Single-mode micro-disk resonator and preparation method and application thereof

Abstract

The invention discloses a single-mode micro-disc resonance device and a preparation method and application thereof. The single-mode micro-disc resonator device based on amorphous gallium oxide comprises an optical coupler used for coupling input light and output light, a semicircular pulley type coupling waveguide structure and a gallium oxide micro-disc resonant cavity structure. The design of a semicircular pulley type coupling waveguide is adopted, and the width and the bending radius of the coupling waveguide are designed, so that the coupling waveguide and the micro-disk meet phase matching conditions, light in different radial modes in the micro-disk is selected, and finally single-mode output is achieved. Meanwhile, a high etching rate of the amorphous gallium oxide coupling waveguide can be obtained by regulating and controlling the proportion of the mixed gas used for etching, the side wall angle of the coupling waveguide is increased, and the surface appearance of the gallium oxide coupling waveguide is improved, and the preparation method of the amorphous gallium oxide coupling waveguide is developed for the first time. The method has important application value in the technical field of integrated photonic chips.

Description

Technical Field

[0001] The present invention particularly relates to a single-mode micro-disk resonant device and a preparation method and application thereof, belonging to the technical field of integrated photonic chips. Background Art

[0002] In recent years, with the rapid development of emerging technologies such as 5G, artificial intelligence, cloud computing and the Internet of Things, major technical challenges have been raised in terms of current signal processing speed, transmission bandwidth and chip power consumption. However, various optoelectronic chips and coupled waveguide devices, as carriers for the transmission and processing of communication signals, will face higher performance requirements. Traditional silicon-based optoelectronic chips face performance bottlenecks and limitations in the development of active chips, which has promoted the development of a large number of new optoelectronic materials and devices, such as lithium niobate, silicon nitride, silicon carbide, III-V semiconductors and gallium nitride, tantalum oxide, gallium oxide and other materials. Integrated optoelectronic chips developed based on these material platforms have their own advantages and suitable application scenarios.

[0003] Among them, gallium oxide (Ga2O3) is the representative of the fourth generation of semiconductor materials. Compared with the third generation semiconductors, Ga2O3 has better control of carrier concentration, high thermal stability, ultra-wide band gap (4.2-4.9eV), solar blind wavelength (200-300nm), ultra-high critical breakdown field strength (8MV / cm), ultra-strong transparent conductivity and lower power consumption (the loss is 1 / 3000 of silicon under the same conditions). It has received extensive attention in the fields of new energy vehicle power devices, radio frequency chips, artificial intelligence and high-speed optical communications. It is expected to achieve "overtaking on the curve" in the field of semiconductor chips for my country in the next decade. Therefore, the development of integrated optoelectronic devices and coupled waveguide processes based on Ga2O3 has become a key link in high-performance chips.

[0004] At present, Ga2O3 devices used in the communication field are all developed based on crystal structure. The preparation process involves complex process steps such as epitaxial growth of high-quality single crystal materials, etching problems caused by different crystal phases, and bonding with silicon-based semiconductor devices, which increases the preparation cost of Ga2O3 coupled waveguide devices. However, amorphous Ga2O3 materials also have most of the characteristics of crystalline Ga2O3, and the preparation technology of amorphous Ga2O3 thin film materials is simple. It is easy to grow on any substrate by sputtering and evaporation methods, and it is also easy to heterogeneously integrate with silicon-based chips. It is widely used in the current field of photonic chip technology. For example, structures such as direct-coupled waveguides, microdisks, microrings and MZIs are all core components in photonic chips. However, photonic devices developed based on amorphous Ga2O3 and their preparation methods are rarely reported. Summary of the invention

[0005] The main purpose of the present invention is to provide a single-mode micro-disk resonator device and a preparation method and application thereof, thereby overcoming the deficiencies in the prior art.

[0006] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention includes:

[0007] A first aspect of an embodiment of the present invention provides a single-mode microdisk resonator device, comprising:

[0008] A first optical coupler, a coupling waveguide, a second optical coupler and a micro-disk resonant cavity are arranged in the same working plane, the coupling waveguide includes a first waveguide, a second waveguide and a third waveguide connected in sequence, the first optical coupler and the second optical coupler are connected to the first waveguide and the third waveguide respectively, the second waveguide is arranged at intervals on one side of the micro-disk resonant cavity, and the second waveguide is an arc structure arranged around the micro-disk resonant cavity,

[0009] The coupling coefficient κ between the coupled waveguide and the microdisk resonant cavity is:

[0010]

[0011] Among them, n wg R wg =n disk R disk , θ is the angle range of the second waveguide coupling around the microdisk resonator, θ is the variable of the coupling angle range, θ is from -θ to θ, i represents the direction of integration, S is a constant determined by the size of the coupling waveguide, E disk and E wg denote the normalized electric field intensity in the microdisk resonant cavity and the coupled waveguide, respectively; ε(r, z) denotes the dielectric constant corresponding to the mode perturbations at different positions in the microdisk resonant cavity when coupling occurs; ε0 denotes the dielectric constant corresponding to the microdisk resonant cavity without coupling; κ0 = 2ππ / λ0, where κ0 is the wave number in free space, λ0 is the input wavelength, m is the azimuthal mode order of the microdisk resonant cavity, and n wg is the effective refractive index of the coupled waveguide, R wg is the radius of curvature of the second waveguide, n disk is the effective refractive index of the microdisk resonator, R disk is the radius of the microdisk resonant cavity, R wg =R disk +g+w / 2, g is the coupling distance between the second waveguide and the micro-disk resonant cavity, and w is the width of the second waveguide.

