Hybrid plasma TE pass-type polarizer and design method thereof

Abstract

The invention belongs to the field of optical communication, and provides a mixed plasma TE pass-type polarizer and a design method thereof. The hybrid plasma waveguide is composed of a linear hybrid plasma waveguide and a bent hybrid plasma waveguide, and the research shows that the introduction of the linear hybrid plasma waveguide reduces the additional loss of TE polarized light and improves the polarization extinction ratio. And secondly, by designing a hybrid plasma waveguide formed by a sandwich structure including a semiconductor layer, a dielectric layer and a metal layer, the TM polarized light is converted into surface plasma light, and the surface plasma light is mainly distributed in the middle dielectric layer for transmission, so that the additional loss caused by metal heating is reduced.

Description

Technical Field

[0001] The present invention belongs to the field of optical communications, and in particular relates to a hybrid plasma TE through-type polarizer and a design method thereof. Background Art

[0002] Optoelectronic integration platforms based on silicon-on-insulator (SOI) architectures have become a major research focus in micro- and nanophotonics. SOI platforms leverage the significant refractive index difference between the encapsulation layer (silicon dioxide or air) and the silicon waveguide to achieve subwavelength dimensions and optical field confinement capabilities. However, the resulting polarization birefringence also presents a serious polarization sensitivity issue.

[0003] TE (Transverse Electric) pass-through polarizers are fundamental components used in optical systems, used to filter out unwanted TM (Transverse Magnetic) polarized light, reduce polarization crosstalk, and retain the desired TE polarized light. Current TE pass-through polarizer designs based on subwavelength gratings (SWGs) or asymmetric coupler structures can achieve a TM polarized light cutoff effect by manipulating the waveguide structure parameters, but they still suffer from the following drawbacks: To achieve a high polarization extinction ratio (>20 dB), they rely on a high duty cycle of the subwavelength grating or a complex asymmetric structure design, resulting in limited process tolerances and large device size, making it difficult to meet the high-density integration requirements of photonic chips. Furthermore, a step-by-step optimization method based on parameter scanning is currently used for device structure design, but this method cannot simultaneously improve both mode field localization and structural robustness. For example, traditional SWG-TE through-type polarizers need to repeatedly adjust single parameters such as grating period and fill factor to approach performance targets. However, due to the local convergence characteristics of point-by-point optimization, it is difficult to balance the relationship between optical binding force, additional loss and polarization selectivity, which ultimately leads to excessive device size and increased process sensitivity. Summary of the Invention

[0004] In order to solve the problems existing in the above-mentioned prior art, the present invention provides a hybrid plasma TE pass-type polarizer and a design method thereof. The structural design of the hybrid plasma TE pass-type polarizer makes it smaller in size and more compact in structure, reduces the additional loss of TE polarized light, improves the polarization extinction ratio, and has a good tolerance for manufacturing errors.

[0005] The present invention is achieved through the following technical solutions: In a first aspect, the present invention provides a hybrid plasma TE pass-type polarizer, comprising: a silicon dioxide cladding, a silicon waveguide and a hybrid plasma grating located within the silicon dioxide cladding; The silicon waveguide includes an input waveguide, a curved waveguide, and an output waveguide connected end to end in sequence, and both the input waveguide and the output waveguide are straight waveguides; The hybrid plasma grating is arranged on the outside of the silicon waveguide, including a plurality of hybrid plasma waveguides arranged in sequence from the silicon waveguide outward; each hybrid plasma waveguide includes a straight hybrid plasma waveguide corresponding to and arranged parallel to the input waveguide and a curved hybrid plasma waveguide arranged concentrically with the curved waveguide; one end of the straight hybrid plasma waveguide is connected to one end of the corresponding curved hybrid plasma waveguide, and the connection position is located on the vertical line of the output end of the input waveguide; the hybrid plasma waveguide includes a semiconductor layer, a dielectric layer and a metal layer from bottom to top, the semiconductor layer is silicon, and the refractive index of the semiconductor layer is higher than the refractive index of the dielectric layer.

[0006] Preferably, the bending radius of the curved hybrid plasma waveguide is calculated by the following formula:

[0007] Where, Λ is the pitch length of the hybrid plasmon grating, R i For the first time, the silicon waveguide i The bending radius of the curved hybrid plasma waveguide, R 0 is the bending radius of the curved waveguide, is the width of the silicon waveguide.

[0008] Preferably, the width of each hybrid plasma waveguide decreases sequentially from the silicon waveguide outward.

[0009] Preferably, the width of the hybrid plasma waveguide is Λ f i , f i Determined by the following formula:

[0010] Where, Λ is the pitch length of the hybrid plasmon grating, f i For the first time, the silicon waveguide i Duty cycle of the strip-bent hybrid plasmonic waveguide, f M and f m are the maximum duty cycle and minimum duty cycle of the hybrid plasma grating, N is the number of hybrid plasma waveguides.

[0011] Preferably, the dielectric layer is made of silicon dioxide.

[0012] Preferably, the metal layer is made of silver.

[0013] Preferably, the height of the semiconductor layer in each hybrid plasma waveguide is equal to the height of the silicon waveguide.

