0 degree incidence angle results in singular matrix error

[hag174]

Plane wave illumination with theta = 0 and phi = 0 degrees angle incidence angle results in singular matrix error. The work arround is to enter for theta a very small angle.

[hag174]

I think this problem can be solved by using np.linalg.pinv() instead of np.linalg.inv().

[yufu-liu]

[Solved]

Hi there,

I am also trying to use theta = 0 and phi = 0 degree for 1D grating diffraction, but the results are weird. (larger than 1)
Maybe my task is a little bit different to yours, but could you help me to find the root cause or give me some suggestion?

Here is my code which I modified from the example in the repository.
I am thinking about the large imaginary part of n and small N_harmonics.

from rcwa.shorthand import complexArray
import numpy as np

def solve_system():
    wavelength = 0.365
    deg = np.pi / 180
    theta = 0 * deg
    phi = 0 * deg
    pTEM = 1/np.sqrt(1)*complexArray([0,1j])
    source = Source(wavelength=wavelength, theta=theta, phi=phi, pTEM=pTEM)
    N_harmonics = 5

    grating_layer = RectangularGrating(period=2, thickness=1.6, er = 10.85241249, ur = 1, n=1.52+3.2943j,
                                        n_void=1, groove_width=0.5, nx=512)
    layer_stack = LayerStack(grating_layer)

    solver_1d = Solver(layer_stack, source, N_harmonics)
    results = solver_1d.solve()

    return results

if __name__ == '__main__':
    results = solve_system()

    # Get the amplitude reflection and transmission coefficients
    (rxCalculated, ryCalculated, rzCalculated) = (results['rx'], results['ry'], results['rz'])
    (txCalculated, tyCalculated, tzCalculated) = (results['tx'], results['ty'], results['tz'])

    # Get the diffraction efficiencies R and T and overall reflection and transmission coefficients R and T
    (R, T, RTot, TTot) = (results['R'], results['T'], results['RTot'], results['TTot'])
    print(RTot, TTot, RTot+TTot)

Best regards,