dtmm.transfer

Main top level calculation functions for light propagation through optical data.

Module Contents

dtmm.transfer.total_intensity(field)

Calculates total intensity of the field. Computes intesity and sums over pixels.

dtmm.transfer.transmitted_field(field, wavenumbers, n=1, betamax=BETAMAX, out=None)

Computes transmitted (forward propagating) part of the field.

Parameters

  • field (ndarray) – Input field array

  • wavenumbers (array_like) – Wavenumbers of the field

  • n (float, optional) – Refractive index of the media (1 by default)

  • betamax (float, optional) – Betamax perameter used.

  • out (ndarray, optinal) – Output array

Returns

out – Transmitted field.

Return type

ndarray

dtmm.transfer.reflected_field(field, wavenumbers, n=1, betamax=BETAMAX, out=None)

Computes reflected (backward propagating) part of the field.

Parameters

  • field (ndarray) – Input field array

  • wavenumbers (array_like) – Wavenumbers of the field

  • n (float, optional) – Refractive index of the media (1 by default)

  • betamax (float) – Betamax perameter used.

  • norm (bool, optional) – Whether to normalize field so that power spectrum of the output field remains the same as that of the input field.

  • out (ndarray, optinal) – Output array

Returns

out – Reflected field.

Return type

ndarray

dtmm.transfer.transfer_field(field_data, optical_data, beta=None, phi=None, nin=None, nout=None, npass=None, nstep=1, diffraction=None, reflection=None, method=None, multiray=False, norm=DTMM_NORM_FFT, betamax=BETAMAX, smooth=SMOOTH, split_rays=False, split_diffraction=False, split_wavelengths=False, eff_data=None, ret_bulk=False, out=None)

Tranfers input field data through optical data.

This function calculates transmitted field and possibly (when npass > 1) updates input field with reflected waves.

Parameters

  • field_data (Field data tuple) – Input field data tuple

  • optical_data (Optical data tuple) – Optical data tuple through which input field is transfered.

  • beta (float or 1D array_like of floats, optional) – Beta parameter of the input field. If it is a 1D array, beta[i] is the beta parameter of the field_data[0][i] field array.f not provided, beta is caluclated from input data (see also multiray option).

  • phi (float or 1D array_like of floats, optional) – Phi angle of the input light field. If it is a 1D array, phi[i] is the phi parameter of the field_data[0][i] field array. If not provided, phi is caluclated from input data (see also multiray option).

  • nin (float, optional) – Refractive index of the input (bottom) surface (1. by default). Used in combination with npass > 1 to determine reflections from input layer, or in combination with reflection = True to include Fresnel reflection from the input surface.

  • nout (float, optional) – Refractive index of the output (top) surface (1. by default). Used in combination with npass > 1 to determine reflections from output layer, or in combination with reflection = True to include Fresnel reflection from the output surface.

  • npass (int, optional) – How many passes (iterations) to perform. For strongly reflecting elements this should be set to a higher value. If npass > 1, then input field data is overwritten and adds reflected light from the sample (defaults to 1).

  • nstep (int or 1D array_like of ints) – Specifies layer propagation computation steps (defaults to 1). For thick layers you may want to increase this number. If layer thickness is greater than pixel size, you should increase this number.

  • diffraction (bool or int, optional) – Defines how diffraction is calculated. Setting this to False or 0 will disable diffraction calculation. Diffraction is enabled by default. If specified as an integer, it defines diffraction calculation quality. 1 for simple (fast) calculation, higher numbers increase accuracy and decrease computation speed. You can set it to np.inf or -1 for max (full) diffraction calculation and very slow computation.

  • reflection (bool or int or None, optional) – Reflection calculation mode for ‘2x2’ method. It can be either 0 or False for no reflections, 1 (default) for reflections in fft space (from effective layers), or 2 for reflections in real space (from individual layers). If this argument is not provided it is automatically set to 0 if npass == 1 and 1 if npass > 1 and diffraction == 1 and to 2 if npass > 1 and diffraction > 1. See documentation for details.

  • method (str, optional) – Specifies which method to use, either ‘2x2’ (default) or ‘4x4’.

  • multiray (bool) – If specified it defines if first axis of the input data is treated as multiray data or not. If beta and phi are not set, you must define this if your data is multiray so that beta and phi values are correctly determined.

  • norm (int, optional) – Normalization mode used when calculating multiple reflections with npass > 1 and 4x4 method. Possible values are 0, 1, 2, default value is 1.

  • smooth (float, optional) – Smoothing parameter when calculating multiple reflections with npass > 1 and 4x4 method. Possible values are values above 0.Setting this to higher values > 1 removes noise but reduces convergence speed. Setting this to < 0.1 increases convergence, but it increases noise.

  • split_diffraction (bool, optional) – In diffraction > 1 calculation this option specifies whether to split computation over single beam to consume less temporary memory storage. For large diffraction values this option should be set.

  • split_rays (bool, optional) – In multi-ray computation this option specifies whether to split computation over single rays to consume less temporary memory storage. For large multi-ray datasets this option should be set.

  • split_wavelengths (bool, optional) – Specifies whether to treat data at each wavelength as an independent ray. With off-axis propagation of eigenmodes with different beta values this should be set to true to assure proper determination of beta parameter for proper reflection calculation. Normally there will be very little difference, however, for small simulation volumes (compared to the wavelength) and at large incidence angles, you should set this to True for simulations of multi-wavelength fields.

  • eff_data (Optical data tuple or symmetry, optional) – Optical data tuple of homogeneous layers through which light is diffracted in the diffraction calculation when diffraction >= 1. If not provided, an effective data is build from optical_data by taking the mean value of the epsilon tensor. You can also provide the symmetry argument, e.g. ‘isotropic’, ‘uniaxial’ or ‘biaxial’, or a list of these values specifying the symmetry of each of the layers. This argument is passed directly to the data.effective_data() function.

  • ret_bulk (bool, optional) – Whether to return bulk field instead of the transfered field (default).

  • out (ndarray, optional) – Output array.

dtmm.transfer.transfer_4x4(field_data, optical_data, beta=0.0, phi=0.0, eff_data=None, nin=1.0, nout=1.0, npass=1, nstep=1, diffraction=True, reflection=1, multiray=False, norm=DTMM_NORM_FFT, smooth=SMOOTH, betamax=BETAMAX, ret_bulk=False, out=None)

Transfers input field data through optical data. See transfer_field.

dtmm.transfer.transfer_2x2(field_data, optical_data, beta=None, phi=None, eff_data=None, nin=1.0, nout=1.0, npass=1, nstep=1, diffraction=True, reflection=True, multiray=False, split_diffraction=False, betamax=BETAMAX, ret_bulk=False, out=None)

Tranfers input field data through optical data using the 2x2 method See transfer_field for documentation.