All notable changes to this project will be documented in this file.

The format is based on Keep a Changelog, and this project adheres to Semantic Versioning.


[1.8.3] - 2023-1-26#


  • Bug in Simulation.epsilon with coord_key="centers" in which structures were not rendered.

  • Missing @functools.wrap in ensure_freq_in_range decorator from causing incorrect docstrings.

1.8.2 - 2023-1-12#


  • Warning if users install via tidy3d-beta on pip, from now on, best to use tidy3d directly.

  • Support for dispersive media in AnisotropicMedium


  • Support shapely version >=2.0 for all python versions.

  • Internally refactor Simulation.epsilon and move eps_diagonal to Structure in preparation for future changes.

  • Readme displays updated instructions for installing tidy3d (remove beta version mention).


  • Field decay warning in mode solver when symmetry present.

  • Formatting bug in Tidy3d custom exceptions.


1.8.1 - 2022-12-30#


  • Environment variable TIDY3D_SSL_VERIFY to optionally disable SSL authentication (default is True).

  • Billed FlexUnit cost displayed at the end of web.monitor.


  • Bug on Windows systems with submitting CustomFieldSource data to the server.

  • Fix to FieldData.symmetry_expanded_copy for monitors with colocate=True.


  • The Simulation version updater is called every time a Simulation object is loaded, not just from_file.

  • Boundary specifications that rely on the default Periodic boundary now print a deprecation warning, as the default boundaries will change to PML in Tidy3D 2.0.

1.8.0 - 2022-12-14#


  • CustomFieldSource that can inject arbitrary source fields.

  • ElectromagneticFieldData.flux property for data corresponding to 2D monitors, and method for computing the overlap integral over two sets of frequency-domain field data.

  • Data corresponding to 2D FieldMonitor and FieldTimeMonitor, as well as to ModeSolverMonitor, now also stores grid_correction data related to the finite grid along the normal direction. This needs to be taken into account to avoid e.g. numerical oscillations of the flux with the exact position of the monitor that is due to the interpolation from the grid cell boundaries. These corrections are automatically applied when using the flux and dot methods.

  • Resonance finding plugin for estimating resonance frequency and Q-factor of multiple resonances from time-domain data. Accessed through tidy3d.plugins.ResonanceFinder.

  • New .updated_copy(**kwargs) method to all tidy3d objects to add a more convenient shortcut to copying an instance with updated fields, i.e. med.copy(update=dict(permittivity=3.0)) becomes med.updated_copy(permittivity=3.0).

  • Test support for python 3.11.

  • sidewall_angle option for Cylinder that allows a Cylinder to be tuned into a conical frustum or a cone.

  • reference_plane for PolySlab that provides options to define the vertices at the bottom, middle, or top of the PolySlab.

  • Automesh generation: MeshOverrideStructure that allows for a direct grid size specification in override structures, and dl_min that bounds the minimal grid size.

  • More material models to the material database such as gold from Olman2012.

  • In AdvancedFitterParam for StableDispersionFitter, random_seed option to set the random seed, and bound_f_lower to set the lower bound of pole frequency.

  • Introduced the option to project fields at near, intermediate, and far distances using an exact Green’s function formalism which does not make far-field approximations. This can be enabled in any AbstractFieldProjectionMonitor by setting far_field_approx=False. A tutorial notebook as a comprehensive reference for field projections was added to the documentation.

  • Tracking of modes in ModeSolverData based on overlap values, controlled through ModeSpec.track_freq.

  • Native broadband support for GassuainBeam AstigmaticGaussianBeam, and ModeSource through the num_freqs argument.

  • Apodization option for frequency-domain monitors to ignore temporal data in the beginning and/or end of a simulation


  • Minimum flex unit charge reduced from 0.1 to 0.025.

  • Default courant factor was changed from 0.9 to 0.99.

