Subwavelength structure embedded in disordered superhomogeneous solid waveguide and design method thereof

Abstract

The application discloses a kind of subwavelength structure embedding disorder super-uniform solid waveguide and design method thereof, it is related to optoelectronic device technical field, including waveguide, waveguide includes core layer and cladding, cladding is arranged in waveguide both sides, disorder super-uniform solid is composed of grid wall and hole structure, simultaneously provided with waveguide defect line, waveguide defect line is provided with subwavelength structure, subwavelength structure is arranged along waveguide defect line direction.The application uses the above-mentioned one subwavelength structure embedding disorder super-uniform solid waveguide and design method thereof, by embedding the subwavelength structure of multiple layers of medium in the core area of waveguide defect line, the interaction of optical field and surrounding environment gas molecule to be measured is enhanced, the sensitivity of gas sensor is improved.By optimizing the distribution mode and geometric parameters of subwavelength structure, the additional transmission loss introduced can still be kept at a low level while enhancing the evanescent field of waveguide.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic device technology, and in particular to a subwavelength structure embedded disordered ultrauniform solid waveguide and its design method. Background Technology

[0002] In recent years, disordered ultrauniform solids have become a research hotspot in the field of optical metamaterials due to their unique photonic bandgap characteristics. Researchers have conducted numerous studies on performance optimization of disordered ultrauniform solid waveguides using various methods. In 2014, researchers at the University of Southampton designed a disordered ultrauniform solid waveguide in the communication band by inserting defect lines into the disordered ultrauniform solid. In 2019, researchers at the University of Southampton further reduced the optical loss of the disordered ultrauniform solid waveguide by adjusting the angle between the waveguide defect lines and the grid walls on both sides to near perpendicularity. In 2023, researchers at Tianjin University proposed a morphology modification method for disordered ultrauniform solids, achieving optical loss optimization in a disordered ultrauniform waveguide modified with Bézier curves, and observing an improvement in the quality factor in a microring modified with Bézier curves.

[0003] Regarding patents, researchers at Etaphase optimized disordered ultrauniform solid-state waveguides by constructing periodic transition regions (US10031288B2). Tianjin University has proposed two optimization methods: a topography modification method (CN202310698203.1) and a mesh optimization method (CN202410659505.2). Although the above studies have effectively reduced the transmission loss and improved the bandgap characteristics of disordered ultrauniform solid-state waveguides, existing disordered ultrauniform solid-state waveguide devices still have significant shortcomings in gas sensing applications. Specifically, the optical field of disordered ultrauniform solid-state waveguides is mainly confined within the waveguide, and its evanescent field intensity is weak, limiting the interaction between the optical field and the surrounding gas molecules, resulting in low sensing sensitivity. Therefore, how to effectively enhance the evanescent field intensity of disordered ultrauniform solid-state waveguides while maintaining their excellent performance such as low loss and wide bandgap, thereby developing high-sensitivity on-chip integrated waveguide devices suitable for gas sensing, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0004] The purpose of this invention is to provide a subwavelength structure embedded disordered ultrauniform solid waveguide and its design method, overcoming the problems of insufficient evanescent field strength and low sensing sensitivity of existing disordered ultrauniform solid waveguide devices in gas sensing applications.

[0005] To achieve the above objectives, the present invention provides a subwavelength structure embedded in a disordered ultrauniform solid waveguide, comprising a waveguide, the waveguide including a core layer and a cladding layer, the cladding layer being disposed on both sides of the waveguide, the cladding layer being composed of a disordered ultrauniform solid, the disordered ultrauniform solid being composed of grid walls and a hole structure, and waveguide defect lines being provided, with subwavelength structures disposed within the waveguide defect lines, the subwavelength structures being arranged along the direction of the waveguide defect lines.

[0006] Preferably, there is at least one waveguide defect line, which can be any number of lines formed by one or more of the following: straight lines, polynomial curves, circular arcs, elliptical arcs, Euler curves, Bezier curves, and Gaussian curves.

[0007] Preferably, the subwavelength structure is composed of multiple dielectric layers, and the multiple dielectric layers, the mesh walls, and the pore structure are all composed of one or more of the following: air, silicon dioxide, silicon, germanium, silicon-germanium alloy, silicon nitride, lithium niobate, and sulfides.

[0008] Preferably, the distribution of the multilayer dielectric along the waveguide defect line is any one of periodic distribution, quasi-periodic distribution, or disordered ultra-uniform distribution. When a periodic distribution is adopted, the multilayer dielectric constitutes a subwavelength grating.

