Edge-emitting laser sensor chip and preparation method thereof

Abstract

The present invention relates to the technical field of laser sensor chips, and discloses an edge-emitting laser sensor chip and a preparation method thereof. The preparation method comprises: forming an epitaxial structure including a stacked substrate layer, a lower cladding layer, a lower waveguide layer, an active layer for generating laser, an upper waveguide layer, an upper cladding layer and a cap layer; forming a first groove and a second groove and a ridge structure including a single-mode filter area, a power amplification area and a functional area on the epitaxial structure; forming an insulating layer, wherein the first opening of the insulating layer exposes a part of the surface of the ridge structure to form a current injection surface; the second opening exposes a part of the surface of the functional area of ​​the ridge structure, and a sensing surface is formed between the first opening and the second opening; forming an oblique groove; and forming a nanosensing structure on the sensing surface. By forming an oblique groove in the ridge structure, the horizontally emitted laser is converted into a laser directed toward the sensing surface; the nanosensing structure is set on the sensing surface to obtain the refractive index of the unknown substance to be detected, which has a wide range of applications and is simple and efficient in detection.

Description

Technical Field

[0001] The present invention relates to the technical field of laser sensor chips, and in particular to an edge-emitting laser sensor chip and a preparation method thereof. Background Art

[0002] Laser sensor chip technology has the advantages of high sensitivity and high precision in measuring the refractive index of unknown liquids, and is applicable to a variety of biochemical sensing fields. The technology of laser sensor chip to measure the refractive index of unknown liquids mainly relies on the combination of fiber laser sensing system and surface plasmon resonance (SPR) effect or localized surface plasmon resonance (LSPR).

[0003] Biochemical detection based on fiber laser sensing system needs to be performed on the upper surface of the laser chip, so most laser chips are VCSEL (Vertical-Cavity Surface-Emitting Laser), which has high reliability and stability. However, when using VCSEL structure as the construction basis, in order to ensure good output beam characteristics, the working area of ​​the active layer must be limited to a smaller aperture, resulting in low laser output power and limited detection effect. Summary of the invention

[0004] In view of this, the present invention provides an edge-emitting laser sensor chip and a preparation method thereof to solve the problem that it is difficult for existing edge-emitting laser sensor chips to achieve both integration and laser detection effect.

[0005] In a first aspect, the present invention provides a method for preparing an edge-emitting laser sensor chip, comprising:

[0006] forming an epitaxial structure, wherein the epitaxial structure comprises a stacked substrate layer, a lower cladding layer, a lower waveguide layer, an active layer, an upper waveguide layer, an upper cladding layer and a cap layer, wherein the active layer is used to generate laser light;

[0007] A first groove and a second groove spaced apart along a first direction are formed on the epitaxial structure, the first groove and the second groove extend from the cap layer to the upper waveguide layer, and a ridge structure is formed between the first groove and the second groove, the ridge structure includes a single-mode filter area, a power amplification area and a functional area sequentially arranged along a second direction, and the first direction and the second direction are perpendicular to each other;

[0008] An insulating layer is formed on a surface of the cover layer away from the substrate layer, the insulating layer comprising a first opening and a second opening spaced apart along a second direction, the first opening at least exposing a portion of the surface of the single-mode filter region and the power amplification region of the ridge structure to form a current injection surface; the second opening exposing a portion of the surface of the functional region of the ridge structure, and the surface of the functional region between the first opening and the second opening forms a sensing surface;

[0009] An oblique groove is formed in the functional area, and the oblique groove extends from the second opening to at least pass through the active layer, so that the sidewall surface of the oblique groove reflects the laser propagating in the second direction in the active layer to the sensing surface for emission;

[0010] A nanometer sensing structure is formed on the insulating layer of the sensing surface, and the nanometer sensing structure is suitable for carrying a substance to be detected.

[0011] Beneficial effects: The method for preparing the edge-emitting laser sensor chip of the present invention forms an oblique groove in the ridge structure of the epitaxial structure, changes the original laser optical path in the laser sensor chip, and converts the laser lasing horizontally in the active layer into the laser emitting on the sensing surface facing the epitaxial structure surface, thereby realizing the change of the optical path from the side wall to the vertical cavity surface, and the chip is formed in an integrated epitaxial structure, with high integration, and can be used in the process route of conventional laser preparation, without the need for complex optical paths and packaging systems, which helps to further realize the miniaturization, low cost and reusability of laser detection. Furthermore, a nanosensing structure is set on the sensing surface, and a surface plasmon resonance mode and a localized surface plasmon resonance mode are used to excite multiple coupling modes in the nanosensing structure. When a certain substance to be detected with a different refractive index is placed on the nanosensing structure, the spectral absorption of the laser is changed by the change of the dominant coupling mode of the nanosensing structure, thereby obtaining the wavelength offset. The relationship between the refractive index of the substance to be detected and the wavelength offset can be established through the offset, so that the refractive index of the unknown substance to be detected can be obtained. This detection method has a wide range of applications and is simple and efficient.

[0012] In an optional embodiment, the angle between the extension direction of the oblique groove and the sensing surface is 45°.

[0013] Beneficial effect: By setting a 45° inclined groove, the horizontal laser in the active layer can be converted into a vertically upward laser, which helps to simplify the calculation of the vertically upward laser optical path, and then simplifies the preparation of each structural layer on the sensing surface, ensuring the consistency and output power of the laser emitted to various parts of the nanosensing structure.

[0014] In an optional embodiment, in the step of forming an oblique groove in the functional area, reactive ion beam etching is used to etch from the second opening toward the functional area to form an oblique groove with an angle of 45° to the sensing surface; the etching gas used in the reactive ion beam etching method is a mixture of chlorine and argon, or a mixture of carbon tetrachloride and argon.

[0015] Beneficial effects: Reactive ion beam etching can achieve high etching rate and anisotropy, which helps to form clear and well-defined sidewalls, and ion bombardment can better control the etching direction, facilitating precise control of the bevel inclination angle; in addition, the use of inert gas as an auxiliary etching gas can improve the stability of etching and avoid unnecessary damage to the epitaxial structure.

[0016] In an optional embodiment, in the step of forming an insulating layer on the surface of the cover layer away from the substrate layer, a portion of the insulating layer is etched by reactive ion beam etching to form a first opening and a second opening on the insulating layer; the ratio of the etching rate of the insulating layer to the etching rate of the epitaxial structure is greater than 10:1.

[0017] Beneficial effects: Reactive ion beam etching is used for etching the oblique groove and etching the insulating layer, and the silicon nitride material for etching the insulating layer and the GaAs / AIGaAs system for etching the functional area are set, and the etching rate ratio between the two is greater than 10:1. By adjusting the proportion of physical and chemical etching, the side wall of the oblique groove is made smooth, which is comparable to the physically understood resonance surface.

[0018] In an optional implementation, the optical thickness of the insulating layer is an integer multiple of half the wavelength of the laser, and the optical thickness of the insulating layer is the product of the film thickness of the insulating layer and the refractive index of the insulating layer.

[0019] Beneficial effect: By setting the thickness of the insulating layer to an integer multiple of half the wavelength of the laser, precise control of the thickness of the insulating layer is achieved, ensuring that the laser that is transformed from horizontal lasing to vertical upward lasing under the action of the 45° inclined groove will not affect the intensity and phase of the laser when it is emitted through the insulating layer, thereby ensuring the consistency of laser emission and output power.

[0020] In an optional embodiment, the nanosensing structure includes: a first metal layer, a dielectric spacer layer and a second metal layer which are stacked, wherein the first metal layer is arranged close to the insulating layer; and the second metal layer includes a grating structure formed by a plurality of nanometal pillars.