  • A point dipole source placed on a symmetry plane now always has twice the amplitude of the same source in a simulation without the symmetry plane, as expected by continuity with the case when the dipole is slightly off the symmetry plane, in which case there are effectively two dipoles, the original one and its mirror image. Previously, the amplitude was only doubled for dipoles polarized normal to the plane, because of Yee grid specifics.

  • FluxMonitor and FluxTimeMonitor no longer snap fields to centers, but instead provide continuous interpolation of the flux over the exact geometry of the monitor.

  • Major refactor to internal handling of data structures, including pure Dataset components that do not depend on other Tidy3D components and may therefore be used to define custom data in Tidy3D models.

  • Speed and memory usage improvement when writing and reading Tidy3d models to and from .hdf5 files.

  • Writing Tidy3D models containing custom data to .json file will log a warning and exclude the raw data from the file for performance reasons.

  • Material database reorganization and fixing a few references to the dispersion data.

  • The name Near2Far has been replaced with FieldProjection. For example, Near2FarAngleMonitor is now FieldProjectionAngleMonitor.

  • The API for far field projections has been simplified and several methods have now become properties. For example, the radar cross section is now accessed as .radar_cross_section, not .radar_cross_section().

  • Added a method renormalize_fields to AbstractFieldProjectionData to re-project far fields to different projection distances.

  • The API for DiffractionData was refactored to unify it with the API for AbstractFieldProjectionData.

  • The user no longer needs to supply orders_x and orders_y when creating a DiffractionMonitor; all allowed orders are automatically generated and returned in the resulting DiffractionData.

  • The user no longer needs to supply a medium when creating a DiffractionMonitor or any AbstractFieldProjectionMonitor; the medium through which fields are to be projected is now determined automatically based on the medium in which the monitor is placed.

  • The following attributes of AbstractFieldProjectionMonitor are now properties rather than methods: fields_spherical, fields_cartesian, power, radar_cross_section.


  • Some issues in DiffractionMonitor that is not z-normal that could lead to solver errors or wrong results.

  • Bug leading to solver error when Absorber boundaries with num_layers = 0 are used.

  • Bug leading to solver error when a FieldMonitor crosses a BlochBoundary and not all field components are recorded.

  • When running a Batch, path_dir is created if not existing.

  • Ignore shapely STRtree deprecation warning.

  • Ignore x axis when plotting 1D Simulation cross sections to avoid plot irregularities.

  • Local web api tests.

  • Use Tidy3D logger for some warnings that used to use default python logging.


  • Replaced gdspy dependency with gdstk.

1.7.1 - 2022-10-10#


  • medium field in DiffractionMonitor for decomposition of fields that are not in vacuum.


  • Bug in meshing an empty simulation with zero size along one dimension.

  • Bug causing error in the solver when a PermittivityMonitor is present in the list of monitors and is not at the end of the list.

1.7.0 - 2022-10-03#


  • DiffractionMonitor to compute the power amplitude distribution in all diffraction orders in simulations of periodic structures.

  • PolySlab can be oriented along x or y, not just z.


  • Loading components without validation no longer supported as it is too unpredictable.

  • Webplots plugin was removed as it was cumbersome to maintain and no longer used in web UI.

1.6.3 - 2022-9-13#


  • Type field for DataArray subclasses written to hdf5.


  • Docstring for FluxMonitor and FluxTimeMonitor.


  • Explicit error message about grid_size deprecation.

1.6.2 - 2022-9-6#


  • Support for Near2Far monitors in the presence of simulation symmetries.


  • Bug in 3D Near2Far monitors where surfaces defined in exclude_surfaces will no actually be excluded.

  • Bug in getting angles from k-space values in Near2FarKSpaceMonitor.

  • Bug in SimulationData.plot_field when getting the position along the normal axis for a 2D plot.

1.6.1 - 2022-8-31#


  • Bug in new simulation upload on Windows machines.

1.6.0 - 2022-8-29#


  • New classes of near-to-far monitors for server-side computation of the near field to far field projection.

