Simulation setup

settings

Specify the simulation settings.

Parameters:

  • wavelength (float) – [nm] wavelength, default: 1550

  • x_resolution (float) – [nm] resolution in the x-direction, default: 10

  • y_resolution (float) – [nm] resolution in the y-direction, default: 10

  • window_width (float) – [nm] simulation window width

  • window_height (float) – [nm] simulation window height

  • boundary_condition (str, length = 2) – boundary condition set as a string with two characters ‘XX’; the first character is the south boundary condition, the second character is the west boundary condition; ‘0’: no symmetry (metal boundary), ‘S’: symmetric Ex, ‘A’: asymmetric Ex; alternatively, ‘TE’ and ‘TM’ can be specified to use the any symmetry available to find the fundamental TE and TM modes; use ‘TE-h’, ‘TE-v’, ‘TM-h’, and ‘TM-v’ to specify only horizontal or vertical symmetry for TE or TM modes; when using an (a)symmetric boundary, the pml_NSEW_bool setting is copied from the north/east perimeter to the south/west perimeter; default: ‘00’

  • num_modes (int) – number of modes to solve for, default: 1

  • field_to_solve (str) – either ‘Et’ or ‘Ht’ to specify whether the transverse electric field or magnetic field is solved, default: ‘Et’

  • max_effective_index (float) – maximum value for the effective refractive index, if max_effective_index is 0 the maximum refractive index found in the simulation window is used, default: 0

  • tolerance (float) – eigenmode solver convergence tolerance, if tolerance = 0 the computer’s precision is used, default: 0

  • bend_radius (float) – [nm] waveguide bend radius relative to the center of the window, must be positive and larger than window_width/2, if bend_radius = 0 no bending is used in the calculation, default: 0

  • pml_NSEW_bool (list, length = 4) – indicates whether to use a pml on each of the 4 boundaries, [north, south, east, west], 0: no pml, 1: use pml, default: [0,0,0,0]

  • num_pml_layers (int or list with length = 4) – number of pml layers to use, either a single value that is applied to all boundaries or a list of 4 values, default: 10

  • remove_pml_modes_bool (bool) – automatically remove pml modes, default: True

  • background_refractive_index (str or float) – background refractive index, either a material name or a value, default: 1.0

  • expansion_resolution (float or list) – [nm] single value or list of 4 values for the stretched grid resolution; [north, south, east, west], the grid is gradually transitioned from res to expansion_resolution, default: 20

  • expansion_size (float or list) – [nm] single value or list of 4 values for the approximate stretched distance; [north, south, east, west], default: 0

  • propagation_resolution – [nm] resolution in the z-direction for plotting EME propagation results, default: wavelength/25

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

add_material

Add a custom material by specifying a wavelength dependent equation.

Parameters:

  • name (str) – material name, this will override the built-in material name if an idential name is used; a variable user_material_[name] will be created

  • refractive_index_equation (str) – refractive index equation to evaluate as a function of the wavelength parameter ‘x’, where imaginary numbers are specified with a preceding ‘j’; only the following characters are allowed in the equation string: “0123456789 x j . + - ^ * / ( ) [ ]”; a list of three equations can also be specified for non-isotropic materials, like ‘[n_xx, n_yy, n_zz]’; the string must have less than 1000 characters

  • wavelength_unit (str) – either ‘nm’ or ‘um’ to specify the unit for the wavelength parameter ‘x’, default: ‘um’

  • wavelength_range (list) – [um] list of the minimum and maximum wavelength recommended for the refractive index equation, default: [0.2, 2.0]

  • citation (str) – reference displayed in material explorer for the custom material, default: ‘User defined.’

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

import_database

Import a custom material database by specifying custom materials in a text file.

Parameters:

  • filename (str) – name of text file to be imported

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

Here is an example of several custom materials in the database text file to be imported. See the add_material function for parameter details. Each custom material must contain the name and refractive_index_equation, separated by a new line. Comments can be added with ‘#’ or ‘%’.

name = custom_name_1
refractive_index_equation = equation_1
wavelength_unit = um (optional)
wavelength_range = [0.2, 2.0] (optional)
citation = reference_1 (optional, default: “User defined by database import.”)

