the convenience of description, the X direction in the figure is set as the first direction, the Y direction in the figure is set as the second direction, and the Z direction in the figure is set as the third direction. The first direction, the second direction and the third direction are orthogonal, and the orthogonal plane of the first direction and the second direction is perpendicular to the stacking direction of the coupling structure.

[0040] Since the lower cladding layer 110 is formed below the active layer 120, the light in the active layer 120 will be restricted by the lower cladding layer 110 and can only be reflected upward, and is transmitted to the dielectric layer 210 through evanescent wave coupling, and then transmitted to the ridge waveguide layer 220 through the dielectric layer 210 through evanescent wave coupling, and is output outwardly from the ridge waveguide layer 220 along the first direction.

[0041] By extending the active layer 120 along the first direction and setting it in a structure with a width gradually decreasing in the second direction, the light in the active layer 120 can be gradually confined to a smaller area during the transmission along the first direction, thereby improving the coupling efficiency of light from the vertical direction to the dielectric layer 210 and further reducing the light coupling loss.

[0042] A second aspect of the embodiments of the present application provides a silicon-based semiconductor laser, such as Figure 3 and Figure 4 As shown, Figure 4 for Figure 3 A schematic longitudinal section view taken along the section line BB shows the semiconductor laser substrate 10, the epitaxial structure and the silicon-based waveguide structure.

[0043] The substrate 10 is used to provide bottom support for the subsequent formation of epitaxial structures and silicon-based waveguide structures, and participates in electrical conduction. The material of the substrate 10 includes but is not limited to a Si substrate 10, an SOI substrate, or a composite substrate 10 bonded or epitaxially deposited on a native substrate. In particular, when the epitaxial structure uses III-V materials, the epitaxial structure can contact with the substrate 10 to form a heterojunction. The thickness of the substrate 10 is preferably 500 μm.

[0044] The epitaxial structure is formed on the substrate 10, and includes a lower cladding layer 110, an active layer 120 and an upper cladding layer 130 stacked sequentially from bottom to top. The active layer 120 also extends laterally along the first direction to form a lateral extension portion with a gradually decreasing width in the second direction.

[0045] The silicon-based waveguide structure is formed on the substrate 10, and includes a dielectric layer 210 and a ridge waveguide layer 220. The dielectric layer 210 is formed on the substrate 10, covering at least part of the sidewall of the epitaxial structure and the top surface of the lateral extension. The ridge waveguide layer 220 is formed on the dielectric layer 210, and includes a coupling portion with a gradually changing width in the second direction, and the coupling portion is located above the lateral extension.

[0046] It can be known from the above contents that when the semiconductor laser is powered on, the light outputted by the epitaxial structure is transmitted to the lateral extension part, and can enter the dielectric layer 210 covering the top surface of the lateral extension part through evanescent wave coupling, and then enter the ridge waveguide layer 220 through evanescent wave coupling, and finally output the light along the direction extending along the ridge waveguide layer 220 through the ridge waveguide layer 220. By setting the lateral extension part as a structure with a gradually smaller width in the second direction, the light outputted by the epitaxial structure can be gradually confined to a smaller area along the first direction after being transmitted to the lateral extension part, thereby improving the coupling efficiency of the light from the lateral extension part to the dielectric layer 210, and further reducing the light coupling loss.

[0047] As an example, the vertical projection of the lateral extending portion in the third direction is a triangular projection, and the vertex angle of the triangular projection is located within the vertical projection plane of the ridge waveguide layer 220 .

[0048] Since the dielectric layer 210 covers at least part of the sidewalls of the epitaxial structure and the top surface of the lateral extension, the dielectric layer 210 needs to cover at least the sidewalls of the lower cladding layer 110 and the active layer 120, and part of the sidewalls of the upper cladding layer 130, so that the upper surface of the dielectric layer 210 in the third direction can be located between the upper surface of the active layer 120 and the upper surface of the upper cladding layer 130. In other words, the dielectric layer 210 located above the lateral extension and covering the upper surface of the lateral extension plays a role of waveguide in the present application, so that the light in the lateral extension can enter the dielectric layer 210 through evanescent wave coupling, and then enter the ridge waveguide layer through evanescent wave coupling. The portion of the dielectric layer 210 directly formed on the substrate 10 and covering the lower cladding 110, the side wall of the active layer 120, and part of the side wall of the upper cladding 130 in the present application mainly plays a role of raising the height, so that the dielectric layer 210 on the substrate 10 and the dielectric layer 210 on the lateral extension portion can be in the same plane, and thus the ridge waveguide layer located on the dielectric layer 210 can extend horizontally along the first direction.