  • Option to exlude DataArray Fields from a Tidy3dBaseModel json.

  • Option to save/load all models to/from hdf5 format.

  • Option to load base models without validation.

  • Support negative sidewall angle for slanted PolySlab-s.

  • Option to specify only a subset of the S-matrix to compute in the S-matrix plugin, as well as to provide mapping between elements (due to symmetries).

  • More Lorentz-Drude material models to the material database.


  • Raise a more meaningful error if login failed after MAX_ATTEMPTS.

  • Environment login credentials set to "" are now ignored and credentials stored to file are still looked for.

  • Improved subpixel coefficients computation around sharp edges, cornes, and three-structure intersections.


  • Major refactor of the way data structures are used internally.

  • ModeFieldMonitor -> ModeSolerMonitor with associated ModeSolverData. ModeSolverData is now also stored internally in ModeSolver, and the plot_field method can be called directly from ModeSolver instead of ModeSolverData.

  • Field data for monitors that have a zero size along a given dimension is now interpolated to the exact along that dimension.

  • Removed nlopt from requirements, user-side material fitting now uses scipy.

  • New Field normalize_index in Simulation - used to be input parameter when loading simulation data. A given SimulationData can still be renormalized to a different source later on using the new SimulationData.renormalize.

  • FluxMonitor and FluxTimeMonitor-s can now have a 3D box geometry, in which case the flux going out of all box surfaces is computed (optionally, some surfaces can be excluded).

  • Frequency-domain monitors require a non-empty list of frequencies.

  • Reduced the minimum flex unit cost to run a simulation to 0.1.

  • Reduced the premium cost for dispersive materials in typical cases.

  • Added a cost for monitors that should be negligible in typical cases but affects large monitors that significantly slow down the simulation.

1.5.0 - 2022-7-21#


  • Bug in computing the bounds of GeometryGroup.

  • Bug in auto-mesh generation.


  • Ability to compute far fields server-side on GPUs.


  • All Tidy3D components apart from data structures are now fully immutable.

  • Stopped support for python 3.6, improved support for python 3.10.

  • Web material fitter for lossless input data (no k data provided) will now return a lossless medium.

  • sort_by changed to filter_pol in ModeSpec.

  • center no longer a field of all Geometry components, instead only present when needed, removed in PolySlab and GeometryGroup. Planar geometries no longer have a mandatory length field, but have center_axis and lengt_axis properties for the center and length along the extrusion axis. PolySlab now defined exclusively through slab_bounds, while Cylinder through center and length.

  • In mode solver, allow precision to switch between double and single precision.

  • Near-to-far transformation tool is no longer a plugin, but is now part of Tidy3D’s new core data structures

1.4.1 - 2022-6-13#


  • Bug in plotting polarization of a nomral incidence source for some angle_phi.

  • Bloch vector values required to be real rather than complex.

  • Web security mitigation.

1.4.0 - 2022-6-3#


  • Bug in plotting when alpha is turned off in permittivity overlay.

  • Bug in plotting polarization of an angled incidence source (S,P -> P,S).

  • Throw warning if user tries to download data instances in yaml or json format.

  • Arrow length plotting issues for infinite sources.

  • Issues with nonuniform mesh not extending exactly to simulation boundaries.


  • Bloch periodic boundary conditions, enabling modeling of angled plane wave.

  • GeometryGroup object to associate several Geometry intances in a single Structure leading to improved performance for many objects.

  • Ability to uniquely specify boundary conditions on all 6 Simulation boundaries.

  • Options in field montitors for spatial downsampling and evaluation at yee grid centers.

  • BatchData.load() can load the data for a batch directly from a directory.

  • Utility for updating Simulation objects from old versions of Tidy3d to current version.

  • Explicit web. functions for downloading only simulation.json and tidy3d.log files.


  • Batch objects automatically download their json file upon download and load.

