Secondary wedge-shaped spot size converter and preparation method thereof

Abstract

The invention relates to the technical field of optical communication, and provides a two-stage wedge-shaped spot size converter, which comprises a first-stage wedge-shaped structure, a second-stage wedge-shaped structure and a transmission waveguide structure, and is characterized in that the first-stage wedge-shaped structure is used for receiving optical fiber output light and carrying out spot size conversion on optical fiber light spots in the vertical direction; the second-stage wedge-shaped structure is used for receiving the first conversion light output by the first-stage wedge-shaped structure and carrying out die spot conversion on a light spot of the first conversion light in the horizontal direction; the transmission waveguide structure is used for receiving the second conversion light output by the second-stage wedge-shaped structure, performing spot size conversion on the second conversion light and then outputting the second conversion light, and the spot size of the light output by the transmission waveguide structure is consistent with the spot size of the waveguide. The invention also provides a preparation method of the secondary wedge-shaped spot size converter. According to the wedge-shaped spot size converter, spot size conversion can be achieved in a shorter length, high coupling efficiency is kept, efficient coupling can be met, coupling space can be saved, and the wedge-shaped spot size converter is a better choice compared with a conventional wedge-shaped spot size converter.

Description

Technical Field

[0001] The present invention relates to the field of optical communication technology, in particular to a two-stage wedge-shaped pattern spot converter and a preparation method thereof. Background Art

[0002] Semiconductor lasers made of indium phosphide have a wide range of applications in the market and mature preparation processes. When these semiconductor lasers are used for optical fiber transmission, the power coupled into the optical fiber limits the transmission distance of the laser. At this time, it is necessary to consider using a spot converter to improve the coupling efficiency.

[0003] The thickness of the waveguide core layer of semiconductor lasers is usually in the hundreds of nanometers, which is equivalent to the thickness of the quantum wells therein, which makes their spot size and shape different from the optical fiber spot. In silicon photonics technology, the coupling efficiency from waveguide to optical fiber is usually improved through the design of a spot converter. However, the conventional wedge-shaped coupler structure is not completely suitable for indium phosphide waveguides. The main reason is that the refractive index of the core cladding of the indium phosphide material and the refractive index of the core cladding of the silicon photonic device are too different. Under the influence of this reason, when the wedge-shaped structure is applied to an indium phosphide-based spot converter, the length will approach or even exceed the millimeter level. Too large a size will take up chip space, which is not conducive to chip integration. Summary of the invention

[0004] The object of the present invention is to provide a two-stage wedge-shaped pattern spot converter and a preparation method thereof, which can at least solve some of the defects in the prior art.

[0005] To achieve the above-mentioned purpose, an embodiment of the present invention provides the following technical solution: a two-stage wedge-shaped spot converter, comprising a first-stage wedge-shaped structure, a second-stage wedge-shaped structure and a transmission waveguide structure, wherein the first-stage wedge-shaped structure is used to receive the optical fiber output light and perform a spot conversion on the optical fiber spot in a vertical direction; the second-stage wedge-shaped structure is used to receive the first converted light output from the first-stage wedge-shaped structure and perform a spot conversion on the spot of the first converted light in a horizontal direction; the transmission waveguide structure is used to receive the second converted light output from the second-stage wedge-shaped structure and perform a spot conversion on the second converted light before outputting it, and the spot size of the light output by the transmission waveguide structure is consistent with the spot size of the waveguide light.

[0006] Furthermore, the first-level wedge-shaped structure includes a first substrate, a first core layer grown on the first substrate, and a first cladding layer covering the first core layer. The optical fiber output light first propagates in the first cladding layer and then gradually vertically couples into the first core layer.

[0007] Furthermore, one end of the first cladding away from the second-level wedge structure extends toward the first substrate until it contacts the first substrate, the length of the first cladding is greater than the length of the first core layer, and the first cladding and the first core layer are aligned near one end of the second-level wedge structure.

[0008] Furthermore, the first core layer is wedge-shaped, and the width of the first core layer gradually expands along the direction from the first-level wedge-shaped structure to the second-level wedge-shaped structure.

[0009] Furthermore, the width of the first core layer at one end away from the second-level wedge structure is 0, and the width of the first core layer at one end close to the second-level wedge structure is equal to the width of the second-level wedge structure at one end close to the first-level wedge structure.