[0049] During the formation of the dielectric layer 210, different positions in the growth process have different growth speeds, which leads to different height differences on the upper surface of the dielectric layer 210 after it is directly formed. In order to obtain a flat upper surface of the dielectric layer 210, the dielectric layer 210 needs to undergo an additional flattening step after it is formed, so that the dielectric layer 210 has a flat upper surface without a large height difference, and the subsequently formed waveguide layer can be formed on the flattened surface of the dielectric layer 210 to ensure the coupling efficiency of light from the dielectric layer 210 to the ridge waveguide layer 220 and reduce coupling loss.

[0050] As an example, the material of the dielectric layer 210 is not limited to BCB, SiO 2 、Al 2 O 3 、Si 3 N 4 and SiC and other materials.

[0051] In some embodiments, the ridge waveguide layer 220 may include an extension portion with a constant width in the second direction and a coupling portion with a gradually changing width. One end of the coupling portion is integrally connected to one end of the extension portion, and the other end thereof extends to the lateral extension portion and is spaced from the upper waveguide layer, so that light can enter the coupling portion from the dielectric layer 210 on the lower surface of the coupling portion through evanescent wave coupling, and then be transmitted from the coupling portion to the extension portion, and output from one end of the extension portion away from the coupling portion.

[0052] By setting the coupling portion to have a gradually changing width in the second direction, and the width first increases and then decreases from the end close to the extension portion along the first direction to the end away from the extension portion, the cross-sectional area of ​​the coupling portion is effectively increased, so that the light output from the lateral extension portion can be coupled to the coupling portion with higher efficiency. The width of the coupling portion decreases from its center to the end close to the extension portion, thereby reducing the optical loss of the light coupled in the coupling portion during the transmission process of entering the extension portion, and improving the output intensity of the laser.

[0053] As an example, in the third direction, the vertical projection of the coupling portion is a rhombus projection, and the two opposite vertex angles of the rhombus projection along the first direction are both acute angles. Thus, one acute vertex angle of the rhombus projection will be located in the vertical projection plane of the extension portion, and the other vertex angle will be located in the vertical projection plane of the lateral extension portion, so that one end of the coupling portion is integrally connected to one end of the extension portion, and the other opposite end extends to the lateral extension portion, and has a structural feature of gradually changing width in the second direction.

[0054] As an example, the ridge waveguide layer 220 is composed of a silicon-based material, including but not limited to Si 3 N 4, Si and the like, and the thickness of the ridge waveguide layer 220 is in the range of 0.05 μm to 1 μm.

[0055] In some embodiments, the upper cladding layer 130 is formed on the active layer 120 and has a strip or ridge structure extending along the first direction. By setting the upper cladding layer 130 as a ridge structure formed on the active layer 120, the contact area between the upper cladding layer 130 and the active layer 120 can be reduced, and two-dimensional confinement of light and carriers can be achieved. In the process of injecting current into the active layer 120 through the upper cladding layer 130, the upper cladding layer 130 with a ridge structure will limit the current from diffusing to both sides of the upper cladding layer 130, or injecting into the active layer 120 from both sides of the upper cladding layer 130, thereby reducing the injection area in the active layer 120 and improving the injection efficiency of carriers.

[0056] Furthermore, by setting the width of the upper cladding 130 in the second direction to be equal to the maximum width of the lateral extension portion, and in the third direction, the projection boundary of the upper cladding 130 close to the lateral extension portion coincides with the projection boundary of the lateral extension portion close to the upper cladding 130, the photon signal excited and output in the active layer 120 can be directly transmitted to the lateral extension portion during the transmission process, and then coupled from the lateral extension portion to the ridge waveguide layer 220 through evanescent wave coupling.

[0057] As an example, the epitaxial structure is mainly composed of III-V materials, including but not limited to one of binary, ternary or quaternary multi-component compounds. Among them, the lower cladding layer 110 is N-type doped AlGaAs with a thickness of 1500μm, which is used for conduction and limits the expansion of the light field to one side of the substrate 10, and the upper cladding layer 130 is P-type doped AlGaAs or GaAs with a thickness of 1500μm, which is used for conduction and limits the expansion of the light field to the side away from the substrate 10. The active layer 120 is a bulk material, quantum well and quantum dot made of compound semiconductors, with a thickness of 400nm, which is used to provide optical gain. Among them, the quantum well can be a single quantum well or a plurality of periodically alternately stacked multiple quantum wells. By arranging the active layer 120 between the upper cladding layer 130 and the lower cladding layer 110, the upper cladding layer 130 and the lower cladding layer 110 can cooperate with each other, thereby increasing the confinement effect on carriers and the distribution of carriers in the active layer 120, improving the light confinement factor, reducing the threshold current, and improving the luminous efficiency.