  • Uses shapely instead of gdspy to merge polygons from a gds cell.

  • ComponentModeler (S matrix tool) stores the Batch rather than the BatchData.

  • Custom caching of properties to speed up subsequent calculations.

  • Tidy3d configuration now done through setting attributes of tidy3d.config object.

1.3.3 - 2022-5-18#


  • Bug in Cylinder.inside when axis != 2.


  • AstigmaticGaussianBeam source.


  • Internal functions that may require hashing the simulation many times now use a make_static decorator. This pre-computes the simulation hash and stores it, and makes sure that the simulation has not changed at the beginning and end of the function execution.

  • Speeding up initialization of PolySlab when there is no dilation or slant angle.

  • Allow customizing data range that colormap covers in plot_field.

  • Speeding up of the automatic grid generation using Rtree and other improvements.

  • Better handling of http response errors.

  • In web.monitor, the estimated cost is only displayed when available; avoid “Unable to get cost” warning.

  • In PolySlab.from_gds, the selected polygons are first merged if possible, before the PolySlab-s are made. This avoids bugs e.g. in the case of slanted walls.

1.3.2 - 2022-4-30#


  • Bug in nonuniform mesh where the simulation background medium may be taken into account if higher than other structures overriding it.

1.3.1 - 2022-4-29#



  • The copy() method of Tidy3d components is deep by default.

  • Maximum allowed number of distinct materials is now 65530.


  • Monitor/source opacity values also applied to associated arrows.

  • Auto meshing in the presence of symmetries ignores anything outside of the main symmetry quadrant.

  • If an interface is completely covered by another structure, it is ignored by the mesher.

1.3.0 - 2022-4-26#


  • New grid_spec Field in Simulation that allows more flexibility in defining the mesh.

  • GridSpec1d class defining how the meshing along each dimension should be done, with sublcasses UniformGrid and CustomGrid that cover the functionality previously offered by supplying a float or a list of floats to Simulation.grid_size. New functionality offered by AutoGrid subclass, with the mesh automatically generated based on the minimum required steps per wavelength.

  • New PointDipole source.

  • Opacity kwargs for monitor and source in sim.plot.

  • Separated plotly-based requirements from core requrements file, can be added with "pip install tidy3d-beta[plotly]".


  • Simulation.grid_spec uses the default GridSpec, which has AutoGrid(min_steps_per_wvl=10) in each direction. To initialize a Simulation then it is no longer needed to provide grid information, if sources are added to the simulation. Otherwise an error will be raised asking to provide a wavelength for the auto mesh.

  • VolumeSource is now called UniformCurrentSource.

  • S-matrix module now places the monitors exactly at the port locations and offsets the source slightly for numerical reasons (more accurate).

  • Fixed bug in PolySlab visualization with sidewalls.

  • Inheritance structure of Source reorganized.

  • Better handling of only one td.inf in Box.from_bounds.

  • Added proper label to intensity plots.

  • Made all attributes Field() objects in to clean up docs.

  • Proper handling of Medium.eps_model at frequency of td.inf and None.


  • Simulation.grid_size is removed in favor of Simulation.grid_spec.

1.2.2 - 2022-4-16#


  • SimulationDataApp GUI for visualizing contents of SimulationData in tidy3d.plugings.

  • SimulationPlotly interface for generating Simulation.plot() figures using plotly instead of matplotlib.

  • New PermittivityMonitor and PermittivityData to store the complex relative permittivity as used in the simulation.

  • The maximum credit cost for a simulation can now be queried using web.estimate_cost. It is also displayed by default during web.upload.


  • Faster plotting for matplotlib and plotly.

  • SimulationData normalization keeps track of source index and can be normalized when loading directly from .hdf5 file.

  • Monitor data with symmetries now store the minimum required data to file and expands the symmetries on the fly.

  • Significant speedup in plotting complicated simulations without patch transparency.

