pypret.pnps module

This module provides classes to calculate parametrized nonlinear process spectra (PNPS), such as frequency-resolved optical gating (FROG), interferometric FROG (iFROG), dispersion scan (d-scan), time-domain ptychography (TDP) and pulse-shaper assisted methods such as multiphoton intrapulse interference phase scan (MIIPS).

The code follows the notation used in [Geib2019] and its supplement.

Currently only the abovementioned methods are implemented. But the code is written in such way that including new pulse measurement methods is very easy. If it is a method using a collinear nonlinearity, subclass from CollinearPNPS, otherwise from NoncollinearPNPS.

In the collinear case only self.mask(parameter) has to be implemented which calculates the used linear parametrization operator. In the non-collinear case the function _calculate has to be implemented which calculates and returns the PNPS trace T_mn and the PNPS signal S_mk.

Public interface

pypret.pnps.PNPS(pulse: pypret.pulse.Pulse, method: str, process: str, **kwargs) → pypret.pnps.BasePNPS

Creates a PNPS instance.

Parameters:

• pulse (Pulse) – A pulse instance that is used to simulate the PNPS trace.
• method (str) –

  The type of PNPS measurement. Should be one of

  • ’frog’ (see here)
  • ’tdp’ (see here)
  • ’dscan’ (see here)
  • ’miips’ (see here)
  • ’ifrog’ (see here)

• process (str) –

  The nonlinear process used in the measurement method. Can be one of

  • ’shg’ : second harmonic generation
  • ’thg’ : third harmonic generation
  • ’sd’ : self-diffraction
  • ’pg’ : polarization gating

  Not all methods support all nonlinear processes. In that case a ValueError will be raised.

• parameters are described in the documentation of the specific (Additional) –
• methods. (PNPS) –

class pypret.pnps.FROG(pulse, process)

Implements frequency-resolved optical gating [Kane1993] [Trebino2000].

__init__(pulse, process)

Creates the instance.

Parameters:

• pulse (Pulse instance) – The pulse object that defines the simulation grid.
• process (str) – The nonlinear process used in the PNPS method.

method = 'frog'

parameter_name = 'delay'

parameter_unit = 's'

class pypret.pnps.IFROG(pulse, process)

Implements the interferometric frequency-resolved optical gating method [1].

[1]	G. Stibenz and G. Steinmeyer, “Interferometric frequency-resolved optical gating,” Opt. Express 13, 2617-2626 (OSA, 2005).

__init__(pulse, process)

Creates the instance.

Parameters:

• pulse (Pulse instance) – The pulse object that defines the simulation grid.
• process (str) – The nonlinear process used in the PNPS method.

mask(tau)

method = 'ifrog'

parameter_name = 'tau'

parameter_unit = 's'

class pypret.pnps.TDP(pulse, process, center, width)

Implements a variant of time-domain ptychography. This version is self-referenced and works like FROG except that in one arm of the correlator the bandwidth of the pulse is heavily filtered [Witting2016]. Other variants are not directly supported by this class.

__init__(pulse, process, center, width)

Creates the instance.

Parameters:

• pulse (Pulse instance) – The pulse object that defines the simulation grid.
• process (str) – The nonlinear process used in the PNPS method.
• center (float) – The center wavelength of the bandwidth filter in m.
• width (float) – The width (FWHM) of the bandwidth filter in m.

method = 'tdp'

parameter_name = 'delay'

parameter_unit = 's'

class pypret.pnps.DSCAN(pulse, process, material)

Implements the dispersion scan method [Miranda2012a] [Miranda2012b].

Not implemented in the public version of the code. Please contact us if you want to use pypret for d-scan measurements.

__init__(pulse, process, material)

Initialize self. See help(type(self)) for accurate signature.

method = 'dscan'

parameter_name = 'insertion'

parameter_unit = 'm'

class pypret.pnps.MIIPS(pulse, process, alpha, gamma)

Implements the multiphoton intrapulse interference phase scan method (MIIPS) [Lozovoy2004] [Xu2006].

__init__(pulse, process, alpha, gamma)

Creates the instance.

Parameters:

• pulse (Pulse instance) – The pulse object that defines the simulation grid.
• process (str) – The nonlinear process used in the PNPS method.
• alpha (float) – The amplitude of the phase pattern (in rad).
• gamma (float) – The frequency of the phase pattern in Hz.

mask(delta)

method = 'miips'

parameter_name = 'delta'

parameter_unit = 'rad'

API

class pypret.pnps.BasePNPS(pulse, process, **kwargs)

The PNPS base class

__init__(pulse, process, **kwargs)

Initialize self. See help(type(self)) for accurate signature.

calculate(spectrum, parameter)

Calculates the PNPS signal S_mk and the PNPS trace T_mn.

Parameters:

• spectrum (1d-array) – The pulse spectrum for which the PNPS trace is calculated.
• parameter (scalar or 1d-array) – The PNPS parameter (array) for which the PNPS trace is calculated.

Returns:

Returns the calculated PNPS trace over the frequency self.process_w. If parameter was a scalar a 1d-array is returned. If it was a 1d-array a 2d-array is returned where the parameter runs along the first axis and the frequency along the second.

Return type:

1d- or 2d-array

gradient(Smk2, parameter)

Calculates the gradient ∇_n Z_m.

intermediate(parameter)

Returns intermediate results as stored by the instance.

measure(Sk)

Simulates the measurement process.

Note that we deal with the spectrum over the frequency! For retrieving from actual data we need to rescale this by lambda^2.

method = None

parameter_name = ''

parameter_unit = ''

process = None

scheme

trace

Returns the last calculated trace as a MeshData object.

class pypret.pnps.CollinearPNPS(pulse, process, **kwargs)

Implements collinear methods: d-scan, iFROG, etc.

class pypret.pnps.NoncollinearPNPS(pulse, process, **kwargs)

Implements non-collinear methods: FROG, TDP, etc.