# comment about my custom_SiO2 material
name = custom_SiO2
refractive_index_equation = (1 + 0.696166/(1 - (0.0684043/x)^2) + 0.4079426/(1 - (0.1162414/x)^2) + 0.8974794/(1 - (9.896161/x)^2))^0.5
wavelength_unit = um
wavelength_range = [0.21, 6.7]
citation = ‘(1) I. H. Malitson, “Interspecimen comparison of the refractive index of fused silica,” J. Opt. Soc. Am. 55, 1205 (1965). (2) C. Z. Tan, “Determination of refractive index of silica glass for infrared wavelengths by IR spectroscopy,” J. Non-Cryst. Solids 223, 158 (1998).’

% comment about my custom_name_3 material
name = custom_name_3
refractive_index_equation = equation_3
wavelength_unit = nm
shape

Create or update a shape with attributes. These parameters are saved with ‘shape_’+name+’/’ preceding the attribute name. If a name is not given, a number will be allocated as the shape name.

Parameters:

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

  • refractive_index (float, list, or str) – refractive index value, list of values [n_xx, n_yy, n_zz], or material name, default: 1.0

  • permeability (float, list, or str) – relative permeability value, list of values [mu_xx, mu_yy, mu_zz], or material name, default: 1.0

  • loss_dB_per_m (float) – [dB/m] material propagation loss, default: 0

  • vertices (list (N,2) or int) – list of N vertices that define a closed polygon, if specified vertices is used to define the shape (width, height, position, mask, etch, fill are ignored), to disable vertices, set vertices to 0, default: 0

  • width (float) – shape width, gets set to the window_width if not specified, default: None

  • height (float) – shape height, default: 0

  • position (list, length = 2) – centered x and y positions relative to the shape width and height, if y position is negative then it is treated like a layer stacked on top of the previous layer, if only a single value is provided it is assumed to be the x position and the y position is set to -1, default: [0,-1]

  • mask (float or list) – mask width for etching, centered on x-position set by position and mask_offset, or a list of arbitrary length to specify multiple mask regions in combination with a list of mask_offset values, default: width

  • mask_offset (float or list) – the x-position offset for the mask parameter, or a list of arbitrary length to specify multiple mask regions in combination with a list of mask values, default: 0

  • tone (str or list) – ‘n’ or ‘p’ to define the pattern tone as negative or positive for the mask parameter, or a list of arbitrary length to specify multiple mask regions in combination with a list of mask values, default: n

  • etch_depth (float) – etch depth for a layer outside the mask region, thickness = height - etch_depth, default: 0

  • sidewall_angle (float) – etched sidewall angle in degrees, 0 is perfectly vertical, 90 is the maximum, this decreases the width at the top of the shape to create the angle, default: 0

  • fill_refractive_index (float, list, or str) – refractive index (similar to refractive_index parameter) to fill the etched region when a planar layer is added on top of the current layer, default: take the background refractive index

  • fill_permeability (float, list, or str) – relative permeability (similar to permeability parameter) to fill the etched region when a planar layer is added on top of the current layer, default: take the background relative permeability

  • correlation_length (float or list) – interfacial roughness correlation length, a single value is applied to all interfaces, a list of 2 applies the first value to all vertical interfaces and the second value to all horizontal interfaces, a list the length of the number of edges applies each value to the corresponding edge, default: [0,0]

  • roughness_rms (float or list) – interfacial roughness standard deviation in nm rms, a single value is applied to all interfaces, a list of 2 applies the first value to all vertical interfaces and the second value to all horizontal interfaces, a list the length of the number of edges applies each value to the corresponding edge, default: [0,0]

  • shape_type (str) – set shape type as ‘planar’, ‘conformal’ (only uses name, refractive_index, and height), or ‘ellipse’ (only uses name, refractive_index, width, height, position, sidewall_angle, and priority), default: ‘planar’

  • priority (float) – a number that signifies the order in which shapes will be drawn, a higher priority gets drawn over a lower number priority, default: auto-generated integer based on order called

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

reset

Clear simulation settings, shape definitions, or both.

Parameters:

  • kind (str) – either ‘shapes’, ‘settings’, or ‘all’ to specify what data is cleared, default: ‘shapes’

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