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lmapexport - Script command

FDTD

Creates a mapping information file (.lmap) for a metalens or a grating with spatial variation. This script command is used with the Lumerical Sub-Wavelength model plugin.

For further information on the Lumerical Sub-Wavelength Model, please see the Knowledge Base article on Lumerical Sub-Wavelength Model plugin: Introduction and data Generation.

Note: This script command does not support the legacy .json file format for the LSWM, only the .lswm format.

Syntax Description
lmapexport(“lswm_file”, map_info);

Exports a .lmap file for a given .lswm file for a grating with spatial variation. The .lmap file is created in the same directory as the .lswm file, and carries the same name as the input .lswm file, except with an .lmap extension.


Note: If the target .lmap file already exists, a suffix of “_n” is appended, and a message is shown in the script prompt to indicate the file saved.


The arguments are as follows:

  • lswm_file: A string pointing to the corresponding .lswm file
  • map_info: A struct with information of the map, see below for further information on its attributes and descriptions.
  • interpolation_flag: Optional. A Boolean flag indicating whether linear interpolation over the spatial coordinate occurs when a ray hits a coordinate between several points, or the closest value is taken. This flag does not affect data in the lmap, only how it is interpreted when it is used. Defaults to false.


This function does not return any data.
lmapexport(“lswm_file”, metalens_info, phase_info, “output_file”, gds_flag);

Exports a .lmap file for a given .lswm file for a metalens, uses the following arguments:

  • lswm_file: A string pointing to the corresponding .lswm file
  • metalens_info: A struct with size and centering information for the metalens, see below for further information on its attributes and descriptions.
  • phase_info: A struct with phase target information, see below for further information on its attributes and descriptions.
  • gds_flag: Optional. A Boolean flag indicating whether a gds file is generated corresponding to the map file. Defaults to false.


This function does not return any data.

Configuration structures for grating with spatial variation

The following table describes fields in the map_info struct.

Field Description
map_type Coordinates of the map, either “rect” for rectilinear coordinates, or “polar” for polar coordinates.
spatial_info

A struct containing the definition of points for the spatial variation.

Contains the following fields if the map is “rect”:

  • size_x: Total size of the grating region in the x-direction in mm.
  • size_y: Total size of the grating region in the y-direction in mm.
  • decenter_x: Decenter x-coordinate.
  • decenter_y: Decenter y-coordinate.

Contains the following fields if the map is “polar”:

  • size_R: Total radius of the polar grating region in mm.
cell_type_map A 2D matrix defining the index map for each grid point, see the subsection “Definition of the index map” in Lumerical Sub-Wavelength Model: How to Simulate a Grating with Spatial Variations for further information.

Configuration structures for metalens

The following tables describes the fields in the metalens_info struct.

Field Description
lens_size A matrix indicating the total size of the x- and y-directions, in mm.

The format of the array is [size_x, size_y].
centering Optional. Coordinates of the center of the phase map on the metalens surface, in mm. 

Defaults to [0,0].

The following table describes the fields in the phase_info struct.

Note: This command supports up to two phase targets. All variables with suffix _1 correspond to the first phase target, and all variables with suffix _2 correspond to the second phase target. Variables with the _2 suffixes are all optional.

Field Description
reference_wavelength

A matrix with reference wavelength for the phase design, in µm.


The format is as follows:

[lambda_1, lambda_2]
jones_vector

A matrix defining Jones vectors defining the target polarization before and after the metalens.


The format is as follows:

[J_in_1; J_out_1; J_in_2; J_out_2]


Each J vector has x, y, and xy phase offset components, as follows

[Jx, Jy, phase_offset_xy]
coefficients

A cell array defining coefficients to define the phase targets.


The overall format is as follows:

{focus_1, coeffA_1, coeffB_1, focus_2, coeffA_2, coeffB_2}


Each variable is as follows:

  • focus: A number for the focus in mm.
  • coeffA: A cell array containing coefficients for the R^2n terms.
  • coeffB: A cell array containing coefficients for the x^nY^m terms.


For further information, see Step 1 of the application gallery article Eye tracking optical system with a metalens.
direction A string indication the direction for all phase targets. Either “forward” or “backward” is accepted.

Example -  Exporting a .lmap file for a spatially varying grating in rectilinear coordinates

map_type = "rect";
lswmFile = "grating.lswm";
cellTypeMap = [ 0,2,0,2;0,2,0,2];
sizeX = 0.1;
sizeY = 0.2;
cx = 0.1;
cy = 0.0;
spatialInfo = {"size_x":sizeX, "size_y": sizeY, "decenter_x":cx, "decenter_y":cy};
mapInfo = {"map_type":map_type, "spatial_info":spatialInfo, "cell_type_map":cellTypeMap};

lmapexport(lswmFile,mapInfo);

Example -  Exporting a .lmap file for a metalens with two phase targets

metalensSize = [2,2]; # size in mm
centering=[0,0];
metalensInfo = {"lens_size":metalensSize,"centering":centering};
reference_wavelength = [0.4, 0.4]; #in micrometers
jones_vector = [1,0,0;1,0,0; 0,1,0; 0,1,0]; # phase angle in degrees
coefficients = {0.5, {3, 30, 0}, {3, 30,0}, 0, {0, 0, 1}, {0, 0,1}}; #{focus_1, r2n_1, xnym_1, focus_2, r2n_2, xnym_2}
phaseInfo={"reference_wavelength":reference_wavelength, "jones_vector":jones_vector, "coefficients":coefficients, "direction":"forward"};

lmapexport("metalens_test.lswm",metalensInfo,phaseInfo," metalens_test.lmap",false);

See Also

List of commands

Associated files

Related articles