[0012] A second aspect of an embodiment of the present invention provides a method for preparing the single-mode micro-disk resonator device, comprising:

[0013] forming an amorphous gallium oxide thin film on an optical substrate substrate, wherein the refractive index of the optical substrate substrate is lower than the refractive index of the amorphous gallium oxide thin film;

[0014] A patterned mask is provided on the amorphous gallium oxide film, and the amorphous gallium oxide film not covered by the mask is etched by a plasma dry etching process, wherein the etching gas used in the plasma dry etching process is a mixed gas formed by BCl3 and Ar, thereby forming the first optical coupler, the coupled waveguide, the second optical coupler and the micro-disk resonant cavity, and making the side walls of the coupled waveguide and the micro-disk resonant cavity smooth and perpendicular to the working surface of the optical substrate;

[0015] The coupled waveguide includes a first waveguide, a second waveguide and a third waveguide connected in sequence, the first optical coupler and the second optical coupler are connected to the first waveguide and the third waveguide respectively, the second waveguide is arranged at intervals on one side of the micro-disk resonant cavity, and the second waveguide is an arc structure arranged around the micro-disk resonant cavity,

[0016] The coupling coefficient κ between the coupled waveguide and the microdisk resonant cavity is:

[0017]

[0018] Among them, n wg R wg =n disk R disk , θ is the angle range of the second waveguide coupling around the microdisk resonator, θ is the variable of the coupling angle range, θ is from -θ to θ, i represents the direction of integration, S is a constant determined by the size of the coupling waveguide, E disk and E wg denote the normalized electric field strength in the microdisk resonant cavity and the coupled waveguide, respectively; ε(r, z) denotes the dielectric constant corresponding to the mode perturbations at different positions in the microdisk resonant cavity when coupling occurs; ε0 denotes the dielectric constant corresponding to the microdisk resonant cavity without coupling; k0 = 2ππ / λ0, κ0 is the wave number in free space, λ0 is the input wavelength, m is the azimuthal mode order of the microdisk resonant cavity, and n wg is the effective refractive index of the coupled waveguide, R wg is the radius of curvature of the second waveguide, n disk is the effective refractive index of the microdisk resonator, R disk is the radius of the microdisk resonant cavity, R wg =R disk +g+w / 2, g is the coupling distance between the second waveguide and the micro-disk resonant cavity, and w is the width of the second waveguide.

[0019] A third aspect of an embodiment of the present invention is an optoelectronic device, which includes the single-mode micro-disk resonator device.

[0020] Compared with the prior art, the advantages of the present invention include:

[0021] (1) The present invention realizes a single-mode output gallium oxide resonant cavity structure by adjusting the phase matching conditions between the coupling waveguide and the microdisk resonant cavity, which can achieve the same function as the microring resonant cavity and realize a single selection of the mode. However, both sides of the microring resonant cavity will interact with the light, increasing light scattering and reducing the transmission performance of the entire device. Only one side of the microdisk resonant cavity will scatter light. Therefore, under the same manufacturing conditions, the optical performance will be better;

[0022] (2) The coupling of existing micro-disk resonant cavities is mostly carried out by coupling with an external single-mode optical fiber, which generates multiple high-order modes during the coupling process and cannot be integrated with an on-chip optical chip (i.e., a silicon-based optoelectronic chip). In the present invention, the coupling waveguide and the micro-disk resonant cavity are prepared simultaneously, which can not only realize efficient single-mode transmission, but also help to increase the integration of on-chip photonic devices (i.e., silicon-based optoelectronic devices), thereby reducing the footprint and power consumption of the chip system using the present invention (e.g., a large-scale on-chip silicon photonic integrated chip system formed by the present invention applied to a silicon photonic chip);

[0023] (3) The present invention obtains a coupled waveguide and microdisk resonant cavity with vertical and smooth side walls by optimizing the ratio of BCl3 and Ar gases;

[0024] (4) The existing technologies all prepare optoelectronic devices in single-crystalline Ga2O3 thin films. The present invention develops a complete coupled waveguide preparation process in amorphous Ga2O3 thin films for the first time, and also provides potential application value for amorphous Ga2O3 coupled waveguides in current photonic chip technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a schematic structural diagram of a single-mode microdisk resonator device based on amorphous gallium oxide in Example 1 of the present invention;

[0026] Figure 2 is a cross-sectional view of a single-mode microdisk resonator device based on amorphous gallium oxide in Example 1 of the present invention;

[0027] Figure 3 is a top view of a single-mode microdisk resonator device based on amorphous gallium oxide in Example 1 of the present invention;

[0028] Figure 4a , Figure 4b They are respectively the electric field distribution diagrams of the TE mode and the TM mode in a single-mode microdisk resonator device based on amorphous gallium oxide in Example 1 of the present invention;

[0029] Figure 5 is a flow chart of preparing a single-mode microdisk resonator device based on amorphous gallium oxide in Example 1 of the present invention;

[0030] Figure 6 is a cross-sectional SEM image of a single-mode microdisk resonator device based on amorphous gallium oxide in Example 1 of the present invention;

[0031] Figure 7 is the relationship between the etching rate and RF power of an amorphous gallium oxide film in Example 1 of the present invention;

[0032] Figure 8 This is the relationship between the etching rate of an amorphous gallium oxide film and the flow rate of BCl3 gas in Example 1 of the present invention. DETAILED DESCRIPTION

[0033] In view of the deficiencies in the prior art, the inventor of this case has proposed the technical solution of the present invention after long-term research and extensive practice. The technical solution, its implementation process and principle will be further explained as follows.

