WO2019218385A1

WO2019218385A1 - Silicon and lithium niobate hybrid integrated optical modulator and preparation method therefor

Info

Publication number: WO2019218385A1
Application number: PCT/CN2018/087918
Authority: WO
Inventors: 蔡鑫伦; 何名博; 徐梦玥; 余思远
Original assignee: 中山大学
Priority date: 2018-05-16
Filing date: 2018-05-22
Publication date: 2019-11-21
Also published as: CN109116590B; CN109116590A

Abstract

A silicon and lithium niobate hybrid integrated optical modulator, comprising a silicon-based optical waveguide structure (1) on an insulator, an optical beam splitting structure (2), a silicon wedge-shaped waveguide optical mode conversion structure (3), a bonding medium layer (4), a lithium niobate waveguide (5), a signal metal electrode (6) and a ground metal electrode (7), the silicon-based optical waveguide structure (1) on an insulator being connected to an input end of the optical beam splitting structure (2), and two output ends of the optical beam splitting structure (2) being connected to the lithium niobate waveguide (5) respectively by means of the silicon wedge-shaped waveguide optical mode conversion structure (3); the signal metal electrode (6) is disposed at a side opposite to the lithium niobate waveguide (5); the ground metal electrode (7) is disposed at a side facing away from the lithium niobate waveguide (5); the hybrid integrated optical modulator is a two-layer structure: the silicon-based optical waveguide structure (1), the optical beam splitting structure (2) and the silicon wedge-shaped waveguide optical mode conversion structure (3) are disposed within the bonding medium layer (4), and the lithium niobate waveguide (5), the signal metal electrode (6) and the ground metal electrode (7) are disposed above the bonding medium layer (4). Further comprised is a corresponding preparation method for the silicon and lithium niobate hybrid integrated optical modulator.

Description

Silicon and lithium niobate mixed integrated light modulator and preparation method thereof

Technical field

The present invention relates to the field of optical modulation technology, and more particularly to a silicon and lithium niobate hybrid integrated light modulator and a method of fabricating the same.

Background technique

The silicon-based photonics platform is the best integrated optical platform available today. The silicon-based photonics platform has a high refractive index difference due to its compatibility with traditional CMOS processes, making the silicon-based photonics platform easy to mass-produce and easy to integrate. Silicon-based platforms are well suited for making passive devices, but the fundamental characteristics of silicon make it challenging to implement some active devices. Silicon itself is a centrally symmetrical crystal structure, so silicon has no linear electro-optical effect, and linear electro-optical effect is required for today's high-performance optical modulators. The silicon-based modulator needs to rely on the plasma dispersion effect, which is usually realized by ion implantation to form a PN junction. The refractive index of the silicon waveguide is changed by changing the carrier concentration of the PN junction, thereby realizing the modulation of the amplitude of the light wave. However, this method changes the refractive index of the silicon waveguide, and also changes the loss of the silicon waveguide. It achieves high bandwidth based on the sacrificial extinction ratio, which makes the application of the silicon-based modulator in long-distance digital optical communication systems. Limited, in addition, because the carrier effect itself is a nonlinear process, the linearity of the silicon-based modulator is far less than the traditional lithium niobate device, and the future 5G mobile communication system, microwave photonics, and In the next generation of fiber-optic communication applications, the linearity requirements are getting higher and higher.

In summary, although silicon-based photonic devices have a very large technical advantage, the carrier-based silicon-based modulators are still not comparable in performance to commercial lithium niobate modulators. Lithium niobate material has superior linear electro-optical effect and is the material of choice for high performance optical modulators.

Summary of the invention

The invention aims at the problem that the existing silicon-based modulator has low extinction ratio, limited linearity, large insertion loss, and the like, and proposes a silicon and lithium niobate hybrid integrated light modulator, which combines silicon and lithium niobate. The advantages of these two materials are to improve the performance of silicon-based light modulators, with high extinction ratio, high linearity, and low insertion loss.

In order to achieve the above object, the technical solution adopted is:

A silicon and lithium niobate hybrid integrated light modulator comprising a silicon-on-insulator optical waveguide structure, an optical splitting structure, a silicon wedge waveguide optical mode conversion structure, a bonded dielectric layer, a lithium niobate waveguide, a signal metal electrode, and a ground a metal electrode, wherein the silicon-on-insulator optical structure is connected to an input end of the optical splitting structure, and the two output ends of the optical splitting structure are respectively connected to the lithium niobate waveguide through a silicon wedge waveguide optical mode conversion structure; the signal metal electrode Provided on an opposite side of the two output ends of the optical splitting structure; the grounded metal electrode is disposed on a side opposite to the two output ends of the optical splitting structure; the silicon-based optical structure, the optical splitting structure, and the silicon wedge waveguide An optical mode switching structure, a lithium niobate waveguide, a signal metal electrode, and a grounded metal electrode are disposed within the bonding dielectric layer.