[0021] Beneficial effects: In the first aspect, a two-dimensional periodic grating composed of multiple nano-metal pillars placed on a dielectric spacer layer constitutes a sensing part, and the dielectric spacer layer and the nano-metal pillars are placed on the thin metal film of the first metal layer, thereby generating an SPR mode on the first metal layer. In the second aspect, the nano-sensing structure of the present invention includes: an LSPR mode excited in the grating structure of the second metal layer on the top layer, an LSPR mode excited at the interface between the grating structure and the dielectric spacer layer, and a Fabry-Perot (Fabry-Perot interference mode) mode between the first metal layer and the second metal layer on both sides of the dielectric spacer layer. The above-mentioned multiple modes can make different substances to be detected produce different light absorption changes at the laser wavelength, thereby completing high-precision sensitive detection. In the third aspect, the nano-sensing structure of the present invention is designed to have at least two peaks in the absorption spectrum and two corresponding anti-peaks in the reflection spectrum, so that these resonances during the above detection occur at the resonant frequencies of the LSPR and SPR modes, which can correspond to wavelengths of 750nm and 944nm.

[0022] In an optional embodiment, the plurality of nano-metal pillars of the second metal layer are arranged in an array, and the nano-metal pillars are square pillars with a side length of 200 nm and a height of 30 nm; and the spacing between adjacent nano-metal pillars is 200 nm.

[0023] Beneficial effect: multiple array-arranged nano-metal pillars are provided to ensure the comprehensiveness and accuracy of laser detection by the grating structure.

[0024] In an optional implementation, the thickness of the first metal layer is 30 nm, the thickness of the dielectric spacer layer is 40 nm, and the thickness of the second metal layer is 35 nm.

[0025] Beneficial effect: Precisely controlling the thickness of the nanosensing structure helps to achieve laser detection for laser sensor chips with a certain wavelength.

[0026] In an optional implementation, along the second direction of the epitaxial structure, the length ratio of the single-mode filtering region, the power amplification region, and the functional region in the ridge structure is 3:3:4.

[0027] Beneficial effect: By limiting the ratio of the length of the area, on the one hand, it is possible to effectively ensure the coordination of each area, achieve laser output with higher output power, and further improve the integration; on the other hand, it is convenient to adjust the specific length of each part along the second direction under the premise of proportion, and the process parameters have a high degree of freedom and are not limited by the intensity, spectrum and other parameter requirements of the detection laser.

[0028] In an optional embodiment, the width dimension of the single-mode filter area in the first direction is smaller than the width dimension of the functional area in the first direction; and the width dimension of the power amplification area in the first direction gradually increases from one side of the single-mode filter area toward one side of the functional area.

[0029] Beneficial effect: By setting the lateral dimensions, the functions of each part are ensured, and the overall enhancement effect on laser emission is improved.

[0030] In an optional implementation, the width of the single-mode filter area in the first direction is 4 μm, the width of the functional area in the first direction is 7 μm, and the projection of the power amplification area on the surface of the epitaxial structure is an equilateral trapezoid.

[0031] Beneficial effect: The width of the single-mode filter area in the first direction is set to 4μm, and the width of the functional area in the first direction is set to 7μm, then the power amplification area is an equilateral trapezoid with a short side of 4μm and a long side of 7μm. The single-mode filter area generates a 750nm single mode by limiting the lateral dimension to 4μm; but because the lateral dimension is too small, it will affect the insufficient output power of the single mode, so the power amplification area is connected in the middle, and the single mode will achieve power amplification after passing through the power amplification area, which is convenient for the subsequent signal adjustment of the laser sensor; the rightmost functional area also allows multiple modes to exist because the lateral dimension is 7μm, so the laser passing through the power amplification area will continue to amplify the power in this area, and finally achieve efficient laser output.

[0032] In an optional embodiment, the angles between the sidewalls of the first trench and the sidewalls of the second trench and the surface normal of the epitaxial structure are in the range of 1° to 2°.

[0033] Beneficial effect: The sidewall surface of the ridge structure is kept as close to vertical as possible to reduce photon loss and promote efficient laser output.

[0034] In an optional embodiment, after forming the oblique groove in the functional area and before forming the nanosensor structure on the insulating layer of the sensing surface, the preparation method further includes: forming a first electrode layer, the first electrode layer at least covering the surface of the ridge structure exposed by the first opening.

[0035] Beneficial effect: The first electrode layer contacts the surface of the exposed ridge structure through the first opening of the insulating layer, so as to facilitate subsequent wire bonding on the first electrode layer to connect to an external power source and inject current into the ridge structure of the epitaxial structure.

[0036] In an optional embodiment, after forming the oblique groove in the functional area and before forming the first electrode layer, the preparation method further includes: forming a seed layer on the side of the insulating layer away from the substrate layer, the seed layer covering the surface of the insulating layer outside the sensing surface and the surface of the ridge structure exposed by the first opening, and the first electrode layer is electrically connected to the ridge structure through the seed layer.

[0037] Beneficial effect: The seed layer helps to form an ohmic contact on the surface of the ridge structure, thereby enhancing the current injection effect of the first electrode layer.

[0038] In an optional implementation, after forming the nanosensing structure on the insulating layer of the sensing surface, the method further includes: forming a second electrode layer on a surface of the substrate layer facing away from the active layer.

[0039] Beneficial effect: The first electrode layer and the second electrode layer are suitable for connecting to the positive and negative electrodes of an external power source respectively, so as to generate photons in the active layer in the epitaxial structure, thereby forming laser emission.

[0040] In an optional embodiment, after forming a second electrode layer on the surface of the substrate layer facing away from the active layer, it also includes: forming a high reflection film layer on the end face of the epitaxial structure along the second direction relatively close to the single-mode filter area; the high reflection film layer includes a composite structure of silicon and silicon nitride.

[0041] Beneficial effect: In the second direction, a high-reflection film layer including stacked silicon and silicon nitride is arranged at one end of the single-mode filter area of ​​the epitaxial structure that generates single-mode laser. The silicon directly contacts the side wall surface of the epitaxial structure. The reflectivity of the high-reflection film layer composed of silicon and silicon nitride is 96%, so that the laser generated by the active layer can be emitted as much as possible.

[0042] In a second aspect, the present invention further provides an edge-emitting laser sensor chip, comprising: an epitaxial structure, a ridge structure, an insulating layer, an oblique groove and a nanosensing structure, wherein the epitaxial structure comprises a substrate layer, a lower cladding layer, a lower waveguide layer, an active layer, an upper waveguide layer, an upper cladding layer and a cover layer which are stacked, wherein the active layer is used to generate laser light; the ridge structure is formed on the epitaxial structure along a second direction, a first groove and a second groove which are connected to the ridge structure are formed on both sides of the ridge structure in the first direction, the first groove and the second groove extend from the cover layer to the upper waveguide layer, the ridge structure comprises a single-mode filtering area, a power amplification area and a functional area which are sequentially arranged along the second direction, and the first direction and the second direction are perpendicular to each other; the insulating layer is formed on The cover layer is away from the surface of one side of the substrate layer, and the insulating layer includes a first opening and a second opening spaced apart along a second direction, the first opening at least exposes a portion of the surface of the single-mode filtering area and the power amplification area of ​​the ridge structure to form a current injection surface; the second opening exposes a portion of the surface of the functional area of ​​the ridge structure, and the surface of the functional area between the first opening and the second opening forms a sensing surface; an oblique groove is formed in the functional area, and the oblique groove extends from the second opening to at least pass through the active layer, and the sidewall surface of the oblique groove is suitable for reflecting the laser propagating along the second direction in the active layer to the sensing surface; a nano-sensing structure is formed on the insulating layer on the sensing surface, and the nano-sensing structure is suitable for carrying a substance to be detected.

[0043] Beneficial effects: The edge-emitting laser sensor chip of the present invention has an oblique groove integrally formed in the ridge structure of the epitaxial structure, which can change the original laser optical path in the laser sensor chip, convert the laser lasing horizontally in the active layer into the laser emitting on the sensing surface facing the epitaxial structure surface, realize the optical path change from the side wall light to the vertical cavity surface light, and is integrally formed in the epitaxial structure, with high integration, and can be used for the process route of conventional laser preparation, without the need for complex optical path and packaging system. Furthermore, a nanosensing structure is arranged on the sensing surface, and a plurality of coupling modes are excited in the nanosensing structure by using the surface plasmon resonance mode and the localized surface plasmon resonance mode. When a certain substance to be detected with different refractive index is placed on the nanosensing structure, the spectral absorption of the changed laser is obtained by the change of the dominant coupling mode of the nanosensing structure, thereby obtaining the offset of the wavelength, and the relationship between the refractive index of the substance to be detected and the wavelength offset can be established through the offset, so that the refractive index of the unknown substance to be detected can be obtained, and this detection method has a wide range of applications and is simple and efficient.