[0034] The present invention proposes a single-mode microdisk resonant device based on amorphous gallium oxide (Ga2O3) and a preparation method thereof. Compared with conventional microdisk resonant cavities, most of which adopt optical fiber coupling or single-point coupling waveguide coupling, it is inevitable that a multi-mode resonant spectrum will appear, which reduces the working efficiency of the microdisk in applications such as on-chip light sources and filters. The present invention designs the coupling waveguide into a pulley structure, which can not only increase the preparation tolerance of the coupling area, but also achieve the phase matching condition of single-mode coupling, and realize a single-mode resonant microdisk resonant cavity structure. At the same time, a preparation method for a single-mode microdisk resonant device based on amorphous gallium oxide is given for the first time, which mainly obtains a single-mode microdisk resonant device with collimated and smooth side walls by controlling the dynamic balance of gas flow size and ratio and combining the heating of the substrate.

[0035] A first aspect of an embodiment of the present invention provides a single-mode microdisk resonator device, comprising:

[0036] A first optical coupler, a coupling waveguide, a second optical coupler and a micro-disk resonant cavity are arranged in the same working plane, the coupling waveguide includes a first waveguide, a second waveguide and a third waveguide connected in sequence, the first optical coupler and the second optical coupler are connected to the first waveguide and the third waveguide respectively, the second waveguide is arranged at intervals on one side of the micro-disk resonant cavity, and the second waveguide is an arc structure arranged around the micro-disk resonant cavity,

[0037] The coupling coefficient κ between the coupled waveguide and the microdisk resonant cavity is:

[0038]

[0039] Among them, n wg R wg =n disk R disk , θ is the angle range of the second waveguide coupling around the microdisk resonant cavity, θ is the variable of the coupling angle variation range, θ is from -θ to θ, i represents the direction of integration, S is a constant determined by the size of the coupling waveguide, S is mainly related to the variation of the mode perturbation in the microdisk resonant cavity introduced by the coupling between the coupling waveguide and the microdisk resonant cavity, for a given coupling condition and microdisk size, the S value is fixed, E disk and E wg denote the normalized electric field strength in the microdisk resonant cavity and the coupled waveguide, respectively; ε(r, z) denotes the dielectric constant corresponding to the mode perturbations at different positions in the microdisk resonant cavity when coupling occurs; ε0 denotes the dielectric constant corresponding to the microdisk resonant cavity without coupling; κ0 = 2π / λ0, where κ0 is the wave number in free space, λ0 is the input wavelength, m is the azimuthal mode order of the microdisk resonant cavity, and n wg is the effective refractive index of the coupled waveguide, R wg is the radius of curvature of the second waveguide, n disk is the effective refractive index of the microdisk resonator, R disk is the radius of the microdisk resonant cavity, R wg =R disk +g+w / 2, g is the coupling distance between the second waveguide and the micro-disk resonant cavity, and w is the width of the second waveguide.

[0040] Furthermore, the phase mismatch between the coupled waveguide and the microdisk resonator is This makes the coupling waveguide in the present invention more difficult to couple than the single-point coupling waveguide. wg R wg =m, the coupling coefficient is a linear function of the coupling length, that is, The phase matching condition is highly dependent on the radial mode excited in the microdisk resonator. The effective refractive index of each radial mode is n disk ≡m / K0R disk , so when n wg R wg =n disk R disk The phase matching condition can only be met when , and under this phase matching condition, the width of the coupling waveguide, the bending radius and the radius of the micro-disk resonant cavity are selected according to the effective refractive index of different order modes, so as to further enable the micro-disk resonant cavity to achieve coupling of a single mode light field, thereby realizing a micro-disk resonant device with a single mode light field output.

[0041] Furthermore, the first optical coupler and the second optical coupler are both one of a focusing Bragg grating, a sub-wavelength Bragg grating and an inverted tapered coupler structure.

[0042] Furthermore, the height of the focusing Bragg grating is 300nm-600nm.

[0043] Furthermore, the focusing Bragg grating corresponds to a TE mode polarization grating period of 1.1 μm to 1.3 μm, a duty cycle of 0.5 to 0.7, and a coupling efficiency of 25% to 40%.

[0044] Furthermore, the micro-disk resonant cavity is a circular structure, and the second waveguide is an arc-shaped structure.

[0045] Furthermore, the second waveguide is a semicircular structure.

[0046] Furthermore, the coupling spacing g between the second waveguide and the micro-disk resonant cavity is equal.

[0047] Furthermore, the linear width of the second waveguide is 700nm to 1200nm, and the curvature radius R of the second waveguide is wg is 40 μm to 60 μm, and the radius R of the microdisk resonant cavity disk The coupling spacing g between the second waveguide and the micro-disk resonant cavity is 35 μm to 55 μm, and the coupling spacing g between the second waveguide and the micro-disk resonant cavity is 500 nm to 900 nm.

[0048] Furthermore, the coupling waveguide is a pulley-type coupling waveguide.

[0049] Furthermore, the first optical coupler, the coupling waveguide, the second optical coupler, and the micro-disk resonant cavity are made of the same material.

[0050] Furthermore, the first optical coupler, the coupling waveguide, the second optical coupler and the micro-disk resonant cavity are integrally formed.

[0051] Furthermore, the first optical coupler, the coupling waveguide, the second optical coupler and the micro-disk resonant cavity are formed by integrally processing an amorphous gallium oxide thin film.