In particular use, the optical splitting structure splits the beam in the silicon-based optical structure into two perfectly equal beams and progressively couples the beam into the lithium niobate waveguide through the silicon wedge waveguide optical mode conversion structure. Applying a voltage to the signal metal electrode and grounding the grounded metal electrode, the refractive index of the lithium niobate waveguide changes due to the Pockels effect, and a refractive index difference Δn is generated between the two lithium niobate waveguides, thereby making the two beams equal. A phase difference occurs between the lights. The two beams are gradually coupled into the silicon waveguide through the silicon wedge waveguide optical mode conversion structure, and the two beams of the optical splitting structure interfere to realize beam intensity modulation.

Preferably, the number of the silicon-based optical waveguide structures is 2, the number of the optical splitting structures is 2, the number of the lithium niobate waveguides is 2, and 2 silicon-based optical waveguide structures are respectively separated from 2 optical points. The input ends of the beam structure are connected; the two output ends of the two optical splitting structures are respectively connected to the left and right ends of the two lithium niobate waveguides through a silicon wedge waveguide optical mode conversion structure.

Preferably, the number of the grounded metal electrodes is two, and the two grounded metal electrodes are respectively disposed on opposite sides of the two output ends of the optical splitting structure.

At the same time, the present invention also provides a method for preparing a hybrid integrated light modulator of silicon and lithium niobate, the specific scheme of which is as follows:

1) using a photolithographic etching technique to fabricate a silicon-based optical structure on a substrate of a silicon-on-insulator film;

2) spin-coating benzocyclobutene on the silicon-based optical structure obtained in the step 1);

3) attaching a wafer of an insulator-buried oxygen layer-lithium niobate film to the insulator-buried oxygen layer-silicon-based optical structure-benzocyclobutene composite obtained in the step 2), and annealing at a high temperature to obtain silicon germanium. Lithium acid combination substrate;

4) using a series of mechanical chemical means to remove the buried oxide layer and the insulator above the lithium niobate film on the lithium silicon niobate composite substrate obtained in the step 3) to obtain a lithium silicon niobate film composite substrate;

5) forming a lithium niobate waveguide by using photolithography and etching on the combined substrate obtained in the step 4);

6) In the structure obtained in the step 5), an adhesion layer and a gold electrode are plated by a metal stripping process to obtain a lithium silicon niobate hybrid integrated optical modulator.

Compared with the prior art, the beneficial effects of the present invention are:

1) The present invention integrates lithium niobate and silicon to introduce a linear electro-optic effect of lithium niobate onto a silicon-based platform, and combines the advantages of two materials, silicon and lithium niobate, to improve the light modulator. performance.

2) The process of dry etching lithium niobate material is adopted to improve the interaction between the electric field and the light field, and a high-efficiency modulator can be realized.

DRAWINGS

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a three dimensional schematic view of an optical device of a lithium silicon niobate hybrid integrated modulator of the present invention.

2 is a top plan view of an optical device of a lithium silicon niobate hybrid integrated modulator of the present invention.

3 is a schematic view showing a silicon wedge waveguide optical mode conversion structure of the present invention.

Detailed ways

The drawings are for illustrative purposes only and are not to be construed as limiting the invention;

The invention will be further described below in conjunction with the drawings and embodiments.

Example 1

Referring to FIGS. 1 to 3, a silicon and lithium niobate hybrid integrated light modulator provided by the present invention includes: a silicon-on-insulator optical waveguide structure, an optical splitting structure 2, a silicon wedge waveguide optical mode conversion structure 3, and bonding. Dielectric layer 4, lithium niobate waveguide 5, signal metal electrode 6, grounding metal electrode 7;

Wherein the silicon-on-insulator optical waveguide structure 1 is connected to the input end of the optical splitting structure 2, and the two output ends of the optical splitting structure 2 are respectively connected to the lithium niobate waveguide 5 through the silicon wedge waveguide optical mode conversion structure 3; The signal metal electrode 6 is disposed on the opposite side of the two output ends of the optical splitting structure 2; the grounded metal electrode 7 is disposed on the opposite side of the two output ends of the optical splitting structure 2; The optical splitting structure 2, the silicon wedge waveguide optical mode conversion structure 3 is disposed in the bonding medium layer 4, and the lithium niobate waveguide 5, the signal metal electrode 6, and the grounding metal electrode 7 are disposed above the bonding medium layer 4.