  • When a list of dl is provided as a grid_size along a given direction, the grid is placed such that the total size np.sum(dl) is centered at the simulation center. Previously, a grid boundary was always placed at the simulation center.

1.2.1 - 2022-3-30#



  • webapi functions now only authenticate when needed.

  • Credentials storing folder only created when needed.

  • Added maximum number of attemtps in authentication.

  • Made plotly plotting faster.

  • Cached Simulation.medium and Simulation.medium_map computation.

1.2.0 - 2022-3-28#


  • PolySlab geometries support dilation and angled sidewalls.

  • Percent done monitoring of jobs running longer than 10 seconds.

  • Can use vectorized spherical coordinates in tidy3d.plugins.Near2Far.

  • ModeSolver returns a ModeSolverData object similar to SimulationData, containing all the information about the modes.

  • ModeFieldMonitor and ModeFieldData allow the results of a mode solve run server-side to be stored.

  • Plotting of ModeFieldData fields in SimulationData.plot_field and ModeSolverData.plot_field.

  • Ordering of modes by polarization fraction can be specified in ModeSpec.

  • Angled mode sources.


  • Significant speed improvement for Near2Far calculations.

  • freq no longer passed to ModeSolver upon init, instead a list of freqs passed to ModeSolver.solve.

  • Mode solver now returns ModeSolverData object containing information about the mode fields and propagation constants as data arrays over frequency and mode index.

  • Reorganized some of the internal Source classes.

  • Major improvements to Batch objects. returns a BatchData object that maps task_name to SimulationData.

  • Infinity stored as str in json outputs, conforming to json file specifications.

  • No longer need to specify one of x/y/z in SimulationData.plot_field if the monitor has a zero-sized dimension.

  • Simulation.run_time but must be > 0 to upload to server.

1.1.1 - 2022-3-2#



  • Fixed issue where smatrix was not uploaded to pyPI.

1.1.0 - 2022-3-1#


  • Simulation symmetries now fully functional.

  • Ability to perform near-to-far transformations from multiple surface monitors oriented along the x, y or z directions using tidy3d.plugins.Near2Far.

  • tidy3d.plugins.ComponentModeler tool for scattering matrix calculations.


  • Major enhancements to near field to far field transformation tool: multiple monitors supported with arbitrary configuration, user control over sampling point density.

  • Fixed visualization bug in symmetry.

1.0.2 - 2022-2-24#


  • Clarified license terms to not include scripts written using the tidy3d python API.

  • Simulation symmetries are now enabled but currently only affect the mode solver, if the mode plane lies on the simulation center and there’s a symmetry.

  • Validator that mode objects with symmetries are either entirely in the main quadrant, or lie on the symmetry axis.

    • Simulation.plotly() makes a plotly figure of the cross section.

    • Dispersion fitter can parse urls from

  • Clarified license terms to not include scripts written using the tidy3d python API.


  • Fixed a bug in python 3.6 where polyslab vertices loaded differently from file.

1.0.1 - 2022-2-16#


  • Selmeier.from_dispersion() method to quickly make a single-pole fit for lossless weakly dispersive materials.

  • Stable dispersive material fits via webservice.

  • Allow to load dispersive data directly by providing URL to txt or csv file

  • Validates simulation based on discretized size.


  • Polyslab.from_gds returns a list of PolySlab objects imported from all polygons in given layer and dtype, can optionally specify single dtype.

  • Warning about structure close to PML disabled if Absorber type.

  • Source dft now ignores insignificant time amplitudes for speed.

  • New color schemes for plots.

1.0.0 - 2022-1-31#


  • Stable dispersive material fits via webservice.


  • Refined and updated documentation.

0.2.0 - 2022-1-29#


  • FieldMonitor.surface() to split volume monitors into their surfaces.

  • Units and annotation to data.

  • Faster preprocessing.

  • Web authentication using environment variables TIDY3D_USER and TIDY3D_PASS.

