阅读说明：本技术 一种带有损耗补偿功能的光栅层间耦合器及其制备方法 (Grating interlayer coupler with loss compensation function and preparation method thereof ) 是由 王菲 曹至庚 尹悦鑫 陶思亮 许崇前 孙潼鹤 张大明 于 2021-10-08 设计创作，主要内容包括：一种带有损耗补偿功能的光栅层间耦合器及其制备方法,属于层间耦合器技术领域。由硅衬底、第一SiO-(2)埋氧层、第一金属反射镜、第二SiO-(2)埋氧层、硅层、SiO-(2)隔离层、第一聚合物包层、铒镱共掺聚合物层、第二聚合物包层和第二金属反射镜构成；硅层由第一硅波导、硅光栅、第二硅波导组成；铒镱共掺聚合物层由铒镱共掺聚合物波导、铒镱共掺聚合物光栅和铒镱共掺聚合物光波导放大器组成；硅光栅及铒镱共掺聚合物光栅的单个光栅单元类似“台阶”结构。该器件分别将硅基光栅耦合器和聚合物光栅耦合器分别置于两层,实现了硅基、聚合物光子回路的三维混合集成,实现了结构紧凑、高效的光栅层间耦合,在三维光子集成领域具有很强的应用潜力。(A grating interlayer coupler with a loss compensation function and a preparation method thereof belong to the technical field of interlayer couplers. Comprises a silicon substrate, a first SiO 2 Buried oxide layer, first metal reflector, and second SiO 2 Buried oxide layer, silicon layer, SiO 2 The isolating layer, the first polymer cladding layer, the erbium ytterbium co-doped polymer layer, the second polymer cladding layer and the second metal reflecting mirror; the silicon layer consists of a first silicon waveguide, a silicon grating and a second silicon waveguide; the erbium-ytterbium co-doped polymer layer consists of an erbium-ytterbium co-doped polymer waveguide, an erbium-ytterbium co-doped polymer grating and an erbium-ytterbium co-doped polymer optical waveguide amplifier; the single grating unit of the silicon grating and the erbium-ytterbium co-doped polymer grating is similar to a step structure. The device respectively arranges the silicon-based grating coupler and the polymer grating coupler in two layers, realizes three-dimensional hybrid integration of silicon-based and polymer photon loops, and realizes grating interlayer coupling with compact and efficient structureAnd the method has strong application potential in the field of three-dimensional photon integration.)

1. A grating interlayer coupler with a loss compensation function is characterized in that: from bottom to top, the silicon substrate (1) and the first SiO are sequentially arranged₂A buried oxide layer (2), a first metal reflector (3), and a second SiO₂Buried oxide layer (4), silicon layer (5), SiO₂The laser reflection mirror comprises an isolation layer (6), a first polymer cladding layer (7), an erbium ytterbium co-doped polymer layer (8), a second polymer cladding layer (9) and a second metal reflection mirror (10); the silicon layer (5) consists of a first silicon waveguide (a1), a silicon grating (b1) and a second silicon waveguide (c 1); the erbium ytterbium co-doped polymer layer (8) consists of three parts of an erbium ytterbium co-doped polymer waveguide (a2), an erbium ytterbium co-doped polymer grating (b2) and an erbium ytterbium co-doped polymer optical waveguide amplifier (c 2); the single grating units of the silicon grating (b1) and the erbium ytterbium co-doped polymer grating (b2) are similar to a 'step' structure, and the widths of the silicon layer (5) and the erbium ytterbium co-doped polymer layer (8) are smaller than those of the rest layers; h is the thickness of the erbium-ytterbium co-doped polymer layer (8) or the silicon layer (5), W is the width of the silicon layer (5) and the erbium-ytterbium co-doped polymer layer (8) after etching, E is the etching depth, L is the length of an un-etched area, lambda is the grating period, and the duty ratio F is L/lambda; the thickness H of a single grating unit of the silicon grating (b1) is 220-340 nm, the etching depth E is 70-150 nm, the period lambda is 590-670 nm, the width W is 5-10 mu m, the length L of an un-etched area is 236-402 nm, and the duty ratio F is 40-60%; the thickness H of a single grating unit of the erbium-ytterbium co-doped polymer grating (b2) is 0.5-1 mu m, the period lambda is 1150-1350 nm, the etching depth E is 0.2-0.6 mu m, the width W is 5-10 mu m, the length L of an un-etched area is 460-810 nm, and the duty ratio F is 40-60%; the polymer grating (b2) and the silicon grating (b1) have a relative displacement d along the light propagation direction, wherein d is 1-2 μm.

2. The grating interlayer coupler with loss compensation function of claim 1, wherein: first SiO₂Buried oxide layer (2) and second SiO₂The thickness of the oxygen buried layer (4) is divided into1 to 3 μm and 0.5 to 1 μm, respectively.

3. The grating interlayer coupler with loss compensation function of claim 1, wherein: the first metal reflector (3) and the second metal reflector (10) are made of one of gold, aluminum or silver, and the thickness of the first metal reflector is 50-100 nm.

4. The grating interlayer coupler with loss compensation function of claim 1, wherein: SiO 2₂The isolation layer (6) is used as the upper cladding of the silicon grating and is also used as the substrate of the polymer grating, and the thickness is 1-2 mu m.

5. The grating interlayer coupler with loss compensation function of claim 1, wherein: the first polymer cladding (7) and the second polymer cladding (9) are made of the same material, are made of polymer materials such as polymethyl methacrylate, polyethylene, polyester, polystyrene, EpoClad or CYTOP and have the thickness of 1-5 mu m.

