Grid

Grid{T<:Real}

Time and frequency grid for GNLSE propagation.

Fields

• N::Int: Number of grid points (resolution)
• t::Vector{T}: Time grid [s], centered at zero
• V::Vector{T}: Relative angular frequency grid ω - ω₀ [rad/s], monotonic
• W::Vector{T}: Absolute optical angular frequency ω = ω₀ + V [rad/s], monotonic
• dt::T: Time step [s]
• omega0::T: Central angular frequency ω₀ [rad/s]
• lambda0::T: Center wavelength λ₀ [m]

Notes

• V = ω - ω₀ is the physical detuning; W = ω₀ + V is the absolute frequency
• ω₀ = 2πc/λ₀ (all frequencies in rad/s)
• V and W are stored in monotonic order, not FFT-natural order

create_grid(resolution::Int, time_window::Real, wavelength::Real)

Create time-frequency grid for GNLSE simulations in natural SI units.

Arguments

• resolution::Int: Number of grid points (power of 2 recommended)
• time_window::Real: Total time window [s]
• wavelength::Real: Center wavelength [m]

Returns

• Grid: Grid structure with:

  • t: time grid [s] spanning [-timewindow/2, timewindow/2]
  • V: relative angular frequency ω - ω₀ [rad/s], monotonic
  • W: absolute angular frequency ω = ω₀ + V [rad/s], monotonic
  • dt: time step [s]
  • omega0: central angular frequency ω₀ [rad/s]
  • lambda0: center wavelength [m]

Notes

• ω₀ = 2πc/λ₀ where c = 299792458 m/s, gives ω₀ in rad/s
• V = 2π · [-N/2, ..., N/2-1] / (N·dt) [rad/s] is the relative frequency (physical detuning ω - ω₀), monotonic ordering
• W = ω₀ + V [rad/s] is the absolute optical frequency

V and W are stored in monotonic (not FFT-natural) order; operators that act on FFT output apply ifftshift as needed.

wavelength_grid(grid::Grid)
wavelength_grid(solution::Solution)

Wavelength grid [m] for the absolute frequency axis, λ = 2πc/ω. The result is aligned element-for-element with grid.W (and with solution.W / the columns of solution.AW), so it is monotonically decreasing in array order.

c

Speed of light in vacuum [m/s] (exact SI value, 299792458.0).