[0044] In an optional embodiment, it also includes: a seed layer, a first electrode layer, a second electrode layer and a high reflection film layer, the seed layer is formed on the side of the insulating layer away from the substrate layer, the seed layer covers the surface of the insulating layer outside the sensing surface and the surface of the ridge structure exposed by the first opening; the first electrode layer is formed on the seed layer to be electrically connected to the ridge structure; the second electrode layer is formed on the surface of the side of the substrate layer away from the active layer; the high reflection film layer is formed on the end face of the epitaxial structure along the second direction relatively close to the single-mode filter area, and the high reflection film layer includes a composite structure of silicon and silicon nitride.

[0045] Beneficial effects: The seed layer helps to form an ohmic contact on the surface of the ridge structure, thereby enhancing the current injection effect of the first electrode layer. The first electrode layer covered on the seed layer can ensure the input range of the current after connecting to the external excitation, so that the current at various locations eventually quickly enters the ridge structure and generates lasers in the active layer. The first electrode layer and the second electrode layer are suitable for connecting the positive and negative electrodes of the external power supply respectively to generate photons in the active layer in the epitaxial structure, thereby forming laser emission. The reflectivity of the high-reflective film layer composed of silicon and silicon nitride is as high as 96%, so that the laser generated by the active layer can be emitted as much as possible. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0047] Figure 1 is a schematic flow chart of a method for preparing an edge-emitting laser sensor chip according to an embodiment of the present invention;

[0048] Figure 2 is a schematic structural diagram of an epitaxial structure of an embodiment of the present invention;

[0049] Figure 3 is a top view schematically showing a first mask layer disposed on the surface of an epitaxial structure according to an embodiment of the present invention;

[0050] Figure 4 yes Figure 3 Schematic diagram of the cross-sectional structure at A1-A1;

[0051] Figure 5 is a schematic top view of a ridge structure formed on the surface of an epitaxial structure according to an embodiment of the present invention;

[0052] Figure 6 yes Figure 5 A schematic diagram of the cross-sectional structure at A2-A2 in the middle;

[0053] Figure 7 is a schematic top view of an embodiment of the present invention after an initial insulating layer and a second mask layer are provided on the surface of the epitaxial structure;

[0054] Figure 8 yes Figure 7 A schematic diagram of the cross-sectional structure at A3-A3 in the middle;

[0055] Fig. 9 is a schematic top view of an embodiment of the present invention after an insulating layer is formed on the surface of the epitaxial structure;

[0056] Fig.10 yes Fig. 9 A schematic diagram of the cross-sectional structure at A4-A4;

[0057] Fig.11 yes Fig. 9 A schematic diagram of the partial cross-sectional structure at B1-B1 in the middle;

[0058] Fig.12 is a top view schematic diagram of an embodiment of the present invention in which a third mask layer is provided on one side of the insulating layer to form an oblique groove;

[0059] Fig.13 yes Fig.12 A schematic diagram of the cross-sectional structure at A5-A5;

[0060] Fig.14 yes Fig.12 A schematic diagram of a partial cross-sectional structure at B2-B2 in the middle;

[0061] Fig.15 is a schematic top view of an embodiment of the present invention after an oblique groove is formed in a functional area;

[0062] Fig.16 yes Fig.15 A schematic diagram of a partial cross-sectional structure at B3-B3 in the middle;

[0063] Fig.17 is a schematic top view of a nanosensing structure formed on a sensing plane according to an embodiment of the present invention;

[0064] Fig.18 yes Fig.17 A schematic diagram of a partial cross-sectional structure at B4-B4;

[0065] Fig.19 is a schematic top view of a nanosensing structure according to an embodiment of the present invention;

[0066] Fig. 20 is a schematic structural diagram of a nanosensor structure according to an embodiment of the present invention;

[0067] Fig.21 is a schematic structural diagram of an edge-emitting laser sensor chip according to an embodiment of the present invention;

[0068] Fig. 22 is a schematic top view of an edge-emitting laser sensor chip according to an embodiment of the present invention;

[0069] Fig.23 is a schematic top view of an embodiment of the present invention after a fourth mask layer is disposed on a sensing plane;

[0070] Fig.24 yes Fig.23 A schematic diagram of the partial cross-sectional structure at B5-B5 in the middle;

[0071] Fig.25 is a schematic top view of a chip having a fourth mask layer after a seed layer material is deposited on the surface of the chip according to an embodiment of the present invention;

[0072] Fig.26 yes Fig.25 A schematic diagram of the cross-sectional structure at A6-A6 in the middle;

[0073] Fig. 27 yes Fig.25 A schematic diagram of the partial cross-sectional structure at B6-B6 in the middle;

[0074] Fig.28 is a schematic top view of an embodiment of the present invention after the fourth mask layer is removed to form a seed layer;

[0075] Fig.29 yes Fig.28 A schematic diagram of the partial cross-sectional structure at B7-B7;

[0076] Fig.30 is a schematic cross-sectional view along a first direction after forming a first electrode layer according to an embodiment of the present invention;

[0077] Fig.31 is a schematic cross-sectional view of a side of the ridge structure close to the functional area along the second direction after the first electrode layer is formed in an embodiment of the present invention;

[0078] Fig.32 is a schematic cross-sectional view of a side of the ridge structure close to the functional area along the second direction after the first metal layer is formed in an embodiment of the present invention;

[0079] Fig.33 is a schematic cross-sectional view of a side of the ridge structure close to the functional area along the second direction after the dielectric spacer layer is formed according to an embodiment of the present invention;

[0080] Fig.34 is a cross-sectional schematic diagram of a ridge structure along the second direction close to a functional area of ​​an initial third metal layer formed according to an embodiment of the present invention;

[0081] Fig.35is a schematic cross-sectional view of a side of the ridge structure close to the functional area along the second direction after the third metal layer is formed in an embodiment of the present invention;

[0082] Fig.36 is a schematic cross-sectional view of a side of the ridge structure close to the functional area along the second direction after the substrate layer is thinned and the second electrode layer is formed in an embodiment of the present invention;

[0083] Fig.37 1 is a schematic cross-sectional view of the edge-emitting laser sensor chip in the second direction after a high-reflection film is formed according to an embodiment of the present invention.

[0084] Description of reference numerals:

[0085] 1. epitaxial structure; 11. substrate layer; 12. lower cladding layer; 13. lower waveguide layer; 14. active layer; 15. upper waveguide layer; 16. upper cladding layer; 17. cap layer; 18. first trench; 19. second trench;

[0086] 2. Ridge structure; 21. Single-mode filter area; 22. Power amplification area; 23. Functional area; 231. Sensing surface;

[0087] 3. Insulating layer; 31. First opening; 32. Second opening; 301. Initial insulating layer;

[0088] 4. Oblique groove;

[0089] 5. Nanosensing structure; 51. First metal layer; 52. Dielectric spacer layer; 53. Second metal layer; 503. Initial second metal layer; 531. Nanometal pillars;

[0090] 6. A first electrode layer;

[0091] 7. Seed layer;

[0092] 8. A second electrode layer;

[0093] 9. High reflective film layer;

[0094] 100, a first mask layer; 200, a second mask layer; 300, a third mask layer; 400, a fourth mask layer. DETAILED DESCRIPTION

[0095] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only some structures related to the present invention are shown in the accompanying drawings, rather than all structures. In the following description, the description of known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention. Various structural schematic diagrams according to embodiments of the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified for the purpose of clear expression, and some details may be omitted. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships between them are only exemplary, and may be deviated due to manufacturing tolerances or technical limitations in practice, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs. In the context of the present invention, when a layer / element is referred to as being "on" another layer / element, the layer / element may be directly on the other layer / element, or there may be an intermediate layer / element between them. In addition, if one layer / element is "on" another layer / element in one orientation, then when the orientation is reversed, the layer / element may be "below" the other layer / element.