6. The grating interlayer coupler with loss compensation function of claim 1, wherein: the erbium-ytterbium co-doped polymer layer (8) has a loss compensation function and is made of doped NaYF₄:Yb³⁺、Er³⁺Nanocrystalline SU-82000.5, SU-82002, SU-82005, or EpoCore polymeric core materials.

7. A method for manufacturing a grating interlayer coupler with a loss compensation function according to any one of claims 1 to 6, comprising the steps of:

(1) optionally growing SiO on the silicon surface₂Respectively as a silicon substrate (1) and a first SiO₂Buried oxide layer (2) on the first SiO₂A metal film is evaporated on the buried oxide layer (2) to be used as a first metal reflector (3);

(2) deposition of SiO on the first metal mirror 3 by means of plasma-enhanced chemical vapor deposition₂As the second SiO₂An oxygen buried layer (4);

(3) in the second SiO₂Depositing a silicon layer (5) on the oxygen burying layer (4) by using a plasma enhanced chemical vapor deposition method; then, the deposited silicon layer (5) is flattened by adopting a chemical mechanical polishing method;

(4) deep etching: spin-coating SU-82005 negative photoresist on the surface of the silicon layer (5), and then pre-baking and cooling curing at 60-90 ℃ for 20-30 minutes on a heating plate; and then carrying out mask exposure under an ultraviolet lithography machine, wherein the mask is in a negative plate structure and has the outline of a silicon grating coupler consisting of a first silicon waveguide (a1), a silicon grating (b1) and a second silicon waveguide (c1), and the ultraviolet wavelength is 365nm, and the light power is 20-25 mW/cm²(ii) a Placing the photoetched substrate on a hot plate, carrying out post-baking treatment at 65-95 ℃ for 20-30 minutes, cooling to room temperature, then placing the substrate in a PGMEA developing solution for developing, and removing unexposed photoresist; after complete development, putting the mixture into isopropanol solution to wash away residual glue, and finally washing the mixture with deionized water to remove the reagent; putting the developed substrate into an oven for hardening treatment at 125-150 ℃, thereby obtaining a photoresist mask plate with the width W on the silicon layer (5); finally, etching the silicon layer (5) by using inductively coupled plasma to prepare a silicon grating coupler profile with the width W; by using SF₆For etching gas, C₄F₈Passivation gas; finally, removing the photoresist mask plate by using an organic solvent;

(5) shallow etching: spin-coating SU-82005 negative photoresist on the surface of the silicon grating coupler profile, then pre-baking at 60-90 ℃ for 20-30 minutes on a heating plate, and cooling and curing; and then carrying out mask exposure under an ultraviolet photoetching machine, wherein the mask is a groove structure in the period of the silicon grating (b1), the mask is a negative plate, the wavelength of ultraviolet light is 365nm, and the light power is 20-25 mW/cm²(ii) a Placing the photoetched substrate on a hot plate, carrying out post-baking treatment at 65-95 ℃ for 20-30 minutes, cooling to room temperature, then placing the substrate in a PGMEA developing solution for developing, and removing unexposed photoresist; after complete development, putting the mixture into isopropanol solution to wash away residual glue, and finally washing the mixture with deionized water to remove the reagent; putting the developed substrate into an oven for hardening at 125-150 ℃, and performing film hardening treatment on the substrate at the middle position of the outline of the silicon grating couplerThe photoresist mask plate with the same structure of the silicon grating (b1) to be prepared; finally, obtaining a silicon grating (b1) with a groove structure by ICP etching; by using SF₆For etching gas, C₄F₈Passivation gas; finally, removing the photoresist mask plate by using an organic solvent;

(6) preparing SiO by PECVD on the silicon layer (5) etched in the step (5)₂Barrier layer (6), SiO₂The isolation layer (6) covers the silicon layer (5) and fills the grating groove; by applying CMP process to deposited SiO₂Carrying out planarization treatment;

(7) in SiO₂The isolating layer (6) is spin-coated with a polymer material as a first polymer cladding (7);

(8) NaYF is added₄: dissolving Yb and Er nanocrystals in 1-2 mL of toluene; then NaYF is added₄: mixing a toluene solution of Yb and Er with SU-82000.5, SU-82002, SU-82005 or EpoCore in a ratio of 1: 4, and performing ultrasonic oscillation to obtain the erbium-ytterbium co-doped polymer grating layer (8) material;

(9) rotationally coating erbium ytterbium co-doped polymer grating layer (8) material on the first polymer cladding layer (7), then placing on a heating plate, carrying out pre-drying treatment at 60-90 ℃ for 20-30 minutes, and cooling and curing; carrying out mask exposure under an ultraviolet lithography machine, wherein the mask has the structure of the profile of a polymer grating coupler consisting of an erbium-ytterbium co-doped polymer waveguide (a2), an erbium-ytterbium co-doped polymer grating (b2) and an erbium-ytterbium co-doped polymer optical waveguide amplifier (c2), and is a negative mask; wherein the wavelength of ultraviolet light is 365nm, and the optical power is 20-25 mW/cm²(ii) a Placing the substrate after photoetching on a hot plate, carrying out post-baking treatment at 65-95 ℃ for 20-30 minutes, cooling to room temperature, then placing the substrate into a developing solution corresponding to the erbium-ytterbium co-doped polymer grating layer material for developing, and removing unexposed photoresist; after complete development, putting the polymer grating coupler into an organic solvent to wash away residual glue, and finally washing the polymer grating coupler with deionized water to remove the reagent to obtain the polymer grating coupler with the same width as the silicon grating; due to the diffraction angle of the diffraction of the grating, in order to realize higher coupling efficiency, the polymer grating and the silicon grating have relative displacement d along the light propagation direction;

