‘py-fmas’ python package

The py-fmas python package solves for the \(z\)-propagation dynamics of spectrally broad ultrashort optical pulses in single mode nonlinear waveguides in terms of a nonlinear unidirectional propagation model for the analytic signal of the optical field. It allows to model propagation scenarios with and without the Raman effect.

Interaction between a fundamental soliton and a dispersive wave in a NL-PM-750 photonic crystal fiber (PCF). Propagation charactersitics of the analytic signal intensities in the time-domain (left) and the frequency domain (right). For the numerical simualtion the forward model for the analytic signal including the Raman effect is used. More details can be found in the usage example Two pulse interaction in a NLPM750 PCF.

For a user-specified propagation setting, the initial real-valued optical field is defined on a periodic one-dimensional temporal grid and converted to the complex-valued analytic signal for the optical field. \(z\)-propagation is performed by pseudospectral methods. The provided software implements a selection of algorithms that are commonly used in nonlinear optics for solving nonlinear Schrödinger type equations. py-fmas implements algorithms with both, fixed or adaptive stepsize.

The provided software allows for the propagation of spectrally broad ultrashort optical pulses and several pulses at pairwise distinct frequencies. Description of the proapgation process in terms of the analytic signal allows to directly neglect non-resonant contributions of four-wave mixing and to derive models that are formally simpler that the forward Maxwell equation. The range of applicability of the software is however equivalent to that of the forward Maxwell equation. If the Raman effect is neglected and a slowly varying envelope approximation is applied, the considered propagation model can be reduced to the standard nonlinear Schrödinger equation. For reasonably chosen initial conditions, the provided software can be used beyond the unidirectional approximation as a bidirectional model for a complex field, allowing to describe forward and backward waves coupled through nonlinear interactions (see the useage example BMCF – Backscattered optical field components).

py-fmas is based on our research code and was implemented with the aim of beeing easily extendible and maintainable. The provided software is aimed at researchers in the field of ultrashort pulse propagation and related disciplines.

The source code of the package is available on gitHub.

Contents:

• 1. Extended user guide
  • 1.1. Basic examples
  • 1.2. More specific examples
  • 1.3. Photon number conservation
  • 1.4. Attenuation
  • 1.5. Performance tests
  • 1.6. Propagation errors
• 2. Usage examples
  • 2.1. Exemplary propagation scenarios
  • 2.2. Two-frequency pulse compounds
  • 2.3. Simulation of other models
• 3. Reference manual
  • 3.1. fmas.models
  • 3.2. fmas.propagation_constant
  • 3.3. fmas.raman_response
  • 3.4. fmas.solver
  • 3.5. fmas.analytic_signal
  • 3.6. fmas.stepper
  • 3.7. fmas.tools
  • 3.8. fmas.data_io
  • 3.9. fmas.config
• 4. Citations

Further resources

Below you find a list of articles that discuss ultrashort optical pulse propagation in terms of the forward model for the analytic signal:

• A. Demircan, Sh. Amiranashvili, C. Bree, U. Morgner, G. Steinmeyer, Supercontinuum generation by multiple scatterings at a group velocity horizon, Opt. Exp. 22 (2014) 3866, https://doi.org/10.1364/OE.22.003866.

• A. Demircan, Sh. Amiranashvili, C. Bree, C. Mahnke, F. Mitschke, G. Steinmeyer, Rogue wave formation by accelerated solitons at an optical event horizon, Appl. Phys. B 115 (2014) 343, http://dx.doi.org/10.1007/s00340-013-5609-9

• Sh. Amiranashvili, A. Demircan, Ultrashort Optical Pulse Propagation in terms of Analytic Signal, Adv. Opt. Tech. 2011 (2011) 989515, http://dx.doi.org/10.1155/2011/989515.

• Sh. Amiranashvili, A. Demircan, Hamiltonian structure of propagation equations for ultrashort optical pulses, Phys. Rev. E 10 (2010) 013812, http://dx.doi.org/10.1103/PhysRevA.82.013812.

Indices and tables

• Index

• Module Index

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