[0096] Laser sensor chip technology has the advantages of high sensitivity and high precision in measuring the refractive index of unknown liquids. The technology of laser sensor chip to measure the refractive index of unknown liquids mainly relies on the combination of fiber laser sensing system and surface plasmon resonance (SPR) effect or localized surface plasmon resonance (LSPR).

[0097] Laser chips used for a variety of biochemical sensing detection need to accommodate the detection surface of the substance to be tested, so they need to use VCSEL (Vertical-Cavity Surface-Emitting Laser). However, when the VCSEL structure is used as the construction basis, in order to ensure good output beam characteristics, the working area of ​​the active layer must be limited to a smaller aperture, resulting in low laser output power. For example, the output power of traditional single-mode VCSEL is only 7mW~8mW, the application surface is narrow, and there are many limiting factors. However, when based on edge-emitting lasers as the construction basis, it is easy to achieve an output power of 100mW for single-mode edge-emitting lasers. Therefore, there is an urgent need for a laser chip that is both versatile and integrated to achieve efficient and accurate biochemical detection.

[0098] Based on this, reference Figures 1 to 37 This embodiment provides a method for preparing an edge-emitting laser sensor chip. Figure 1 The figure is a flow chart of a method for preparing an edge-emitting laser sensor chip, and the method comprises the following steps:

[0099] Step S101, forming an epitaxial structure 1, the epitaxial structure 1 includes a stacked substrate layer 11, a lower cladding layer 12, a lower waveguide layer 13, an active layer 14, an upper waveguide layer 15, an upper cladding layer 16 and a cap layer 17, wherein the active layer 14 is used to generate laser.

[0100] like Figure 2 As shown, the epitaxial structure 1 of this embodiment includes a substrate layer 11, a lower cladding layer 12, a lower waveguide layer 13, an active layer 14, an upper waveguide layer 15, an upper cladding layer 16 and a cap layer 17 stacked from bottom to top, and a multi-layer quantum well is arranged in the active layer 14 to generate laser. Exemplarily, the laser wavelength of the epitaxial structure 1 used in this embodiment is 750nm, and the epitaxial structure 1 is a GaAs / AIGaAs system as a whole, for example, the topmost cap layer 17 is highly doped GaAs, which can realize current injection by forming an ohmic contact with the metal eutectic, and the remaining layers also contain a certain proportion of AIGaAs components.

[0101] Step S102, forming a first groove 18 and a second groove 19 spaced apart along a first direction on the epitaxial structure 1, the first groove 18 and the second groove 19 extend from the cover layer 17 to the upper waveguide layer 15, and a ridge structure 2 is formed between the first groove 18 and the second groove 19, the ridge structure 2 includes a single-mode filtering area 21, a power amplification area 22 and a functional area 23 arranged in sequence along a second direction, and the first direction and the second direction are perpendicular to each other.

[0102] A photoresist is coated on the upper surface of the epitaxial structure 1, and the photoresist is exposed and developed to remove part of the photoresist by photolithography to form a first mask layer 100, and the first mask layer 100 exposes a part of the uppermost cover of the epitaxial structure 1, such as Figure 3 and Figure 4 As shown, the thickness of the first mask layer 100 is set to 1.4 μm in this embodiment. The epitaxial structure 1 exposed by the first mask layer 100 is etched. For example, inductively coupled plasma etching (ICP etching) is used to etch the unshielded area of ​​the first mask layer 100, and the etching penetrates the cap layer 17 and the upper cladding layer 16 until the upper waveguide layer 15 is etched to form a first groove 18 and a second groove 19 spaced apart in the first direction. The portion sandwiched between the first groove 18 and the second groove 19 forms a ridge structure 2. The ridge structure 2 includes a single-mode filter area 21, a power amplification area 22 and a functional area 23 in the second direction, as shown in FIG. Figure 5 and Figure 6As shown. The single-mode filter area 21 generates a single-mode laser by limiting the lateral size; the power amplification area 22 is used to amplify the power of the single-mode laser passing therethrough, so as to facilitate the subsequent signal adjustment of the laser sensor; the functional area 23 amplifies the power of the multi-mode lasers passing therethrough, including continuing to amplify the power of the above-mentioned single-mode laser. It should be noted that the first direction in this embodiment is the width direction of the laser sensor chip, and the second direction is the length direction of the laser sensor chip, that is, the length direction of the laser cavity. The etching depth of the above-mentioned ICP etching is 1μm, and the etching width is 25μm, that is, the depth of the first groove 18 and the second groove 19 is 1μm, the etching width in the first direction is 25μm, and the etching length in the second direction can be the same as the length of the epitaxial structure 1; since the size of the epitaxial structure 1 such as the ridge structure 2 is very small relative to the initial complete epitaxial structure 1, in order to clearly illustrate each structure in this embodiment, some structures are relatively enlarged or reduced, and the specific values ​​are subject to the given values.

[0103] In step S103, an insulating layer 3 is formed on the surface of the cover layer 17 on one side away from the substrate layer 11, and the insulating layer 3 includes a first opening 31 and a second opening 32 spaced apart along the second direction, and the first opening 31 at least exposes a portion of the surface of the single-mode filter area 21 and the power amplification area 22 of the ridge structure 2 to form a current injection surface; the second opening 32 exposes a portion of the surface of the functional area 23 of the ridge structure 2, and the surface of the functional area 23 between the first opening 31 and the second opening 32 forms a sensing surface 231.

[0104] For example, the insulating layer 3 of this embodiment is made of silicon nitride material, which has good surface characteristics and insulating properties. In this embodiment, silicon nitride is first deposited on the entire upper surface of the cap layer 17 to form an initial insulating layer 301, and then a photoresist is coated on the entire surface of the initial insulating layer 301, and the photoresist is exposed and developed to remove part of the photoresist by photolithography to form a second mask layer 200, such as Figure 7 and Figure 8 The second mask layer 200 exposes a portion of the initial insulating layer 301 located on the upper surface of the ridge structure 2, and this portion of the initial insulating layer 301 is etched to form a first opening 31 and a second opening 32 spaced apart in the second direction, see Fig. 9 The first opening 31 continuously exposes the single-mode filter area 21, the power amplification area 22 and a part of the length of the functional area 23 from left to right, forming a current injection surface for connecting external excitation, that is, forming an ohmic contact window, such as Fig.10 As shown; the second opening 32 is located at the edge area on the right side of the functional area 23, and the insulating layer 3 of this part is removed to facilitate the subsequent etching and forming of the oblique groove 4. The maximum width of the first opening 31 and the second opening 32 in the first direction is the same; in this embodiment, the insulating layer 3 retained between the first opening 31 and the second opening 32 in the second direction, as shown Fig.11 As shown, the insulating layer 3 on the sensing surface 231 ensures relative insulation between the epitaxial structure 1 and the subsequently formed nanosensing structure 5, and can adjust the luminous intensity and phase of the laser reaching the nanosensing structure 5 to ensure the accuracy of laser detection on the nanosensing structure 5. It should be noted that the insulating layer 3 covers the inner wall surface of the first groove 18 and the second groove 19 ( Fig. 9 The inner wall surfaces of the first groove 18 and the second groove 19 shown in the figure are not provided with the insulating layer 3 (illustrated).

[0105] Step S104 , forming an oblique groove 4 in the functional area 23 , the oblique groove 4 extending from the second opening 32 to at least pass through the active layer 14 , so that the sidewall surface of the oblique groove 4 reflects the laser propagating in the second direction in the active layer 14 to the sensing surface 231 for emission.