[0010] Furthermore, the second-level wedge-shaped structure includes a second substrate, a second core layer grown on the second substrate, and a second cladding layer covering the second core layer.

[0011] Furthermore, the second core layer and the second cladding are both wedge-shaped and have the same width. Along the direction from the first-level wedge-shaped structure to the second-level wedge-shaped structure, the width of the second core layer gradually expands. The width of the second core layer at an end away from the transmission waveguide structure is equal to the width of the end of the first-level wedge-shaped structure close to the second-level wedge structure. The width of the second core layer at an end close to the transmission waveguide structure is equal to the width of the end of the transmission waveguide structure close to the second-level wedge structure.

[0012] Furthermore, the cladding of the first-level wedge-shaped structure, the cladding of the second-level wedge-shaped structure and the cladding of the transmission waveguide structure are made of the same material.

[0013] The embodiment of the present invention provides another technical solution: a method for preparing a two-stage wedge-shaped pattern spot converter, comprising the following steps:

[0014] Multiple epitaxial growth and semiconductor manufacturing process are used to prepare a three-stage mode spot conversion structure;

[0015] The three sections of the pattern spot conversion structure are respectively made into a first-level wedge-shaped structure, a second-level wedge-shaped structure and a transmission waveguide structure, wherein the first-level wedge-shaped structure, the second-level wedge-shaped structure and the transmission waveguide structure are arranged in sequence along the optical fiber to waveguide coupling direction;

[0016] The optical fiber output light is incident on the first-level wedge-shaped structure, and the first-level wedge-shaped structure performs a mode spot conversion on the optical fiber spot in a vertical direction. The first converted light output by the first-level wedge-shaped structure is incident on the second-level wedge-shaped structure, and the second-level wedge-shaped structure performs a mode spot conversion on the spot of the first converted light in a horizontal direction. The second converted light output by the second-level wedge-shaped structure is incident on the transmission waveguide structure, and the transmission waveguide structure performs a mode spot conversion on the second converted light and then outputs it. The spot size of the light output by the transmission waveguide structure is consistent with the waveguide spot size.

[0017] Furthermore, the first-level wedge-shaped structure, the second-level wedge-shaped structure and the transmission waveguide structure are specifically prepared as follows:

[0018] First, a primary epitaxial structure is prepared, wherein the primary epitaxial structure includes a lower cladding layer, a core layer, and an upper cladding layer that are grown in sequence;

[0019] The primary epitaxial structure is etched by photolithography, development and etching processes to obtain a three-segment mode spot conversion structure, wherein the three-segment mode spot conversion structures are arranged in sequence along the optical fiber to waveguide coupling direction;

[0020] The first-stage pattern spot conversion structure is subjected to photolithography, development and etching treatments, the upper cladding of the first-stage pattern spot conversion structure is removed, and the core layer of the first-stage pattern spot conversion structure is processed into a wedge-shaped structure to obtain a first-level wedge-shaped structure, and the width of the core layer of the first-level wedge-shaped structure gradually increases from 0 to W2 along the optical fiber to waveguide coupling direction;

[0021] The second-stage pattern conversion structure is subjected to photolithography, development and etching, and the upper cladding layer and the core layer of the second-stage pattern conversion structure are processed into a wedge-shaped structure to obtain a second-level wedge-shaped structure, and the width of the second-level wedge-shaped structure gradually increases from W2 to W3 along the optical fiber to waveguide coupling direction;

[0022] Processing the third-segment mode spot conversion structure into a transmission waveguide structure, wherein the width W3 is equal to the width of the transmission waveguide structure;

[0023] A new cladding is secondarily epitaxially grown on the core layer of the first-level wedge-shaped structure, and the spot size of the new cladding matches the spot size of the input optical fiber.

[0024] Compared with the prior art, the beneficial effects of the present invention are: it can realize mode spot conversion in a shorter length and maintain high coupling efficiency, which can not only meet the requirements of efficient coupling but also save coupling space. It is a better choice compared with conventional wedge-shaped mode spot converters. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic side view of a two-stage wedge-shaped pattern spot converter provided by an embodiment of the present invention;

[0026] Figure 2 A schematic top view of a two-stage wedge-shaped pattern spot converter provided by an embodiment of the present invention;

[0027] Figure 3 for Figure 2 A schematic diagram of a cross section 1;

[0028] Figure 4 for Figure 2 A schematic diagram of a cross section 2;

[0029] Figure 5 for Figure 2 A schematic diagram of a cross section 3;

