Mode 🎯

Mode Source

tidy3d.ModeSource	Injects current source to excite modal profile on finite extent plane.
tidy3d.ModeSpec	Stores specifications for the mode solver to find an electromagnetic mode.
tidy3d.PECFrame	PEC source frame.

The ModeSource class represents a propagating mode in a given structure cross section.

Behind the scenes, the desired mode is initially obtained by running the mode solver on the ModeSource plane. The ModeSpec class provides the settings for the mode solver. Once the desired mode is found, it is injected into the 3D simulation along the plane normal. The user does not need to invoke the mode solver explicitly; it is performed automatically whenever a ModeSource or ModeMonitor is included in a Tidy3D simulation.

# custom mode specification tells the mode solver to search for
# two modes around effective index = 1.5
my_mode_spec = ModeSpec(num_modes=2, target_neff=1.5)

# custom mode source injects the first mode along the +x direction
my_mode_source = ModeSource(
    size=(0,10,10),
    source_time=my_source_time,
    direction='+',
    mode_spec=my_mode_spec,
    mode_index=0,
)

See also

For more detailed explanation and examples, please see the following learning center resources:

• Defining mode sources and monitors

• Injecting modes in bent and angled waveguides

For a short introduction to the use of mode sources, see the following FDTD101 lecture:

• Mode injection

Interpolation Specifications

tidy3d.ModeInterpSpec

Specification for mode frequency interpolation.

Sort Specifications

tidy3d.ModeSortSpec

Specification for filtering and sorting modes within each frequency.

Sampling Specifications

tidy3d.UniformSampling	Uniform frequency sampling specification.
tidy3d.ChebSampling	Chebyshev node frequency sampling specification.
tidy3d.CustomSampling	Custom frequency sampling specification.