[0009] Preferably, the waveguide surface is coated with a gas-sensitizing medium, which is one or a combination of polyhexamethylene biguanide hydrochloride, low-dimensional materials, and metal oxides.

[0010] Preferably, the disordered ultra-uniform solid is a two-dimensional planar structure or a three-dimensional solid structure.

[0011] A design method for embedding subwavelength structures into disordered ultrauniform solid waveguides includes the following steps: Step 1: Introduce at least one waveguide defect line into the disordered, ultra-uniform solid; Step 2: Design a multilayer dielectric subwavelength structure arranged along the waveguide defect line in the region where the waveguide defect line is introduced; Step 3: Use optimization algorithms to design and optimize the subwavelength structure embedded disordered ultrauniform solid waveguide based on the given objective function; Step 4: Construct a disordered, ultrauniform solid waveguide for gas sensing using optimized structural parameters.

[0012] Preferably, the optimization algorithm described in step three is one of exhaustive search, neural network algorithm, Bayesian optimization, genetic algorithm, particle swarm optimization, differential evolution algorithm, and simulated annealing.

[0013] Preferably, the objective function in step three is one of the external confinement factor and the ratio of external confinement factor to transmission loss. The external confinement factor is the proportion of optical power in the waveguide's surrounding environment to the total transmission power. The higher the external confinement factor, the stronger the evanescent field and the higher the sensing sensitivity.

[0014] Therefore, the present invention employs the aforementioned method of embedding a subwavelength structure into a disordered ultrauniform solid waveguide, which has the following advantages: high sensing sensitivity. By embedding a subwavelength structure composed of multiple dielectric layers into the core region of the waveguide defect line, the strong evanescent field provided by the subwavelength structure enhances the interaction between the optical field and the surrounding gas molecules, thereby improving the sensitivity of the gas sensor. Low optical loss. By optimizing the distribution and geometric parameters of the subwavelength structure, the additional transmission loss introduced can be kept at a low level while enhancing the waveguide evanescent field.

[0015] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0016] Figure 1 This is a flowchart of a design method for embedding a subwavelength structure into a disordered ultrauniform solid waveguide according to the present invention; Figure 2 This is an image of a silicon-air subwavelength structure embedded in a disordered ultrauniform solid waveguide in Embodiment 1 of the present invention; Figure 3 This describes the optimization process for embedding a disordered ultrauniform solid waveguide into a silicon-air subwavelength structure in Embodiment 1 of the present invention. Figure 4 The transmission spectrum of the silicon-air subwavelength structure embedded in the disordered ultrauniform solid waveguide obtained in Embodiment 1 of the present invention; Figure 5 This is an image of a disordered ultrauniform solid Mach-Jendr interferometer embedded in a silicon-polyhexamethylene biguanide hydrochloride subwavelength structure in specific embodiment 2 of the present invention; Figure 6 The transmission spectrum of the silicon-polyhexamethylene biguanide hydrochloride subwavelength structure embedded in the disordered ultrauniform solid Mach-Jendr interferometer in Example 2 of the present invention; Figure 7 The results show the measurement of the resonant peak shift of the silicon-polyhexamethylene biguanide hydrochloride subwavelength structure embedded in the disordered ultrauniform solid Mach-Jendr interferometer in Embodiment 2 of the present invention under different carbon dioxide gas concentrations. Detailed Implementation

[0017] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0018] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0019] Example Please see Figures 1-7 The present invention provides a subwavelength structure embedded in a disordered ultrauniform solid waveguide. The waveguide includes a core layer and a cladding layer. The cladding layer is disposed on both sides and is composed of a disordered ultrauniform solid, which is composed of grid walls and a hole structure. The core layer is composed of a subwavelength structure, which is composed of multiple dielectric layers and is arranged along the defect line direction in the disordered ultrauniform solid.

[0020] At least one waveguide defect line is provided. The waveguide defect line is any number of lines composed of one or more of the following: straight lines with arbitrary orientation, polynomial curves, circular arcs, elliptical arcs, Euler curves, Bezier curves, and Gaussian curves.

[0021] The distribution of the multilayer dielectric subwavelength structure along the waveguide defect line can be any of the following: periodic, quasi-periodic, or disordered ultrauniform. When a periodic distribution is used, the multilayer dielectric forms a subwavelength grating.

