Laser#

class lasy.laser.Laser(dim, lo, hi, npoints, profile, n_azimuthal_modes=1, n_theta_evals=None)[source]#

Evaluate a laser profile on a grid, propagate it, and write it to a file.

This is a top-level class.

Parameters:

dimstring

Dimensionality of the array. Options are:

'xyt': The laser pulse is represented on a 3D grid:
Cartesian (x,y) transversely, and temporal (t) longitudinally.
'rt'The laser pulse is represented on a 2D grid:
Cylindrical (r) transversely, and temporal (t) longitudinally.

lo, hilist of scalars

Lower and higher end of the physical domain of the box. One element per direction (2 for dim='rt', 3 for dim='xyt')

npointstuple of int

Number of points in each direction. One element per direction (2 for dim='rt', 3 for dim='xyt') For the moment, the lower end is assumed to be (0,0) in rt and (0,0,0) in xyt

profilean object of type lasy.profiles.profile.Profile

Defines how to evaluate the envelope field

n_azimuthal_modesint (optional)

Only used if dim is 'rt'. The number of azimuthal modes used in order to represent the laser field.

n_theta_evalsint (optional)

Only used if dim is 'rt'. The number of points in the theta (azimuthal) direction at which to evaluate the laser field, before decomposing it into n_azimuthal_modes azimuthal modes. By default, this is set to 2*n_azimuthal_modes - 1. However, for highly asymmetrical profiles, it may be necessary to increase this number.

For instance, using n_theta_evals=20 and n_azimuthal_modes=1 will evaluate the laser field at 20 points in the azimuthal direction and then average the values to extract the amplitude of the azimuthal mode 0.

Examples

>>> import matplotlib.pyplot as plt
>>> from lasy.backend import xp, to_cpu
>>> from lasy.laser import Laser
>>> from lasy.profiles.gaussian_profile import GaussianProfile
>>> from lasy.utils.laser_utils import get_full_field
>>> # Create profile.
>>> profile = GaussianProfile(
...     wavelength=0.6e-6,  # m
...     pol=(1, 0),
...     laser_energy=1.0,  # J
...     w0=5e-6,  # m
...     tau=30e-15,  # s
...     t_peak=0.0,  # s
... )
>>> # Create laser with given profile in `rt` geometry.
>>> laser = Laser(
...     dim="rt",
...     lo=(0e-6, -60e-15),
...     hi=(10e-6, +60e-15),
...     npoints=(50, 400),
...     profile=profile,
... )
>>> # Propagate and visualize.
>>> n_steps = 3
>>> propagate_step = 1e-3
>>> fig, axes = plt.subplots(1, n_steps, sharey=True)
>>> for step in range(n_steps):
>>>     laser.propagate(propagate_step)
>>>     E_rt, extent = get_full_field(laser)
>>>     extent[2:] *= 1e6
>>>     extent[:2] *= 1e12
>>>     tmin, tmax, rmin, rmax = extent
>>>     vmax = xp.abs(E_rt).max()
>>>     axes[step].imshow(
...         to_cpu(E_rt),
...         origin="lower",
...         aspect="auto",
...         vmax=vmax,
...         vmin=-vmax,
...         extent=[tmin, tmax, rmin, rmax],
...         cmap='bwr',
...     )
>>>     axes[step].set(xlabel='t (ps)')
>>>     if step == 0:
>>>         axes[step].set(ylabel='r (µm)')

add_propagator(propagator)[source]#

Apply a propagator object to the laser pulse.

Parameters:

propagator: a :class:`.Propagator` object (optional): Represents a propagation method.

apply_optics(optical_element)[source]#

Propagate the laser pulse through a thin optical element.

Parameters:

optical_element: an :class:`.OpticalElement` object (optional): Represents a thin optical element, through which the laser propagates.

normalize(value, kind='energy')[source]#

Normalize the pulse either to the energy, peak field amplitude, peak fluence, peak power, peak intensity, or average intensity. The average intensity option operates on the envelope.

Parameters:

valuescalar: Value to which to normalize the field property that is defined in kind
kindstring (optional): Options: 'energy’, 'field', 'intensity', 'average_intensity', 'peak_fluence', 'peak_power', (default is 'energy')

propagate(distance, **kwargs)[source]#

Propagate the laser pulse by the distance specified.

Parameters:

distancescalar: Distance by which the laser pulse should be propagated
gridGrid object (optional): Resample the field onto a new grid of different radial size and/or different number of radial grid points. Only works for 'rt'.

show(envelope_type='field', t_shift=0, show_lineout=True, show_max=False, udict={}, **kw)[source]#

Show a 2D image of the laser amplitude or intensity.

Parameters:

envelope_typestring, default: “field”: Options are: - 'field': Show the envelope of the laser field. - 'intensity': Show the intensity of the laser field. - 'vector_potential': Show the vector potential of the laser field.
t_shiftfloat, default: 0: Shift the temporal axis by t_shift seconds. It also can be a string with “left”, “right” or “center”, to shift the temporal axis such that the t=0 lies at the left, right or center of the x-axis.
show_lineoutbool, default: True: Show the lineout of the laser field.
show_maxbool, default: False: Print the maximum intensity of the laser field.
udictdict, default: {}: Dictionary with the information of the unit scales of the axes, e.g. {'t': {'value': 1e-15, 'label': 'fs'}, 'x': {'value': 1e-6, 'label': r'\mu m'}} Override the default unit scales.
**kwadditional arguments to be passed to matplotlib’s imshow command

write_to_file(file_prefix='laser', file_format='h5', write_dir='diags', save_as_vector_potential=False)[source]#

Write the laser profile + metadata to file.

Parameters:

write_dirstring: The directory where the file will be written.
file_prefixstring: The file name will start with this prefix.
file_formatstring: Format to be used for the output file. Options are "h5" and "bp".
save_as_vector_potentialbool (optional): Whether the envelope is converted to normalized vector potential before writing to file.