[0030] Figure 6 for Figure 2 A schematic diagram of a cross section 4;

[0031] Figure 7 A schematic top view of a core layer of a first-stage wedge structure, a core layer of a second-stage wedge structure, and a core layer of a transmission waveguide structure of a two-stage wedge-shaped pattern spot converter provided by an embodiment of the present invention;

[0032] Figure 8 The node pattern spot shape of the first-stage wedge-shaped structure of a two-stage wedge-shaped pattern spot converter provided by an embodiment of the present invention;

[0033] Fig. 9 A corresponding relationship between the conversion efficiency of the first-stage wedge structure and the first-stage wedge length of a two-stage wedge pattern converter provided by an embodiment of the present invention;

[0034] Fig.10 The corresponding relationship between the conversion efficiency and wedge length of the InP-based wedge-shaped pattern converter under conventional design;

[0035] Fig.11 The working process of the first-stage wedge structure of a two-stage wedge-shaped pattern converter provided by an embodiment of the present invention;

[0036] In the accompanying drawings: 1-first-level wedge-shaped structure; 10-first core layer; 11-first cladding layer; 2-second-level wedge-shaped structure; 20-second core layer; 21-second cladding layer; 3-transmission waveguide structure; 30-third core layer; 31-third cladding layer; 4-substrate. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] See also Figures 1 to 7 The embodiment of the present invention provides a two-stage wedge-shaped pattern spot converter, comprising a first-stage wedge-shaped structure 1, a second-stage wedge-shaped structure 2 and a transmission waveguide structure 3, wherein the first-stage wedge-shaped structure 1 is used to receive the optical fiber output light and perform pattern spot conversion on the optical fiber spot in the vertical direction; the second-stage wedge-shaped structure 2 is used to receive the first converted light output from the first-stage wedge-shaped structure 1 and perform pattern spot conversion on the spot of the first converted light in the horizontal direction; the transmission waveguide structure 3 is used to receive the second converted light output from the second-stage wedge-shaped structure 2 and perform pattern spot conversion on the second converted light before outputting it, and the spot size of the light output by the transmission waveguide structure 3 is consistent with the waveguide spot size. In this embodiment, the two-stage habitual pattern spot converter can realize the pattern spot conversion from optical fiber to waveguide in a shorter length and maintain a high coupling efficiency, which can not only meet the requirements of efficient coupling, but also save coupling space, and is a better choice compared with the conventional wedge-shaped pattern spot converter. Specifically, the first-level wedge structure 1, the second-level wedge structure 2 and the transmission waveguide structure 3 are sequentially arranged along the optical fiber to waveguide coupling direction. Through the cooperation of the three, the optical fiber to waveguide mode spot conversion can be completed, which can not only meet the high-efficiency coupling but also save the coupling space. Among them, the light output by the optical fiber enters the first-level wedge structure 1, and the large-size optical fiber output light first propagates in the first cladding 11 of the first-level wedge structure 1, and then gradually couples into the first cladding of the first-level wedge structure 1. The coupling process is the mode spot conversion in the vertical direction completed in the first-level wedge structure 1, and then the first conversion light after the conversion of the first-level wedge structure 1 enters the second-level wedge structure 2, and is converted into the size of the waveguide spot through the second-level wedge structure 2. The coupling process is the mode spot conversion in the horizontal direction completed in the second-level wedge structure 2, and then the second conversion light after the conversion of the second-level wedge structure 2 enters the transmission waveguide structure 3, and the spot size of the light output by the transmission waveguide structure 3 is consistent with the waveguide spot size. The mode spot converter is decomposed into two stages, and the light spot is converted successively through the two stages to realize the mode spot conversion function from optical fiber to waveguide.

[0039] See also Figures 1 to 7, the first-level wedge-shaped structure 1 is refined. The first-level wedge-shaped structure 1 includes a first substrate, a first core layer 10 grown on the first substrate, and a first cladding layer 11 covering the first core layer 10. The optical fiber output light first propagates in the first cladding layer 11, and then gradually vertically couples into the first core layer 10. The first-level wedge-shaped structure 1 is composed of a three-layer structure, in which the first core layer 10 is surrounded by the first substrate and the first cladding layer 11. The optical fiber output light first propagates in the first cladding layer 11, and then gradually vertically couples into the first core layer 10, completing the mode spot conversion of this section of the structure.