The optical splitting structure 2 splits the light beam in the silicon-based optical structure 1 into two completely equal beams, and the light beam is gradually coupled into the lithium niobate waveguide 5 through the mode conversion structure 3. A voltage is applied to the signal metal electrode 6, and the grounded metal electrode 7 is grounded. Due to the change in the refractive index of the Pockels effect lithium niobate waveguide, a refractive index difference Δn is generated between the two lithium niobate waveguides 5, thereby causing two A phase difference occurs between the beams of equal light. The two beams are gradually coupled into the silicon waveguide through the mode conversion structure 3, and interfere with the two beams of the optical splitting structure 2 to realize beam intensity modulation.

The specific process steps of the invention for preparing a lithium silicon niobate hybrid integrated modulator are as follows:

It is apparent that the above-described embodiments of the present invention are merely illustrative of the present invention and are not intended to limit the embodiments of the present invention. Other variations or modifications of the various forms may be made by those skilled in the art in light of the above description. There is no need and no way to exhaust all of the implementations. Any modifications, equivalent substitutions and improvements made within the spirit and scope of the invention are intended to be included within the scope of the appended claims.

Claims

A silicon and lithium niobate hybrid integrated light modulator, comprising: a silicon-on-insulator optical waveguide structure, an optical splitting structure, a silicon wedge waveguide optical mode conversion structure, a bonding dielectric layer, a lithium niobate waveguide, and a signal a metal electrode and a grounded metal electrode, wherein the silicon-based optical structure on the insulator is connected to the input end of the optical splitting structure, and the two output ends of the optical splitting structure are respectively connected to the lithium niobate waveguide through a silicon wedge waveguide optical mode conversion structure; The signal metal electrode is disposed on an opposite side of the two output ends of the optical splitting structure; the grounded metal electrode is disposed on a side opposite to the two output ends of the optical splitting structure; the hybrid integrated light modulator is a double The layer structure: the silicon-based optical waveguide structure, the optical splitting structure, and the silicon wedge-shaped waveguide optical mode conversion structure are disposed in the bonding medium layer, and the lithium niobate waveguide, the signal metal electrode, and the grounding metal electrode are disposed above the bonding medium layer.
The silicon and lithium niobate hybrid integrated light modulator according to claim 1, wherein the number of the silicon-based optical waveguide structures is two, and the number of the optical splitting structures is two, the lithium niobate The number of waveguides is 2, and the two silicon-based optical waveguide structures are respectively connected to the input ends of the two optical splitting structures; the two output ends of the two optical splitting structures respectively pass through the silicon wedge-shaped waveguide optical mode conversion structure and two turns The left and right ends of the lithium acid waveguide are connected.
The silicon and lithium niobate hybrid integrated light modulator according to claim 2, wherein the number of the grounded metal electrodes is two, and the two grounded metal electrodes are respectively disposed at two output ends of the optical splitting structure. The side of the back.
A method for preparing a silicon and lithium niobate hybrid integrated light modulator according to any one of claims 1 to 3, comprising the steps of:

1) using a photolithographic etching technique to fabricate a silicon-based optical structure on a substrate of a silicon-on-insulator film;

2) spin-coating benzocyclobutene on the silicon-based optical structure obtained in the step 1);

3) attaching a wafer of an insulator-buried oxygen layer-lithium niobate film to the insulator-buried oxygen layer-silicon-based optical structure-benzocyclobutene composite obtained in the step 2), and annealing at a high temperature to obtain silicon germanium. Lithium acid combination substrate;

4) using a series of mechanical chemical means to remove the buried oxide layer and the insulator above the lithium niobate film on the lithium silicon niobate composite substrate obtained in the step 3) to obtain a lithium silicon niobate film composite substrate;

5) forming a lithium niobate waveguide by using photolithography and etching on the combined substrate obtained in the step 4);

6) In the structure obtained in the step 5), an adhesion layer and a gold electrode are plated by a metal stripping process to obtain a lithium silicon niobate hybrid integrated optical modulator.