Hi,

when I try to simulate a lamellar grating with period < 0, the function GetEpsilon gives out some unexpected values. Is there anything that needs to be considered when choosing the grating period? Below are the links to the diagrams for period=0.9 and 1:

http://s28.postimg.org/oi9iym1kt/eps09.png

http://s11.postimg.org/y7xnhuz83/eps1.png

Thanks and best regards,

Olf

Here is the python code I use:

from __future__ import division, print_function

import matplotlib.pyplot as plt
import numpy as np

import S4

period = 1
s = 0.5*period #grating bar width
thickness = .5
freq_vac = 1/.633 #incident wavelength

S = S4.New(Lattice=period, NumBasis=200)

S.SetMaterial(Name = 'mymaterial', Epsilon = 2**2)
S.SetMaterial(Name = 'Vacuum', Epsilon = 1)

S.AddLayer(Name='AirAbove', Thickness=0, Material='Vacuum')
S.AddLayer(Name='grating', Thickness=thickness, Material='mymaterial')
S.AddLayerCopy(Name='AirBelow', Thickness=0, Layer='AirAbove')

S.SetRegionRectangle(Layer='grating', Material='Vacuum', Center=(0,0), Angle=0, Halfwidths=(s/2,1))

S.SetExcitationPlanewave(IncidenceAngles=(0,0), sAmplitude = 1,
                         pAmplitude = 0, Order = 0)

S.SetFrequency(freq_vac)

xlist = np.linspace(0, period, num=200)
plt.figure()
plt.plot(xlist, [S.GetEpsilon(x,0,thickness/2).real for x in xlist])