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Port

1 FDTD Port​

Feature description: Ports are usually viewed as a combination of mode source and field monitor. Ports can be used either separately or together with the S-parameter sweep tool.

Notes: Click the "Port" button in the menu bar, and select "FDTD Port" from the drop-down menu to add a port. Note that the prerequisite is that an FDTD simulation region must be already added into simulation project. After adding a port, a port group named “Ports” is automatically generated as the child of the “Object Tree” , and all port objects are enclosed in this group. In particular, the port hierarchy is arranged in such a manner that ports cannot be moved outside the “Ports group”, and other objects are not allowed to be moved into the group.

1.1 Geometry​

1) X,Y,Z: The center position of the simulation region.

2) X Min, X Max: X min, X max position.

3) Y Min, Y Max: Y min, Y max position.

4) Z Min, Z Max: Z min, Z max position.

5) X Span, Y SP, Z Span: X, Y, Z span of the simulation region.

1.2 Modal Properties​

1) Injection Axis: This indicates the axis of propagation. The geometry parameters that will work under the "Geometry" tab may depend on this setting (For instance, if the incident wave is along the X-axis, the port object possesses accordingly a 2D X-Normal geometry).

2) Direction: This indicates the direction of source propagation. Forward means the propagation is along a positive direction, while Backward means the propagation is along a negative direction.

3) Amplitude: "Amplitude" specifies the peak magnitude of electric field measured by V/m in the beam sources. (Default :1)

4) Phase: This refers to the phase of the source measured by degrees.

5) Mode Selection: This enables the user to select the modes used in the FDTD simulation or Matrix Sweep function. The Mode selection includes Fundamental, Fundamental TE , Fundamental TM , and Use Select, with the default set to Fundamental .

  • In the Matrix Sweep function, the output will include the S-matrix results for the selected modes.
  • The selected modes can also be used as input sources for the propagation.

After selecting the "User Select" option, you can specify the parameters required for mode solving in the Select Mode window. After the calculations, the number of computed modes will be displayed in the mode list. Users can then specify the plotting options of interest in the mode plotting options section.

6) Number of Trial Modes: The number of solving modes.

7) Mode Index: The mode index will be indicated alongside each mode in the list, allowing us to identify and select the specific mode of interest.

8) Bent Waveguide: Selecting this option enables the bent waveguide solver to work with the following settings:

  • Bend Radius:This specifies the bend radius in units of μm counted from the center of the port region. (Default value: 1e6 μm)

  • Bend Orientation: This specifies the orientation of the cylindrical coordinates employed for the computation of modes. Orientation of the cylindrical coordinate system used for calculating modes.

  • Bend Location: This option specifies the location of bend. (Note that only the Simulation Center is supported at present)

1.3 FDTD Port Group​

Feature Description: After adding an FDTD Port, we can locate the Ports in the Object Tree. By right-clicking on Ports and selecting "Edit" from the context menu, you can configure the FDTD Port Group settings.

1) Source Port: Specifies the port to be used as the source.

2) Monitor Frequency Points (Override Global): Specifies the number of frequency points for the monitor.

3) Calculate Group Delay: Indicates whether to calculate the group delay.

4) Fractional Offset for Group Delay: This setting is effective only when the "Calculate Group Delay" option is enabled. Numerically, the group delay of a device is computed by approximating the derivative of the phase with respect to frequency. The fractional offset for group delay refers to the decimal portion of the frequency used in the finite difference step size. If this setting is too small, phase changes may be significantly affected by noise, whereas a setting that is too large could lead to unrealistic group delays due to phase changes potentially exceeding 2π. For longer devices where the phase changes rapidly with frequency, it is recommended that users reduce this setting from the default value. Otherwise, it is generally advisable to use the default setting (default value: 0.0001 μm).

1) Waveform: This field sets the waveform of the source. We can use predefined waveforms such as Waveform_1550, Waveform_1310, or Visible_Light. Additionally, we can also create new custom waveforms through this interface.

2) Set Frequency/Wavelength:

  • Range Type: Choose the type "Wavelength" or "Frequency" to set the waveform.

  • RangeLimit: Min/Max, Center/Span: Set Min/Max or Center/Span to set the values of waveform. Take the Wavelength option as an example:

    • Wavelength Min/Max ：The wavelength of the minimum and maximum values is used to calculate the pulse waveform and bandwidth of the light source.

    • Wavelength Center/Span ：The wavelength center and wavelength span values is used to calculate the pulse waveform and bandwidth of the light source.

3) Save to Waveform List: To save user defined waveforms.

2 EME Port​

Feature Description: The EME solver region contains 2 ports by default. The Port button found in the menu bar adds additional port to the solver.

2.1 Geometry​

'Port8'

1) Port Location: The port can be selected to locate at the left or right end of the EME solver region.

2) Use Full Simulation Span: By checking this option, the whole simulation span inheritted from the EME simulation region is employed. (Default: on) You need to uncheck this option if you wish to specify your own spans for the port. Therefore the following parameters settings are invalid when "Use Full Simulation Span" is enabled.

3) X, Y, Z: The center position of the simulation region.

4) X MIN, X MAX: X min, X max position.

5) Y MIN, Y MAX: Y min, Y max position.

6) Z MIN, Z MAX: Z min, Z max position.

7) X SPAN, Y SPAN, Z SPAN: X, Y, Z span of the simulation region.

2.2 EME Port​

'Port8'

1) Mode Selection:

To select the modes to use for the mode expansion calculation.The Mode Selection in EME Port includes Fundamental Mode, Fundamental TE Mode, Fundamental TM Mode, Fundamental TE and TM Mode, Use Select and User Import options. (Default: Fundamental Mode)

2) Number of Trial Modes: This specifies the number of modes to search for finding a fundamental mode. The modes eventually found by the solver may depend on that. If one uses a too small number, the expected modes could be missing. Usually, setting this number to 100 suffices to guarantee no physical modes would have been missed. However, users who are interested in higher order modes should set a even larger value, since in such cases more than 100 modes may be present. (Default value: 20)

3) Mode Index: When the Mode Selection is set to "User Select," the mode index option is activated, allowing you to choose the appropriate mode number.

4) Theta: This is the angle between the incident axis after rotating the port. In 3D simulations, it refers to the propagation angle relative to the incident axis of the port, measured in degrees. In 2D simulations, it is the propagation angle measured in degrees around the global Z-axis according to the right-hand rule, i.e., the angle of propagation in the XY plane.

5) Phi: This is the rotation angle of the port around the incident axis, which may affect the polarization of the mode source. In 3D simulations, it refers to the propagation angle measured in degrees around the incident axis of the port according to the right-hand rule. In 2D simulations, this value does not take effect.

6) Offset: An offset can be endowed to the plane upon which the modes are computed. This guarantees that monitors placed at an angle do not interfere with unexpected structures.