[0014] In a second aspect, the present invention provides a design method for the hybrid plasma TE pass-type polarizer, which sets: the height and width of the silicon waveguide, the bending angle and bending radius of the curved waveguide, the heights of the semiconductor layer, the dielectric layer, and the metal layer, and the number of hybrid plasma waveguides; and uses an inverse design optimization algorithm to optimize: the pitch length, maximum duty cycle, and minimum duty cycle of the hybrid plasma grating, the bending angle and bending radius of each curved hybrid plasma waveguide, the length of each linear hybrid plasma waveguide, and the width of each hybrid plasma waveguide.

[0015] Preferably, the design method of the hybrid plasma TE pass-type polarizer specifically includes: Setting: The height of the silicon waveguide is h 1. Width is w wg , the bending angle of the curved waveguide is θ 0. The bending radius is R 0, the heights of the semiconductor layer, dielectric layer and metal layer are h 1. h 2 and h 3. The number of hybrid plasma waveguides is N ; Set the pitch length of the hybrid plasma grating Λ , maximum duty cycle f M and minimum duty cycle f m The initial value and search space of the bending angle of each curved hybrid plasma waveguide are set. θ i and the length of each linear hybrid plasmonic waveguide l i The initial value and search space of ; The initial value of the bending radius of the curved hybrid plasma waveguide is calculated according to formula (1), and the initial value of the bending radius of the curved hybrid plasma waveguide is obtained according to formula (2). f i , the width of the hybrid plasma waveguide is calculated Λ f i Initial value of: (1) (2) Where, Ri For the first time, the silicon waveguide i The bending radius of the curved hybrid plasma waveguide, f i For the first time, the silicon waveguide i Duty cycle of strip-bent hybrid plasmonic waveguide; Set the objective function as: FOM =[1-(1-| T TM |)] 2 (3) Where, T TM The transmission efficiency of TM polarized light is obtained by using FDTD simulation software to construct the structure of the hybrid plasma TE through-type polarizer and setting a transmission efficiency monitor on the output waveguide. T TM ; by FOM The optimization goal is to minimize the value. The inverse design optimization algorithm is used to search for the optimal structure of the hybrid plasma TE through-type polarizer, and the optimal structure corresponding to the Λ 、 f M 、 f m 、 θ i 、 l i 、 R i and Λ f i .

[0016] Preferably, the pitch length of the hybrid plasma grating is set to Λ The search space is 0.3 µm~0.4 µm, and the maximum duty cycle of the hybrid plasmon grating is f M The search space is 0.7~0.85, and the minimum duty cycle of the hybrid plasma grating f m The search space is 0.2~0.3, and the bending angle of each curved hybrid plasma waveguide is θ i The search space is 0~90°, and the length of each linear hybrid plasma waveguide is l i The search space is 1 µm~2 µm.

[0017] Compared with the prior art, the present invention has the following beneficial effects: First, the hybrid plasma TE-pass polarizer of the present invention is configured with a hybrid plasma grating disposed outside a silicon waveguide. The hybrid plasma grating comprises a plurality of hybrid plasma waveguides, each of which comprises a linear hybrid plasma waveguide and a curved hybrid plasma waveguide. The hybrid plasma waveguides are sequentially arranged outward from the silicon waveguide. Thus, the curvature radius of the curved hybrid plasma waveguide increases progressively as it moves outward from the silicon waveguide. This gradient variation in curvature radius reduces mode coupling (decoupling) between the waveguides, thereby enabling the hybrid plasma grating to more efficiently couple TM polarized light from the silicon waveguide to the hybrid plasma waveguide, thereby achieving coupled absorption of TM polarized light at the hybrid plasma grating. Furthermore, the hybrid plasma waveguide of the present invention is composed of a linear hybrid plasma waveguide and a curved hybrid plasma waveguide. Studies have shown that the introduction of the linear hybrid plasma waveguide reduces the additional loss of TE polarized light and improves the polarization extinction ratio. Secondly, by designing a hybrid plasma waveguide formed into a sandwich structure consisting of a semiconductor layer, a dielectric layer, and a metal layer, TM polarized light is converted into surface plasmon light, which is primarily distributed and transmitted in the central dielectric layer, reducing additional loss caused by metal heating. By rationally designing the parameters of the hybrid plasma waveguide, the effective refractive index of TM polarized light entering the silicon waveguide can be aligned with that of the hybrid plasma waveguide, achieving phase matching. However, TE polarized light is phase mismatched and is forced to exit the output waveguide along the silicon waveguide. By combining the diffraction-limited properties of linear and curved hybrid plasma waveguides, the hybrid plasma TE-pass polarizer designed in this invention can be significantly reduced in size, facilitating integration while offering good tolerance to manufacturing errors.

[0018] Furthermore, by designing the bending radius and width of the curved hybrid plasma waveguide, the polarization extinction ratio of the hybrid plasma TE pass polarizer can be improved and the additional loss can be reduced.

[0019] Furthermore, the dielectric layer of the present invention is made of silicon dioxide, and the metal layer is made of silver. Using low-refractive-index silicon dioxide as the dielectric layer effectively isolates the silicon waveguide from the metal layer, reducing scattering and absorption losses at the metal-dielectric interface. Silver was chosen as the metal layer material due to its low optical loss characteristics and compatibility with silicon photonics processes. The combination of silver and silicon dioxide achieves an optimal balance of low added loss, strong localization, and process compatibility in hybrid plasmon waveguides.

