Novel heterogeneous integrated light source heat insulation coupling structure

Abstract

The invention discloses a novel heterogeneous integrated light source adiabatic coupling structure, which comprises an active waveguide structure and a passive waveguide structure, and is characterized in that the passive waveguide structure comprises a flat silicon core and a ridge silicon core 003, one end of the ridge silicon core 003 is provided with a passive coupling section 011 of which the width is gradually reduced, and an active waveguide structure 002 is superposed above the passive coupling section 011; and an active coupling section 012 of the active waveguide structure 002 is wedge-shaped. Light is input into the passive coupling section 011 from the passive waveguide, the width of the ridge silicon core 003 of the passive coupling section 011 is gradually reduced, the width of the active coupling section 012 is gradually increased, in the process, the effective refractive index of the silicon waveguide is matched with that of the active waveguide, and part of optical signals enter the active coupling section 012 from the passive coupling section 011 in an adiabatic coupling mode. Through the conical coupling structure provided by the invention, extremely low loss transmission of light between the passive silicon waveguide and the heterogeneous integrated light source active waveguide can be realized, and the coupling loss between the passive silicon waveguide and the heterogeneous integrated light source active waveguide is effectively reduced.

Description

Technical Field

[0001] The invention belongs to the field of optoelectronic integration, and in particular relates to an optical waveguide adiabatic coupling structure. Background Art

[0002] Integrated optoelectronics is a discipline that studies how to integrate photonic devices at the micro-nano scale. Its development is of great significance for improving the integration of optoelectronic devices, reducing their size and power consumption. Among them, heterogeneous integrated light sources and lasers are important optical devices that enhance the intensity and quality of optical signals. By injecting current to excite carriers in semiconductor materials, lasers can be used as light sources for communications, and optical amplifiers can amplify input optical signals. Their high-speed response and tunability make them one of the key components in silicon-based integrated photonic chip circuits.

[0003] However, due to the special working principle and structural characteristics of the heterogeneous integrated light source itself, it is difficult to couple it with the passive silicon waveguide after on-chip integration. In order to improve the coupling efficiency between the optical amplifier and the passive silicon waveguide, the mode spot conversion can be used to achieve mode field matching between the heterogeneous integrated light source and the passive silicon waveguide, but this method requires extremely high alignment accuracy between the two, and the alignment tolerance is small, which greatly increases the complexity of the process and structural design. The passive silicon waveguide and the active waveguide of the optical amplifier can also be made into a cone, and optical coupling is performed by adiabatic coupling. However, the alignment tolerance in the traditional symmetrical adiabatic cone coupling structure is still very small, and the width of the active waveguide section of the heterogeneous integrated light source needs to be very narrow to couple with the passive silicon waveguide, so the process requirements are extremely high, which further increases the cost.

[0004] The existing technical solutions lack a technical solution for coupling heterogeneous integrated light sources with relatively simple manufacturing process, low manufacturing cost, high success rate and good coupling effect. Summary of the invention

[0005] The technical problem to be solved by the present invention is: in view of the problem of coupling a heterogeneous integrated light source with a passive silicon waveguide, an adiabatic coupling method different from the traditional symmetrical cone structure is proposed. The silicon waveguide is gradually bent; at the same time, the III-V active waveguide superimposed thereon is gradually tapered, so that the light mode in the single-mode silicon waveguide smoothly transitions to the light mode in the gain section active waveguide. By optimizing the cone structure and the length of the coupling region, the coupling loss between the two is reduced as much as possible; at the same time, the minimum processing width of the cone tip is enlarged, so that the processing tolerance of the cone tip can be enlarged to the micron level.

[0006] The technical solution of the present invention:

[0007] A novel heterogeneous integrated light source adiabatic coupling structure includes an active waveguide structure and a passive waveguide structure. The passive waveguide structure includes a flat silicon core and a ridge silicon core 003. One end of the ridge silicon core 003 is provided with a passive coupling section 011 with a gradually decreasing width. An active waveguide structure 002 is superimposed on the passive coupling section 011. The active coupling section 012 of the active waveguide structure 002 is wedge-shaped.

[0008] The active waveguide structure 002 includes n-InP cladding 008, n-SCH 007, quantum well 006, P-SCH 005 and P-InP cladding 004 from bottom to top, wherein the width of n-InP cladding 008 is greater than that of other layer structures and has no wedge-shaped structure.

[0009] There is a silicon dioxide buried oxide layer 009 at the bottom of the passive waveguide structure, and a silicon dioxide cladding layer 001 is provided on the upper surface of the planar silicon core to cover the ridge silicon core 003.

[0010] The left edge line of the passive coupling section 011 of the ridge silicon core 003 gradually shifts inward with a larger slope, and the right edge line shifts outward with a smaller slope. When the width of the tip of the passive coupling section 011 reaches w, it stops shifting and continues to extend one end as a gain section.