[0022] Multilayer media are composed of one or more media in the direction perpendicular to the waveguide defect line. For example, a groove structure of "high refractive index medium A-air-high refractive index medium B" can be formed to enhance the intensity of the evanescent field distributed in the air region that can directly interact with the gas molecules to be measured, thereby achieving higher sensing sensitivity.

[0023] Multilayer dielectrics, mesh walls, and porous structures are composed of one or more of the following: air, silicon dioxide, silicon, germanium, silicon-germanium alloys, silicon nitride, lithium niobate, and sulfides.

[0024] The waveguide surface can be coated with a gas-sensitizing material to increase measurement sensitivity. The sensitizing material can be one or a combination of several of the following: polyhexamethylene biguanide hydrochloride, low-dimensional materials, and metal oxides.

[0025] Disordered ultrauniform solid waveguide devices can be two-dimensional planar structures or three-dimensional solid structures, and different structural dimensions can be selected according to specific application requirements.

[0026] A subwavelength structure embedded in a disordered ultrauniform solid waveguide for gas sensing and its design method are disclosed. The waveguide structure is manipulated to comprehensively optimize the sensing limit of the waveguide across multiple parameters, including the following steps: Step 1: Introduce at least one waveguide defect line into the disordered ultrauniform solid.

[0027] Step 2: In the region where the waveguide defect line is introduced, design a multilayer dielectric subwavelength structure arranged along the direction of the waveguide defect line. By embedding the subwavelength structure, the evanescent field intensity of the waveguide can be effectively enhanced.

[0028] Step 3: Use optimization algorithms to design and optimize the subwavelength structure embedded disordered ultrauniform solid waveguide based on a given objective function, so as to balance the evanescent field intensity and transmission loss, thereby optimizing the sensing performance of the waveguide.

[0029] The optimization algorithm can be one of the following: exhaustive search, neural network algorithm, Bayesian optimization, genetic algorithm, particle swarm optimization, differential evolution algorithm, or simulated annealing. These algorithms can efficiently search for the optimal solution in a multi-parameter space while avoiding getting trapped in local optima.

[0030] The objective function can be one of the external confinement factor or the ratio of external confinement factor to transmission loss. The external confinement factor (Γ) is defined as the proportion of optical power in the waveguide's surrounding environment (such as an air trough or functionalized layer) to the total transmitted power; a higher value indicates a stronger evanescent field and higher sensing sensitivity. Using the ratio of external confinement factor to transmission loss (Γ / α) as the objective function can achieve the optimal balance between enhancing the evanescent field and maintaining low loss.

[0031] Step 4: Construct a disordered, ultrauniform solid waveguide for gas sensing using optimized structural parameters.

[0032] Example 1 Figure 2 The diagram illustrates a subwavelength structure embedded in a disordered ultrauniform solid waveguide for gas sensing. The waveguide's cladding consists of two layers of disordered ultrauniform solid, with silicon as the grid wall material and air-filled pores. The core layer comprises a subwavelength structure. A straight waveguide defect line with a width of 1 μm is introduced into this structure, resulting in a total waveguide length of 36 μm. Within the silicon waveguide defect line region, a subwavelength structure composed of multiple air media periodically arranged along the defect line is designed and embedded. The initial design parameters for the subwavelength grating are: the period of the subwavelength structure distribution is... Λ s =380nm, length of the air subwavelength structure along the waveguide directionl s =190nm, width of the air subwavelength structure along the direction perpendicular to the waveguide. w s =200nm.

[0033] Figure 3 The figure shows the objective function distribution obtained by using an optimization algorithm to optimize the structure of a subwavelength embedded disordered ultrauniform solid waveguide based on a given objective function. In this embodiment, the optimal solution range is first narrowed down using variable step-size scanning, and then structural optimization is performed within the narrowed optimal solution range. The objective function is defined as the ratio of the external confinement factor to the transmission loss, Γ / α, where Γ is the proportion of optical power in the air slot surrounding the waveguide. α Transmission loss. Under a pre-defined medium combination and distribution, the air subwavelength structure... l s and w s Optimization was performed. The optimal parameters obtained are: l s =160nm, w s =200nm, at which point the objective function value is 15.9.