[0040] See also Figures 1 to 7 , the first cladding 11 is refined, the end of the first cladding 11 away from the second-level wedge-shaped structure 2 extends toward the first substrate until it contacts the first substrate, the length of the first cladding 11 is greater than the length of the first core layer 10, and the first cladding 11 and the end of the first core layer 10 close to the second-level wedge-shaped structure 2 are aligned. Figure 1 It can be seen that the first cladding 11 on the far left extends downward to directly contact the first substrate. Therefore, the first cladding 11 is the first to connect with the optical fiber at the incident end of the mode spot converter. The pure cladding waveguide structure can protect the wedge-shaped narrow port of the first core layer 10 (that is, the end with a width of 0). The first cladding 11 is grown by secondary epitaxial growth, and the manufacturing steps are different from the conventional cladding preparation.

[0041] See also Figures 1 to 7 , the first core layer 10 is refined, the first core layer 10 is wedge-shaped, and the width of the first core layer 10 gradually expands along the direction from the first-level wedge-shaped structure to the second-level wedge-shaped structure. The first core layer 10 is designed to be wedge-shaped, which can achieve a shorter length required for adiabatic conversion, especially the starting point of the gradual expansion starts from 0, that is, the width of the end of the first core layer 10 away from the second-level wedge-shaped structure is 0, and the width W2 of the end of the first core layer 10 close to the second-level wedge structure is equal to the width of the end of the second-level wedge structure close to the first-level wedge structure, and the width W2 of the widest end is also smaller than the waveguide width. This design form can achieve the minimum length required for adiabatic conversion.

[0042] See also Figures 1 to 7, the second-level wedge-shaped structure 2 is refined, and the second-level wedge-shaped structure 2 includes a second substrate, a second core layer 20 grown on the second substrate, and a second cladding layer 21 covering the second core layer 20. The second-level wedge-shaped structure 2 is similar to the first-level wedge-shaped structure 1, and also has three layers, namely, the second substrate, the second core layer 20 and the second cladding layer 21. The light emitted from the first-level wedge-shaped structure 1 enters the second-level wedge-shaped structure 2 and then undergoes a second mode spot conversion, so that the spot size can be converted to match the waveguide size. The conversion direction is horizontal, that is, along the length direction of the second-level wedge-shaped structure 2, that is, along the direction from the first-level wedge-shaped structure 1 to the transmission waveguide structure 3.

[0043] See also Figures 1 to 7 , the structure of the second core layer 20 and the second cladding layer 21 is refined, the second core layer 20 and the second cladding layer 21 are both wedge-shaped and have the same width, along the direction from the first-level wedge-shaped structure 1 to the second-level wedge-shaped structure 2, the width of the second core layer 20 gradually expands, the width of the second core layer 20 at one end away from the transmission waveguide structure 3 is equal to the width of the first-level wedge-shaped structure 1 at one end close to the second-level wedge-shaped structure 2, both of which are width W2, and W2 needs to satisfy the requirement of limiting the light field to about the transmission waveguide structure 3 in the vertical direction. The height of the cladding can be 0.8 to 1.2 μm. At the width W2, the second core layer 20 of the second-level wedge-shaped structure 2 is directly connected to the first core layer 10 of the first-level wedge-shaped structure 1, that is, at the width W2, the widths of the second core layer 20 and the first core layer 10 are equal. Since the shape of the first cladding 11 is different from the shape of the second cladding 21, the widths of the first cladding 11 and the second cladding 21 at the connection are not equal. Specifically, the first cladding 11 is square as a whole when viewed from above, rather than the trapezoid of the second cladding 21. The width of the second core layer 20 at one end close to the transmission waveguide structure 3 is equal to the width of the transmission waveguide structure 3 at one end close to the second-level wedge-shaped structure 2, both of which are width W3, and W3 can be 2-2.4 μm. At the width W3, the second core layer 20 of the second-level wedge-shaped structure 2 is directly connected to the third core layer 30 of the transmission waveguide structure 3, that is, at the width W3, the widths of the second core layer 20 and the third core layer 30 are equal. At the same time, at the width W3, the second cladding 21 of the second-level wedge-shaped structure is also directly connected to the third cladding 31 of the transmission waveguide structure 3, that is, at the width W3, the widths of the second cladding 21 and the third cladding 31 are equal. Specifically, Figure 1 , Figure 2 and Figure 7As shown. The width of the second core layer 20 and the second cladding layer 21 of the second-level wedge-shaped structure 2 increases from W2 to W3. Since the light spot has achieved vertical conversion at this time, it only needs to be converted horizontally in the second-level wedge. The function is close to a tapered tape with gradually widening width, and the length for achieving adiabatic conversion is still very small. The width of the first-level wedge-shaped structure 1 gradually decreases from W2 to 0; the width of the second-level wedge-shaped structure 2 gradually decreases from W3 to W2; where 0≤W2≤W3, the minimum size requirement of W2 is that the vertical height of the light field it limits is close to the height of the wedge-shaped core layer.