[0020] The present invention utilizes an inverse design optimization algorithm to optimize some parameters of a hybrid plasma TE pass-type polarizer (the pitch length of the hybrid plasma grating, the maximum duty cycle, the minimum duty cycle, the bending angle of each curved hybrid plasma waveguide, and the length of each linear hybrid plasma waveguide). This gives the hybrid plasma TE pass-type polarizer structure a great degree of parameter freedom, significantly increases the exploration and design of global parameters, further reduces the size of the hybrid plasma TE pass-type polarizer, and enables the hybrid plasma TE pass-type polarizer to have the characteristics of a large bandwidth, a high polarization extinction ratio, and low additional loss, thereby overcoming the problems caused by specific structural designs. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 1 is a top view of the initial structure of the hybrid plasma TE through-type polarizer in an embodiment of the present invention; Figure 2 3. This is a top view of the coupling region structure of the initial structure of the hybrid plasma TE pass-type polarizer in an embodiment of the present invention; Figure 3 1 is a cross-sectional structural diagram of the coupling region of a hybrid plasma TE-pass type polarizer according to an embodiment of the present invention; Figure 4 The reverse design optimization algorithm is used in the embodiment of the present invention to optimize FOM Relationship with the number of iterations; Figure 5 1 is a top view of the optimal structure of the hybrid plasma TE pass-type polarizer obtained by searching through a reverse design optimization algorithm in an embodiment of the present invention; Figure 6 The optimal effect field distribution diagram at an operating wavelength of 1550 nm is obtained by searching through the inverse design optimization algorithm in an embodiment of the present invention; (a) is the optimal effect field distribution diagram of TE polarized light at an operating wavelength of 1550 nm, and (b) is the optimal effect field distribution diagram of TM polarized light at an operating wavelength of 1550 nm; Figure 7 is the relationship between the transmittance and wavelength of the hybrid plasma TE pass type polarizer according to the embodiment of the present invention, based on the initial structure and the optimal structure of the hybrid plasma TE pass type polarizer obtained by searching with the inverse design optimization algorithm; Figure 8 : is the relationship between the polarization extinction ratio (a), additional loss (b) and wavelength of the initial structure of the hybrid plasma TE pass-type polarizer in the embodiment of the present invention; Figure 9 : This is the relationship between the polarization extinction ratio (a), additional loss (b) and wavelength of the optimal structure of the hybrid plasma TE pass-type polarizer obtained by searching through the inverse design optimization algorithm in an embodiment of the present invention; Figure 10: The optimal structure of a TE-passing polarizer containing only a curved hybrid plasma waveguide, obtained by searching through an inverse design optimization algorithm in an embodiment of the present invention, and the relationship curves of its polarization extinction ratio, additional loss, and wavelength; (a) is the optimal structure of a TE-passing polarizer containing only a curved hybrid plasma waveguide, obtained by searching through an inverse design optimization algorithm; (b) is the relationship between the polarization extinction ratio and wavelength of the optimal structure; (c) is the relationship between the additional loss and wavelength of the optimal structure; Figure 11 1 is the effect of the manufacturing tolerance of the width of each hybrid plasma waveguide on the device performance of the hybrid plasma TE-pass polarizer in an embodiment of the present invention; (a) is a curve showing the relationship between the additional loss and the width of each hybrid plasma waveguide, and (b) is a curve showing the relationship between the polarization extinction ratio and the width of each hybrid plasma waveguide; Figure 12 Figure 1 shows the effect of the manufacturing tolerance of the input waveguide width on the device performance of the hybrid plasma TE-pass polarizer in an embodiment of the present invention; (a) shows the relationship between the additional loss and the input waveguide width; (b) shows the relationship between the polarization extinction ratio and the input waveguide width; Figure 13 1. The effect of the manufacturing tolerance of the silicon dioxide dielectric layer height on the device performance of the hybrid plasma TE-pass polarizer in the embodiment of the present invention; (a) is a curve showing the relationship between the additional loss and the silicon dioxide dielectric layer height; (b) is a curve showing the relationship between the polarization extinction ratio and the silicon dioxide dielectric layer height.

[0022] In the figure: 1 is an input waveguide, 2 is a curved waveguide, 3 is an output waveguide, 4 is a first straight hybrid plasma waveguide, 5 is a second straight hybrid plasma waveguide, 6 is a third straight hybrid plasma waveguide, 7 is a fourth straight hybrid plasma waveguide, 8 is a fifth straight hybrid plasma waveguide, 9 is a first curved hybrid plasma waveguide, 10 is a second curved hybrid plasma waveguide, 11 is a third curved hybrid plasma waveguide, 12 is a fourth curved hybrid plasma waveguide, and 13 is a fifth curved hybrid plasma waveguide. DETAILED DESCRIPTION

[0023] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0024] It should be noted that the process equipment or devices not specifically specified in the following embodiments are all conventional equipment or devices in the art.

[0025] It should be noted that the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products, or apparatuses. Furthermore, unless otherwise specified, the numbering of each method step is merely a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or to define the scope of the invention. Changes or adjustments to their relative relationships, without substantially changing the technical content, should also be considered within the scope of the invention.

[0026] In the description of the present invention, it should be noted that the terms "upper", "lower", "inner" and "outer" etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention; the terms "first", "second" etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0027] like Figure 1 As shown, the hybrid plasma TE pass polarizer of the present invention includes: a silicon waveguide, a hybrid plasma grating and a silicon dioxide cladding; the silicon waveguide and the hybrid plasma grating are located in the silicon dioxide cladding.