[0034] Figure 4 The figure shows the simulation results of the transmission spectrum of the optimized silicon-air subwavelength structure embedded in a disordered ultrauniform solid waveguide. The simulation results show that the peak transmittance of the waveguide is -3.8 dB, and the 3 dB bandwidth is approximately 280 nm. Compared with a disordered ultrauniform solid waveguide without subwavelength embedding, the optical loss is not significantly increased, and the 3 dB bandwidth remains in the ~300 nm range. This indicates that the method proposed in this invention can effectively control the perturbation of the disordered ultrauniform solid waveguide by subwavelength structure embedding, avoiding significant changes in the photonic bandgap characteristics. Furthermore, the outer confinement factor Γ of this waveguide reaches 0.42, which is significantly enhanced compared to traditional silicon-based waveguides with an outer confinement factor typically not exceeding 0.15, thus improving the evanescent field intensity and enhancing the sensitivity of the gas sensor.

[0035] Finally, the method in this embodiment is merely a preferred implementation and is not intended to limit the scope of protection of this invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

[0036] Example 2 Figure 5The diagram shows a subwavelength structure embedded in a disordered ultrauniform solid Mach-Jendr interferometer for gas sensing. The grid walls of the disordered ultrauniform solid on both sides of the Mach-Jendr interferometer are made of silicon, and the pore structure is coated with a polyhexamethylene biguanide hydrochloride gas-sensitizing medium. A 1 μm wide linear waveguide defect line is introduced, and the waveguide lengths on both sides are... L 1=72μm and L 2 = 36 μm. Multiple subwavelength structures, periodically arranged along the waveguide defect line direction, are designed and embedded in the defect line region of a waveguide composed of silicon dielectric. The subwavelength structures are coated with a polyhexamethylene biguanide hydrochloride gas sensitizing medium. The initial design parameters of the subwavelength grating are: the period of the subwavelength structure distribution is... Λ s =380nm, length of the subwavelength structure of polyhexamethylene biguanide hydrochloride along the waveguide direction l s =200nm, width of the subwavelength structure along the direction perpendicular to the waveguide w s =160nm.

[0037] Figure 6 The image shows the transmission spectrum measured by a Mach-Jendr interferometer embedded in a disordered ultrahomogeneous solid with a subwavelength structure. Based on the rational optimization of the subwavelength structure, the optical loss of the disordered ultrahomogeneous solid is controlled, resulting in a high resonance peak contrast for the Mach-Jendr interferometer. A significant resonance peak is observed in the transmission spectrum. This clear resonance peak effectively reduces the reading error of wavelength detection, thereby improving the accuracy of gas concentration inversion.

[0038] Figure 7 The figure shows the measurement results of the resonant peak shift of a disordered ultrauniform solid Mach-Jendl interferometer with a subwavelength structure embedded at different carbon dioxide gas concentrations. By enhancing the evanescent field that can directly interact with carbon dioxide gas through the embedding of a subwavelength structure, the use of polyhexamethylene biguanide hydrochloride as a gas-sensitizing medium further increases the effective refractive index change of the waveguide induced by carbon dioxide gas, thereby increasing the resonant peak shift of the Mach-Jendl interferometer at the same carbon dioxide gas concentration. Ultimately, within the range of 0–400 ppm, the carbon dioxide sensing sensitivity was measured to be -2.91 pm / ppm, with a detection limit of approximately 29 ppm. This sensitivity is 2.2 times that of the previous carbon dioxide sensing sensitivity based on a silicon microring resonator using polyhexamethylene biguanide hydrochloride.