[0044] See also Figures 1 to 7 , the transmission waveguide structure 3 is refined, and the transmission waveguide structure 3 includes a third substrate, a third core layer 30 grown on the third substrate, and a third cladding layer 31 covering the third core layer 30. The top view angles of the third core layer 30 and the third cladding layer 31 are both rectangular, and the widths of the third core layer 30 and the third cladding layer 31 are consistent. After the light spot is adjusted to match the waveguide light spot in the second-level wedge structure 2, the transmission waveguide structure 3 will no longer adjust the waveguide, so the light spot it outputs is matched with the waveguide light spot, so the width of the third core layer 30 and the second core layer 20 are equal, and the width of the third cladding layer 31 and the second cladding layer 21 are also equal. As for the specific width selection, please refer to the above embodiment, which will not be repeated here. Similarly, the lengths of the third core layer 30 and the third cladding layer 31 are also equal. For the specific size selection, please refer to the following embodiment, which will not be repeated here.

[0045] See also Figures 1 to 7, the cladding of the first-level wedge-shaped structure 1, the cladding of the second-level wedge-shaped structure 2, and the cladding of the transmission waveguide structure 3 are made of the same material. In this embodiment, the core layers of the first-level wedge-shaped structure 1, the second-level wedge-shaped structure 2, and the transmission waveguide structure 3 are all high-refractive-index materials, including but not limited to bulk materials and quantum wells; the cladding of the first-level wedge-shaped structure 1 is a low-refractive-index material, including but not limited to indium phosphide and its ternary and quaternary compounds, etc., and is in the shape of a rectangular structure that wraps the core wedge; the cladding of the second-level wedge-shaped structure 2 is a low-refractive-index material, including but not limited to indium phosphide and its ternary and quaternary compounds, etc., and is in the shape of a wedge-shaped structure with the same width as the core; the cladding material of the transmission waveguide structure 3 is the same as that of the second-level wedge-shaped structure 2, and is in the shape of a rectangular structure with the same width as the core. This pattern spot converter is made on indium phosphide materials and their derivatives, including but not limited to indium phosphide and related ternary or quaternary compounds. Part of the low-refractive-index region of the pattern spot converter can be replaced by other non-indium phosphide system materials, including but not limited to silicon dioxide, organic polymers, lithium niobate materials, etc. The core material is a high refractive index bulk material, or MQW structure, which constitutes the waveguide core layer and is the main area for light propagation. The cladding material of the second-level wedge structure 2 and the subsequent waveguide is InP, or it can be a low refractive index material such as SiO2, which limits the light field and provides protection for the waveguide core layer. The cladding material of the first-level wedge structure 1 is InP, or other bulk materials with a refractive index not lower than that of the substrate material. In addition, the height of the substrate is H1, which can be 1.8 to 2.2 μm. In this embodiment, the optical fiber used is a tapered optical fiber with a spot size of 2.3 to 2.7 μm. The optimal height of the first cladding 11 close to one end of the optical fiber can be 1.8 to 2.2 μm; the height H2 of the first core layer 10, the second core layer 20, and the third core layer 30 are the same, and the value can be 0.2 to 0.6 μm; the height H3 of the cladding of the transmission waveguide structure 3 can be 1.8 to 2.2 μm. In addition, L1 is the length of the first cladding layer 11, which is greater than the length of the first core layer 10L2, so as to protect the tip of the first core layer 10, and L1 is preferably 250μm. The length of the first core layer 10L2 needs to meet the minimum requirements of adiabatic conversion of light spots, and the value in this embodiment can be 180-220μm. The length L3 of the second core layer 20 and the second cladding layer 21 also needs to meet the minimum requirements of adiabatic conversion of light spots, and the value in this embodiment can be 30-70μm.