[0028] The silicon waveguide includes an input waveguide 1, a curved waveguide 2 and an output waveguide 3. The input waveguide 1 and the output waveguide 3 are both linear waveguides; the curved waveguide 2 is an arc-shaped waveguide; one end of the curved waveguide 2 is connected to one end of the input waveguide 1, and the other end of the curved waveguide 2 is connected to one end of the output waveguide 3.

[0029] The hybrid plasma grating is disposed outside the silicon waveguide and comprises a plurality of hybrid plasma waveguides arranged sequentially outward from the silicon waveguide. Each hybrid plasma waveguide comprises a straight hybrid plasma waveguide and a curved hybrid plasma waveguide. The straight hybrid plasma waveguide is parallel to and corresponding to the input waveguide 1, while the curved hybrid plasma waveguide is concentric with the curved waveguide 2. One end of the straight hybrid plasma waveguide is connected to one end of the corresponding curved hybrid plasma waveguide, and the connection position is located perpendicular to the output end of the input waveguide 1. The hybrid plasma waveguide comprises, from bottom to top, a semiconductor layer, a dielectric layer, and a metal layer. The semiconductor layer is silicon, and the refractive index of the semiconductor layer is higher than that of the dielectric layer. A perpendicular line to the output end of the input waveguide 1 lies within the plane of the silicon waveguide and passes through the connection between the input waveguide 1 and the curved waveguide 2.

[0030] The curved waveguide 2 in the silicon waveguide of the present invention has the important function of transmitting optical signals to any position within the chip. Compared with traditional straight waveguides, the curved waveguide 2 can realize the transmission of optical signals in a limited space, thereby improving the integration and reducing the size of the device.

[0031] The present invention employs a hybrid plasma grating (HPG) on the outside of a silicon waveguide. The HPG comprises several HPG waveguides, which are arranged sequentially from the silicon waveguide. As a result, the bending radius of the curved HPG waveguides increases from the silicon waveguide outward, thereby achieving decoupling between the curved HPG waveguides and coupling absorption of TM polarized light at the HPG waveguides. Furthermore, the HPG waveguides comprise both linear and curved HPG waveguides. The introduction of the linear HPG waveguides reduces the additional loss of TE polarized light and improves the polarization extinction ratio.

[0032] In the present invention, the bending radius of the curved hybrid plasma waveguide can be determined according to formula (1): (1) Where, Λ is the pitch length of the hybrid plasmon grating, R i For the first time, the silicon waveguide i The bending radius of the curved hybrid plasma waveguide, R 0 is the bending radius of the curved waveguide 2, is the width of the silicon waveguide.

[0033] In some embodiments of the present invention, the input waveguide 1, curved waveguide 2, and output waveguide 3 have equal heights and widths. The linear hybrid plasma waveguide and the corresponding curved hybrid plasma waveguide have the same width, corresponding to the hybrid plasma waveguide. The width of each hybrid plasma waveguide decreases from the silicon waveguide outward.

[0034] Width of hybrid plasmonic waveguide Λ f i It can be determined by the following formula: (2) Where, Λ is the pitch length of the hybrid plasmon grating, f i For the first time, the silicon waveguide i Duty cycle of the strip-bent hybrid plasmonic waveguide, fM and f m are the maximum duty cycle and minimum duty cycle of the hybrid plasma grating, N is the number of hybrid plasma waveguides.

[0035] In some embodiments of the present invention, the heights of the semiconductor layer, dielectric layer, and metal layer in each hybrid plasma waveguide are equal in a one-to-one correspondence. That is, in each hybrid plasma waveguide, the semiconductor layer heights are all equal, the dielectric layer heights are all equal, and the metal layer heights are all equal. Furthermore, the height of the semiconductor layer in the hybrid plasma waveguide is equal to that of the silicon waveguide.

[0036] In one specific embodiment of the present invention, the dielectric layer is made of silicon dioxide, and the metal layer is made of silver. In the hybrid plasma waveguide structure, low-refractive-index silicon dioxide is used as the dielectric layer to effectively isolate the silicon waveguide from the metal layer, reducing scattering and absorption losses at the metal-dielectric interface. Silver is chosen as the metal layer because of its low optical loss characteristics and compatibility with silicon photonics processes. The combination of silver and silicon dioxide achieves an optimal balance of low added loss, strong localization, and process compatibility in the hybrid plasma waveguide.

[0037] The hybrid plasma TE pass polarizer of the present invention is designed by setting the height and width of a silicon waveguide, the bending angle and bending radius of a curved waveguide, the heights of a semiconductor layer, a dielectric layer, and a metal layer, and the number of hybrid plasma waveguides; and optimizing using a reverse design optimization algorithm to obtain the pitch length, maximum duty cycle, and minimum duty cycle of a hybrid plasma grating, the bending angle and bending radius of each curved hybrid plasma waveguide, the length of each linear hybrid plasma waveguide, and the width of each hybrid plasma waveguide.