[0106] Exemplarily, a photoresist is first coated on one side of the upper surface of the epitaxial structure 1 having the insulating layer 3, and the region where the second opening 32 is located on the photoresist is exposed and developed to form a third mask layer 300 covering the region outside the second opening 32, so that the second opening 32 is exposed. Figure 12 to Figure 14 As shown, the third mask layer 300 blocks other areas to facilitate etching at the second opening 32; Fig.14 At this time, an oblique etching process is performed from the second opening 32, so that the structural layer in the functional area 23 is partially removed, forming an oblique groove 4 extending from the second opening 32 to the functional area 23; then the third mask layer 300 is removed, as shown in FIG. Fig.15 and Fig.16 As shown, when the laser sensor chip is powered on and external excitation is applied, the quantum well in the active layer 14 generates photons under the action of the external excitation, and finally forms a laser propagating along the second direction. When the laser reaches the oblique groove 4, the side wall surface of the oblique groove 4 reflects the laser, so that the laser is reflected upward to the sensing surface 231.

[0107] Step S105 , forming a nanometer sensing structure 5 on the insulating layer 3 of the sensing surface 231 , wherein the nanometer sensing structure 5 is suitable for carrying a substance to be detected.

[0108] refer to Fig.17 and Fig.18, a nanosensing structure 5 is formed on the insulating layer 3 located on the sensing surface 231 between the first opening 31 and the second opening 32. The nanosensing structure 5 of this embodiment has a surface plasmon resonance mode (Surface Plasmon Resonance, hereinafter referred to as SPR mode) and a localized surface plasmon resonance mode (Localized Surface Plasmon Resonance, hereinafter referred to as LSPR mode), which can excite multiple coupling modes in the nanosensing structure 5, and has high detection sensitivity. When a certain substance to be detected with different refractive indices is placed on the nanosensing structure 5, the dominant coupling mode of the nanosensing structure 5 will change, at this time, the spectral absorption of the laser will change, and the wavelength will shift to a certain extent, thereby establishing a relationship between the refractive index and wavelength shift of the substance to be detected, so that when the substance to be detected with an unknown refractive index is placed later, the refractive index of the substance to be detected can be obtained by reading the wavelength shift, that is, the refractive index of the substance to be detected can be obtained by the laser sensor chip of this embodiment, and this method has a wide range of applications, and the detection is simple and efficient.

[0109] For example, a solution with a known refractive index can be changed by adjusting the concentration. If the solution with a known refractive index is placed on the nanosensing structure 5, the wavelength corresponding to the solution with different refractive indices can be measured by laser, so as to establish the relationship between the wavelength and concentration of the solution, that is, to complete the calibration of the refractive index and wavelength of the solution; then, according to the calibration, when a solution with an unknown refractive index is placed on the nanosensing structure 5 of the laser sensor chip of this embodiment, the accurate refractive index of the solution can be inferred based on the read wavelength.

[0110] In summary, the preparation method of the edge-emitting laser sensor chip of this embodiment, by forming an oblique groove 4 in the ridge structure 2 of the epitaxial structure 1, changes the original laser optical path in the laser sensor chip, and converts the laser horizontally lasing in the active layer 14 into a laser facing the sensing surface 231 on the surface of the epitaxial structure 1, so as to realize the change of the optical path from the side wall light to the vertical cavity surface light, and the integrated epitaxial structure 1 is formed, with high integration, and the process route of conventional laser preparation can be universal, without complex optical path and packaging system, which helps to further realize the miniaturization, low cost and reusability of laser detection. Furthermore, a nano-sensing structure 5 is set on the sensing surface 231, and a plurality of coupling modes are excited in the nano-sensing structure 5 by using the surface plasmon resonance mode and the localized surface plasmon resonance mode. When a certain substance to be detected with a different refractive index is placed on the nanosensing structure 5, the spectral absorption of the laser is changed by the change of the dominant coupling mode of the nanosensing structure 5, thereby obtaining the offset of the wavelength. The relationship between the refractive index of the substance to be detected and the wavelength offset can be established through the offset, so that the refractive index of the unknown substance to be detected can be obtained. This detection method has a wide range of applications and is simple and efficient.

[0111] As a preferred implementation, in this embodiment, the angle between the extension direction of the oblique groove 4 and the sensing surface 231 is 45°.

[0112] By setting the inclined groove 4 at an angle of 45°, the horizontally emitted laser in the active layer 14 can be converted into a vertically upward laser, which helps to simplify the calculation of the vertically upward laser optical path, and further simplifies the preparation of each structural layer on the sensing surface 231, ensuring the consistency and output power of the laser emitted to various parts of the nanosensing structure 5.

[0113] In one embodiment, in the step S104 of forming the oblique groove 4 in the functional area 23, reactive ion beam etching is used to etch from the second opening 32 toward the functional area 23 to form the oblique groove 4 with an angle of 45° to the sensing surface 231; the etching gas used in the reactive ion beam etching method is a mixture of chlorine and argon, or a mixture of carbon tetrachloride and argon.

[0114] The use of reactive ion beam etching can achieve high etching rate and anisotropy, which helps to form a clear and well-defined inner wall of the groove, and ion bombardment can better control the etching direction, facilitating precise control of the inclination angle of the bevel; in addition, the use of inert gas as an auxiliary etching gas can improve the stability of etching and avoid unnecessary damage to the epitaxial structure 1.

[0115] Furthermore, in step S103 of forming an insulating layer 3 on the surface of the side of the cap layer 17 away from the substrate layer 11, a portion of the insulating layer 3 is etched by reactive ion beam etching to form a first opening 31 and a second opening 32 on the insulating layer 3; the ratio of the etching rate of the insulating layer 3 to the etching rate of the epitaxial structure 1 is greater than 10:1.

[0116] That is, both etching to form the oblique groove 4 and etching the insulating layer 3 adopt reactive ion beam etching, and the silicon nitride material for etching the insulating layer 3 and the GaAs / AIGaAs system for etching the functional area 23 are set, and the etching rate ratio between the two is greater than 10:1. By adjusting the proportion of physical and chemical etching, the side wall of the oblique groove 4 is made smooth, which is comparable to the physically understood resonance surface.

[0117] On the basis of the above scheme, in this embodiment, the optical thickness of the insulating layer 3 is set to an integer multiple of half the wavelength of the laser, and the optical thickness of the insulating layer 3 is the product of the film thickness of the insulating layer 3 and the refractive index of the insulating layer 3.

[0118] By setting the thickness of the insulating layer 3 to an integer multiple of the half wavelength of the laser, the thickness of the insulating layer 3 can be precisely controlled to ensure that the laser that is transformed from horizontal lasing to vertical upward lasing under the action of the 45° inclined groove 4 will not affect the intensity and phase of the laser when it is emitted through the insulating layer 3, thereby ensuring the emission consistency and output power of the laser.

[0119] For example, in this embodiment, taking the laser wavelength of 750nm as an example, the half-wavelength is 375nm, that is, the thickness of the insulating layer 3 is controlled to be half-wavelength / refractive index. The refractive index of the silicon nitride material is 2.01, so the thickness of the insulating layer 3 called silicon nitride material should be precisely controlled at 186nm. In the specific practice, it can be slightly offset by ±10nm to ensure the intensity and phase of the laser passing through the insulating layer 3.

[0120] In one embodiment, the nanosensing structure 5 includes: a first metal layer 51 , a dielectric spacer layer 52 and a second metal layer 53 which are stacked, wherein the first metal layer 51 is disposed close to the insulating layer 3 , and the second metal layer 53 includes a grating structure formed by a plurality of nanometal pillars 531 .