[0052] Furthermore, at least the side walls of the coupling waveguide and the micro-disk resonant cavity are perpendicular to the working surface and the side walls of the coupling waveguide are smooth, thereby reducing the coupling loss of the single-mode micro-disk resonant device and improving the quality factor of the single-mode micro-disk resonant device. In nonlinear optical applications, the waveguide dispersion can be flexibly controlled by changing the dimensions of the coupling waveguide and the micro-disk resonant cavity.

[0053] Specifically, the design that the side walls of the coupling waveguide and the micro-disk resonant cavity are perpendicular to the working surface and the side walls of the coupling waveguide are smooth has at least the following advantages: first, in the application of nonlinear optics, the dispersion of the single-mode micro-disk resonant device can be precisely controlled by adjusting the dimensions of the coupling waveguide and the micro-disk resonant cavity; second, in the application of on-chip nonlinear light sources, the pump threshold of the device can be reduced, thereby reducing power consumption.

[0054] In a more specific embodiment, the single-mode micro-disk resonator device further includes: an optical substrate substrate, the first optical coupler, the coupling waveguide, the second optical coupler and the micro-disk resonant cavity are arranged on the optical substrate substrate, and the working surface is the surface of the optical substrate substrate.

[0055] Furthermore, the refractive index of the material forming the optical substrate is lower than the refractive index of the material forming the first optical coupler, the coupling waveguide, the second optical coupler and the micro-disk resonant cavity.

[0056] Furthermore, the optical substrate substrate includes a base and a thermal silicon oxide layer stacked on the base, the working surface is the surface of the thermal silicon oxide layer facing away from the base, and the material of the base includes at least one of silicon wafer, sapphire, calcium oxide and magnesium oxide.

[0057] Furthermore, the optical substrate base has a thickness of 300 μm to 500 μm.

[0058] A second aspect of an embodiment of the present invention provides a method for preparing the single-mode micro-disk resonator device, comprising:

[0059] forming an amorphous gallium oxide thin film on an optical substrate substrate, wherein the refractive index of the optical substrate substrate is lower than the refractive index of the amorphous gallium oxide thin film;

[0060] A patterned mask is provided on the amorphous gallium oxide film, and the amorphous gallium oxide film not covered by the mask is etched by a plasma dry etching process, wherein the etching gas used in the plasma dry etching process is a mixed gas formed by BCl3 and Ar, thereby forming the first optical coupler, the coupled waveguide, the second optical coupler and the micro-disk resonant cavity, and making the side walls of the coupled waveguide and the micro-disk resonant cavity smooth and perpendicular to the working surface of the optical substrate;

[0061] The coupled waveguide includes a first waveguide, a second waveguide and a third waveguide connected in sequence, the first optical coupler and the second optical coupler are connected to the first waveguide and the third waveguide respectively, the second waveguide is arranged at intervals on one side of the micro-disk resonant cavity, and the second waveguide is an arc structure arranged around the micro-disk resonant cavity,

[0062] The coupling coefficient κ between the coupled waveguide and the microdisk resonant cavity is:

[0063]

[0064] Among them, n wg R wg =n disk R disk , θ is the angle range of the second waveguide coupling around the microdisk resonant cavity, θ is the variable of the coupling angle variation range, θ is from -θ to θ, i represents the direction of integration, S is a constant determined by the size of the coupling waveguide, S is mainly related to the variation of the mode perturbation in the microdisk resonant cavity introduced by the coupling between the coupling waveguide and the microdisk resonant cavity, for a given coupling condition and microdisk size, the S value is fixed, E disk and E wg denote the normalized electric field intensity in the microdisk resonant cavity and the coupled waveguide, respectively; ε(r, z) denotes the dielectric constant corresponding to the mode perturbations at different positions in the microdisk resonant cavity when coupling occurs; ε0 denotes the dielectric constant corresponding to the microdisk resonant cavity without coupling; κ0 = 2πλ0, where κ0 is the wave number in free space, λ0 is the input wavelength, m is the azimuthal mode order of the microdisk resonant cavity, and n wg is the effective refractive index of the coupled waveguide, R wg is the radius of curvature of the second waveguide, n disk is the effective refractive index of the microdisk resonator, R disk is the radius of the microdisk resonant cavity, R wg =R disk +g+w / 2, g is the coupling distance between the second waveguide and the micro-disk resonant cavity, and w is the width of the second waveguide.

[0065] Furthermore, the volume ratio of BCl3 and Ar in the etching gas is (20-50): (5-20).

[0066] Furthermore, when plasma dry etching is performed on amorphous gallium oxide film, the gas flow rate of BCl3 is 20 sccm to 50 sccm, the gas flow rate of Ar is 2 sccm to 20 sccm, the power of RF is 50 W to 300 W, the power of ICP is 200 W to 1000 W, and the pressure of the etching chamber is 5 mTorr to 15 mTorr.

[0067] Specifically, the amorphous gallium oxide film does not have a fixed crystal orientation like the crystalline film. The isotropic etching rate and the formation rate of the product during the etching process need to be dynamically controlled and balanced, otherwise difficult-to-remove residues will be generated on the surface of the single-mode microdisk resonator, making it very rough. The present invention controls the generation of BCl in the plasma by adjusting parameters such as the ratio and flow rate of the BCl3 / Ar mixed gas. 2+ The rate of ions is then reduced, and oxygen is removed from Ga2O3 to form volatile B3Cl3O3. At the same time, combined with the substrate heating method, the generation rate of etching products and etching passivation layer is dynamically balanced, so that a smooth structure can be obtained.