[0038] Specifically, the design method of the present invention includes: Setting: The height of the silicon waveguide is h 1. Width is w wg The bending angle of the curved waveguide is θ0 and the bending radius is R 0, the heights of the semiconductor layer, dielectric layer and metal layer are h 1. h 2 and h 3. The number of hybrid plasma waveguides is N ; Set the pitch length of the hybrid plasma grating Λ , maximum duty cycle f M , minimum duty cycle f m The initial value and search space of the bending angle of each curved hybrid plasma waveguide are set. θi and the length of each linear hybrid plasmonic waveguide l i The initial value and search space of ; The initial value of the bending radius of the curved hybrid plasma waveguide is calculated according to formula (1), and the initial value of the bending radius of the curved hybrid plasma waveguide is obtained according to formula (2). f i , the width of the hybrid plasma waveguide is calculated Λ f i Initial value of: (1) (2) Where, Λ is the pitch length of the hybrid plasmon grating, R i For the first time, the silicon waveguide i The bending radius of the curved hybrid plasma waveguide, f i For the first time, the silicon waveguide i Duty cycle of the strip-bent hybrid plasmonic waveguide, f M and f m are the maximum duty cycle and minimum duty cycle of the hybrid plasma grating, N is the number of hybrid plasma waveguides, R 0 is the bending radius of the curved waveguide 2, is the width of the silicon waveguide; Set the objective function as: FOM =[1-(1-| T TM |)] 2 (3) Where, T TM The transmission efficiency of TM polarized light is obtained by using the finite difference in time domain (FDTD) simulation software to construct the structure of the hybrid plasma TE through-type polarizer and setting a transmission efficiency monitor in the output waveguide 3. T TM ;by FOM The optimization goal is to minimize the value. The inverse design optimization algorithm is used to search for the optimal structure of the hybrid plasma TE pass polarizer, and the optimal structure is obtained: the pitch length of the hybrid plasma grating Λ , maximum duty cycle fM and minimum duty cycle f m , the bending angle of each curved hybrid plasma waveguide θ i and bending radius R i , the length of each linear hybrid plasma waveguide l i , and the width of each hybrid plasmonic waveguide Λ f i .

[0039] Example like Figure 1 and 3 As shown, the hybrid plasma TE pass polarizer of the present invention includes: a silicon substrate (not shown in the figure), a silicon waveguide, a hybrid plasma grating and a silicon dioxide cladding; the silicon waveguide and the hybrid plasma grating are located inside the silicon dioxide cladding, and the silicon dioxide cladding is located on the silicon substrate.

[0040] The silicon waveguide includes an input waveguide 1, a curved waveguide 2 and an output waveguide 3. The input waveguide 1 and the output waveguide 3 are both linear waveguides; the curved waveguide 2 is an arc-shaped waveguide; one end of the curved waveguide 2 is connected to one end of the input waveguide 1, and the other end of the curved waveguide 2 is connected to one end of the output waveguide 3.

[0041] The hybrid plasma grating is disposed outside the silicon waveguide and comprises a plurality of hybrid plasma waveguides sequentially arranged outward from the silicon waveguide. Each hybrid plasma waveguide comprises a linear hybrid plasma waveguide and a curved hybrid plasma waveguide. The linear hybrid plasma waveguide is parallel to and corresponding to the input waveguide 1, while the curved hybrid plasma waveguide is concentric with the curved waveguide 2. One end of the linear hybrid plasma waveguide is connected to one end of the corresponding curved hybrid plasma waveguide, and the connection position is located perpendicular to the output end of the input waveguide 1. The hybrid plasma waveguide comprises, from bottom to top, a semiconductor layer, a dielectric layer, and a metal layer. The refractive index of the semiconductor layer is higher than that of the dielectric layer. The input waveguide 1, the curved waveguide 2, and the hybrid plasma grating form a coupling region.

[0042] The input waveguide 1, the curved waveguide 2 and the output waveguide 3 have the same height and width. The width of the linear hybrid plasma waveguide is consistent with that of the corresponding curved hybrid plasma waveguide, which is the same as the width of the hybrid plasma waveguide.

[0043] like Figure 3, which is a cross-sectional schematic diagram of the coupling region, the semiconductor layer is made of silicon, the dielectric layer is made of silicon dioxide, and the metal layer is made of silver.

[0044] The design method of the hybrid plasma TE pass-type polarizer described in this embodiment includes: First, design an initial structure (such as Figure 1 and Figure 2 As shown), in the initial structure: the heights of the input waveguide 1, the output waveguide 3 and the curved waveguide 2 are all h 1=340 nm, width is w wg =360 nm; bending angle of curved waveguide 2 θ 0=90°, bending radius R 0=3.5 μm; the heights of the semiconductor layer, dielectric layer, and metal layer are h 1=340 nm, h 2 = 50 nm, h 3 = 100 nm; pitch length of the hybrid plasmonic grating Λ =0.3 μm, the maximum duty cycle of the hybrid plasmonic grating f M =0.72, the minimum duty cycle of the hybrid plasma grating f m =0.2, number of hybrid plasma waveguides N =5. The hybrid plasma waveguide includes a first linear hybrid plasma waveguide 4, a second linear hybrid plasma waveguide 5, a third linear hybrid plasma waveguide 6, a fourth linear hybrid plasma waveguide 7, a fifth linear hybrid plasma waveguide 8, a first curved hybrid plasma waveguide 9, a second curved hybrid plasma waveguide 10, a third curved hybrid plasma waveguide 11, a fourth curved hybrid plasma waveguide 12, and a fifth curved hybrid plasma waveguide 13. The length of each of the five linear hybrid plasma waveguides is 2 μm, and the bending angle of each of the five curved hybrid plasma waveguides is 90°.

[0045] Setting the pitch length of the hybrid plasmon grating Λ The search space is 0.3 µm~0.4 µm, and the maximum duty cycle of the hybrid plasmon grating is f M The search space is 0.7~0.85, and the minimum duty cycle of the hybrid plasma grating f m The search space is 0.2~0.3, and the bending angle of each curved hybrid plasma waveguide is θ iThe search space is 0~90°, and the length of each linear hybrid plasma waveguide is l i The search space is 1 µm~2 µm.