[0046] See also Figures 3 to 6 Section 1 is a pure cladding structure without the first wedge, which is used for the initial coupling of the optical fiber spot. Its cross section is a rectangular structure of W1*H1. Section 2 is a cladding plus core structure including the first wedge. The first adiabatic conversion has begun here. At this time, the core layer is W x *H2 rectangular structure, where 0 <W x<W2; The cladding plus core layer structure of the second stage with a wedge-shaped cross-section 3, where the second adiabatic conversion has started. At this time, the core layer and the cladding are W y *H2, W y *The rectangular structure of H3, where W2 < W y <W3; The waveguide cross-section after the spot conversion is completed. At this time, the core layer and the cladding are the rectangular structures of W3*H2 and W3*H3 respectively.

[0047] As an optimized solution of the embodiment of the present invention, this mode spot converter can be used for bidirectional coupling between an optical fiber and a waveguide, that is, it can not only couple from left to right, but also couple from right to left. When coupling from right to left, the coupling direction is exactly opposite to the above coupling direction, that is, first horizontally couple in the transmission waveguide structure 3 and the second-stage wedge-shaped structure 2, and then enter the first core layer 10 of the first-stage wedge-shaped structure 1 and gradually vertically couple towards the first cladding 11, and finally output to the optical fiber from the first cladding 11.

[0048] Please refer to Figures 1 to 7 , in the above embodiment, the first substrate of the first-stage wedge-shaped structure 1, the second substrate of the second-stage wedge-shaped structure 2, and the third substrate of the transmission waveguide structure 3 can be the same layer of substrate 4, that is, they are grown at one time during epitaxial growth. The material of this substrate 4 can be InP, and there is no requirement for the doping concentration. The main function is to support the waveguide as a substrate and provide a lower cladding structure for the waveguide.

[0049] Please refer to Figure 1 , S1, S2, and S3 are the key nodes of the spot conversion, and the corresponding spot shapes are as Figure 8 shown, where: S1 is the spot in the coupling region between the mode spot converter and the tapered optical fiber in this embodiment. Here, the spot should be designed to have as high an overlap integral factor as possible with the fiber spot. The overlap integral factor in this embodiment can be selected from 0.960 to 0.990; S2 is the junction between the first stage and the second stage of the wedge. Here, the height of the spot should be limited near the height of the core layer. The vertical mode spot conversion is completed through the first stage of the wedge. In this embodiment, the optional cross-section height is 0.2 - 0.6 μm, and the width is 0.8 - 1.2 μm; S3 is the junction between the second stage of the wedge and the transmission waveguide. Here, the width of the spot should be the same as the actual waveguide width. The horizontal mode spot conversion is completed through the second stage of the wedge. In this embodiment, the optional cross-section height is 0.2 - 0.6 μm, and the width is 2 - 2.4 μm. In Figure 2In the figure, L2 and L3 are the lengths of the first-stage wedge structure 1 and the second-stage wedge structure 2, respectively. The minimum length required for adiabatic conversion must be met when selecting. The second-stage wedge structure 2 is actually a tapered tape with a gradually widening width. Adiabatic conversion can be achieved when the length is greater than 20 μm. In this embodiment, a length of 50 μm can be selected to provide fault tolerance. The first-stage wedge structure 1 is relatively complex because it involves the transformation of both the spot width and height. Therefore, the relationship between the first-stage length and the conversion efficiency is calculated, as shown in Figure 1. Fig. 9 As shown. It can be seen that when the length is greater than 150 μm, the first-level adiabatic conversion can be achieved. In this embodiment, in order to provide fault tolerance, a length of 200 μm is selected. Fig.10 The corresponding relationship between the length of the conventional indium phosphide-based wedge-shaped spot converter and the spot conversion efficiency. It can be seen that in the single-stage case, the minimum length that meets the adiabatic conversion requirements is about 600 μm. The two-stage wedge structure adopted in this embodiment effectively reduces the on-chip length required for the indium phosphide spot converter and meets the design requirements. Fig.11 As shown in the figure, the optimized parameters are substituted into the simulation software to obtain a schematic diagram of the spot converter working. The optical fiber transmission light with a larger light field enters from the left side, and after passing through the two-stage wedge converter structure, it is transformed into a small spot output light that matches the waveguide structure. At this time, the conversion efficiency in the wavelength range of 1.4μm-1.7μm is higher than 90%.