(10) on an erbium-ytterbium co-doped polymer grating layer (8)Depositing a layer of aluminum metal film with the thickness of 2-5 microns in an empty mode, spin-coating BP212 positive photoresist with the thickness of 4-5 microns on the aluminum film, placing a substrate on a heating plate, performing pre-drying treatment at the temperature of 60-90 ℃ for 20-30 minutes, and cooling and curing; exposing the substrate under an ultraviolet photoetching machine, wherein the mask is a groove structure in the period of the erbium-ytterbium co-doped polymer grating (b2), and the mask is a positive plate, wherein the wavelength of ultraviolet light is 365nm, and the optical power is 20-25 mW/cm²(ii) a Placing the photoetched substrate on a hot plate for post-baking treatment at 65-95 ℃ for 20-30 minutes; developing in 0.5-1 wt% of sodium hydroxide solution, and removing the photoresist and the aluminum film of the exposed part to obtain a grating aluminum mask for ICP etching; preparing a polymer grating coupler with a gain medium on a polymer layer by ICP etching, wherein SF is adopted₆For etching gas, C₄F₈Passivation gas; removing residual glue by using ethanol, and removing an aluminum mask plate by using a sodium hydroxide solution to obtain an erbium-ytterbium co-doped polymer grating layer (8) with a groove structure;

(11) spin coating a polymer cladding material as a second polymer cladding (9) over the erbium ytterbium co-doped polymer grating layer (8);

(12) and (3) vacuum evaporating a metal film on the second polymer cladding (9) to be used as a second metal reflector (10), thereby preparing the grating interlayer coupler with the loss compensation function.

Technical Field

The invention belongs to the technical field of interlayer couplers, and particularly relates to a grating interlayer coupler with a loss compensation function and a preparation method thereof.

Background

Over the twenty-first century, with the development of information technology, the communication capacity of data centers and high-performance computers has increased rapidly, which has challenged the performance of traditional integrated circuits, such as bandwidth and power consumption. As the size of the device is reduced, the metal wires for transmitting electrical signals are more and more dense, and the problems of power consumption, time delay, leakage current and the like of electrical interconnection are more and more serious, which will severely limit the communication capacity. To further break through the bottleneck of electrical interconnects, attempts have been made to replace electrical interconnects with optical interconnects to achieve larger capacity transmission. The silicon-based Photonic Integrated Circuits (PICs) are compatible with a conventional Complementary Metal Oxide Semiconductor (CMOS) process by virtue of the PICs, can realize low-cost and large-scale manufacturing, can realize photonic interconnection with large bandwidth, low power consumption and low delay by using light as a transmission medium, and have great application potential in the fields of data centers, high-performance computers and the like.

On the other hand, insertion loss, scattering loss, bending loss, etc. are inevitably generated during the transmission of light, and the advantage of the optical amplifier that the optical signal can be directly amplified by avoiding the optical-electrical-optical conversion is gradually a hot spot of research. Based on the stimulated radiation principle of erbium ions, the erbium-ytterbium co-doped optical waveguide amplifier with the polymer material as the matrix can realize low-noise and high-gain amplification in a 1550nm wavelength region. The polymer photonic amplifier is easy to realize the hybrid integration with the silicon-based photonic integrated optical circuit by virtue of compact structure, easy manufacture, low manufacturing cost and the like.

At present, as the integration scale is gradually increased, the number of devices in a unit area is gradually increased, the traditional two-dimensional plane integration is limited, and three-dimensional photon integration is generated in order to further improve the integration level of an integrated optical circuit. Three-dimensional photonic integrated circuits (3D-PICs) can realize high-density and multi-functional integration under limited wafer size by setting different functional photonic devices in different layers, thereby realizing functions that cannot be realized by conventional PICs. In 3D-PICs, the most critical device is the interlayer coupler, but most of the interlayer couplers have the disadvantage of excessive loss, and the number of the interlayer coupler fingers capable of achieving coupling efficiency of 90% or more is large.

Disclosure of Invention

The invention provides a grating interlayer coupler with a loss compensation function and a preparation method thereof. The device respectively arranges the silicon-based grating coupler and the polymer grating coupler in two layers, and can realize high-efficiency interlayer coupling based on the diffraction principle of the grating. Meanwhile, the polymer grating coupler is prepared by erbium-ytterbium co-doped polymer material with light amplification function, so that loss generated in an optical transmission path is compensated; the device realizes three-dimensional hybrid integration of silicon-based and polymer photon loops, realizes grating interlayer coupling with compact and high efficiency, and has strong application potential in the field of three-dimensional photon integration.

The grating interlayer grating coupler with the loss compensation function is characterized in that a part of the structure of the device is schematically shown in figure 1, figure 2 is a cross-sectional view of the device in the direction of A-A' shown in figure 1, and the grating interlayer grating coupler sequentially comprises a silicon substrate 1 and a first SiO layer from bottom to top₂Buried oxide layer 2, first metal reflector 3 and second SiO₂Buried oxide layer 4, silicon layer 5, SiO₂Isolation layer 6, first polymer clad layer 7, erbium ytterbium co-doped polymer layer 8, second polymer clad layer9 and a second metal reflector 10; as shown in fig. 3, the erbium-ytterbium co-doped polymer layer 8 is composed of three parts, i.e., erbium-ytterbium co-doped polymer waveguide a2, erbium-ytterbium co-doped polymer grating b2, and erbium-ytterbium co-doped polymer optical waveguide amplifier c 2; the silicon layer 5 consists of three parts, namely a first silicon waveguide a1, a silicon grating b1 and a second silicon waveguide c 1; the single grating units of the silicon grating b1 and the erbium ytterbium co-doped polymer grating b2 are shown as the dotted line boxes in FIG. 3, and are similar to a step structure; h is the thickness of the erbium-ytterbium co-doped polymer layer 8 or the silicon layer 5, W is the width of the silicon layer 5 and the erbium-ytterbium co-doped polymer layer 8 after etching, the widths of other layers are all larger than W, E is the etching depth, L is the length of an un-etched region, λ is the grating period, and the duty ratio F is L/λ; the thickness H of a single grating unit of the silicon grating b1 is 220-340 nm, the etching depth E is 70-150 nm, the period lambda is 590-670 nm, the width W is 5-10 mu m, the length L of an un-etched area is 236-402 nm, and the duty ratio F is 40-60%; the thickness H of a single grating unit of the erbium-ytterbium co-doped polymer grating b2 is 0.5-1 mu m, the period lambda is 1150-1350 nm, the etching depth E is 0.2-0.6 mu m, the width W is 5-10 mu m, the length L of an un-etched area is 460-810 nm, and the duty ratio F is 40-60%.