[0011] The active coupling section 012 of the active waveguide structure 002 overlaps with the passive coupling section 011 of the passive waveguide structure, and the center line of the straight segment of the active waveguide structure 002 overlaps with the center line of the gain segment of the silicon core 003 .

[0012] The left edge of the active coupling section 012 of the active waveguide structure 002 is a straight line, and the right edge line is an oblique line. The active coupling section 012 is a right-angled trapezoid as a whole.

[0013] The width w of the tip of the passive coupling section 011 is in the micrometer order, and the width of the wedge-shaped tip of the active coupling section 012 is in the micrometer order.

[0014] The working principle of the novel coupling structure of the present invention is as follows: light is input from the passive waveguide into the passive coupling section 011, the width of the ridge silicon core 003 of this section gradually decreases, while the width of the active coupling section 012 gradually increases. During this process, the effective refractive index of the silicon waveguide matches that of the active waveguide, and part of the optical signal enters the active coupling section 012 from the passive coupling section 011 through adiabatic coupling.

[0015] The beneficial effects of the present invention are:

[0016] 1. The tapered coupling structure proposed in the present invention can realize extremely low-loss transmission of light between the passive silicon waveguide and the active waveguide of the heterogeneous integrated light source, effectively reducing the coupling loss between the two.

[0017] 2. When the active waveguide cone tip width is 1 μm, the coupling loss is still very low. Therefore, the structure proposed by the present invention can be used to increase the process tolerance of heterogeneous integrated light sources, effectively reducing the processing cost and difficulty of heterogeneous integrated light sources. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Top view of the new adiabatic conical coupling structure.

[0019] Figure 2 Schematic diagram of the interface of the coupling structure.

[0020] Figure 3 Schematic diagram of the coupling area between silicon waveguide and on-chip light source.

[0021] Figure 4 Side view of the new adiabatic conical coupling structure.

[0022] Figure 5 It is a schematic diagram of the three-dimensional structure of the coupling structure of Example 2.

[0023] Figure numerals: 001 - silicon dioxide cladding; 002 - active waveguide structure; 003 - passive ridge silicon core; 004 - p-InP cladding; 005 - p-SCH; 006 - quantum well; 007 - n-SCH; 008 - n-InP cladding; 009 - silicon dioxide cladding; 010 - silicon waveguide optical input end; 011 passive coupling section; 012 active coupling section. DETAILED DESCRIPTION

[0024] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0025] Embodiment 1:

[0026] Refer to the attached Figure 1 , Figure 2 , Figure 3 and Figure 4 The novel coupling structure provided by the present invention consists of two parts: a passive waveguide structure and an active waveguide structure 002. The main structure of the passive part includes: a silicon dioxide cladding layer 001, a passive silicon waveguide and a silicon dioxide buried oxide layer 009. The thickness of the silicon buried oxide layer is 2μ.

[0027] According to the process requirements provided by the wafer factory, the silicon waveguides involved in the present invention are all ridge waveguides, and the photolithography method adopts 250nm deep etching, that is, the total height of the passive silicon waveguide is 500nm, and the etching area is 250nm. After etching, the passive silicon waveguide consists of a flat silicon core and a ridge silicon core 003, and the flat silicon core and the ridge silicon core 003 are covered with a silicon dioxide cladding 001. The passive silicon waveguide includes a straight waveguide section and a curved gradient waveguide section. The width of the straight waveguide section is greater than or equal to 2.5 microns. The straight waveguide section is the silicon waveguide light input end 010; the curved gradient waveguide section is used as a coupling section.

[0028] According to the requirements of the wafer production process, the epitaxial layer of the heterogeneous integrated light source, that is, the active waveguide structure, is composed of p-InP cladding 004, p-SCH005, quantum well 006, n-SCH007, and n-InP cladding 008, and the area near the light input end is the active coupling section 012. The shape is different from the traditional symmetrical cone structure, but an inclined cone, and the length is consistent with the length of the curved silicon waveguide 011 section, and the positions of the starting end and the end correspond. The heterogeneous integrated light source structure (active waveguide structure 002) is in close contact with the silicon dioxide cladding 001, wherein the n-InP cladding 008 has no wedge structure and is wider than other layer structures. The widening of the bottom n-InP cladding 008 is more conducive to coupling on the one hand, and it is convenient to add electrodes on the other hand; the spacing between the active waveguide structure 002 and the ridge silicon core 003 is 100nm-300nm.

[0029] The optical signal enters through the optical input end of the silicon waveguide and enters the curved silicon waveguide section through the straight waveguide. Since the width of the silicon waveguide and the active waveguide changes and the passive silicon waveguide adopts a new type of slowly tapered structure transition, the effective refractive index of the passive silicon waveguide and the source waveguide are matched. The optical signal is adiabatically transmitted in this section, and part of the optical signal is coupled to the active waveguide. According to the FDTD simulation results, the optical field is stably distributed in the passive silicon waveguide and the active waveguide, and lossless transmission can be basically achieved when the length of the passive coupling section 011 and the inclined tapered active coupling section 012 is greater than 200μm. The numerical analysis results show that the coupling efficiency does not change much when the cone tip width of the inclined tapered active coupling section 012 changes from 500nm to 1μm, which can greatly relax the process requirements for active waveguide processing.

