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CN-115693389-B - End face coupling structure of low-loss silicon optical chip

CN115693389BCN 115693389 BCN115693389 BCN 115693389BCN-115693389-B

Abstract

The invention relates to an end face coupling structure of a low-loss silicon optical chip, which comprises a silicon substrate, wherein a laser installation area is arranged on the silicon substrate, an oxygen burying layer is arranged on one side of the laser installation area, a shallow etching area is arranged on the oxygen burying layer, a beveled end face is etched on a section formed by the oxygen burying layer and the shallow etching area, the beveled end face is used for reducing reflection loss, a ridge waveguide facing the laser installation area is arranged on the shallow etching area, and an incident end of the ridge waveguide is positioned at the beveled end face. The invention can realize higher coupling efficiency and alignment tolerance.

Inventors

  • WU AIMIN
  • LV DONGSHENG
  • FENG DAZENG
  • LI ANG

Assignees

  • 中国科学院上海微系统与信息技术研究所

Dates

Publication Date
20260505
Application Date
20221012

Claims (7)

  1. 1. The end face coupling structure of the low-loss silicon optical chip is characterized by comprising a silicon substrate (1), wherein a laser installation area is arranged on the silicon substrate (1), an oxygen burying layer (2) is arranged on one side of the laser installation area and on the silicon substrate (1), a shallow etching area (3) is arranged on the oxygen burying layer (2), a beveled end face (5) is etched on a cross section formed by the oxygen burying layer (2) and the shallow etching area (3), the beveled end face (5) is used for reducing reflection loss, a ridge waveguide (4) facing the laser installation area is arranged on the shallow etching area (3), an incident end of the ridge waveguide (4) is located at the beveled end face (5), a focusing curved surface (6) is arranged on the beveled end face (5), the focusing curved surface (6) is located right below an input end of the ridge waveguide (4), the focusing curved surface (6) is used for compensating the phase and the size of an incident end face light spot of the ridge waveguide (4), and the shape of the focusing curved surface (6) is calculated according to the position relation of a DFB and the beveled end face (5). The focusing curved surface (6) satisfies an equation n 1 sinθ 1 ＝n 2 sinθ 2 ; And the focusing curved surface (6) also satisfies equation n 1 L 1 ＝n 2 L 2 ; wherein n 1 is the refractive index between the end face coupling structure of the DFB laser and the silicon optical chip, θ 1 is the angle between the light and the normal between the end face coupling structure of the DFB laser and the silicon optical chip, the normal is perpendicular to the beveled end face, n 2 is the refractive index of the ridge waveguide, θ 2 is the angle between the light and the normal in the ridge waveguide, L 1 is the propagation distance between the end face coupling structure of the DFB laser and the silicon optical chip, and L 2 is the propagation distance in the ridge waveguide.
  2. 2. The end-face coupling structure of a low-loss silicon optical chip according to claim 1, wherein the chamfer angle of the chamfer end face (5) is calculated according to the incident energy of the DFB laser, and the chamfer angle of the chamfer end face (5) is satisfied that the energy loss reflected back to the light-emitting face of the DFB laser by the chamfer end face (5) is at least less than-30 dB.
  3. 3. The end-face coupling structure of a low-loss silicon optical chip according to claim 1, characterized in that the beveled end face (5) is plated with an anti-reflection layer.
  4. 4. The end-face coupling structure of a low-loss silicon optical chip of claim 3, wherein the thickness of the anti-reflection layer is calculated according to the output wavelength of the DFB laser, and the formula is 2kd=pi, where k is a wave vector in the anti-reflection layer, and d is the thickness of the anti-reflection layer.
  5. 5. The end-face coupling structure of a low-loss silicon optical chip of claim 3, wherein the anti-reflection layer is a silicon nitride layer.
  6. 6. The end-face coupling structure of a low-loss silicon optical chip according to claim 1, characterized in that the ridge waveguide (4) is provided with a mode filtering structure to attenuate the transmission of higher order modes.
  7. 7. The end-face coupling structure of a low-loss silicon optical chip according to claim 1, wherein the buried oxide layer (2) is made of silicon dioxide.