[0046] The bending radius of the curved hybrid plasma waveguide is determined according to formula (1): R i , the width of the hybrid plasma waveguide is determined according to formula (2) Λ f i : (1) (2) Where, Λ is the pitch length of the hybrid plasmon grating, R i For the first time, the silicon waveguide i The bending radius of the curved hybrid plasma waveguide, f i For the first time, the silicon waveguide i Duty cycle of the strip-bent hybrid plasmonic waveguide, f M and f m are the maximum duty cycle and minimum duty cycle of the hybrid plasma grating, N is the number of hybrid plasma waveguides, R 0 is the bending radius of the curved waveguide 2, is the width of the silicon waveguide.

[0047] Set the objective function as: FOM =[1-(1-| T TM |)] 2 (3) Where, T TM The transmission efficiency of TM polarized light is obtained by using FDTD simulation software to build the structure of the hybrid plasma TE through-type polarizer and setting a transmission efficiency monitor in the output waveguide 3. T TM .

[0048] by FOM The minimum value is taken as the optimization goal, and the inverse design optimization algorithm is used to search for the optimal structural parameters of the hybrid plasma TE pass-type polarizer. Figure 4 The reverse design optimization algorithm is used in the embodiment of the present invention to optimize FOMRelationship with the number of iterations, it can be seen that as the number of iterations increases FOM The value gradually decreases and eventually approaches 0 and remains stable.

[0049] Figure 5 The optimal structure of the hybrid plasma TE through-type polarizer obtained by the reverse design optimization algorithm in the embodiment of the present invention. The structural parameters of the optimal structure are: the heights of the input waveguide 1, the output waveguide 3 and the curved waveguide 2 are all h 1=340 nm, width is w wg =360 nm; the bending angle of the curved waveguide 2 is 90°, and the bending radius R 0=3.5 μm; the heights of the semiconductor layer, dielectric layer, and metal layer are h 1=340 nm, h 2 = 50 nm and h 3 = 100 nm; pitch length of the hybrid plasmonic grating Λ =0.3 μm, the maximum duty cycle of the hybrid plasmonic grating f M =0.712612, the minimum duty cycle of the hybrid plasma grating f m= 0.264818; the length of the first straight hybrid plasma waveguide 4 is 2 μm, the length of the second straight hybrid plasma waveguide 5 is 1.9 μm, the length of the third straight hybrid plasma waveguide 6 is 1.8 μm, the length of the fourth straight hybrid plasma waveguide 7 is 1.7 μm, and the length of the fifth straight hybrid plasma waveguide 8 is 1.6 μm; the bending angles of the first curved hybrid plasma waveguide 9, the second curved hybrid plasma waveguide 10, the third curved hybrid plasma waveguide 11, the fourth curved hybrid plasma waveguide 12, and the fifth curved hybrid plasma waveguide 13 are 90°, 63.0719°, 75.9226°, 69.0117°, and 90°, respectively; the widths of the first curved hybrid plasma waveguide 9, the second curved hybrid plasma waveguide 10, the third curved hybrid plasma waveguide 11, the fourth curved hybrid plasma waveguide 12, and the fifth curved hybrid plasma waveguide 13 are 0.2137836 The first curved hybrid plasma waveguide 9, the second curved hybrid plasma waveguide 10, the third curved hybrid plasma waveguide 11, the fourth curved hybrid plasma waveguide 12, and the fifth curved hybrid plasma waveguide 13 have bending radii of 3.83 μm, 4.13 μm, 4.43 μm, 4.73 μm, and 5.03 μm, respectively. It can be seen that, from the silicon waveguide outward, the width of each hybrid plasma waveguide decreases, while the bending radius of each curved hybrid plasma waveguide increases.

[0050] Figure 6 The optical field distribution diagrams for TE-polarized and TM-polarized light at 1550 nm are shown in order to determine the optimal structure of the hybrid plasmon TE-pass polarizer using an inverse design optimization algorithm. It can be seen that TE-polarized light is output from output waveguide 3 and experiences almost no coupling at the hybrid plasmon grating. In contrast, TM-polarized light is coupled and absorbed at the hybrid plasmon grating and experiences almost no transmission at output waveguide 3.

[0051] The performance of TE through-type polarizers mainly includes two performance indicators: excess loss (EL) and polarization extinction ratio (PER): EL =-10 log 10 (T TE ) (4) PER= 10 log 10 (T TE / T TM ) (5) T TE 、 T TM are the transmission efficiencies of TE polarized light and TM polarized light at the output waveguide 3, respectively.

[0052] Figure 7 This figure shows the relationship between transmittance and wavelength for the initial and optimal structures of the hybrid plasma TE pass polarizer of the present invention. By introducing an inverse design optimization algorithm to search and optimize the structural parameters of the hybrid plasma TE pass polarizer, it can be seen that the optimal structure of the hybrid plasma TE pass polarizer effectively couples TM polarized light to the hybrid plasma grating compared to the initial structure, effectively improving the polarization extinction ratio of the hybrid plasma TE pass polarizer. Furthermore, by using the inverse design optimization algorithm to search for optimal values ​​for some structural parameters of the hybrid plasma TE pass polarizer, the structural dimensions of the hybrid plasma TE pass polarizer were further reduced, with the bending radius of the fifth curved hybrid plasma waveguide 13 being only 5.03 μm.