  • callback_url in web API to put job metadata when a job is finished.

  • Support for non uniform grid size definition.

  • Gaussian beam source.

  • Automated testing through tox and github actions.

0.1.1 - 2021-11-09#



0.1.0 - 2021-10-21#


  • Web API implemented by converting simulations to old tidy3D

Alpha Release Changes#


  • Solver speed improvement (gain depending on simulation + hardware details).

  • Bringing the speed of the non-angled mode solver back to pre-21.4.2 levels.


  • Improvements to subpixel averaging for dispersive materials.

  • Enabled web login using environment variables TIDY3D_USER and TIDY3D_PASS.


  • Bugfix when running simulation with zero run_time.

  • More internal logging.

  • Fixed unstable 'Li1993_293K' variant of cSi in the material library.

  • Bugfix when downloading data on Windows.

  • Bugfix in material fitting tool when target tolerance is not reached.


  • New Gaussian beam source and example usage.

  • Modal sources and monitors in bent and in angled waveguides with tutorial.

  • Nyquist-limit sampling in frequency-domain monitors (much faster without loss of accuracy).

  • Support for Drude model of material dispersion.

  • Small bugfixes to some of the other dispersion models.

  • PEC boundaries applied by default at the truncation of any boundary with PML, avoiding potential

    issues with using periodic boundaries under the PML instead.

  • Source normalization no longer adding a spurious frequency-dependent phase to the fields.

  • Fixed bug in unpacking monitor fields with symmetries and interpolate=False.

  • Lots of streamlining on the backend side.


  • Fixed bug with zero-size monitor plotting.

  • Fixed bug with empty simulation run introduced in 21.4.0.


  • A few small fixes.

  • Fixed nonlinear constraint in dispersive material fitting tool.

  • Fixed potential issue when a monitor stores neither 'E' nor 'H'.

  • Fixed some backwards compatibility issues introduced in

  • Frequency monitors can now optionally store the complex permittivity at the same locations where the E-fields are recorded, at the monitor frequencies.

  • Frequency monitors now also have an 'interpolate' keyword, which defaults to True and reproduces the behavior of previous versions. If set to False, however, the raw fields evaluated at their corresponding Yee grid locations are returned, instead of the fields interpolated to the Yee cell centers. This also affects the returned permittivity, if requested.

  • Reorganized internal source time dependence handling, enabling more complicated functionality in the future, like custom source time.

  • Total field in the simulation now sampled at the time step of the peak of the source time dependence, for better estimation of the shutoff factor.

  • A number of bug fixes, especially in the new plotting introduced in

  • Reorganized plotting:

  • Speeding up structure visualizations.

  • Structures now shown based on primitive definitions rather than grid discretization. This

    then shows the physical structures but not what the simulation “sees”. Will add an option to display the grid lines in next version.

  • Bumped down matplotlib version requirement to 3.2 and python version requirement to 3.6.

  • Improved handling of PEC interfaces.- Reorganized and extended internal logging.

  • Added tidy3d.__version__.

  • A number of fixes to the example notebooks and the colab integration.

  • Bumping back python version requirement from 3.8 to 3.7.

  • Hotfix to an internal bug in some simulation runs.

  • New dispersion fitting tool for material data and accompanying tutorial.

  • (beta) Non-uniform Cartesian meshing now supported. The grid coordinates are provided

    by hand to Simulation. Next step is implementing auto-meshing.

  • DispersionModel objects can now be directly used as materials.

  • Fixed bug to Cylinder subpixel averaging.

  • Small bugs fixes/added checks for some edge cases.

  • Rehash of symmetries and support for mode sources and monitors with symmetries.

  • Anisotropic materials (diagonal epsilon tensor).

  • Rehashed error handling to output more runtime errors to tidy3d.log.

  • Job and Batch classes for better simulation handling (eventually to fully replace webapi functions).

  • A large number of small improvements and bug fixes.