[0068] In a more specific implementation scheme, during the process of etching the amorphous gallium oxide film not covered by the mask using a plasma dry etching process, the temperature of the optical substrate is maintained at 80°C to 120°C. The main purpose is to increase the temperature of the surface of the optical substrate to the boiling point of the etching products, so that the products generated during the etching process can be quickly pumped away by a mechanical pump and are not easy to adhere to the device surface, otherwise it will affect the etching rate and the morphology of the device.

[0069] In a more specific embodiment, the method for preparing the single-mode microdisk resonator device also includes: first annealing the amorphous gallium oxide film at 500°C to 700°C in an oxygen atmosphere, and then etching the amorphous gallium oxide film. Through the annealing treatment, the gallium element in the amorphous gallium oxide film can be more fully oxidized, so that the quality of the film is better and the optical performance is more stable.

[0070] In a more specific embodiment, a method for preparing a single-mode microdisk resonator device based on amorphous gallium oxide may specifically include the following steps:

[0071] Providing an optical substrate substrate, the optical substrate substrate can be one of a silicon wafer with a silicon dioxide cladding, sapphire, magnesium oxide or calcium oxide substrate;

[0072] An amorphous gallium oxide film is grown on the optical substrate by ion beam evaporation, and the thickness of the gallium oxide film is 200nm to 600nm;

[0073] A mask layer is grown on the gallium oxide film by plasma enhanced chemical vapor deposition (PECVD). The material of the mask layer can be SiN, SiO2 or a metal mask. The thickness of the optional SiO2 mask layer is 0.6 μm to 1 μm.

[0074] Spin coating ultraviolet photoresist on the mask layer, wherein the ultraviolet photoresist includes a positive photoresist, and the ultraviolet photoresist may be AZ5214, and the thickness thereof is 1 μm to 1.5 μm;

[0075] The pattern is transferred to the UV photoresist through UV exposure and development technology;

[0076] The mask layer is fully etched by plasma dry etching technology, and the pattern on the photoresist is further transferred to the mask layer to serve as a hard mask, and at the same time, the temperature of the optical substrate is maintained at 80° C. to 120° C.;

[0077] Using N-methylpyrrolidone (NMP) and oxygen plasma to remove the residual photoresist on the surface of the hard mask after etching;

[0078] Annealing the gallium oxide film in an oxygen atmosphere at a temperature of 500° C. to 700° C., etching the gallium oxide film again using a plasma etcher (ICP-RIE) and a substrate heating method, transferring the pattern on the hard mask to the gallium oxide film to form an optically coupled waveguide structure;

[0079] The gallium oxide optical coupling waveguide structure containing the hard mask is immersed in a BOE solution to remove the hard mask, and finally a complete amorphous gallium oxide coupled waveguide device is obtained.

[0080] Furthermore, in the process for preparing the amorphous gallium oxide coupled waveguide, all thin film substrates further include steps such as substrate cleaning and baking before spin coating the photoresist.

[0081] Furthermore, in the process for preparing the amorphous gallium oxide coupled waveguide, the photoresist needs to be pre-baked and post-baked before exposure and after development.

[0082] A third aspect of an embodiment of the present invention is an optoelectronic device, which includes the single-mode micro-disk resonator device.

[0083] The technical solution, its implementation process and principle, etc. will be further explained below in conjunction with the accompanying drawings and specific implementation cases. Unless otherwise specified, the etching equipment used in the embodiments of the present invention are all known in the art.

[0084] Example 1

[0085] The present embodiment 1 provides a single-mode microdisk resonant device (also referred to as a single-mode microdisk resonant cavity device, etc.) based on amorphous gallium oxide. A coupling waveguide and a microdisk resonant cavity are simultaneously prepared on an amorphous gallium oxide film. The coupling waveguide is designed as a semicircular pulley structure. The phase matching condition between the coupling waveguide and the microdisk resonant cavity is strictly controlled so that the single-mode microdisk resonant device can achieve a single selection of the light field mode. The single-mode output of the single-mode microdisk resonant device can be achieved by adjusting the width and radius of the coupling waveguide and the radius of the microdisk resonant cavity. At the same time, compared with the usual single-mode optical fiber coupling, this structure is more conducive to the integration of current optical chips and reduces the chip area and power consumption.

[0086] See also Figure 1 As shown, a single-mode micro-disk resonator device based on amorphous gallium oxide in this embodiment comprises an optical substrate 1, a silicon dioxide layer 2, a first grating coupler 3 for coupling a light field into a coupling waveguide, an amorphous gallium oxide micro-disk resonant cavity (hereinafter referred to as a micro-disk resonant cavity) 4, a pulley-type gallium oxide coupling waveguide (hereinafter referred to as a coupling waveguide) 5, and a second grating coupler 7 for outputting the resonated light. There is a coupling spacing 6 between the pulley-type gallium oxide coupling waveguide 5 and the amorphous gallium oxide micro-disk resonant cavity 4. Specifically, the optical substrate 1 is a silicon wafer, the silicon dioxide layer 2 is deposited on the optical substrate 1 to form a lower cladding layer with a low refractive index, a layer of amorphous gallium oxide thin film is deposited on the silicon dioxide layer 2, and the first grating coupler 3, the amorphous gallium oxide micro-disk resonant cavity 4, the pulley-type gallium oxide coupling waveguide 5, and the second grating coupler 7 are prepared by micro-nano processing technology;