[0053] Figure 8 The figure shows the relationship between the polarization extinction ratio, additional loss, and wavelength of the initial structure of the hybrid plasma TE pass-type polarizer of the present invention. It can be seen that when the inverse design optimization algorithm is not introduced to search for the optimal structure, the PER of the initial structure of the hybrid plasma TE pass-type polarizer is 12 dB to 26 dB and the EL is 0.2 dB to 0.8 dB in the wavelength range of 1450 nm to 1650 nm.

[0054] Figure 9 The figure is a curve showing the relationship between the polarization extinction ratio, additional loss and wavelength of the optimal structure of the hybrid plasma TE pass-type polarizer obtained by searching the reverse design optimization algorithm in the embodiment of the present invention. It can be seen that within the wavelength range of 1450 nm to 1650 nm, the PER of the optimal structure of the hybrid plasma TE pass-type polarizer is 15 dB to 46 dB, the EL is 0.3 dB to 0.55 dB, the 1 dB bandwidth is 200 nm, and within the wavelength range of 1450 nm to 1580 nm, the PER is greater than 20 dB. Figure 8 Compared with the initial structure of the hybrid plasma TE pass type polarizer, the polarization extinction ratio of the optimal structure of the hybrid plasma TE pass type polarizer obtained by the inverse design optimization algorithm is improved and the additional loss is reduced.

[0055] Figure 10 The optimal structure of a TE-pass polarizer containing only curved hybrid plasma waveguides, as found through a reverse design optimization algorithm, and the relationship curve between its polarization extinction ratio, additional loss, and wavelength are shown. The method for constructing a TE-pass polarizer containing only curved hybrid plasma waveguides comprises: constructing an initial structure of a TE-pass polarizer containing only curved hybrid plasma waveguides. This initial structure has the same structural parameters as the initial structure of the hybrid plasma TE-pass polarizer of the present invention, differing only in that a linear hybrid plasma waveguide is not provided. Then, a search is performed using the reverse design optimization algorithm of this embodiment to obtain the optimal structure of a TE-pass polarizer containing only curved hybrid plasma waveguides. Comparison Figure 10 and Figure 9 It can be seen that compared with the TE-pass polarizer containing only a curved hybrid plasma waveguide, the TE-pass polarizer composed of a linear hybrid plasma waveguide and a curved hybrid plasma waveguide of the present invention has smaller additional loss within the same working bandwidth and a significantly improved polarization extinction ratio.

[0056] Figure 11 is the effect of the manufacturing tolerance of the width of each hybrid plasma waveguide of the optimal structure of the hybrid plasma TE-pass polarizer on the device performance in the embodiment of the present invention; Λ f i The tolerance is When the wavelength changes, EL is less than 1 dB and PER is greater than 15 dB within the wavelength range of 1450 nm to 1650 nm, indicating that the hybrid plasma TE-pass polarizer of the present invention has a good tolerance for the manufacturing error of the hybrid plasma waveguide width.

[0057] Figure 12 The manufacturing tolerance of the input waveguide width of the optimal structure of the hybrid plasma TE through-type polarizer in the embodiment of the present invention affects the device performance; the input waveguide width w wg The tolerance is When the wavelength changes, EL < 1.1 dB and PER > 13 dB in the range of 1450 nm to 1650 nm, indicating that the hybrid plasma TE-pass polarizer of the present invention has a good tolerance to the manufacturing error of the input waveguide width. w wg The decrease in EL and the increase in PER are significant. This is because the effective refractive index of TM polarized light is more sensitive to changes in waveguide width when the waveguide width is small. Therefore, when the input waveguide width of the optimal structure hybrid plasmon TE pass polarizer changes, the polarization extinction ratio changes rapidly.

[0058] Figure 13The manufacturing tolerance of the silicon dioxide dielectric layer height of the hybrid plasma TE through-type polarizer in the embodiment of the present invention affects the device performance; the silicon dioxide dielectric layer height h The tolerance of 2 is When the wavelength changes, EL < 1 dB and PER > 10 dB in the range of 1450 nm to 1650 nm, indicating that the hybrid plasma TE-pass polarizer of the present invention has a good tolerance to the manufacturing error of the dielectric layer height. h 2 decreases, the polarization extinction ratio changes greatly and decreases significantly. The height change of the silica dielectric layer in the hybrid plasma waveguide will also change the effective refractive index of the light, thereby destroying the phase matching of the TM polarized light and causing the polarization extinction ratio of the polarizer to decrease.

[0059] The hybrid plasma TE-pass polarizer of the present invention has a compact structure, greatly saving space and facilitating the realization of highly integrated photonic devices. The hybrid plasma TE-pass polarizer of the present invention has the performance of a high polarization extinction ratio and low additional loss, which can significantly reduce the interference of stray light and ensure the stability of light waves. In addition, the extremely low additional loss characteristic makes the energy loss of TM polarized light waves during transmission negligible, improving the overall transmission efficiency, and the device has a certain tolerance for process manufacturing errors. The hybrid plasma TE-pass polarizer of the present invention only transmits TE polarized light, which can avoid the performance degradation of photonic devices caused by the different transmission characteristics of TE polarized light and TM polarized light.