[0058] Furthermore, in order to improve the epitaxial quality of the lower cladding layer 110, the active layer 120 and the upper cladding layer 130 on the substrate 10, before the lower cladding layer 110 is epitaxially formed on the substrate 10, a buffer layer can be epitaxially grown on the substrate 10 in advance to provide a good buffer for the subsequent epitaxial growth of the lower cladding layer 110, the active layer 120 and the upper cladding layer 130. The higher surface flatness and lower internal defect density of the buffer layer can reduce the stress generated by the lattice mismatch between the lower cladding layer 110 and the substrate 10, and improve the epitaxial quality of the subsequent epitaxial growth process.

[0059] As an example, the buffer layer is a multilayer polynary compound, which may include a GaAs waveguide layer and an InGaAs / InAs superlattice filter layer, etc., with a total thickness of 0 to 10 μm. Its function is to provide good buffering, good interface flatness and low defect density for subsequent material growth.

[0060] In addition, since the lateral extension portion is formed by the lateral extension of the active layer 120 along the first direction, in order to make the lateral extension portion have a stable structure, the lateral extension portion should also include a portion of the active layer 120 and the buffer layer. That is to say, the lower cladding layer 110 and the buffer layer located below the active layer 120 also need to extend laterally along the first direction to provide bottom support for the active layer 120 extending laterally along the first direction. The lower cladding layer 110 in the lateral extension portion can also be carried out in the lateral extension portion. The light field of the active layer 120, after entering this portion of the active layer 120, will only be reflected upward and coupled to the dielectric layer 210 covering the upper surface of the active layer 120 through the evanescent wave.

[0061] It should be noted that the above-mentioned specific thickness data of the epitaxial structure are only used as examples, and the present application does not specifically limit the thickness of the lower cladding layer 110, the active layer 120 and the upper cladding layer 130 stacked in sequence.

[0062] In some embodiments, Figure 5 As shown, the semiconductor laser further includes a grating layer 140 and a Bragg reflection layer 150. The grating layer 140 is formed on the active layer 120 and is located on the upper cladding layer 130 along the second opposite sides, and is used to provide a mode selection resonant cavity for the semiconductor laser, so that the semiconductor laser can be single-mode lasered. The Bragg emission layer is formed on the active layer 120 at one end of the upper cladding layer 130 away from the lateral extension portion, and is a periodic Bragg structure, which is used to provide a highly reflective back cavity surface for the semiconductor laser.

[0063] Furthermore, in some other embodiments, the grating layer 140 may also be extended and formed in the active layer to provide a resonant cavity for the semiconductor laser.

[0064] Furthermore, the semiconductor laser of the present application also includes a first electrode and a second electrode. The first electrode is formed on the substrate 10 and is spaced apart from the epitaxial structure, and the second electrode is formed on the upper cladding layer 130. Thus, the first electrode and the second electrode are electrically connected externally, so that the epitaxial structure can be excited by an external current and emit laser light outward. Among them, an ohmic contact layer can also be pre-formed between the second electrode and the upper cladding layer 130, and the second electrode is electrically connected to the upper cladding layer 130 through the ohmic contact layer, so that the second electrode can avoid direct contact with the upper cladding layer 130 and form a Schottky contact, which plays a role in reducing the contact resistance, thereby improving the current transmission efficiency and use stability of the semiconductor laser.

[0065] It should be noted that the semiconductor laser structure described in the present application includes but is not limited to being applied to lasers, and can also be applied to active light-emitting devices such as optical amplifiers or super radiant tubes.

[0066] According to a third aspect of the embodiments of the present application, a laser device is provided, comprising the evanescent wave coupling structure described in any of the above embodiments and a silicon-based semiconductor laser.

[0067] In summary, the present application provides an evanescent wave coupling structure, a silicon-based semiconductor laser and a laser device, including a lower cladding layer 110, an active layer 120, a dielectric layer 210 and a ridge waveguide layer 220, wherein the lower cladding layer 110 is formed below the active layer 120, so that the light in the active layer 120 will be restricted by the lower cladding layer 110 and can only be reflected upward, and transmitted to the dielectric layer 210 through evanescent wave coupling, and then the light is transmitted from the dielectric layer 210 to the ridge waveguide layer 220 through evanescent wave coupling, and the ridge waveguide layer 220 outputs the light outward. By setting the active layer 120 as a structure with a gradually changing width from large to small, the light in the active layer 120 is gradually constrained within a smaller area during the transmission process, thereby improving the coupling efficiency of the light in the vertical direction coupling process and reducing the optical coupling loss. The present application solves the problems of low coupling efficiency, weak scalability and high process difficulty of silicon-based waveguides directly coupling with III-V epitaxial material waveguides.