First SiO₂Buried oxide layer 2 and second SiO₂The thickness of the oxygen burying layer 4 is 1-3 μm and 0.5-1 μm respectively;

the first metal reflector 3 and the second metal reflector 10 are made of one of high-reflectivity metals such as gold, aluminum and silver, the thickness of the metal is 50-100 nm, and the metal is used for improving the coupling efficiency of the grating interlayer coupler;

SiO₂the isolation layer 6 is used as an upper cladding of the silicon grating and is also used as a substrate of the polymer grating, and the thickness is 1-2 mu m;

the first polymer cladding 7 and the second polymer cladding 9 are made of the same material, are made of polymer materials such as polymethyl methacrylate (PMMA), Polyethylene (PE), Polyester (PET), Polystyrene (PS), EpoClad, CYTOP and the like, and have the thickness of 1-5 mu m;

the erbium-ytterbium co-doped polymer layer 8 has a loss compensation function and is made of doped NaYF₄:Yb³⁺、Er³⁺And (3) nanocrystalline SU-82000.5, SU-82002, SU-82005, EpoCore and other polymer core layer materials. Erbium ytterbium co-doped with erbiumThe working principle of the optical waveguide doped amplifier is based on Er³⁺Excited radiation and Er of³⁺、Yb³⁺Energy transfer between energy levels is used for realizing amplification of signal light. Yb of³⁺Has a typical two-level structure, has a large absorption cross section for 980nm pump light, and is usually doped in Er-containing materials as a sensitizer³⁺In the material system of (1), under the excitation of 980nm pump light, Yb³⁺Absorbing pump light energy to transition to²F_5/2Energy level and transfer pumping energy to Er through cross relaxation process³⁺Er in the ground state³⁺Excited absorption transition to excited state energy level⁴I_11/2However, the excited state energy level has a short lifetime and rapidly transits to the metastable state energy level in a non-radiative transition manner⁴I_13/2The metastable state has a longer life than the stable energy level, and can stay in the metastable state for a longer time. Er³⁺Ground state energy level of⁴I_15/2And metastable energy level⁴I_13/2The particle number inversion can occur, and under the action of the signal light, the metastable state energy level is subjected to stimulated radiation transition to the ground state energy level to generate light with the same frequency and phase as the signal light, so that the amplification of the signal light is realized, and Er is an element³⁺、Yb³⁺The energy level structure is shown in figure 4. The pumping mode of the optical amplifier can be divided into co-pumping and reverse pumping according to the propagation direction of the pump light, that is, the same propagation direction of the pump light and the signal light is co-pumping, and the opposite propagation direction of the pump light and the signal light is reverse pumping. Fig. 5 is a schematic diagram of transmission paths of signal light and pump light in the grating interlayer coupler with the loss compensation function. According to the grating Bragg condition, the grating can change the transmission direction of light, change the light transmitted in the horizontal direction into the vertical direction and change the light transmitted in the vertical direction into the horizontal direction. According to this principle, the signal light first propagates along the silicon layer 5 from left to right, changes the propagation direction to propagate upward when propagating to the silicon grating b1, then propagates to the erbium ytterbium co-doped polymer grating b2 changes the propagation direction to propagate horizontally, and then propagates in the erbium ytterbium co-doped polymer optical waveguide amplifier c 2. The backward pump light inputted at the right side of the erbium ytterbium co-doped polymer optical waveguide amplifier c2 is transmitted to the left side, and the backward pump light is transmitted from the silicon layer5 the signal light coupled to the polymer grating layer 8 is amplified in the erbium ytterbium co-doped polymer optical waveguide amplifier c2, and the amplified signal light is then transmitted to the output end along the right of the erbium ytterbium co-doped polymer optical waveguide amplifier c 2; the silicon-based photonic loop can realize the size conversion of the mode spot through the grating interlayer coupler and can realize efficient packaging test.

The specific preparation method of the grating interlayer coupler with the loss compensation function comprises the following steps:

(1) SiO with the thickness of 1-3 mu m is grown on the silicon surface₂As the silicon substrate 1 and the first SiO, respectively₂A buried oxide layer 2 having a wafer diameter of 2-8 inches on the first SiO layer₂A metal film with the thickness of 50-100 nm is evaporated on the oxygen burying layer 2 to be used as a first metal reflector 3, and the vacuum degree of an evaporation system is 6 multiplied by 10^-4Pa or less, and a deposition rate of

(2) Depositing a layer of SiO 0.5-1 μm thick on the first metal reflector 3 by Plasma-Enhanced Chemical Vapor Deposition (PECVD)₂As the second SiO₂An oxygen burying layer 4, wherein the pressure of a chamber of the PECVD equipment is 1500-2000 mTorr, the temperature of a substrate is 300-350 ℃, the radio frequency power is 100-200W, the flow rate of silane is 15-30 sccm, the flow rate of nitric oxide is 1800-2000 ccm, and the deposition rate is 150-220 nm/min;

