odak.learn.wave.impulse_response_fresnel¶

A definition to calculate impulse response based Fresnel approximation for beam propagation.

Parameters:

Name	Type	Description	Default
`field`	`np.complex`	Complex field (MxN).	required
`k`	`odak.wave.wavenumber`	Wave number of a wave, see odak.wave.wavenumber for more.	required
`distance`	`float`	Propagation distance.	required
`dx`	`float`	Size of one single pixel in the field grid (in meters).	required
`wavelength`	`float`	Wavelength of the electric field.	required

Returns:

Type	Description
`np.complex`	Final complex field (MxN).

Source code in odak/learn/wave/classical.py

def impulse_response_fresnel(field, k, distance, dx, wavelength):
    """
    A definition to calculate impulse response based Fresnel approximation for beam propagation.

    Parameters
    ----------
    field            : np.complex
                       Complex field (MxN).
    k                : odak.wave.wavenumber
                       Wave number of a wave, see odak.wave.wavenumber for more.
    distance         : float
                       Propagation distance.
    dx               : float
                       Size of one single pixel in the field grid (in meters).
    wavelength       : float
                       Wavelength of the electric field.

    Returns
    -------
    result           : np.complex
                       Final complex field (MxN).
    """
    assert True == False, "Refer to Issue 19 for more. This definition is unreliable."
    nv, nu = field.shape[-1], field.shape[-2]
    x = torch.linspace(-nu/2*dx, nu/2*dx, nu)
    y = torch.linspace(-nv/2*dx, nv/2*dx, nv)
    X, Y = torch.meshgrid(x, y, indexing='ij')
    Z = X**2+Y**2
    distance = torch.tensor([distance]).to(field.device)
    h = torch.exp(1j*k*distance)/(1j*wavelength*distance) * \
        torch.exp(1j*k/2/distance*Z)
    h = torch.fft.fft2(torch.fft.fftshift(h))*dx**2
    h = h.to(field.device)
    U1 = torch.fft.fft2(torch.fft.fftshift(field))
    U2 = h*U1
    result = torch.fft.ifftshift(torch.fft.ifft2(U2))
    return result

Notes¶

Unless you know what you are doing, we do not suggest you to use this function directly. Rather stick to odak.learn.wave.propagate_beam for your beam propagation code.

odak.learn.wave.impulse_response_fresnel¶

Notes¶

See also¶