EME

EME_settings

Declare global EME defaults that are inherited by sections created afterward. Each parameter left unspecified leaves the corresponding stored default unchanged. A section’s own settings argument at creation still overrides these globals. Sections created before this call are not affected.

Parameters:

• apply_scattering (bool or list[float]) – whether interfacial scattering loss is automatically applied to the S-matrix, either for every wavelength (True), no wavelengths (False), or only the listed wavelengths, default: False

• beta_interpolation (str) – either ‘uniform’ or ‘linear’ to specify how the propagation constant is interpolated between z-slices of a taper/gds section, default: ‘uniform’

• junction_normalization (bool or str or dict) – controls how junction S-matrices are power-normalized; either a single bool/’gain’ value applied to both junction kinds, or a dict with ‘inter_section’ and ‘intra_section’ keys, each accepting True (full SVD unitarization), False (raw, unnormalized), or ‘gain’ (clip singular values at 1 while keeping the raw lossy mode-matching), default: ‘gain’ for inter-section junctions and True for intra-section junctions

• overlap_variation (float) – threshold of mode-list overlap between z-slices used by the automatic z-slicing bisection for taper/gds sections, default: 0.01

• minimum_z_step (float) – [nm] the minimum allowed z-step for the automatic z-slicing bisection, default: 0.1

• simulation_name (str) – simulation name, default: ‘emode’

straight_section

Define a uniform-cross-section waveguide section for the EME solver. Sections are placed sequentially in the z-direction in the order they are declared (or updated, if name already exists).

Parameters:

• name (str) – section name, default: an auto-generated number

• profile (str) – label of the profile that defines the section’s cross-section

• length (float) – [nm] the length of the section

• offset (float or tuple[float, float]) – the x- and y-offset of the section’s port window, if only a single value is given it is assumed to be the x-offset, default: (0, 0)

• settings (dict or None) – per-section overrides of the EME_settings, merged onto the current global EME settings (or onto the section’s existing settings, when updating), default: None

• simulation_name (str) – simulation name, default: ‘emode’

taper_section

Define a section that linearly interpolates its cross-section between two profiles for the EME solver, automatically slicing the z-direction to track the mode evolution.

Parameters:

• name (str) – section name, default: an auto-generated number

• profile (str) – label of the profile that defines the section beginning

• profile_end (str) – label of the profile that defines the section ending

• length (float) – [nm] the length of the section

• settings (dict or None) – per-section overrides of the EME_settings (notably overlap_variation and minimum_z_step, which control the automatic z-slicing), default: None

• simulation_name (str) – simulation name, default: ‘emode’

gds_section

Define a section whose cross-section varies along z according to a mask imported from a GDS file, for more complex geometries defined with third-party layout tools.

Parameters:

• name (str) – section name, default: an auto-generated number

• profile (str) – label of the profile that defines the section’s cross-section outside of the GDS mask

• gds_path (str) – path to the GDS file used to mask the section

• layer_map (dict[str, int]) – mapping of profile shape names to GDS layer numbers, used to determine which shapes in profile are masked by which GDS layer

• length (float) – [nm] the length of the section, default: derived from the GDS bounding box

• cell_index (int or str) – the cell index (or name) in the specified GDS file, default: 0

• scale (float) – unit scale factor applied to the GDS coordinates (e.g. use 1000 if the GDS file is drawn in microns but the simulation is in nanometers), default: 1

• port_poses (dict) – explicit port positions/orientations at the section boundaries, default: derived from the GDS bounding box (left port at w=0, right port at w=length)

• heal (bool) – whether to heal small gaps/self-intersections in the imported GDS polygons before meshing, default: True

• grow (float) – amount to grow imported GDS polygons by, to close small gaps, default: 1e-3

• settings (dict or None) – per-section overrides of the EME_settings, default: None

• simulation_name (str) – simulation name, default: ‘emode’

copy_section

Place a second instance of an already-declared section in the chain, reusing its already-computed S-matrix instead of re-solving it.

Parameters:

• name (str) – section name, default: an auto-generated number

• section_name (str) – name of the existing section to copy

• mirror (bool) – whether to reverse the placement along the propagation direction (swapping the left/right ports), default: False

• port_swap (dict) – explicit port-name mapping to use instead of the automatically computed left/right swap when mirror is True, default: None

• settings (dict or None) – per-section overrides of the EME_settings, default: None

• simulation_name (str) – simulation name, default: ‘emode’

EME

Calculate the complete scattering matrix of all defined sections using the eigenmode expansion method (EME).

Parameters:

• warm_start (bool) – whether to seed each taper/gds section’s automatic z-slice refinement from the previously solved chain (when available), instead of re-refining from scratch, default: False

• simulation_name (str) – simulation name, default: ‘emode’

plot_S_matrix

Colormap plot of the transmission or reflection component of the EME scattering matrix.

Parameters:

• input (int or str) – input field (first number of the scattering matrix identifier), default: 0

• output (int or str) – output field (second number of the scattering matrix identifier), default: 1

• plot_function (str or None) – specify the function to apply to the plot data (‘abs^2’, ‘angle’, ‘real’, ‘imag’), default: ‘abs^2’

• file_name (str) – if specified, forces the function to save a file with the given parameters and will not display the interactive plot, file is saved under a directory called EM_figures, default: None

• file_type (str) – file type for saving a plot, ‘pdf’ or ‘png’, default: ‘’ (no extension is added to file_name unless a file type is given)

• simulation_name (str) – simulation name, default: ‘emode’