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For terahertz systems where reflected signals carry effective information, such as terahertz time-domain reflection systems and full-duplex communication systems, existing nonreciprocal terahertz devices often treat reflected signals as interference and suppress them during isolation. This makes them incompatible with the requirements of such systems for isolating incident signals while directionally extracting and detecting reflected signals. To address this limitation, this study innovatively proposes a terahertz isolator based on a magneto-optical selection–multi-port architecture. The device converts linearly polarized light into a specific circular polarization state through orthogonal double gratings, and by combining the magneto-optical selectivity of InSb material, a nonreciprocal transmission path is constructed. Furthermore, the magneto-optical regulation mechanism innovatively combines branch waveguides with multiple ports and the characteristic of regulating terahertz transmission paths, while achieving isolation of incident/reflected signals and directionally extracting the reflected signals. The simulations of the influences of structural dimensions and external environmental conditions on the nonreciprocal characteristics of the device indicate that when the temperature is 250 K, the magnetic field is 0.3 T, and the structural parameters are set as follows: branch length of 170 μm, center-to-center spacings of adjacent branches of 125 μm, 125 μm, 120 μm, and 120 μm, InSb layer thickness of 5 μm, grating layer thickness of 50 μm, and substrate layer thickness of 20 μm, then the device achieves a high isolation of 63.12 dB at 0.73 THz. Additionally, at 0.78 THz, the bidirectional transmission efficiency reaches 36.31%, with a 3 dB bandwidth of 0.25 THz. This device has the advantages such as high isolation, low operating magnetic field strength, and integration of dual functions. It reduces interference from incident signals on reflected signals, simplifies subsequent processing steps such as noise reduction and localization of effective reflected signals, and improves the system's detection performance for weak signals. This provides essential support for expanding terahertz applications to more fields, including non-destructive testing and communication.
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图 1 基于磁光选择-多端口架构的太赫兹隔离器结构图 (a) 整体结构图; (b) InSb复合结构重复单元结构图与三视图
Figure 1. Schematic diagrams of the four-port nonreciprocal terahertz device based on InSb-branch waveguide: (a) Overall structure; (b) schematic diagram and standard three-view drawings of the unit cell in the InSb composite structure.
图 2 太赫兹波传输路径图
Figure 2. Schematic diagram of terahertz wave propagation path.
图 3 分支的长度对器件性能的影响 (a) 双向传输效率变化关系; (b) 隔离度变化关系
Figure 3. Impact of branch length on device performance: (a) Dependence of bidirectional transmission efficiency; (b) dependence of isolation characteristics.
图 4 相邻分支中心间距j1a1b, j1b2b, j2b3b, j3b2a与双向传输效率、隔离度的关系图 (a) j1a1b与双向传输效率的关系图; (b) j1a1b与隔离度的关系图; (c) j1b2b与双向传输效率的关系图; (d) j1b2b与隔离度的关系图; (e) j2b3b与双向传输效率的关系图; (f) j2b3b与隔离度的关系图; (g) j3b2a与双向传输效率的关系图; (h) j3b2a与隔离度的关系图
Figure 4. Correlation between center-to-center spacings of adjacent branches (j1a1b, j1b2b, j2b3b, j3b2a) and bidirectional transmission efficiency/isolation characteristics: (a) Relationship between j1a1b and bidirectional transmission efficiency; (b) relationship between j1a1b and isolation; (c) relationship between j1b2b and bidirectional transmission efficiency; (d) relationship between j1b2b and isolation; (e) relationship between j2b3b and bidirectional transmission efficiency; (f) relationship between j2b3b and isolation; (g) relationship between j3b2a and bidirectional transmission efficiency; (h) relationship between j3b2a and isolation.
图 5 InSb层高度$ {h}_{1} $对器件性能的影响 (a) $ {h}_{1} $小于等于5 μm时双向传输效率变化关系; (b) $ {h}_{1} $大于5 μm时双向传输效率变化关系; (c) 隔离度变化关系
Figure 5. Influence of InSb layer thickness $ {h}_{1} $ on device performance: (a) Variation of bidirectional transmission efficiency at $ {h}_{1} $ ≤ 5 μm; (b) variation of bidirectional transmission efficiency at $ {h}_{1} $ > 5 μm; (c) variation of isolation.
图 6 光栅层高度$ {h}_{2} $对器件性能的影响 (a) 双向传输效率变化关系; (b) 隔离度变化关系
Figure 6. Influence of grating layer thickness $ {h}_{2} $ on device performance: (a) Variation of bidirectional transmission efficiency with thickness; (b) variation of isolation with thickness.
图 7 光栅层高度$ {h}_{3} $对器件性能的影响 (a) 双向传输效率变化关系; (b) 隔离度变化关系
Figure 7. Influence of grating layer thickness $ {h}_{3} $ on device performance: (a) Variation of bidirectional transmission efficiency with thickness; (b) variation of isolation with thickness.
图 8 双向传输效率、隔离度与频率的关系图
Figure 8. The diagram of bidirectional transmission efficiency and isolation versus frequency.
图 9 温度对器件性能的影响 (a) 双向传输效率随温度变化关系; (b) 隔离度随温度变化关系
Figure 9. Effect of temperature on device performance: (a) Variation of bidirectional transmission efficiency with temperature; (b) variation of isolation with temperature.
图 10 磁场强度对器件性能的影响 (a) 双向传输效率随磁场强度变化关系; (b) 隔离度随磁场强度变化关系
Figure 10. Effect of magnetic field intensity on device performance: (a) Variation of bidirectional transmission efficiency with magnetic field intensity; (b) variation of isolation with magnetic field intensity.
表 2 器件参数设定
Table 2. Device parameter configuration.
结构参数 结构尺寸/μm InSb层高度h1 5 光栅层高度h2 50 衬底层高度h3 20 光栅周期p 25 光栅条宽度wid 15 中心分支的高度比例因子b 0.618 两端分支的高度比例因子a 0.618 分支的长度h0 170 相邻分支中心间距j1a1b 125 相邻分支中心间距j1b2b 125 相邻分支中心间距j2b3b 120 相邻分支中心间距j3b2a 120 
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