[0121] See also Figures 17 to 20, the nanosensing structure 5 includes a first metal layer 51, a dielectric spacer layer 52, and a second metal layer 53 stacked from bottom to top, and the second metal layer 53 is formed into a grating structure formed by a plurality of nanometal pillars 531. Exemplarily, the materials of the first metal layer 51 and the second metal layer 53 are both metal gold, and the dielectric spacer layer 52 is silicon oxide nitride (SiON). In this embodiment, on the first hand, a two-dimensional periodic grating composed of a plurality of nanometal pillars 531 placed on the dielectric spacer layer 52 constitutes the sensing part, and the dielectric spacer layer 52 and the nanometal pillars 531 are both placed on the thin metal film of the first metal layer 51, thereby generating an SPR mode on the first metal layer 51. On the second hand, in this embodiment, such a nanosensing structure 5 includes: an LSPR mode excited in the grating structure of the second metal layer 53 on the top layer, an LSPR mode excited at the interface between the grating structure and the dielectric spacer layer 52, and a Fabry-Perot interference mode between the first metal layer 51 and the second metal layer 53 on both sides of the dielectric spacer layer 52. The above-mentioned multiple modes can make different substances to be detected produce different light absorption changes under the laser wavelength, thereby completing high-precision sensitive detection. Thirdly, the nanosensing structure 5 in this embodiment is designed to have at least two peaks in the absorption spectrum and two corresponding anti-peaks in the reflection spectrum, so that these resonances during the above-mentioned detection occur at the resonant frequencies of the LSPR and SPR modes, which can correspond to wavelengths of 750nm and 944nm.

[0122] This embodiment specifically uses 750nm as the excitation light source, and the thickness of the first metal layer 51 is set to 35nm, the thickness of the dielectric spacer layer 52 is set to 40nm, and the thickness of the second metal layer 53 is set to 35nm; such thickness control can realize laser detection for the laser sensor chip with a certain wavelength (750nm).

[0123] refer to Fig.19 In this embodiment, the second metal layer 53 has a plurality of nano-metal pillars 531, specifically due to size limitations, Fig.19 Not fully shown.

[0124] Specifically, the plurality of nanometal pillars 531 of the second metal layer 53 of the present embodiment are arranged in an array. The nanometal pillars 531 are square pillars with a side length of 200 nm and a height of 30 nm. The spacing between adjacent nanometal pillars 531 is 200 nm.

[0125] refer to Fig.17 and Fig.19In this embodiment, after the initial second metal layer 503 is grown on the entire surface of the dielectric material layer, the nano-metal pillars 531 are formed by a focused ion beam etching method. The surface of the first metal layer 51 and the dielectric material layer above the sensing surface 231 is a rectangular surface of 20μm×7μm, and the nano-metal pillars 531 of the second metal layer 53 are prepared in 35 in the first direction where the length is 7μm, and in the second direction where the length is 20μm, 100 are prepared to ensure the comprehensiveness of laser detection in this area. Fig.17 and Fig.19 It is only for illustration and not fully shown.

[0126] In one embodiment, reference Fig.21 and Fig. 22 Along the second direction of the epitaxial structure 1 , the length ratio of the single-mode filtering region 21 , the power amplification region 22 , and the functional region 23 in the ridge structure 2 is 3:3:4.

[0127] For example, in this embodiment, the size of the epitaxial structure 1 of the entire laser sensor chip is set to 4000μm×400μm, that is, the width along the first direction is 400μm, and the length along the second direction is 4000μm. Therefore, the length of the single-mode filter area 21 is set to 1200μm, the length of the power amplification area 22 is set to 1200μm, and the length of the functional area 23 is set to 1600μm. Such a ratio limitation can effectively ensure the coordination of various areas and achieve laser output with higher output power.

[0128] In this embodiment, a highly integrated small-scale sensor detection system is formed by a single-mode 750nm edge-emitting laser sensor chip. The process parameters have a high degree of freedom and are not limited by the intensity, spectrum and other parameters of the detection laser not meeting the requirements. Moreover, the key parameters can be adjusted by adjusting the overall specific cavity length, that is, the specific length of each part along the second direction, and the proportion of different functional parts.

[0129] Furthermore, the width dimension of the single-mode filter area 21 in the first direction is set to be smaller than the width dimension of the functional area 23 in the first direction; and the width dimension of the power amplification area 22 in the first direction gradually increases from one side of the single-mode filter area 21 toward one side of the functional area 23.

[0130] For example, in this embodiment, the width of the single-mode filter area 21 in the first direction is set to 4μm, and the width of the functional area 23 in the first direction is set to 7μm, then the power amplification area 22 is an equilateral trapezoid with a short side of 4μm and a long side of 7μm. The single-mode filter area 21 generates a 750nm single mode by limiting the lateral dimension to 4μm; but because the lateral dimension is too small, it will affect the insufficient output power of the single mode, so the power amplification area 22 is connected in the middle, and the single mode will achieve power amplification after passing through the power amplification area 22, which is convenient for the subsequent signal adjustment of the laser sensor; the rightmost functional area 23 also allows multiple modes to exist because of the lateral dimension of 7μm, so the laser passing through the power amplification area 22 will continue to amplify the power in this area, and finally achieve efficient output of the laser.

[0131] In one embodiment, the angle between the sidewall of the first groove 18 and the sidewall of the second groove 19 and the surface normal of the epitaxial structure 1 is in the range of 1° to 2°. The sidewall surface of the ridge structure 2 is kept as close to vertical as possible to reduce photon loss and promote efficient laser output.

[0132] In one embodiment, after step S104 of forming the oblique groove 4 in the functional area 23 and before step S105 of forming the nanosensing structure 5 on the insulating layer 3 of the sensing surface 231, the preparation method of this embodiment further includes: forming a first electrode layer 6, the first electrode layer 6 at least covering the surface of the ridge structure 2 exposed by the first opening 31.

[0133] Exemplarily, the first electrode layer 6 can be a gold thin film formed by electroplating, and the first electrode layer 6 contacts the surface of the exposed ridge structure 2 through the first opening 31 of the insulating layer 3, so as to facilitate subsequent wire bonding on the first electrode layer 6 to connect to an external power supply and inject current at the ridge structure 2 of the epitaxial structure 1.

[0134] Based on the above scheme, refer to Figure 22 to Figure 29 , after step S104 of forming the oblique groove 4 in the functional area 23 and before the above-mentioned formation of the first electrode layer 6, it also includes: forming a seed layer 7 on the side of the insulating layer 3 away from the substrate layer 11, the seed layer 7 covers the surface of the insulating layer 3 outside the sensing surface 231 and the surface of the ridge structure 2 exposed by the first opening 31, and the first electrode layer 6 is electrically connected to the ridge structure 2 through the seed layer 7.

[0135] Specifically, firstly, a fourth mask layer 400 is disposed on a portion of the insulating layer 3. The fourth mask layer 400 is also a photoresist. The fourth mask layer 400 at least covers the insulating layer 3 above the sensing surface 231. Fig.24 Specifically in this embodiment, Fig.23As shown, the formed fourth mask layer 400 covers the sensing surface 231, the second opening 32, and part of the first groove 18 and part of the second groove 19 on both sides of the sensing surface 231 and the second opening 32 along the first direction. The size of the fourth mask layer 400 in this embodiment is 22μm×57μm, that is, the size in the second direction is 22μm, including 20μm of the sensing area and 2μm of the second opening 32; the size in the first direction is 57μm, including 25μm of the first groove 18, 25μm of the second groove 19, and 7μm of the width of the ridge structure 2 in the functional area 23. The fourth mask layer 400 is extended outward to ensure the absolute cleanliness of the sensing area. Then, the seed layer 7 material is deposited on one side of the upper surface of the epitaxial structure 1, referring to Figure 25 to Figure 27 In this embodiment, the seed layer 7 is made of metal gold; and then the fourth mask layer 400 is removed by a lift-off process, that is, the seed layer 7 material in the sensing area is removed to form a seed layer 7, such as Fig.28 and Fig.29 The seed layer 7 helps to form an ohmic contact on the surface of the ridge structure 2 , thereby enhancing the current injection effect of the first electrode layer 6 .

[0136] In this embodiment, after the seed layer 7 is formed, the first electrode layer 6 is then covered in the region where the seed layer 7 is located. Fig.30 and Fig.31 , to ensure the input range of the current after connecting to the external excitation, so that the current at various places finally quickly enters the ridge structure 2 and generates laser in the active layer 14. In addition, the same mask as that for forming the seed layer 7 can be used when forming the first electrode layer 6, which helps to simplify the process, and the first electrode layer 6 is formed by electroplating, and the electrode material will not be deposited on the photoresist, so lift-off stripping technology is not required, and only degumming and cleaning are required after electroplating. The thickness of the first electrode layer 6 in this embodiment is 2μm.