(3) in the second SiO₂Depositing a silicon layer 5 with the thickness of 220-340 nm on the oxygen burying layer 4 by utilizing a Plasma-Enhanced Chemical Vapor Deposition (PECVD) method, wherein the pressure of a chamber of a PECVD device is 1500-2000 mTorr, the temperature of a substrate is 200-300 ℃, the radio frequency power is 100-200W, the flow rate of silane is 15-30 sccm, and the Deposition rate is 150-220 nm/min; then, a Chemical Mechanical Polishing (CMP) method is adopted to perform planarization treatment on the deposited silicon layer 5;

(4) deep etching: the surface of the silicon layer 5 was spin-coated with SU-82005 negative photoresist from Micro Chem, Inc., and thenPre-drying the mixture for 20 to 30 minutes at the temperature of between 60 and 90 ℃ on a heating plate, and cooling and curing the mixture; and performing mask exposure under an ultraviolet lithography machine, wherein the mask plate has a structure of the outline of a silicon grating coupler consisting of a first silicon waveguide a1, a silicon grating b1 and a second silicon waveguide c1, and is a negative plate, the ultraviolet wavelength is 365nm, and the light power is 20-25 mW/cm²(ii) a Placing the photoetched substrate on a hot plate, carrying out post-baking treatment at 65-95 ℃ for 20-30 minutes, cooling to room temperature, then placing the substrate into a PGMEA (propylene glycol monomethylether acetate) developing solution for development, and removing unexposed photoresist; after complete development, putting the mixture into isopropanol solution to wash away residual glue, and finally washing the mixture with deionized water to remove the reagent; putting the developed substrate into an oven for hardening treatment at 125-150 ℃, thereby obtaining a photoresist mask plate with the width of W on the silicon layer 5; finally, a silicon grating coupler profile with the width W of 5-10 μm is prepared on the silicon layer 5 through inductively Coupled Plasma etching (ICP), namely, under the mask of the photoresist mask plate, the silicon layer 5 which is not shielded by the photoresist and except the silicon grating coupler profile area is completely etched, and the second SiO which is leaked below is completely etched₂An oxygen buried layer 4; by using SF₆For etching gas, C₄F₈Passivation gas; finally, removing the photoresist mask plate by using an organic solvent;

(5) shallow etching: the surface of the silicon grating coupler profile is coated with SU-82005 negative photoresist of Micro Chem company in a spin mode, and then pre-baking is carried out on the surface of a heating plate at the temperature of 60-90 ℃ for 20-30 minutes, and cooling and curing are carried out; and then carrying out mask exposure under an ultraviolet photoetching machine, wherein the mask plate is a groove structure in a silicon grating b1 period and is a negative plate, the wavelength of ultraviolet light is 365nm, and the light power is 20-25 mW/cm²(ii) a Placing the photoetched substrate on a hot plate, carrying out post-baking treatment at 65-95 ℃ for 20-30 minutes, cooling to room temperature, then placing the substrate into a PGMEA (propylene glycol monomethylether acetate) developing solution for development, and removing unexposed photoresist; after complete development, putting the mixture into isopropanol solution to wash away residual glue, and finally washing the mixture with deionized water to remove the reagent; putting the developed substrate into an oven for hardening at 125-150 ℃ to form a film on the outline of the silicon grating couplerObtaining a photoresist mask plate with the same structure as the silicon grating b1 to be prepared at the middle position; finally, carrying out ICP etching to obtain a silicon grating b1 with a groove structure, wherein the period lambda of the silicon grating b1 is 590-670 nm, the grating unit number of the silicon grating b 8912 is 8-12, and the etching depth E of the silicon grating b1 is 70-150 nm; by using SF₆For etching gas, C₄F₈Passivation gas; finally, removing the photoresist mask plate by using an organic solvent;

(6) preparing SiO with the thickness of 1-2 mu m on the silicon layer 5 etched in the step (5) through PECVD₂Barrier layer 6, SiO₂The isolation layer 6 covers the silicon layer 5 and fills the grating groove; the pressure of a chamber of the PECVD equipment is 1500-2000 mTorr, the temperature of a substrate is 300-350 ℃, the radio frequency power is 100-200W, and SiH is adopted₄The gas flow is 15-30 sccm, the NO gas flow is 1800-2000 ccm, and the deposition rate is 150-220 nm/min; by applying CMP process to deposited SiO₂Carrying out planarization treatment;

(7) in SiO₂Spin-coating a polymer material with the thickness of 1-5 μm on the isolation layer 6 to serve as a first polymer cladding 7;

(8) preparing 1-2 mmol NaYF by using a full-automatic nano synthesizer (ANS02) and adopting a high-temperature thermal decomposition method₄: yb and Er nanocrystals (development of full-automatic nanometer material synthesizer, Song Wei industry, Jilin university, 2016 doctor academic paper, Er doping mol% of 2% and Yb of 18%), and mixing NaYF with the mixture of crystal and crystal₄: dissolving Yb and Er nanocrystals in 1-2 mL of toluene; then NaYF is added₄: mixing a toluene solution of Yb and Er with SU-82000.5, SU-82002, SU-82005 or EpoCore in a ratio of 1: 4, and performing ultrasonic oscillation to obtain an erbium-ytterbium co-doped polymer grating layer 8 material;