[0087] The pulley-type gallium oxide coupled waveguide 5 includes a first waveguide, a second waveguide and a third waveguide connected in sequence, the first optical coupler 3 and the second optical coupler 7 are connected to the first waveguide and the third waveguide respectively, the second waveguide is arranged at intervals on one side of the amorphous gallium oxide microdisk resonant cavity 4, and the second waveguide is an arc structure arranged around the amorphous gallium oxide microdisk resonant cavity,

[0088] The coupling coefficient κ between the pulley-type gallium oxide coupling waveguide 5 and the amorphous gallium oxide microdisk resonant cavity 4 is:

[0089]

[0090] Among them, n wg R wg =n disk R disk, θ is the angle range of the second waveguide coupling around the microdisk resonant cavity, θ is the variable of the coupling angle variation range, θ is from -θ to θ, i represents the direction of integration, S is a constant determined by the size of the coupling waveguide, S is mainly related to the variation of the mode perturbation in the microdisk resonant cavity introduced by the coupling between the coupling waveguide and the microdisk resonant cavity, for a given coupling condition and microdisk size, the S value is fixed, E disk and E wg denote the normalized electric field strength in the microdisk resonant cavity and the coupled waveguide, respectively; ε(r, z) denotes the dielectric constant corresponding to the mode perturbations at different positions in the microdisk resonant cavity when coupling occurs; ε0 denotes the dielectric constant corresponding to the microdisk resonant cavity without coupling; k0 = 2π / λ0, κ0 is the wave number in free space, λ0 is the input wavelength, m is the azimuthal mode order of the microdisk resonant cavity, and n wg is the effective refractive index of the coupled waveguide, R wg is the radius of curvature of the second waveguide, n disk is the effective refractive index of the microdisk resonator, R disk is the radius of the microdisk resonant cavity, R wg =R disk +g+w / 2, g is the coupling distance between the second waveguide and the micro-disk resonant cavity, and w is the width of the second waveguide.

[0091] The principle of selecting the resonant light field mode during operation of the single-mode microdisk resonator device is as follows: the coupling between the coupling waveguide and the microdisk resonant cavity needs to meet more stringent phase matching conditions. There will be multiple radial mode resonant peaks in the microdisk resonant cavity. When the product of the effective refractive index of a specific radial mode and the bending radius of the coupling waveguide is equal to the product of the effective refractive index of the microdisk resonant cavity and the corresponding radius, a better phase matching condition can be achieved. At the same time, it can be ensured that the light field of this specific radial mode in the microdisk is coupled and has a uniform free spectral range (FSR), thereby realizing the output of a single mode light field. In this process, a specific single selection of multiple radial modes can be made by adjusting the width and bending radius of the coupling waveguide.

[0092] See also Figure 2 As shown, this embodiment provides a cross-sectional view of a single-mode microdisk resonator device based on amorphous gallium oxide, wherein the optical substrate substrate 1 has a thickness of 0.5 mm-1 mm, the silicon dioxide layer 2 has a thickness of 2 μm-10 μm, and the amorphous gallium oxide film has a thickness of 300 nm-600 nm.

[0093] See also Figure 3 As shown, Figure 3It is a top view of a single-mode microdisk resonant device based on amorphous gallium oxide. Here, the first grating coupler 3 and the second grating coupler 7 of light both adopt TE mode polarization focusing Bragg grating couplers, the grating period is 1.1-1.3μm, the duty cycle is 0.5-0.7, the grating coupling efficiency is 25-40%, and the full etching depth is 300-600nm. The width of the pulley-type gallium oxide coupling waveguide 5 is 700-1200nm, the bending radius is 40-60μm, the corresponding radius of the amorphous gallium oxide microdisk resonant cavity 4 is 35-55μm, and the coupling spacing 6 is 500-900nm. The size of the coupling waveguide can be designed according to the phase matching condition, so as to achieve a single mode selection and a single-mode output.

[0094] See also Figure 4a , Figure 4b As shown, the single-mode micro-disk resonator device described in Example 1 of the present invention is simulated using the Mode Solution simulation software at a TE mode ( Figure 4a ) and TM mode ( Figure 4b ) was simulated, and it can be seen that most of the electric field is confined in the central area of ​​the pulley-type gallium oxide coupled waveguide 5, which fully demonstrates that the amorphous gallium oxide coupled waveguide prepared by the method of the present invention has a good confinement ability for light in the communication band.

[0095] This embodiment 1 provides a preparation process of a single-mode microdisk resonator device based on amorphous gallium oxide, and adopts dry etching with a mixture of BCl3 and Ar gases to obtain a coupled waveguide with vertical and smooth side walls on an amorphous gallium oxide film for the first time.

[0096] See also Figure 5 As shown, a preparation process of a single-mode microdisk resonator device based on amorphous gallium oxide includes the following steps:

[0097] Step 1) depositing a 500nm thick amorphous gallium oxide film on an optical substrate by magnetron sputtering or ion beam evaporation.

[0098] Step 2) placing the amorphous gallium oxide film in an annealing furnace filled with oxygen atmosphere for annealing at a temperature of 600° C. for 10 hours. This step is mainly used to further reduce defects inside the amorphous gallium oxide film.

[0099] Step 3) A layer of amorphous silicon dioxide film with a thickness of 800 nm is deposited on the amorphous gallium oxide film by plasma enhanced chemical vapor deposition, which mainly serves as a hard mask.

[0100] Step 4) Spin-coat a layer of AZ5214 photoresist with a thickness of 1300 nm on the amorphous silicon dioxide film.

[0101] Step 5) Use contact ultraviolet lithography equipment to expose AZ5214 photoresist, and after development, transfer the coupled waveguide pattern on the layout to the photoresist.