[0137] In this embodiment, after the seed layer 7 and the first electrode layer 6 are formed, the first metal layer 51, the dielectric spacer layer 52 and the initial second metal layer 503 are formed on the sensing surface 231 in sequence, and then the initial second metal layer 503 is etched to form a grating structure composed of nano metal pillars 531, thereby finally forming a nano sensor structure 5, such as Figure 32 to Figure 35 As shown, the arrow in the figure indicates the propagation path of the laser.

[0138] It is worth noting that the first metal layer 51 and the second metal layer 53 can be deposited on the entire surface at the beginning of deposition, and the preparation process is relatively simple. This is because since they are both metal materials, even if the first metal layer 51 and the second metal layer 53 are deposited in other areas, they will not affect the metal connection and current injection in other areas. However, the dielectric spacer layer 52 only needs to be formed above the sensing surface 231. In the specific formation process, the dielectric spacer material deposited on the surface outside the sensing surface 231 needs to be removed.

[0139] refer to Fig.36 After the step S105 of forming the nano-sensing structure 5 on the insulating layer 3 of the sensing surface 231 , the method further includes: forming a second electrode layer 8 on a surface of the substrate layer 11 which is away from the active layer 14 .

[0140] Similarly, the second electrode layer 8 can also be made of metal gold, and the first electrode layer 6 and the second electrode layer 8 are suitable for connecting the positive and negative electrodes of the external power supply respectively, so as to generate photons in the active layer 14 in the epitaxial structure 1, thereby forming laser emission. It should be noted that before forming the second electrode layer 8, the substrate layer 11 needs to be thinned to ensure the efficiency of current injection. From then on, the light-emitting part of the edge-emitting laser sensor chip of this embodiment is completed.

[0141] In one embodiment, after forming the second electrode layer 8 on the surface of the substrate layer 11 facing away from the active layer 14, the preparation method further includes: forming a high-reflective film layer 9 on the end face of the epitaxial structure 1 relatively close to the single-mode filter area 21 along the second direction; the high-reflective film layer 9 includes a composite structure of silicon and silicon nitride.

[0142] refer to Fig.37 That is, after the integrated preparation of the light-emitting part of the laser sensor chip is completed, the cleavage and coating step is performed. Specifically, in the second direction, a high-reflective film layer 9 composed of stacked silicon and silicon nitride is arranged at one end of the single-mode filter area 21 of the epitaxial structure 1 that generates single-mode lasers, and the silicon directly contacts the side wall surface of the epitaxial structure 1. The reflectivity of the high-reflective film layer 9 composed of silicon and silicon nitride is 96%, so that the laser generated by the active layer 14 can be emitted as much as possible.

[0143] This embodiment also provides an edge emitting laser sensor chip, which is manufactured by the above-mentioned method for manufacturing an edge emitting laser sensor chip. Figures 2 to 37As shown, the edge-emitting laser sensor chip includes: an epitaxial structure 1, a ridge structure 2, an insulating layer 3, an oblique groove 4 and a nanosensor structure 5, wherein the epitaxial structure 1 includes a substrate layer 11, a lower cladding layer 12, a lower waveguide layer 13, an active layer 14, an upper waveguide layer 15, an upper cladding layer 16 and a cap layer 17 which are stacked, wherein the active layer 14 is used to generate laser light; the ridge structure 2 is formed on the epitaxial structure 1 along the second direction, and a first groove 18 and a second groove 19 which are connected to the ridge structure 2 are formed on both sides of the ridge structure 2 in the first direction, and the first groove 18 and the second groove 19 extend from the cap layer 17 to the upper waveguide layer 15, and the ridge structure 2 includes a single-mode filtering area 21, a power amplification area 22 and a functional area 23 which are sequentially arranged along the second direction, and the first direction and the second direction are perpendicular to each other; the insulating layer 3 is formed on the cap layer 17 away from the cap layer 17. On one side surface of the substrate layer 11, the insulating layer 3 includes a first opening 31 and a second opening 32 spaced apart along the second direction, the first opening 31 at least exposing a portion of the surface of the single-mode filtering area 21 and the power amplification area 22 of the ridge structure 2 to form a current injection surface; the second opening 32 exposes a portion of the surface of the functional area 23 of the ridge structure 2, and the surface of the functional area 23 between the first opening 31 and the second opening 32 forms a sensing surface 231; an oblique groove 4 is formed in the functional area 23, the oblique groove 4 extends from the second opening 32 to at least pass through the active layer 14, and the sidewall surface of the oblique groove 4 is suitable for reflecting the laser propagating along the second direction in the active layer 14 to the sensing surface 231; a nano-sensing structure 5 is formed on the insulating layer 3 of the sensing surface 231, and the nano-sensing structure 5 is suitable for carrying a substance to be detected.

[0144] In the preparation method of the edge-emitting laser sensor chip of this embodiment, the oblique groove 4 is integrally formed in the ridge structure 2 of the epitaxial structure 1, which can change the original laser optical path in the laser sensor chip, and convert the laser horizontally lasing in the active layer 14 into the laser facing the sensing surface 231 on the surface of the epitaxial structure 1, so as to realize the optical path change from the side wall light to the vertical cavity surface light, and the integral epitaxial structure 1 is formed, with high integration, and the process route of conventional laser preparation can be used, without complex optical path and packaging system. Furthermore, a nanosensing structure 5 is set on the sensing surface 231, and a plurality of coupling modes are excited in the nanosensing structure 5 by using the surface plasmon resonance mode and the localized surface plasmon resonance mode. When a certain substance to be detected with a different refractive index is placed on the nanosensing structure 5, the spectral absorption of the laser is changed by the change of the dominant coupling mode of the nanosensing structure 5, thereby obtaining the offset of the wavelength. The relationship between the refractive index of the substance to be detected and the wavelength offset can be established through the offset, so that the refractive index of the unknown substance to be detected can be obtained. This detection method has a wide range of applications and is simple and efficient.

[0145] refer to Fig.30 and Fig.37In one embodiment, the edge-emitting laser sensor chip further includes: a seed layer 7, a first electrode layer 6, a second electrode layer 8 and a high-reflection film layer 9, wherein the seed layer 7 is formed on the side of the insulating layer 3 facing away from the substrate layer 11, and the seed layer 7 covers the surface of the insulating layer 3 outside the sensing surface 231 and the surface of the ridge structure 2 exposed by the first opening 31; the first electrode layer 6 is formed on the seed layer 7 to be electrically connected to the ridge structure 2; the second electrode layer 8 is formed on the surface of the side of the substrate layer 11 facing away from the active layer 14; the high-reflection film layer 9 is formed on the end face of the epitaxial structure 1 relatively close to the single-mode filter area 21 along the second direction, and the high-reflection film layer 9 includes a composite structure of silicon and silicon nitride.

[0146] The seed layer 7 helps to form an ohmic contact on the surface of the ridge structure 2, thereby enhancing the current injection effect of the first electrode layer 6. The first electrode layer 6 covered on the seed layer 7 can ensure the input range of the current after connecting to the external excitation, so that the current at various places eventually quickly enters the ridge structure 2 and generates laser in the active layer 14. The first electrode layer 6 and the second electrode layer 8 are suitable for connecting the positive and negative poles of the external power supply respectively to generate photons in the active layer 14 in the epitaxial structure 1, thereby forming laser emission. The reflectivity of the high-reflective film layer 9 composed of silicon and silicon nitride is as high as 96%, so that the laser generated by the active layer 14 can be emitted as much as possible.

[0147] The further functional description of each of the above structures is the same as that of the above corresponding embodiments and will not be repeated here.

[0148] In the above description, the technical details of the patterning and etching of each layer are not described in detail. However, those skilled in the art should understand that various technical means can be used to form layers, regions, etc. of desired shapes. In addition, in order to form the same structure, those skilled in the art can also design methods that are not completely the same as the methods described above. In addition, although the various embodiments are described above separately, this does not mean that the measures in the various embodiments cannot be used in combination to advantage.