(9) spin-coating a erbium-ytterbium co-doped polymer grating layer 8 material with the thickness of 0.5-1 mu m on the first polymer cladding 7, then placing the mixture on a heating plate, carrying out pre-drying treatment at the temperature of 60-90 ℃ for 20-30 minutes, and cooling and curing; carrying out mask exposure under an ultraviolet lithography machine, wherein the mask has the structure of a polymer grating coupler profile formed by an erbium-ytterbium co-doped polymer waveguide a2, an erbium-ytterbium co-doped polymer grating b2 and an erbium-ytterbium co-doped polymer optical waveguide amplifier c2, and is a negative mask; wherein the wavelength of ultraviolet light is 365nm, and the optical power is 20-25 mW/cm²(ii) a Placing the substrate after photoetching on a hot plate, carrying out post-baking treatment at 65-95 ℃ for 20-30 minutes, cooling to room temperature, then placing the substrate into a developing solution corresponding to the erbium-ytterbium co-doped polymer grating layer material for developing, and removing unexposed photoresist; after complete development, putting the polymer grating coupler into an organic solvent to wash away residual glue, and finally washing the polymer grating coupler with deionized water to remove the reagent to obtain a polymer grating coupler profile with the width W of 5-10 mu m, wherein the polymer grating coupler profile is as wide as a silicon grating profile; due to the diffraction angle of the grating diffraction, in order to realize higher coupling efficiency, the polymer grating and the silicon grating have relative displacement d along the light propagation direction, wherein d is 1-2 μm, as shown in figure 5;

(10) vacuum evaporating an aluminum metal film with the thickness of 2-5 microns on the erbium-ytterbium co-doped polymer grating layer 8, spin-coating 4-5 microns of BP212 positive photoresist on the aluminum film, placing the substrate on a heating plate, carrying out pre-drying treatment at the temperature of 60-90 ℃ for 20-30 minutes, and cooling and curing; exposing the substrate under an ultraviolet photoetching machine, wherein the mask is a groove structure in a b2 period of the erbium-ytterbium co-doped polymer grating and is a positive mask, the wavelength of ultraviolet light is 365nm, and the optical power is 20-25 mW/cm²(ii) a Placing the photoetched substrate on a hot plate for post-baking treatment at 65-95 ℃ for 20-30 minutes; developing in 0.5-1 wt% of sodium hydroxide solution, and removing the photoresist and the aluminum film of the exposed part to obtain a grating aluminum mask for ICP etching; preparing a polymer grating coupler with a gain medium on a polymer layer by ICP etching, wherein SF is adopted₆For etching gas, C₄F₈Passivation gas; removing residual glue by using ethanol, and removing the aluminum mask plate by using a sodium hydroxide solution; obtaining a erbium-ytterbium co-doped polymer grating layer 8 with a groove structure, wherein the etching depth is 0.2-0.6 mu m, the period is 1150-1350 nm, and the grating unit number is 10-15;

(11) spin-coating 1-2 μm polymer cladding material on the erbium-ytterbium co-doped polymer grating layer 8 as a second polymer cladding 9;

(12) vacuum-depositing a metal thin film having a thickness of 50 to 100nm as a second metal mirror 10 on the second polymer clad layer 9, wherein the vacuum degree of the deposition system is 6X 10^-4Pa or less, and a deposition rate ofThereby preparing the grating interlayer coupler with the loss compensation function.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a schematic diagram of a three-dimensional structure of a grating interlayer coupler with loss compensation function;

FIG. 2 is a cross-sectional view of a grating interlayer coupler with loss compensation along the plane A-A';

fig. 3 is a schematic diagram of a silicon layer and an erbium-ytterbium co-doped polymer layer and a schematic diagram of a unit structure of a silicon grating and an erbium-ytterbium co-doped polymer grating in a grating interlayer coupler with a loss compensation function, where H is a layer thickness, W is a width, E is an etching depth, L is an unetched region length, λ is a period, and a duty ratio F is L/λ;

FIG. 4Er³⁺、Yb³⁺Energy level structure and operating principle of optical waveguide amplifier Yb³⁺Has a typical two-level structure, has a large absorption cross section for 980nm pump light, and is usually doped in Er-containing materials as a sensitizer³⁺In the material system of (1), under the excitation of 980nm pump light, Yb³⁺Absorbing pump light energy to transition to²F_5/2Energy level and transfer pumping energy to Er through cross relaxation process³⁺Er in the ground state³⁺Excited absorption transition to excited state energy level⁴I_11/2However, the excited state energy level has a short lifetime and rapidly transits to the metastable state energy level in a non-radiative transition manner⁴I_13/2The metastable state has a longer life than the stable energy level, and can stay in the metastable state for a longer time. Er³⁺Ground state energy level of⁴I_15/2And metastable energy level⁴I_13/2The population inversion can occur, and under the action of the signal light, the metastable state energy level is subjected to stimulated radiation transition to the ground state energy level to generate light with the same frequency and phase as the signal light, so that the signal light is amplified;

fig. 5 is a schematic diagram of transmission paths of signal light and pump light in the grating interlayer coupler with loss compensation function, in principle, the signal light first propagates along the silicon layer 5 from left to right, changes the propagation direction to propagate upward when propagating to the silicon grating b1, then changes the propagation direction to propagate horizontally when propagating to the erbium-ytterbium co-doped polymer grating b2, then propagates in the erbium-ytterbium co-doped polymer optical waveguide amplifier c2, the reverse pump light input at the right side of the erbium-ytterbium co-doped polymer optical waveguide amplifier c2 propagates to the left side, the signal light coupled from the silicon layer 5 to the polymer grating layer 8 is amplified in the erbium-ytterbium co-doped polymer optical waveguide amplifier c2, and the amplified signal light then propagates to the right along the erbium-ytterbium co-doped polymer optical waveguide amplifier c2 to the output end;

fig. 6 is a graph of interlayer coupling efficiency of the grating interlayer coupler, which is calculated by a logical FDTD software according to a finite difference time domain method, and the coupling efficiency of the proposed structure at a wavelength of 1545.54nm is 55.56% (loss is 2.55dB), thereby realizing an interlayer coupling function;

FIG. 7 is a gain curve of-2.55 dB (@1545.54nm) signal light of the polymer optical waveguide amplifier under excitation of 980nm pump light obtained by Matlab simulation calculation, and an amplification effect of 1dB/mm is obtained, so that an amplification function of the signal light is realized;

fig. 8 is a schematic diagram of optical field distribution of a grating interlayer coupler coupling region with a loss compensation function calculated by a logical FDTD software according to a finite difference time domain method, and light is input from a lower waveguide, passes through the coupling region, and is transmitted in an upper waveguide, thereby realizing the coupling function.

