laserfields

laserfields is a python library to describe the time-dependent electric fields of a laser pulse, and can be installed with pip install laserfields or conda -c conda-forge install laserfields. It implements the same pulse shapes and most of the features of the laserfields library written in Fortran (and as the Julia variant LaserFields.jl), please see the documentation of that library for the parameter meanings, conventions used, etc. In particular, the "main" function make_laserfield(**kwargs...) accepts the same parameters as the Fortran library parameter files as keyword arguments, and returns an instance of a subtype of the base class LaserField depending on the parameters. E.g., to create a Gaussian pulse with a duration (defined as the FWHM of the intensity) of 6 fs, a wavelength of 800 nm, a peak intensity of 1e14 W/cm^2, and with the peak at time t=7fs, one should call

lf = make_laserfield(form="gaussianI", is_vecpot=true, lambda_nm=800,
                      intensity_Wcm2=1e16, duration_as=6000, peak_time_as=7000)

Given a LaserField instance lf, the functions lf.E(t), lf.E_fourier(ω), lf.A(t), and lf.A_fourier(ω) can be used to obtain, respectively, the electric field as a function of time, its Fourier transform (implemented for most pulse shapes), the vector potential as a function of time, and its Fourier transform. Calling the instance as a function, lf(t) returns the electric field, i.e., is equivalent to lf.E(t). The notebooks in the examples folder show some ways to use the library, including how to define a set of fields through a YAML configuration file.

In addition to the pulses described by each LaserField instance, the library also implements a LaserFieldCollection class that can be used to combine multiple fields into a single effective one (i.e., the sum of the individual ones). It is also a LaserField instance and supports much of the same interface. Note that some of the parameters it contains are just "best-effort" values and may not be fully meaningful for the combined field - e.g., for the carrier frequency lf.ω0, it returns the highest value in the collection, to support use cases where this is used to define maximum time step in a numerical propagation, or the maximum frequency evaluated in a Fourier transform.

The "effective" duration of the pulse for n-photon processes can be obtained as lf.Teff(n_photon), which is the integral over the pulse intensity envelope to the n-th power (i.e., electric field envelope to the (2n)th power) over the pulse, see, e.g., https://doi.org/10.1103/PhysRevA.77.043420 (Eq. 14).