[0030] The working principle of the novel coupling structure of the present invention is:

[0031] The 1550nm optical signal output by the external laser source is input to the silicon waveguide optical input end 010 through the end coupler or the grating coupler, and enters the passive coupling section 011 through the silicon waveguide optical input end 010. The width of this section of the silicon waveguide gradually decreases, while the width of the active coupling section 012 gradually increases. In this process, the effective refractive index of the silicon waveguide matches that of the active waveguide, and part of the optical signal enters the active waveguide 012 from the passive coupling section 011 through adiabatic coupling.

[0032] Embodiment 2:

[0033] like Figure 5 As shown in the figure, we designed a new coupling structure, where light is transmitted in a passive silicon waveguide structure and an active waveguide structure (SOA waveguide), the passive part is composed of a silicon dioxide buried oxide layer 009, a silicon waveguide 003 and a silicon dioxide cladding; the active waveguide SOA. The overlapping part of the passive silicon waveguide structure and the active waveguide structure 002 is a coupling section, where the coupling section of the passive silicon waveguide is a slightly curved pointed cone structure with gradually changing edge lines on both sides, and the coupling section of the active waveguide is a wedge-shaped pointed cone structure.

[0034] The arrow direction is the light transmission direction. The light signal enters from one end of the silicon waveguide and is transmitted to the coupling section. Since the passive silicon waveguide adopts a new type of slowly tapered structure transition, the effective refractive index of the passive silicon waveguide matches that of the active waveguide, and the light signal is adiabatically transmitted in this section. This design improves the coupling efficiency between the passive silicon waveguide and the active waveguide, and allows more light signals to be transmitted through the heterogeneous integrated light source, effectively coupling the light signal in the silicon waveguide to the active waveguide.

[0035] The above-mentioned specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above-mentioned embodiments are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A novel heterogeneous integrated light source adiabatic coupling structure, including an active waveguide structure and a passive waveguide structure, characterized in that: The passive waveguide structure comprises a flat silicon core and a ridge silicon core (003), one end of the ridge silicon core (003) is provided with a passive coupling section (011) with a gradually decreasing width, an active waveguide structure (002) is superimposed on the passive coupling section (011), and the active coupling section (012) of the active waveguide structure (002) is wedge-shaped.

2. The novel heterogeneous integrated light source adiabatic coupling structure according to claim 1 is characterized in that: The active waveguide structure (002) is composed of n-InP cladding (008), n-SCH (007), quantum well (006), P-SCH (005) and P-InP cladding (004) from bottom to top, wherein the width of the n-InP cladding (008) is greater than that of other layer structures and has no wedge-shaped structure.

3. The novel heterogeneous integrated light source adiabatic coupling structure according to claim 2 is characterized in that: The bottom of the passive waveguide structure is provided with a silicon dioxide buried oxide layer (009), and the upper surface of the planar silicon core is provided with a silicon dioxide cladding layer (001) to cover the ridge silicon core (003).

4. The novel heterogeneous integrated light source adiabatic coupling structure according to any one of claims 1 to 3, characterized in that: The left edge line of the passive coupling section (011) of the ridge silicon core (003) gradually shifts inward with a larger slope, and the right edge line shifts outward with a smaller slope. When the width of the tip of the passive coupling section (011) reaches w, the shift stops and continues to extend at one end as a gain section.

5. According to claim 4, the novel heterogeneous integrated light source adiabatic coupling structure is characterized in that From a top view, the active coupling section (012) of the active waveguide structure (002) overlaps with the passive coupling section (011) of the passive waveguide structure, and the center line of the straight line section of the active waveguide structure (002) overlaps with the center line of the gain section of the silicon core (003).

6. The novel heterogeneous integrated light source adiabatic coupling structure according to claim 5, characterized in that: The left edge of the active coupling section (012) of the active waveguide structure (002) is a straight line, the right edge line is an oblique line, and the active coupling section (012) is a right-angle trapezoid as a whole.

7. The novel heterogeneous integrated light source adiabatic coupling structure according to claim 4, characterized in that: The width of the tapered tip of the active coupling section (012) is in the micrometer order.

8. The novel heterogeneous integrated light source adiabatic coupling structure according to claim 4, characterized in that: Light is input from the passive waveguide and enters the passive coupling section (011). The width of the ridge silicon core (003) in this section gradually decreases, while the width of the active coupling section (012) gradually increases. During this process, the effective refractive index of the silicon waveguide and the active waveguide match, and part of the optical signal enters the active coupling section (012) from the passive coupling section (011) through adiabatic coupling.

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