Detailed Description

The grating interlayer coupler with the loss compensation function is shown in the figure 1, the figure 2 is a cross-sectional view of the device in the A-A' direction, the lower layer is a silicon grating, a silicon layer with the thickness of 220nm is adopted, the upper layer is a polymer grating, and a SU-8 layer with the thickness of 0.8 mu m, a CYTOP lower cladding layer with the thickness of 1 mu m and a CYTOP upper cladding layer with the thickness of 1.7 mu m are adopted. The lower silicon-based grating and the upper polymer grating are respectively positioned in the upper waveguide layer and the lower waveguide layer. The top grating is integrated with the reverse pumping optical waveguide amplifier, and the bottom grating is connected with the bottom waveguide. The invention also includes two gold mirrors: the two gold reflectors are respectively positioned in the buried oxide layer and above the CYTOP grating, and the distance between the two reflectors is 3 mu m, so that light diffracted by the grating resonates between the two reflectors, and the directivity and the coupling efficiency of the grating are improved.

The specific implementation steps are as follows:

(1) here we select 2 inch diameter, SiO₂A wafer having a thickness of 3 μm was prepared. A metal film with a thickness of 50nm is vacuum-evaporated on a wafer to be used as a first metal reflector 3, in the embodiment, gold is used as a metal reflector material, and the specific method comprises the following steps: putting the substrate into a vacuum evaporation system, and spreading gold powder on the bottom of a crucible; starting a mechanical pump to pump the vacuum degree of the system to be below 10 Pa; starting the molecular pump to pump the vacuum degree of the system to 6X 10^-4Pa below; opening the baffle of the evaporation system and the film thickness meter, evaporating gold powder, and setting the evaporation rate asThe evaporation thickness is 50 nm; after the evaporation is finished, nitrogen is injected into the system after the system is cooled, and the substrate is taken out;

(2) 1 μm SiO by Plasma Enhanced Chemical Vapor Deposition (PECVD) on the first metal mirror 3₂As the second SiO₂An oxygen burying layer 4, wherein the chamber pressure of the PECVD equipment is 1500mTorr, the substrate temperature is 350 ℃, the radio frequency power is 180W, the silane gas flow is 15sccm, the nitric oxide gas flow is 1800sccm, and the deposition rate is 180 nm/min; the deposited SiO is subsequently polished by Chemical Mechanical Polishing (CMP)₂Carrying out planarization treatment and thinning to 0.6 mu m;

(3) in the second SiO₂Preparing a silicon layer 5 with a thickness of 300nm on the buried oxide layer 4 by Plasma Enhanced Chemical Vapor Deposition (PECVD), wherein the pressure of a chamber of the PECVD device is 1500mTorr, the temperature of the substrate is 250 ℃, and the radio frequency power is highThe flow rate of silane gas is 15sccm, and the deposition rate is 150nm/min, wherein the flow rate is 180W; then, carrying out planarization treatment on the deposited Si by adopting a chemical mechanical polishing method and thinning the deposited Si to 220 nm;

(4) SU-82005 of Micro Chem is spin-coated on the surface of the silicon layer, SU-82005 of Micro Chem is spin-coated on the surface of the silicon layer 5, and an SU-8 mask plate is prepared by adopting a wet etching process. Placing the substrate on a heating plate, carrying out pre-drying treatment at 60 ℃ (10 minutes) and 90 ℃ (20 minutes), and cooling and solidifying; and then carrying out mask exposure under an ultraviolet lithography machine, wherein the mask plate has the structure of the outlines of a first silicon waveguide a1, a silicon grating b1 and a second silicon waveguide c1, and is a negative plate, the ultraviolet wavelength is 365nm, and the light power is 23mW/cm²(ii) a Placing the photoetched substrate on a hot plate, carrying out post-baking treatment at 65 ℃ (10 minutes) and 95 ℃ (20 minutes), cooling to room temperature, then placing the substrate into a PGMEA (propylene glycol monomethyl ether acetate) developing solution for development, after the development is completed, placing the substrate into an isopropanol solution to wash away residual glue, and finally washing the substrate with deionized water to remove a reagent; putting the developed substrate into an oven for 125 ℃ (30 minutes) for hardening treatment; obtaining a photoresist mask plate with the width of 5 mu m on the silicon layer 5; finally, a silicon grating coupler profile with the width of 5 mu m and the thickness of 220nm is prepared on the silicon layer 5 by inductively coupled plasma etching, namely, under the mask of the photoresist mask, the silicon layer 5 which is not shielded by the photoresist and is except the silicon grating coupler profile area is completely etched, and the second SiO which is leaked below is completely etched₂An oxygen buried layer 4; by using SF₆For etching gas, C₄F₈Passivation gas; finally, removing the photoresist mask plate by using an organic solvent;