[0039] Therefore, this invention employs a subwavelength structure embedded in a disordered ultrauniform solid waveguide and its design method, resulting in high sensing sensitivity. By embedding a subwavelength structure composed of multiple dielectric layers in the core region of the waveguide defect line, the strong evanescent field provided by the subwavelength structure enhances the interaction between the optical field and the surrounding gas molecules, thereby improving the sensitivity of the gas sensor. The device exhibits low optical loss. By optimizing the distribution (periodic, quasi-periodic, or disordered ultrauniform distribution) and geometric parameters of the subwavelength structure, the additional transmission loss introduced while enhancing the waveguide evanescent field remains at a low level. The design is highly flexible. The subwavelength structure in this invention can adopt various distribution methods (periodic, quasi-periodic, or disordered ultrauniform distribution), and the multiple dielectric layers can be composed of various dielectrics in the direction perpendicular to the waveguide defect line. The dielectrics can be any combination of high-refractive-index, low-refractive-index, and functional dielectrics. This high flexibility allows this invention to be applied to different wavelength bands, different gas detection targets, and different sensor types. The design boasts a high degree of automation. This invention introduces intelligent optimization algorithms (such as Bayesian optimization, genetic algorithms, and particle swarm optimization) to automatically optimize the parameters of the subwavelength structure, avoiding the high cost and low efficiency of traditional trial-and-error methods. Given only the objective function (such as the external constraint factor), the algorithm can efficiently optimize the structure within a given design space, improving design efficiency. Compatible with existing manufacturing processes, the subwavelength structure proposed in this invention can be directly realized on standard silicon-based optoelectronic manufacturing platforms using electron beam lithography or deep ultraviolet lithography combined with inductively coupled plasma etching processes, without the need for additional complex steps. Since the subwavelength structure size is on the order of hundreds of nanometers, it is fully compatible with current mainstream complementary metal-oxide-semiconductor (CMOS) manufacturing technologies. This invention is applicable to the development of disordered ultrauniform solid-state devices for various optical sensing applications, exhibiting broad applicability. It can be applied not only to the design of on-chip disordered ultrauniform solid-state waveguide gas sensors but also to the design of on-chip integrated optical sensing devices such as liquid phase sensors, temperature sensors, humidity sensors, pressure sensors, and photodetectors.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A subwavelength structure embedded in a disordered ultrauniform solid waveguide, characterized in that: The device includes a waveguide, which comprises a core layer and a cladding layer. The cladding layer is disposed on both sides of the waveguide and is composed of a disordered ultrauniform solid. The disordered ultrauniform solid is composed of grid walls and a hole structure. Waveguide defect lines are also provided, and subwavelength structures are provided within the waveguide defect lines. The subwavelength structures are arranged along the direction of the waveguide defect lines.

2. The subwavelength structure embedded disordered ultrauniform solid waveguide according to claim 1, characterized in that: The waveguide defect line shall be provided in a number of ways, and the waveguide defect line shall be any number of lines formed by one or more of the following: straight lines, polynomial curves, circular arcs, elliptical arcs, Euler curves, Bezier curves, and Gaussian curves.

3. The subwavelength structure embedded disordered ultrauniform solid waveguide according to claim 1, characterized in that: The subwavelength structure is composed of multiple dielectric layers, and the multiple dielectric layers, the mesh walls, and the pore structure are all composed of one or more of the following: air, silicon dioxide, silicon, germanium, silicon-germanium alloy, silicon nitride, lithium niobate, and sulfides.

4. The subwavelength structure embedded disordered ultrauniform solid waveguide according to claim 3, characterized in that: The distribution of the multilayer dielectric along the waveguide defect line can be any one of periodic distribution, quasi-periodic distribution, or disordered ultra-uniform distribution. When periodic distribution is adopted, the multilayer dielectric constitutes a subwavelength grating.

5. The subwavelength structure embedded disordered ultrauniform solid waveguide according to claim 1, characterized in that: The waveguide surface is coated with a gas-sensitive medium, which is one or a combination of polyhexamethylene biguanide hydrochloride, low-dimensional materials, and metal oxides.

6. The subwavelength structure embedded disordered ultrauniform solid waveguide according to claim 1, characterized in that: The disordered ultra-uniform solid is a two-dimensional planar structure or a three-dimensional solid structure.

7. A design method for a subwavelength structure embedded in a disordered ultrauniform solid waveguide, applied to the subwavelength structure embedded in a disordered ultrauniform solid waveguide as described in any one of claims 1-6, characterized in that, Includes the following steps: Step 1: Introduce at least one waveguide defect line into the disordered, ultra-uniform solid; Step 2: Design a multilayer dielectric subwavelength structure arranged along the waveguide defect line in the region where the waveguide defect line is introduced; Step 3: Use optimization algorithms to design and optimize the subwavelength structure embedded disordered ultrauniform solid waveguide based on the given objective function; Step 4: Construct a disordered, ultrauniform solid waveguide for gas sensing using optimized structural parameters.

8. The design method for a subwavelength structure embedded in a disordered ultrauniform solid waveguide according to claim 7, characterized in that: The optimization algorithm described in step three is one of the following: exhaustive search, neural network algorithm, Bayesian optimization, genetic algorithm, particle swarm optimization, differential evolution algorithm, and simulated annealing.

9. The design method for a subwavelength structure embedded in a disordered ultrauniform solid waveguide according to claim 8, characterized in that: The objective function in step three is one of the external confinement factor or the ratio of external confinement factor to transmission loss. The external confinement factor is the proportion of optical power in the waveguide's surrounding environment to the total transmission power. The higher the external confinement factor, the stronger the evanescent field and the higher the sensing sensitivity.

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