pychi 0.0.4

Simulation package for the propagation of optical pulses in nonlinear media

pychi

A Python package for simulating the propagation of optical pulses in nonlinear materials.

To install the package, run

pip install pychi

The documentation is available under https://pychi.readthedocs.io/en/latest/

Here is a typical example of the use of pychi to simulate the propagation of a short optical pulse in a nonlinear waveguide exhibiting both cubic and quadratic nonlinearities.

# -*- coding: utf-8 -*-
"""
Created on Mon Feb 28 15:31:47 2022
The waveguide/fiber parameters are first provided, and a Waveguide instance
is created. Then, the pulse parameters are used to create a Light object.
A physical model is then chosen, taking into account different nonlinear
interactions based on the user choice. Finally, a solver is instantiated
and computes the propagation of the pulse in the waveguide with the chosen
nonlinear interactions.
@author: voumardt
"""
import matplotlib.pyplot as plt
import numpy as np
from scipy.constants import c

import pychi


"""
User parameters
"""
### Simulation
t_pts = 2**15

### Light
pulse_duration = 100e-15
pulse_wavelength = 1.56e-06
pulse_energy = 1e-9

### Waveguide
wg_length = 0.001
wg_chi_2 = 1.1e-12
wg_chi_3 = 3.4e-21
wg_a_eff = 1e-12
wg_freq, wg_n_eff = np.load('effective_index.npy')
# wg_n_eff is the effective dispersion of the waveguide considered, sampled on the grid wg_freq


"""
Nonlinear propagation
"""
### Prepare waveguide
waveguide = pychi.materials.Waveguide(wg_freq, wg_n_eff, wg_chi_2, wg_chi_3,
                                wg_a_eff, wg_length, t_pts=t_pts)
# Additional options:
# One can provide beta coefficients (strongly discouraged) overwriting the refractive
# index using waveguide.set_betas(betas, wavelength)
#
# wg_n_eff can be a 2 dimensional array, with first dimension the wavelength dependence
# and second dimension the z dependence.
#
# chi2 and chi3 can be callables, returning a z dependent value. Alternatively, they
# can be defined as one dimensional arrays describing their z dependence, or
# two dimensional arrays describing their z and frequency dependence.
#
# One can use waveguide.set_gamma(gamma) or waveguide.set_n2(n2) to provide
# nonlinear coefficient or nonlinear refractive index and overwrite chi3.
#
# Check documentation for more options and details.


### Prepare input pulse
pulse = pychi.light.Sech(waveguide, pulse_duration, pulse_energy, pulse_wavelength)
# Other available pulse shapes:
# pulse = pychi.light.Gaussian(waveguide, pulse_duration, pulse_energy, pulse_wavelength)
# pulse = pychi.light.Cw(waveguide, pulse_average_power, pulse_wavelength)
# pulse = pychi.light.Arbitrary(waveguide, pulse_frequency_axis, pulse_electric_field, pulse_energy)


### Prepare model
model = pychi.models.SpmChi2Chi3(waveguide, pulse)
# Other models available:
# model = pychi.models.Spm(waveguide, pulse)
# model = pychi.models.Chi2(waveguide, pulse)
# model = pychi.models.Chi3(waveguide, pulse)
# model = pychi.models.SpmChi2(waveguide, pulse)
# model = pychi.models.SpmChi3(waveguide, pulse)
# model = pychi.models.Chi2Chi3(waveguide, pulse)


### Prepare solver, solve
solver = pychi.solvers.Solver(model)
solver.solve()


"""
Plots
"""
pulse.plot_propagation()
# Results can also be accessed via pulse.z_save, pulse.freq, pulse.spectrum, pulse.waveform
# The refractive index and GVD can be seen with waveguide.plot_refractive_index()

Typical propagation results would look as follows:

Check the examples folder for some specific cases and validation against experimental data.

pychi has been developped at DESY by the Ultrafast Microphotonics group. If you use it for publications, please cite the associated paper https://doi.org/10.1063/5.0135252