[0068] In the description of the aforementioned embodiments, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0069] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

Claims

1. An evanescent wave coupling structure, characterized in that: include: Lower cladding; An active layer is formed on the lower cladding layer, the active layer extends along a first direction and has a width gradually reduced in a second direction; The first direction and the second direction are orthogonal; A dielectric layer is formed above the active layer and covers the upper surface of the active layer; A ridge waveguide layer is formed on the dielectric layer, one end of the ridge waveguide layer is located above the active layer, and the other end thereof extends along the first direction, so that the light emitted from the active layer can be transmitted to the ridge waveguide layer through the dielectric layer by evanescent wave coupling and output by the ridge waveguide layer.

2. A silicon-based semiconductor laser, characterized in that: It comprises the evanescent wave coupling structure as claimed in claim 1.

3. A silicon-based semiconductor laser, characterized in that: include: substrate; An epitaxial structure, the epitaxial structure comprising a lower cladding layer, an upper cladding layer and an active layer therebetween, the epitaxial structure further comprising a lateral extension formed by lateral extension of the active layer, the lateral extension extending laterally along a first direction and gradually decreasing in width in a second direction; the first direction and the second direction are orthogonal, and the orthogonal plane is parallel to the substrate surface; A silicon-based waveguide structure comprises a dielectric layer and a ridge waveguide layer; the dielectric layer is formed on the substrate, covers at least part of the sidewalls of the epitaxial structure, and covers the top surface of the lateral extension; the ridge waveguide layer is formed on the dielectric layer, and extends along the first direction to the lateral extension, so that the light emitted from the lateral extension can be transmitted to the ridge waveguide layer through the dielectric layer by evanescent wave coupling, and output by the ridge waveguide layer.

4. The semiconductor laser according to claim 3, characterized in that: The ridge waveguide layer includes an extension portion with a constant width in the second direction and a coupling portion with a gradually changing width, wherein one end of the coupling portion is integrally connected to one end of the extension portion, and the other opposite end extends to above the lateral extension portion; wherein the width of the coupling portion in the second direction increases first and then decreases from a side close to the extension portion along the first direction toward a side away from the extension portion.

5. The semiconductor laser according to claim 4, characterized in that: A vertical projection of the coupling portion on the substrate is a rhombus-shaped projection, and two vertex angles of the rhombus-shaped projection along the first direction are acute angles.

6. The semiconductor laser according to claim 5, characterized in that: One acute vertex angle of the rhombus projection is located in the vertical projection plane of the extension end, and the other acute vertex angle opposite to the rhombus projection is located in the vertical projection plane of the lateral extension portion.

7. The semiconductor laser according to claim 3, characterized in that: The vertical projection of the lateral extension portion is a triangular projection, and the vertex angle of the triangular projection is located within the vertical shadow plane of the ridge waveguide layer.

8. The semiconductor laser according to claim 7, characterized in that: The upper cladding is a ridge-shaped layer formed on the active layer and extending along the first direction. The width of the upper cladding in the second direction is equal to the maximum width of the lateral extension portion, and the projection boundary of the upper cladding close to the lateral extension portion coincides with the bottom edge boundary of the triangle projection.

9. The semiconductor laser according to claim 3, characterized in that: The epitaxial structure further includes a buffer layer, which is formed between the substrate and the lower cladding layer, and has a thickness ranging from 0 to 10 μm.

10. The semiconductor laser according to claim 3, characterized in that: The ridge waveguide layer is composed of a silicon-based material, and the thickness of the ridge waveguide layer ranges from 0.05 μm to 1 μm.

11. The semiconductor laser according to claim 3, characterized in that: The epitaxial structure is composed of III-V materials, including at least one of binary, ternary and quaternary compounds.

12. The semiconductor laser according to claim 3, characterized in that: The dielectric layer at least covers the side walls of the lower cladding layer and the active layer, and part of the side walls of the upper cladding layer; the upper surface of the dielectric layer is between the upper surface of the active layer and the upper surface of the upper cladding layer.

13. The semiconductor laser according to claim 3, characterized in that: The semiconductor laser further comprises a grating layer. The grating ruler is formed on the active layer and is located on two opposite sides of the upper cladding layer along the second direction.

14. The semiconductor laser according to claim 3, characterized in that: The semiconductor laser further comprises a Bragg reflection layer, which is formed on the active layer and connected to an end of the upper cladding layer away from the lateral extension portion.

15. A laser device, characterized in that: The method comprises adopting the semiconductor laser according to any one of claims 2 to 9.

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