[0050] The embodiment of the present invention provides a method for preparing a two-stage wedge-shaped spot converter, comprising the following steps: performing multiple epitaxial growths and adopting a semiconductor manufacturing process to prepare a three-stage spot conversion structure; respectively manufacturing the three-stage spot conversion structure into a first-stage wedge structure 1, a second-stage wedge structure 2 and a transmission waveguide structure 3, wherein the first-stage wedge structure 1, the second-stage wedge structure 2 and the transmission waveguide structure 3 are arranged in sequence along the optical fiber to waveguide coupling direction; optical fiber output light is incident on the first-stage wedge structure 1, the first-stage wedge structure 1 performs a spot conversion on the optical fiber spot in a vertical direction, the first converted light output by the first-stage wedge structure 1 is incident on the second-stage wedge structure 2, the second-stage wedge structure 2 performs a spot conversion on the spot of the first converted light in a horizontal direction, the second converted light output by the second-stage wedge structure is incident on the transmission waveguide structure 3, the transmission waveguide structure 3 performs a spot conversion on the second converted light and then outputs it, and the spot size of the light output by the transmission waveguide structure 3 is consistent with the waveguide spot size. This method is used to prepare the above-mentioned spot converter, and realizes the spot conversion from optical fiber to waveguide by preparing the first-level wedge-shaped structure 1, the second-level wedge-shaped structure 2 and the transmission waveguide structure 3.

[0051] Specifically, a primary epitaxial structure is first prepared, wherein the primary epitaxial structure includes a lower cladding layer, a core layer and an upper cladding layer grown in sequence, and the epitaxial structure can be produced by MOCVD or MBE;

[0052] The primary epitaxial structure is etched by photolithography, development and etching processes to obtain a three-segment mode spot conversion structure, wherein the three-segment mode spot conversion structures are arranged in sequence along the optical fiber to waveguide coupling direction;

[0053] The first-stage pattern spot conversion structure is subjected to photolithography, development and etching treatments, and the upper cladding of the first-stage pattern spot conversion structure is removed. The etching depth of the upper cladding is determined by the actual cladding thickness, and the first core layer 10 needs to be exposed. The core layer of the first-stage pattern spot conversion structure is processed into a wedge-shaped structure to obtain a first-level wedge-shaped structure 1. Along the optical fiber to waveguide coupling direction, the width of the core layer of the first-level wedge-shaped structure 1 gradually increases from 0 to W2;

[0054] The second-stage pattern conversion structure is subjected to photolithography, development and etching, and the upper cladding layer and the core layer of the second-stage pattern conversion structure are processed into a wedge-shaped structure to obtain a second-stage wedge-shaped structure 2. Along the optical fiber to waveguide coupling direction, the width of the second-stage wedge-shaped structure 2 gradually increases from W2 to W3;

[0055] Processing the third-segment mode spot conversion structure into a transmission waveguide structure 3, wherein the width W3 is equal to the width of the transmission waveguide structure 3;

[0056] A new cladding is secondarily epitaxially grown on the core layer of the first-level wedge-shaped structure 1 , and the spot size of the new cladding matches the spot size of the input optical fiber. The epitaxy can be produced by MOCVD or MBE.

[0057] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A two-stage wedge-shaped pattern converter, characterized in that: The invention comprises a first-level wedge-shaped structure, a second-level wedge-shaped structure and a transmission waveguide structure, wherein the first-level wedge-shaped structure is used to receive the optical fiber output light and perform a mode spot conversion on the optical fiber light spot in a vertical direction; the second-level wedge-shaped structure is used to receive the first converted light output from the first-level wedge-shaped structure and perform a mode spot conversion on the light spot of the first converted light in a horizontal direction; The transmission waveguide structure is used to receive the second converted light output by the second-stage wedge-shaped structure and output the second converted light after performing pattern spot conversion. The spot size of the light output by the transmission waveguide structure is consistent with the waveguide spot size.

2. The two-stage wedge-shaped pattern converter according to claim 1, characterized in that: The first-level wedge-shaped structure includes a first substrate, a first core layer grown on the first substrate, and a first cladding layer covering the first core layer. The optical fiber output light first propagates in the first cladding layer and then gradually and vertically couples into the first core layer.

3. The two-stage wedge-shaped pattern converter according to claim 2, characterized in that: One end of the first cladding away from the second-level wedge structure extends toward the first substrate until it contacts the first substrate, the length of the first cladding is greater than the length of the first core layer, and the first cladding and the first core layer are aligned near one end of the second-level wedge structure.