Description

End face coupling structure of low-loss silicon optical chip Technical Field The invention relates to the technical field of low-loss silicon optical chip structural design, in particular to an end face coupling structure of a low-loss silicon optical chip. Background Communication networks are the technology base of the whole information society, and today, technologies such as huge heat 5G and cloud computing depend on developed communication technologies to be born and developed. In the past decade of China, the project of 'optical copper advance and retreat' is steadily advanced, and optical interconnection occupies an increasingly important position in the field of data communication. Silicon-based optoelectronics is an emerging technology, and can realize large-scale integration of photoelectric devices by using the existing mature CMOS technology, so that the method has a wide development prospect. Since silicon is an indirect bandgap semiconductor, it is difficult to generate stimulated radiation like a III-V semiconductor, on-chip light sources are a problem in silicon photonics chips. One common approach is to integrate an external laser on a silicon optical chip. Distributed Feedback (DFB) lasers are extremely narrow linewidths, high power, and are suitable for long-range high-rate optical communications, and are thus used in large numbers as light sources. The light source hybrid integration mode can be divided into an end face (horizontal) coupling mode and a grating (vertical) coupling mode according to different silicon optical process platforms and different laser light emitting positions. The end surface coupling structure is naturally compatible with the DFB laser with side light emission, and is widely applied to a Silicon-on-Insulator (SOI) platform with a top layer Silicon thickness of 3 um. However, the loss of the existing end-face coupling structure is generally larger, on one hand, the optical power coupled into the chip is seriously attenuated, and on the other hand, the integration accuracy of the laser is strictly required, and the tolerable alignment error is very small. Disclosure of Invention The invention aims to solve the technical problem of providing an end surface coupling structure of a low-loss silicon optical chip, which can realize higher coupling efficiency and alignment tolerance. The technical scheme includes that the end face coupling structure of the low-loss silicon optical chip comprises a silicon substrate, wherein a laser installation area is arranged on the silicon substrate, an oxygen burying layer is arranged on one side of the laser installation area and on the silicon substrate, a shallow etching area is arranged on the oxygen burying layer, a bevel end face is etched on a cross section formed by the oxygen burying layer and the shallow etching area, the bevel end face is used for reducing reflection loss, a ridge waveguide facing the laser installation area is arranged on the shallow etching area, and an incident end of the ridge waveguide is located at the bevel end face. The beveling angle of the beveling end face is calculated according to the incident energy of the DFB laser, and the beveling angle of the beveling end face meets the condition that the energy loss reflected back to the light emitting surface of the DFB laser by the beveling end face is at least less than-30 dB. The beveled end face is plated with an anti-reflection layer. The thickness of the anti-reflection layer is calculated according to the output wavelength of the DFB laser, the formula is 2 kd=pi, wherein k is a wave vector in the anti-reflection layer, and d is the thickness of the anti-reflection layer. The anti-reflection layer is a silicon nitride layer. The inclined cutting end face is provided with a focusing curved surface, the focusing curved surface is positioned right below the ridge waveguide input end, and the focusing curved surface is used for compensating the phase and the size of a light spot on the incident end face of the ridge waveguide. The shape of the focusing curved surface is calculated according to the position relation between the DFB laser and the beveling end surface; The focusing curved surface satisfies equation n 1sinθ1＝n2sinθ2; and the focusing curved surface also satisfies equation n 1L1＝n2L2; wherein n 1 is the refractive index between the end face coupling structure of the DFB laser and the silicon optical chip, θ 1 is the angle between the light and the normal between the end face coupling structure of the DFB laser and the silicon optical chip, the normal is perpendicular to the beveled end face, n 2 is the refractive index of the ridge waveguide, θ 2 is the angle between the light and the normal in the ridge waveguide, L 1 is the propagation distance between the end face coupling structure of the DFB laser and the silicon optical chip, and L 2 is the propagation distance in the ridge waveguide. The ridge waveguide is provided with a mode fi