Gaussian laser pulse

We will try a simple example to get familiar with the code structure and to verify the installation was successful. Let’s generate a Gaussian pulse at focus, propagate it backwards by one Rayleigh length (the pulse is then located upstream of the focal plane) and then output it to a file.

First let’s load in the required functions from the library.

from lasy.laser import Laser
from lasy.profiles.gaussian_profile import GaussianProfile

LASY: using backend NP

Next, define the physical parameters of the laser pulse and create the laser profile object.

wavelength = 800e-9  # Laser wavelength in meters
polarization = (1, 0)  # Linearly polarized in the x direction
energy = 1.5  # Energy of the laser pulse in joules
spot_size = 25e-6  # Waist of the laser pulse in meters
pulse_duration = 30e-15  # Pulse duration of the laser in seconds
t_peak = 0.0  # Location of the peak of the laser pulse in time

laser_profile = GaussianProfile(
    wavelength, polarization, energy, spot_size, pulse_duration, t_peak
)

Now create a full laser object containing the above physical parameters together with the computational settings.

dimensions = "rt"  # Use cylindrical geometry
lo = (0, -2.5 * pulse_duration)  # Lower bounds of the simulation box
hi = (5 * spot_size, 2.5 * pulse_duration)  # Upper bounds of the simulation box
num_points = (300, 500)  # Number of points in each dimension

laser = Laser(dimensions, lo, hi, num_points, laser_profile)

The laser pulse can be visualized with the show method.

laser.show()

By default, the values of the laser envelope are injected on the focal plan. One can propagate it backwards by one Rayleigh length (optional).

z_R = 3.14159 * spot_size**2 / wavelength  # The Rayleigh length
laser.propagate(-z_R)  # Propagate the pulse upstream of the focal plane

Available backends are: NP
NP is chosen

laser.show()

Output the result to a file. Here we utilise the openPMD standard.

file_prefix = "test_output"  # The file name will start with this prefix
file_format = "h5"  # Format to be used for the output file

laser.write_to_file(file_prefix, file_format)

The generated file may now be viewed or used as a laser input to a variety of other simulation tools.