[0102] Step 6) Use inductively coupled plasma etching equipment (CF4 and O2 mixed gas) to fully etch the silicon dioxide film and transfer the coupled waveguide pattern on the photoresist to the silicon dioxide hard mask. During this process, overetching for 10 seconds is required to ensure that the silicon dioxide is completely etched.

[0103] Step 7) The sample in step 6 is placed in a NMP solution heated to 75°C and soaked for 20 minutes, and then treated with oxygen plasma for 10 minutes to remove the residual glue on the surface of the hard mask, and finally a hard mask with a coupled waveguide pattern is obtained. The thickness of the hard mask is 800nm.

[0104] Step 8) The temperature of the optical substrate is maintained at 80°C ~ 120°C, and the amorphous gallium oxide film is etched again using an inductively coupled plasma etcher. Specifically, the BCl3 gas flow rate is 30sccm, the Ar gas flow rate is 10sccm, the RF power is 100W, the ICP power is 750W, the cavity gas pressure is 10mTorr, the substrate heating temperature is 90°C, and the etching time is 120s. Finally, a single-mode microdisk resonator device based on amorphous gallium oxide with an etching depth of 500nm is obtained.

[0105] The BCl3 and Ar mixed gas selected in this embodiment 1 fully utilizes their respective characteristics. The BCl3 gas is used to enhance the chemical reaction during the etching process, which can provide a higher etching rate, while Ar can enhance the ability of physical bombardment and remove the non-volatile substances produced during the etching process, which helps to improve the smoothness of the coupled waveguide surface.

[0106] Step 9) Soaking the etched single-mode microdisk resonator device in a BOE solution for a period of time, removing the remaining silicon dioxide mask, and finally obtaining a single-mode microdisk resonator device with a structure of silicon-silicon dioxide-gallium oxide.

[0107] See also Figure 6 , Figure 6 This is a physical picture of the single-mode microdisk resonator device prepared in Example 1. It can be seen that the side walls of the coupled waveguide are vertical and have good morphology, indicating that the preparation method of the single-mode microdisk resonator device developed by the present invention can obtain a single-mode microdisk resonator device with excellent morphology.

[0108] See also Figure 7 , Figure 7The relationship between the etching rate and RF power of the single-mode microdisk resonator in Example 1 shows that as the RF power increases from 100 W to 250 W, the etching rate of the gallium oxide film gradually increases. This is mainly because the increase in RF power enhances the combined effects of physical etching and chemical etching, and the increase in the proportion of physical etching can effectively remove the non-volatile products produced during the etching process, exposing the unetched gallium oxide film, and the enhanced chemical etching will continue etching.

[0109] join Figure 8 As shown, the relationship between the etching rate of the amorphous gallium oxide film and the BCl3 gas flow rate in this embodiment 1 can be seen that increasing the BCl3 gas flow rate will gradually increase the etching rate of the gallium oxide film. When the gas flow rate is greater than 30sccm, the etching rate weakens. This is mainly because before BCl3 is 30sccm, the ratio with Ar is moderate, and the products generated by increasing chemical etching will also be removed by physical etching of Ar, so the etching rate will increase accordingly. Then, when the gas flow rate increases to 35sccm, the role of chemical etching dominates, making the rate of physical etching out the products less than the rate of chemical etching to produce the products, so the etching rate has a downward trend.

[0110] It should be understood that the above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A single-mode microdisk resonator device, characterized in that: include: A first optical coupler, a coupling waveguide, a second optical coupler and a micro-disk resonant cavity are arranged in the same working plane, the coupling waveguide includes a first waveguide, a second waveguide and a third waveguide connected in sequence, the first optical coupler and the second optical coupler are connected to the first waveguide and the third waveguide respectively, the second waveguide is arranged at intervals on one side of the micro-disk resonant cavity, and the second waveguide is an arc structure arranged around the micro-disk resonant cavity, The coupling coefficient κ between the coupled waveguide and the microdisk resonant cavity is: Among them, n wg R wg =n disk R disk , θ is the angle range of the second waveguide coupling around the microdisk resonator, θ is the variable of the coupling angle range, θ is from -θ to θ, i represents the direction of integration, S is a constant determined by the size of the coupling waveguide, E disk and E wg denote the normalized electric field strength in the microdisk resonant cavity and the coupled waveguide, respectively; ε(r, z) denotes the dielectric constant corresponding to the mode perturbations at different positions in the microdisk resonant cavity when coupling occurs; ε0 denotes the dielectric constant corresponding to the microdisk resonant cavity without coupling; κ0 = 2π / λ0, where κ0 is the wave number in free space, λ0 is the input wavelength, m is the azimuthal mode order of the microdisk resonant cavity, and n wg is the effective refractive index of the coupled waveguide, R wg is the radius of curvature of the second waveguide, n disk is the effective refractive index of the microdisk resonator, R disk is the radius of the microdisk resonant cavity, R wg =R disk +g+w / 2, g is the coupling distance between the second waveguide and the micro-disk resonant cavity, and w is the width of the second waveguide.

2. The single-mode microdisk resonator device according to claim 1, characterized in that: The first optical coupler and the second optical coupler are each one of a focusing Bragg grating, a sub-wavelength Bragg grating, and an inverted tapered coupler structure.

3. The single-mode microdisk resonator device according to claim 2, characterized in that: The height of the focusing Bragg grating is 300nm to 600nm; And / or, the focusing Bragg grating corresponds to a TE mode polarization grating period of 1.1 μm to 1.3 μm, a duty cycle of 0.5 to 0.7, and a coupling efficiency of 25% to 40%.