(5) spin-coating SU-82005 negative photoresist of Micro Chem company on the profile surface of the silicon grating coupler, placing the substrate on a heating plate, pre-baking at 60 deg.C (10 min) and 90 deg.C (20 min), and cooling for curing; exposing the grating etching area under an ultraviolet photoetching machine, wherein the wavelength of ultraviolet light is 365nm, and the optical power is 23mW/cm²(ii) a Placing the photoetched substrate on a hot plate for post-baking treatment at 95 ℃ (30 minutes), cooling to room temperature, then placing the substrate into PGMEA developing solution for development, and removing unexposed photoresist; after the development is completed, put into the developerWashing off residual glue in the propanol solution, and finally washing with deionized water to remove the reagent; putting the developed substrate into an oven for hardening treatment at 150 ℃ for 30 minutes; finally, obtaining a photoresist mask plate with the same structure as the silicon grating b1 needing to be prepared at the middle position of the silicon grating coupler profile through photoetching and developing; preparing a silicon grating coupler on the silicon layer by ICP etching, and adopting SF₆For etching gas, C₄F₈The obtained silicon grating is a uniform grating with the etching depth of 70nm, the period of 616nm, the width of 5 μm, the duty ratio of 50% and the number of grating units of 12 for passivating gas; finally, removing the photoresist mask plate by using an organic solvent;

(6) depositing SiO with the thickness of 1.5 mu m on the silicon layer 5 etched in the step (5) by PECVD₂Barrier layer 6, SiO₂The isolation layer 6 covers the silicon layer 5 and fills the grating groove; wherein the pressure of a cavity of the PECVD equipment is 1500mTorr, the temperature of a substrate is 350 ℃, the radio frequency power is 180W, the flow rate of silane gas is 15sccm, the flow rate of nitric oxide gas is 1800sccm, and the deposition rate is 180 nm/min; followed by CMP process on SiO₂Carrying out planarization treatment and thinning to 1 μm;

(7) in SiO₂A polymer material with a thickness of 2 μm is spin-coated on the isolation layer to serve as a lower cladding layer of the polymer grating, in this embodiment, a CYTOP (1-butyl vinyl ether) material is selected as the first polymer cladding layer 7;

(8) 2mmol of NaYF4 is prepared by a full-automatic nanometer synthesizer (ANS02) by adopting a high-temperature thermal decomposition method: yb and Er nanocrystals, NaYF 4: dissolving Yb and Er nanocrystals in 2mL of toluene, and then adding NaYF 4: mixing a toluene solution of Yb and Er with a polymer waveguide core layer material in a ratio of 1: 4, and performing ultrasonic oscillation, wherein the polymer waveguide core layer material in this embodiment is SU-82000.5 negative photoresist, thereby obtaining the erbium-ytterbium co-doped polymer grating layer 8 material;

(9) spin coating 0.8 μm erbium ytterbium co-doped polymer grating layer 8 material on the first polymer cladding 7, placing the substrate on a heating plate, pre-baking at 60 deg.C (10 min) and 90 deg.C (20 min), and cooling to solidify; then mask exposure is carried out under an ultraviolet photoetching machine, and the structure of the mask is erbium-ytterbium co-doped polymerThe profiles of the waveguide a2, the erbium ytterbium co-doped polymer grating b2 and the erbium ytterbium co-doped polymer optical waveguide amplifier c2 are negative versions; wherein the wavelength of ultraviolet light is 365nm, and the optical power is 23mW/cm²(ii) a Placing the photoetched substrate on a hot plate for post-baking treatment at 65 ℃ (10 minutes) and 95 ℃ (20 minutes), cooling to room temperature, placing the substrate in a PGMEA developer for development, and removing unexposed photoresist; after complete development, putting the mixture into isopropanol solution to wash away residual glue, and finally washing the mixture with deionized water to remove the reagent; obtaining a polymer grating profile with the width of 5 mu m, wherein the width of the polymer grating profile is the same as that of the silicon grating profile; due to the diffraction angle of the grating diffraction, in order to realize higher coupling efficiency, the polymer grating and the silicon grating have relative displacement d along the light propagation direction, and the length is 1.2 μm, as shown in the attached figure 5;

(10) vacuum evaporating an aluminum metal film with the thickness of 2-5 microns on the erbium-ytterbium co-doped polymer grating layer 8, spin-coating 5 microns of BP212 positive photoresist on the aluminum film, placing the substrate on a heating plate, carrying out pre-drying treatment at 60 ℃ (10 minutes) and 90 ℃ (20 minutes), and cooling and curing; exposing with mask of ultraviolet photoetching machine, wherein the mask is a groove structure in erbium-ytterbium co-doped polymer grating b2 period, the mask is a positive plate, the ultraviolet wavelength is 365nm, and the optical power is 23mW/cm²(ii) a Placing the photoetched substrate on a hot plate to carry out post-baking treatment at 65 ℃ (10 minutes) and 95 ℃ (20 minutes); developing by using 0.5 wt% sodium hydroxide solution, and removing the photoresist and aluminum of the exposed part to obtain an aluminum mask for ICP etching; preparing a polymer grating coupler with a gain medium and a polymer waveguide on a polymer layer by ICP etching, wherein SF is adopted₆For etching gas, C₄F₈The polymer grating is a passivation gas, the obtained polymer grating is a uniform grating, the grating period is 1261nm, the width is 5 μm, the duty ratio is 50%, the etching depth is 70nm, and the number of grating units is 12; removing residual glue by using ethanol, and removing the aluminum mask plate by using 0.5 wt% of sodium hydroxide solution;

(11) spin-coating 1.7 μm polymer cladding material on erbium-ytterbium co-doped polymer grating layer 8 as second polymer cladding 9, in this example the polymer cladding material is CYTOP;

(12) and (3) performing vacuum evaporation on the CYTOP upper cladding layer to form a second metal reflector 10 with the thickness of 50nm, wherein gold is selected as the metal reflector material in the embodiment, and the specific method is the same as the method in the step (1).