4. The two-stage wedge-shaped pattern converter according to claim 2, characterized in that: The first core layer is wedge-shaped, and the width of the first core layer gradually expands along the direction from the first-level wedge-shaped structure to the second-level wedge-shaped structure.

5. The two-stage wedge-shaped pattern converter according to claim 4, characterized in that: The width of the first core layer at one end away from the second-level wedge-shaped structure is 0, and the width of the first core layer at one end close to the second-level wedge-shaped structure is equal to the width of the second-level wedge-shaped structure at one end close to the first-level wedge-shaped structure.

6. The two-stage wedge-shaped pattern converter according to claim 1, characterized in that: The second-level wedge-shaped structure includes a second substrate, a second core layer grown on the second substrate, and a second cladding layer covering the second core layer.

7. The two-stage wedge-shaped pattern converter according to claim 6, characterized in that: The second core layer and the second cladding layer are both wedge-shaped and have the same width. The width of the second core layer gradually expands along the direction from the first-level wedge-shaped structure to the second-level wedge-shaped structure. The width of the second core layer at an end away from the transmission waveguide structure is equal to the width of an end of the first-level wedge-shaped structure close to the second-level wedge structure. The width of the second core layer at an end close to the transmission waveguide structure is equal to the width of an end of the transmission waveguide structure close to the second-level wedge structure.

8. The two-stage wedge-shaped pattern converter according to claim 1, characterized in that: The cladding of the first-level wedge-shaped structure, the cladding of the second-level wedge-shaped structure and the cladding of the transmission waveguide structure are made of the same material.

9. A method for preparing a two-stage wedge-shaped pattern spot converter, characterized in that: The steps include: Multiple epitaxial growth and semiconductor manufacturing process are used to prepare a three-stage mode spot conversion structure; The three sections of the pattern spot conversion structure are respectively made into a first-level wedge-shaped structure, a second-level wedge-shaped structure and a transmission waveguide structure, wherein the first-level wedge-shaped structure, the second-level wedge-shaped structure and the transmission waveguide structure are arranged in sequence along the optical fiber to waveguide coupling direction; The optical fiber output light is incident on the first-level wedge-shaped structure, and the first-level wedge-shaped structure performs a mode spot conversion on the optical fiber spot in a vertical direction. The first converted light output by the first-level wedge-shaped structure is incident on the second-level wedge-shaped structure, and the second-level wedge-shaped structure performs a mode spot conversion on the spot of the first converted light in a horizontal direction. The second converted light output by the second-level wedge-shaped structure is incident on the transmission waveguide structure, and the transmission waveguide structure performs a mode spot conversion on the second converted light and then outputs it. The spot size of the light output by the transmission waveguide structure is consistent with the waveguide spot size.

10. The method for preparing the two-stage wedge-shaped pattern spot converter according to claim 9, characterized in that: The specific preparation method of the first-level wedge-shaped structure, the second-level wedge-shaped structure and the transmission waveguide structure is: First, a primary epitaxial structure is prepared, wherein the primary epitaxial structure includes a lower cladding layer, a core layer, and an upper cladding layer that are grown in sequence; The primary epitaxial structure is etched by photolithography, development and etching processes to obtain a three-segment mode spot conversion structure, wherein the three-segment mode spot conversion structures are arranged in sequence along the optical fiber to waveguide coupling direction; The first-stage pattern spot conversion structure is subjected to photolithography, development and etching treatments, the upper cladding of the first-stage pattern spot conversion structure is removed, and the core layer of the first-stage pattern spot conversion structure is processed into a wedge-shaped structure to obtain a first-level wedge-shaped structure, and the width of the core layer of the first-level wedge-shaped structure gradually increases from 0 to W2 along the optical fiber to waveguide coupling direction; The second-stage pattern conversion structure is subjected to photolithography, development and etching, and the upper cladding layer and the core layer of the second-stage pattern conversion structure are processed into a wedge-shaped structure to obtain a second-level wedge-shaped structure, and the width of the second-level wedge-shaped structure gradually increases from W2 to W3 along the optical fiber to waveguide coupling direction; Processing the third-segment mode spot conversion structure into a transmission waveguide structure, wherein the width W3 is equal to the width of the transmission waveguide structure; A new cladding is secondarily epitaxially grown on the core layer of the first-level wedge-shaped structure, and the spot size of the new cladding matches the spot size of the input optical fiber.

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