4. The single-mode microdisk resonator device according to claim 1, characterized in that: The micro-disk resonant cavity is a circular structure, and the second waveguide is an arc-shaped structure; Preferably, the second waveguide is a semicircular structure; Preferably, the coupling spacing g between the second waveguide and the micro-disk resonant cavity is equal.

5. The single-mode microdisk resonator device according to claim 1, characterized in that: The linear width of the second waveguide is 700 nm to 1200 nm, and the curvature radius R of the second waveguide is wg is 40 μm to 60 μm, and the radius R of the microdisk resonant cavity disk The coupling spacing g between the second waveguide and the micro-disk resonant cavity is 35 μm to 55 μm, and the coupling spacing g between the second waveguide and the micro-disk resonant cavity is 500 nm to 900 nm.

6. The single-mode microdisk resonator device according to claim 1, characterized in that: The first optical coupler, the coupling waveguide, the second optical coupler and the micro-disk resonant cavity are made of the same material; Preferably, the first optical coupler, the coupling waveguide, the second optical coupler and the micro-disk resonant cavity are integrally formed; Preferably, the first optical coupler, the coupling waveguide, the second optical coupler and the micro-disk resonant cavity are formed by integrally processing an amorphous gallium oxide thin film; Preferably, at least the side walls of the coupling waveguide and the micro-disk resonant cavity are perpendicular to the working surface and the side walls of the coupling waveguide and the micro-disk resonant cavity are smooth.

7. The single-mode microdisk resonator device according to claim 1, characterized in that: Also includes: An optical substrate substrate, the first optical coupler, the coupling waveguide, the second optical coupler and the micro-disk resonant cavity are arranged on the optical substrate substrate, and the working surface is a surface of the optical substrate substrate; Preferably, the refractive index of the material forming the optical substrate is lower than the refractive index of the material forming the first optical coupler, the coupling waveguide, the second optical coupler and the micro-disk resonant cavity; Preferably, the optical substrate substrate comprises a base and a thermal silicon oxide layer stacked on the base, the working surface is the surface of the thermal silicon oxide layer facing away from the base, and the material of the base comprises at least one of silicon wafer, sapphire, calcium oxide and magnesium oxide.

8. The method for preparing a single-mode microdisk resonator device according to any one of claims 1 to 7, characterized in that: include: forming an amorphous gallium oxide thin film on an optical substrate substrate, wherein the refractive index of the optical substrate substrate is lower than the refractive index of the amorphous gallium oxide thin film; A patterned mask is provided on the amorphous gallium oxide film, and the amorphous gallium oxide film not covered by the mask is etched by a plasma dry etching process, wherein the etching gas used in the plasma dry etching process is a mixed gas formed by BCl3 and Ar, thereby forming the first optical coupler, the coupled waveguide, the second optical coupler and the micro-disk resonant cavity, and making the side walls of the coupled waveguide and the micro-disk resonant cavity smooth and perpendicular to the working surface of the optical substrate; The coupled waveguide includes a first waveguide, a second waveguide and a third waveguide connected in sequence, the first optical coupler and the second optical coupler are connected to the first waveguide and the third waveguide respectively, the second waveguide is arranged at intervals on one side of the micro-disk resonant cavity, and the second waveguide is an arc structure arranged around the micro-disk resonant cavity, The coupling coefficient κ between the coupled waveguide and the microdisk resonant cavity is: Among them, n wg R wg =n disk R disk , θ is the angle range of the second waveguide coupling around the microdisk resonator, θ is the variable of the coupling angle range, θ is from -θ to θ, i represents the direction of integration, S is a constant determined by the size of the coupling waveguide, E disk and E wg denote the normalized electric field strength in the microdisk resonant cavity and the coupled waveguide, respectively; ε(r, z) denotes the dielectric constant corresponding to the mode perturbations at different positions in the microdisk resonant cavity when coupling occurs; ε0 denotes the dielectric constant corresponding to the microdisk resonant cavity without coupling; x0 = 2πτ / λ0, κ0 is the wave number in free space, λ0 is the input wavelength, m is the azimuthal mode order of the microdisk resonant cavity, and n wg is the effective refractive index of the coupled waveguide, R wg is the radius of curvature of the second waveguide, n disk is the effective refractive index of the microdisk resonator, R disk is the radius of the microdisk resonant cavity, R wg =R disk +g+w / 2, g is the coupling distance between the second waveguide and the micro-disk resonant cavity, and w is the width of the second waveguide.

9. The method for preparing a single-mode microdisk resonator device according to claim 8, characterized in that: The volume ratio of BCl3 and Ar in the etching gas is (20-50): (5-20); Preferably, when plasma dry etching amorphous gallium oxide film, the gas flow rate of BCl3 is 20 sccm to 50 sccm, the gas flow rate of Ar is 2 sccm to 20 sccm, the power of RF is 50 W to 300 W, the power of ICP is 200 W to 1000 W, and the pressure of the etching chamber is 5 mTorr to 15 mTorr; Preferably, the preparation method further comprises: during the process of etching the amorphous gallium oxide thin film not covered by the mask using a plasma dry etching process, maintaining the temperature of the optical substrate substrate at 80° C. to 120° C.; Preferably, the preparation method further comprises: firstly annealing the amorphous gallium oxide film at 500° C. to 700° C. in an oxygen atmosphere, and then etching the amorphous gallium oxide film.

10. An optoelectronic device, characterized in that: include: The single-mode microdisk resonator device according to any one of claims 1 to 7.

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