[0149] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A method for preparing an edge-emitting laser sensor chip, characterized in that: include: forming an epitaxial structure, wherein the epitaxial structure comprises a stacked substrate layer, a lower cladding layer, a lower waveguide layer, an active layer, an upper waveguide layer, an upper cladding layer and a cap layer, wherein the active layer is used to generate laser light; A first groove and a second groove spaced apart along a first direction are formed on the epitaxial structure, the first groove and the second groove extend from the cap layer to the upper waveguide layer, and a ridge structure is formed between the first groove and the second groove, the ridge structure includes a single-mode filter area, a power amplification area and a functional area sequentially arranged along a second direction, and the first direction and the second direction are perpendicular to each other; An insulating layer is formed on a surface of the cover layer away from the substrate layer, the insulating layer comprising a first opening and a second opening spaced apart along the second direction, the first opening at least exposing a portion of the surface of the single-mode filter region and the power amplification region of the ridge structure to form a current injection surface; The second opening exposes a portion of the surface of the functional area of ​​the ridge structure, and the surface of the functional area between the first opening and the second opening forms a sensing surface; forming an oblique groove in the functional area, the oblique groove extending from the second opening to at least pass through the active layer, so that the sidewall surface of the oblique groove reflects the laser propagating in the second direction in the active layer to the sensing surface for emission; A nanometer sensing structure is formed on the insulating layer of the sensing surface, and the nanometer sensing structure is suitable for carrying a substance to be detected.

2. The method for preparing an edge-emitting laser sensor chip according to claim 1, characterized in that: The included angle between the extending direction of the oblique groove and the sensing surface is 45°.

3. The method for preparing an edge-emitting laser sensor chip according to claim 2, characterized in that: In the step of forming the oblique groove in the functional area, reactive ion beam etching is used to etch from the second opening toward the functional area to form an oblique groove with an angle of 45° with the sensing surface; the etching gas used in the reactive ion beam etching method is a mixed gas of chlorine and argon, or a mixed gas of carbon tetrachloride and argon.

4. The method for preparing an edge-emitting laser sensor chip according to claim 3, characterized in that: In the step of forming an insulating layer on a surface of the cover layer away from the substrate layer, a portion of the insulating layer is etched by reactive ion beam etching to form the first opening and the second opening on the insulating layer; The ratio of the etching rate of etching the insulating layer to the etching rate of etching the epitaxial structure is greater than 10:

1.

5. The method for preparing an edge-emitting laser sensor chip according to claim 4, characterized in that: The optical thickness of the insulating layer is an integral multiple of a half wavelength of the laser, and the optical thickness of the insulating layer is the product of the film thickness of the insulating layer and the refractive index of the insulating layer.

6. The method for preparing an edge-emitting laser sensor chip according to claim 1, characterized in that: The nano-sensing structure comprises: a first metal layer, a dielectric spacer layer and a second metal layer which are stacked, wherein the first metal layer is arranged close to the insulating layer, and the second metal layer comprises a grating structure formed by a plurality of nano-metal pillars.

7. The method for preparing an edge-emitting laser sensor chip according to claim 6, characterized in that: The plurality of nano-metal pillars of the second metal layer are arranged in an array, and the nano-metal pillars are square pillars with a side length of 200 nm and a height of 30 nm; the spacing between adjacent nano-metal pillars is 200 nm.

8. The method for preparing an edge-emitting laser sensor chip according to claim 7, characterized in that: The thickness of the first metal layer is 30 nm, the thickness of the dielectric spacer layer is 40 nm, and the thickness of the second metal layer is 35 nm.

9. The method for preparing an edge-emitting laser sensor chip according to claim 1, characterized in that: Along the second direction of the epitaxial structure, the length ratio of the single-mode filtering area, the power amplification area and the functional area in the ridge structure is 3:3:

4.

10. The method for preparing an edge-emitting laser sensor chip according to claim 9, characterized in that: The width of the single-mode filter area in the first direction is smaller than the width of the functional area in the first direction; the width of the power amplification area in the first direction gradually increases from one side of the single-mode filter area to one side of the functional area.

11. The method for preparing an edge-emitting laser sensor chip according to claim 10, characterized in that: The width of the single-mode filter area in the first direction is 4 μm, the width of the functional area in the first direction is 7 μm, and the projection of the power amplification area on the surface of the epitaxial structure is an equilateral trapezoid.

12. The method for preparing an edge-emitting laser sensor chip according to claim 1, characterized in that: The angles between the sidewalls of the first trench and the sidewalls of the second trench and the surface normal of the epitaxial structure are in the range of 1° to 2°.

13. The method for preparing an edge-emitting laser sensor chip according to any one of claims 1 to 12, characterized in that: After forming the oblique grooves in the functional area and before forming the nanosensor structure on the insulating layer of the sensing surface, the preparation method further comprises: A first electrode layer is formed, wherein the first electrode layer at least covers the surface of the ridge structure exposed by the first opening.

14. The method for preparing an edge-emitting laser sensor chip according to claim 13, characterized in that: After forming the oblique groove in the functional area and before forming the first electrode layer, the preparation method further includes: A seed layer is formed on a side of the insulating layer away from the substrate layer, the seed layer covers the surface of the insulating layer outside the sensing surface and the surface of the ridge structure exposed by the first opening, and the first electrode layer is electrically connected to the ridge structure through the seed layer.

15. The method for preparing an edge-emitting laser sensor chip according to claim 14, characterized in that: After forming a nanometer sensing structure on the insulating layer of the sensing surface, the method further comprises: A second electrode layer is formed on a surface of the substrate layer that is away from the active layer.

16. The method for preparing an edge-emitting laser sensor chip according to claim 15, characterized in that: After forming a second electrode layer on a surface of the substrate layer facing away from the active layer, the method further comprises: A high-reflective film layer is formed on the end surface of the epitaxial structure relatively close to the single-mode filter area along the second direction; the high-reflective film layer includes a composite structure of silicon and silicon nitride.

17. An edge-emitting laser sensor chip, manufactured by the method for manufacturing an edge-emitting laser sensor chip according to any one of claims 1 to 16, characterized in that: include: An epitaxial structure, the epitaxial structure comprising a stacked substrate layer, a lower cladding layer, a lower waveguide layer, an active layer, an upper waveguide layer, an upper cladding layer and a cap layer, wherein the active layer is used to generate laser light; a ridge structure formed on the epitaxial structure along a second direction; The ridge structure forms a first groove and a second groove connected to the ridge structure on both sides of the ridge structure in the first direction, and the first groove and the second groove extend from the cover layer to the upper waveguide layer; the ridge structure includes a single-mode filtering area, a power amplification area and a functional area arranged in sequence along the second direction, and the first direction and the second direction are perpendicular to each other; an insulating layer formed on a surface of the cover layer away from the substrate layer, the insulating layer comprising a first opening and a second opening spaced apart along the second direction, the first opening at least exposing a portion of the surface of the single-mode filter region and the power amplification region of the ridge structure to form a current injection surface; The second opening exposes a portion of the surface of the functional area of ​​the ridge structure, and the surface of the functional area between the first opening and the second opening forms a sensing surface; an oblique groove formed in the functional area, the oblique groove extending from the second opening to at least pass through the active layer, and a sidewall surface of the oblique groove being suitable for reflecting the laser propagating in the second direction in the active layer to a sensing surface; A nanometer sensing structure is formed on the insulating layer of the sensing surface, and the nanometer sensing structure is suitable for carrying a substance to be detected.

18. The edge-emitting laser sensor chip according to claim 17, characterized in that: Also includes: a seed layer formed on a side of the insulating layer away from the substrate layer, the seed layer covering a surface of the insulating layer other than the sensing surface and a surface of the ridge structure exposed by the first opening; a first electrode layer formed on the seed layer to be electrically connected to the ridge structure; A second electrode layer is formed on a surface of the substrate layer facing away from the active layer; A high reflection film layer is formed on an end surface of the epitaxial structure relatively close to the single-mode filter region along the second direction, and the high reflection film layer comprises a composite structure of silicon and silicon nitride.

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