Laser profiles

Warning

This section is currently in development.

class picmistandard.PICMI_GaussianLaser(wavelength, waist, duration, propagation_direction, polarization_direction, focal_position, centroid_position, a0=None, E0=None, phi0=None, zeta=None, beta=None, phi2=None, name=None, fill_in=True, **kw)[source]

Specifies a Gaussian laser distribution.

More precisely, the electric field near the focal plane is given by:

\[E(\boldsymbol{x},t) = a_0\times E_0\, \exp\left( -\frac{r^2}{w_0^2} - \frac{(z-z_0-ct)^2}{c^2\tau^2} \right) \cos[ k_0( z - z_0 - ct ) - \phi_{cep} ]\]

where \(k_0 = 2\pi/\lambda_0\) is the wavevector and where \(E_0 = m_e c^2 k_0 / q_e\) is the field amplitude for \(a_0=1\).

Note

The additional terms that arise far from the focal plane (Gouy phase, wavefront curvature, …) are not included in the above formula for simplicity, but are of course taken into account by the code, when initializing the laser pulse away from the focal plane.

Parameters:

  • wavelength (float) – Laser wavelength [m], defined as \(\lambda_0\) in the above formula

  • waist (float) – Waist of the Gaussian pulse at focus [m], defined as \(w_0\) in the above formula

  • duration (float) – Duration of the Gaussian pulse [s], defined as \(\tau\) in the above formula

  • propagation_direction (unit vector of length 3 of floats) – Direction of propagation [1]

  • polarization_direction (unit vector of length 3 of floats) – Direction of polarization [1]

  • focal_position (vector of length 3 of floats) – Position of the laser focus [m]

  • centroid_position (vector of length 3 of floats) – Position of the laser centroid at time 0 [m]

  • a0 (float) – Normalized vector potential at focus Specify either a0 or E0 (E0 takes precedence).

  • E0 (float) – Maximum amplitude of the laser field [V/m] Specify either a0 or E0 (E0 takes precedence).

  • phi0 (float) – Carrier envelope phase (CEP) [rad]

  • zeta (float) – Spatial chirp at focus (in the lab frame) [m.s]

  • beta (float) – Angular dispersion at focus (in the lab frame) [rad.s]

  • phi2 (float) – Temporal chirp at focus (in the lab frame) [s^2]

  • fill_in (bool, default=True) – Flags whether to fill in the empty spaced opened up when the grid moves

  • name (string, optional) – Optional name of the laser

class picmistandard.PICMI_AnalyticLaser(field_expression, wavelength, propagation_direction, polarization_direction, amax=None, Emax=None, name=None, fill_in=True, **kw)[source]

Specifies a laser with an analytically described distribution

Parameters:

  • name=None (string, optional) – Optional name of the laser

  • field_expression (string) – Analytic expression describing the electric field of the laser [V/m] Expression should be in terms of the position, ‘X’, ‘Y’, in the plane orthogonal to the propagation direction, and ‘t’ the time. The expression should describe the full field, including the oscillitory component. Parameters can be used in the expression with the values given as keyword arguments.

  • wavelength (float) – Laser wavelength. This should be built into the expression, but some codes require a specified value for numerical purposes.

  • propagation_direction (unit vector of length 3 of floats) – Direction of propagation [1]

  • polarization_direction (unit vector of length 3 of floats) – Direction of polarization [1]

  • amax (float, optional) – Maximum normalized vector potential. Specify either amax or Emax (Emax takes precedence). This should be built into the expression, but some codes require a specified value for numerical purposes.

  • Emax (float, optional) – Maximum amplitude of the laser field [V/m]. Specify either amax or Emax (Emax takes precedence). This should be built into the expression, but some codes require a specified value for numerical purposes.

  • fill_in (bool, default=True) – Flags whether to fill in the empty spaced opened up when the grid moves