CN-121995575-A - Suspended grating coupler with variable period and gradual tooth height

CN121995575ACN 121995575 ACN121995575 ACN 121995575ACN-121995575-A

Abstract

The invention relates to a suspended grating coupler with variable period and gradual tooth height, belonging to the technical field of integrated optics and silicon-based photonics. The grating comprises a silicon substrate layer, a silicon dioxide oxygen-buried layer, a grating device layer and a silicon dioxide upper cladding layer which are arranged from bottom to top, wherein the tooth height of the whole grating region continuously changes in the light propagation direction according to a preset change rule and is in a monotonically increasing trend as a whole, a suspended structure is formed by selectively etching the silicon dioxide oxygen-buried layer below the grating, and the leakage loss of light energy to the substrate is effectively inhibited by utilizing the refractive index difference between air and grating materials. The invention solves the problem that the bandwidth and the efficiency of the traditional grating coupler are difficult to be compatible by the multidimensional collaborative optimization of the tooth height, the period and the suspension structure, the gradual change tooth height structure is realized by adopting the gray scale exposure and etching process, the device has compact structure and compatibility with the CMOS process, and the device has wide application prospect in the fields of high-speed optical interconnection, sensing, large-scale photon integrated chips and the like.

Inventors

FANG QING
YUAN SHUXUAN
ZHANG ZHIQUN
CHEN HUA

Assignees

昆明理工大学

Dates

Publication Date: 20260508
Application Date: 20260322

Claims (6)

1. The suspended grating coupler with the variable period and the gradual change tooth height is characterized by comprising a substrate layer (1), a silicon dioxide oxygen burying layer (2), a grating device layer (3) and a silicon dioxide upper cladding layer (4) which are sequentially arranged from bottom to top; The grating device layer (3) sequentially comprises a single-mode waveguide region (31), a mode field conversion region (32), an apodization grating region (33) and a uniform grating region (34) which are tightly connected from the front end to the rear end; The apodized grating region (33) and the uniform grating region (34) together form a grating region; The grating period of the apodization grating region (33) changes along the light propagation direction, and the grating period of the uniform grating region (34) is constant; The silicon dioxide oxygen-buried layer (2) is selectively removed below the grating region to form a region (21) suspending the grating region, which is used for inhibiting leakage of light energy to the substrate direction and improving coupling efficiency.
2. The variable period and gradual change tooth height suspended grating coupler according to claim 1, wherein the tooth heights of the grating teeth in the grating region continuously change along the light propagation direction according to a preset change rule and are in monotone increasing trend as a whole.
3. The period-varying and tooth-height-varying suspended grating coupler of claim 1, wherein the tooth-height variations of the apodized grating region (33) and the uniform grating region (34) are continuously joined at a junction to form an overall continuously varying tooth-height distribution.
4. The variable period and tapered tooth height floating grating coupler of claim 1, wherein the lateral dimension of the region (21) floating the grating region covers the grating region such that the grating region is entirely floating.
5. The variable period and tapered tooth height floating grating coupler of claim 1, wherein the grating tooth height variation, grating period variation and the floating grating region (21) cooperate to simultaneously adjust the optical field distribution and phase matching relationship.
6. A method of manufacturing a variable period and tapered tooth height suspended grating coupler as claimed in any one of claims 1 to 5, comprising: the tooth heights of the grating teeth in the grating region are gradually changed tooth heights, and the gradually changed tooth heights are prepared by adopting gray exposure and etching processes; The silicon dioxide oxygen-buried layer (2) below the grating region is selectively etched to form a region (21) suspending the grating region; The grating device layer (3) defines patterns on a top layer film through a gray level exposure technology, and then a required grating structure is formed through a dry etching process or a wet etching process, wherein in a variable period and tooth height variable grating region, the grating period is gradually changed in an apodization grating region (33), and the tooth height is gradually changed in the grating region, so that broadband matching and high-efficiency mode field conversion are realized.

Description

Suspended grating coupler with variable period and gradual tooth height Technical Field The invention relates to a suspended grating coupler with variable period and gradual tooth height, belonging to the technical field of integrated optics and silicon-based photonics. Background In recent years, photonic integrated circuit (Photonic Integrated Circuit ‌, PIC) technology has exhibited significant advantages in terms of power consumption, bandwidth, cost, and the like, which have advantages that are difficult to replace in terms of information transmission and processing, and thus is widely used in the fields of optical communication, optical sensing, quantum information processing, and the like. One key issue in PICs is achieving efficient coupling between single mode fiber and sub-micron waveguides. The Grating Coupler (GC) with flexible space position and simple manufacturing process is a core device for realizing efficient coupling between a chip and an optical fiber in a silicon-based photon chip. The traditional uniform period grating coupler has two main bottlenecks, namely one is mode field mismatch, the optical field distribution of the traditional grating coupler is approximately in an exponential decay form because the gratings of the traditional grating coupler are uniformly distributed, and the optical field in the optical fiber is in a near Gaussian distribution, so that certain mismatch exists between the two optical fields to cause errors, and the other is substrate leakage, because part of light energy is downwards coupled into a silicon substrate with high refractive index to cause loss. To improve mode field mismatch, the prior art proposes an apodized grating design. However, while the simple variable period and variable tooth height design increases the bandwidth, it is often not solved because of substrate leakage, resulting in limited improvement of peak coupling efficiency, and even possible introduction of additional loss due to mode mismatch. To reduce substrate leakage, suspended structures are introduced. In view of the foregoing, there is a strong need in the art for a solution for a grating coupler capable of achieving both high coupling efficiency and wide bandwidth, which has the advantages of simple fabrication process, flexible control, and high compatibility with advanced complementary metal oxide semiconductor (Complementary Metal Oxide Semiconductor, CMOS) photonic platforms. Disclosure of Invention Aiming at the problems and the defects of the prior art, the invention provides a suspended grating coupler based on variable period and variable tooth height design, and the three components form a coupling effect in the aspects of regulating light field distribution, phase matching and inhibiting substrate leakage by carrying out cooperative design on grating tooth height change, grating period change and suspended structure, so that the synchronous improvement of coupling efficiency and working bandwidth is realized without additional complex structure. The invention adopts the technical scheme that the suspended grating coupler with variable period and gradual tooth height comprises a substrate layer 1, a silicon dioxide oxygen burying layer 2, a grating device layer 3 and a silicon dioxide upper cladding layer 4 which are sequentially arranged from bottom to top; the grating device layer 3 sequentially comprises a single-mode waveguide region 31, a mode field conversion region 32, an apodization grating region 33 and a uniform grating region 34 which are tightly connected from the front end to the rear end; the apodized grating region 33 and the uniform grating region 34 together constitute a grating region; the grating period of the apodized grating region 33 varies along the light propagation direction, and the grating period of the uniform grating region 34 is constant; The silicon oxide buried oxide layer 2 is selectively removed below the grating region to form a region 21 suspending the grating region for suppressing leakage of light energy to the substrate direction and improving coupling efficiency. Further, tooth heights of the plurality of grating teeth in the grating region continuously change along the light propagation direction according to a preset change rule, and the whole grating teeth have monotonous increasing trend. Further, the variation of the tooth height of the apodized grating region 33 and the uniform grating region 34 are continuously joined at a junction to form an overall continuously varying tooth height distribution. Further, the lateral dimension of the region 21 suspending the grating region covers the grating region, so that the grating region is in a suspended state as a whole. Further, the grating tooth height variation, the grating period variation and the suspended grating region 21 cooperate to regulate and control the light field distribution and the phase matching relationship. The invention also provides a preparation method of