[0060] The above content is only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A hybrid plasma TE through-type polarizer, characterized in that: include: A silica cladding and a silicon waveguide and a hybrid plasmonic grating located within the silica cladding; The silicon waveguide includes an input waveguide (1), a curved waveguide (2), and an output waveguide (3) connected end to end in sequence, and both the input waveguide (1) and the output waveguide (3) are linear waveguides; The hybrid plasma grating is arranged outside the silicon waveguide, and includes a plurality of hybrid plasma waveguides arranged in sequence from the silicon waveguide outward; each hybrid plasma waveguide includes a straight hybrid plasma waveguide corresponding to and arranged in parallel with the input waveguide (1) and a curved hybrid plasma waveguide concentrically arranged with the curved waveguide (2); one end of the straight hybrid plasma waveguide is connected to one end of the corresponding curved hybrid plasma waveguide, and the connection position is located on the vertical line of the output end of the input waveguide (1); the hybrid plasma waveguide includes a semiconductor layer, a dielectric layer and a metal layer from bottom to top, the semiconductor layer is silicon, and the refractive index of the semiconductor layer is higher than the refractive index of the dielectric layer.

2. The hybrid plasma TE through-type polarizer according to claim 1, characterized in that: The bending radius of the curved hybrid plasma waveguide is calculated by the following formula: Where, Λ is the pitch length of the hybrid plasmon grating, R i For the first time, the silicon waveguide i The bending radius of the curved hybrid plasma waveguide, R 0 is the bending radius of the curved waveguide (2), is the width of the silicon waveguide.

3. The hybrid plasma TE through-type polarizer according to claim 1, characterized in that: From the silicon waveguide outward, the width of each hybrid plasma waveguide decreases successively.

4. The hybrid plasma TE through-type polarizer according to claim 1, characterized in that: The width of the hybrid plasmonic waveguide is Λ f i , f i Determined by the following formula: Where, Λ is the pitch length of the hybrid plasmon grating, f i For the first time, the silicon waveguide i Duty cycle of the strip-bent hybrid plasmonic waveguide, f M and f m are the maximum duty cycle and minimum duty cycle of the hybrid plasma grating, N is the number of hybrid plasma waveguides.

5. The hybrid plasma TE through-type polarizer according to claim 1, characterized in that: The dielectric layer is made of silicon dioxide.

6. The hybrid plasma TE through-type polarizer according to claim 1, characterized in that: The material of the metal layer is silver.

7. The hybrid plasma TE through-type polarizer according to claim 1, characterized in that: The height of the semiconductor layer in each hybrid plasma waveguide is equal to the height of the silicon waveguide.

8. The method for designing a hybrid plasma TE pass-type polarizer according to any one of claims 1 to 7, characterized in that: Settings: the height and width of the silicon waveguide, the bending angle and bending radius of the curved waveguide (2), the heights of the semiconductor layer, dielectric layer and metal layer, and the number of hybrid plasma waveguides; The inverse design optimization algorithm was used to optimize the following: the pitch length, maximum duty cycle and minimum duty cycle of the hybrid plasma grating, the bending angle and bending radius of each curved hybrid plasma waveguide, the length of each straight hybrid plasma waveguide, and the width of each hybrid plasma waveguide.

9. The design method of the hybrid plasma TE pass type polarizer according to claim 8, characterized in that: Specifically include: Setting: The height of the silicon waveguide is h 1. Width is w wg , the bending angle of the curved waveguide (2) is θ 0. The bending radius is R 0, the heights of the semiconductor layer, dielectric layer and metal layer are h 1. h 2 and h 3. The number of hybrid plasma waveguides is N ; Set the pitch length of the hybrid plasma grating Λ , maximum duty cycle f M and minimum duty cycle f m The initial value and search space of the bending angle of each curved hybrid plasma waveguide are set. θ i and the length of each linear hybrid plasmonic waveguide l i The initial value and search space of ; The initial value of the bending radius of the curved hybrid plasma waveguide is calculated according to formula (1), and the initial value of the bending radius of the curved hybrid plasma waveguide is obtained according to formula (2). f i , the width of the hybrid plasma waveguide is calculated Λ f i Initial value of: （1） （2） Where, R i For the first time, the silicon waveguide i The bending radius of the curved hybrid plasma waveguide, f i For the first time, the silicon waveguide i Duty cycle of strip-bent hybrid plasmonic waveguide; Set the objective function as: FOM =[1-(1-| T TM |)] 2 （3） Where, T TM The transmission efficiency of TM polarized light is obtained by using FDTD simulation software to construct the structure of the hybrid plasma TE through-type polarizer and setting a transmission efficiency monitor in the output waveguide (3). T TM ; by FOM The optimization goal is to minimize the value. The inverse design optimization algorithm is used to search for the optimal structure of the hybrid plasma TE through-type polarizer, and the optimal structure corresponding to the Λ 、 f M 、 f m 、 θ i 、 l i 、 R i and Λ f i .

10. The design method of the hybrid plasma TE through-type polarizer according to claim 9, characterized in that: Setting the pitch length of the hybrid plasmon grating Λ The search space is 0.3 µm~0.4 µm, and the maximum duty cycle of the hybrid plasmon grating is f M The search space is 0.7~0.85, and the minimum duty cycle of the hybrid plasma grating f m The search space is 0.2~0.3, and the bending angle of each curved hybrid plasma waveguide is θ i The search space is 0~90°, and the length of each linear hybrid plasma waveguide is l i The search space is 1 µm~2 µm.

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