Unable to verify Fresnel equations

[matt8s]

Thank you for your transparent and usable Python port of S4.

To verify that the code works correctly, I attempted to reproduce the Fresnel equations using a simple two layer model -- the first layer with n=1, and the second with n=1.5. I have been unable to get this to work in Inkstone, but I did get it to work with an equivalent code for Phoebe-P S4 . Attached are the codes I used for both Inkstone, fresnel_inkstone_te.py (which doesn't work); and S4, Fresnel_S4_TE.py (working).

In inkstone, when I use angle = np.linspace(0, 90, 91) , I get the error: /inkstone/params.py:525: RuntimeWarning: Vacuum propagation constant 0 encountered. Possibly Wood's anomaly. warn("Vacuum propagation constant 0 encountered. Possibly Wood's anomaly.", RuntimeWarning)

When I use angle = np.linspace(1, 90, 90) , I get the error: Traceback (most recent call last): File "fresnel_inkstone_te.py", line 71, in glapf, glapb = s.GetPowerFlux('gla') File "/inkstone/simulator.py", line 1204, in GetPowerFlux self.solve() File "/inkstone/simulator.py", line 890, in solve self._calc_sm() File "/inkstone/simulator.py", line 704, in _calc_sm s = next(ll[-1] for ll in self.csms if ll[-1][1] == n_layers-2) StopIteration

If between the "air" air and "gla" glass layers, I add an intermediate layer: s.AddLayer(name='gla-int', thickness=1, material_background='glass')

and still keep angle = np.linspace(1, 90, 90) then I get the error

/.local/lib/python3.9/site-packages/inkstone/layer.py:545: RuntimeWarning: divide by zero encountered in divide vh = -1j p @ v / w[:, None, :] /.local/lib/python3.9/site-packages/inkstone/layer.py:545: RuntimeWarning: invalid value encountered in divide vh = -1j p @ v / w[:, None, :] Traceback (most recent call last): File "/inkstone/Fresnel_Inkstone/fresnel_inkstone_te.py", line 72, in glapf, glapb = s.GetPowerFlux('gla') File "/.local/lib/python3.9/site-packages/inkstone/simulator.py", line 1204, in GetPowerFlux self.solve() File "/.local/lib/python3.9/site-packages/inkstone/simulator.py", line 890, in solve self._calc_sm() File "/.local/lib/python3.9/site-packages/inkstone/simulator.py", line 682, in _calc_sm ll[ilm].solve() File "/.local/lib/python3.9/site-packages/inkstone/layer.py", line 702, in solve self._calc_im() File "/.local/lib/python3.9/site-packages/inkstone/layer.py", line 652, in _calc_im al0, bl0 = im(self.phil, self.psil, self.pr.phi0, self.pr.psi0, self._phil_is_idt) File "/.local/lib/python3.9/site-packages/inkstone/im.py", line 36, in im term2 = sla.solve(psi1, psi2) File "/.local/lib/python3.9/site-packages/scipy/linalg/_basic.py", line 140, in solve a1 = atleast_2d(_asarray_validated(a, check_finite=check_finite)) File "/.local/lib/python3.9/site-packages/scipy/_lib/_util.py", line 287, in _asarray_validated a = toarray(a) File "/.local/lib/python3.9/site-packages/numpy/lib/function_base.py", line 627, in asarray_chkfinite raise ValueError( ValueError: array must not contain infs or NaNs

[alexysong]

Update: Your original script contains a wave channel (i.e. diffraction order) exactly parallel to the $xy$ plane, which is at the Wood's anomaly condition.

Now, the convergence issue near and at Wood's anomaly is solved in v0.3.3.

Inkstone is developed independently from S4.

[alexysong]

close for now; feel free to comment/reopen

[matt8s]

This explains the error at angle of incidence = 0 degrees, but it doesn't explain why there are still errors at 1 degree. I describe these additional errors in my original post.

[alexysong]

Hi @matt8s, Can yo please update to ver 0.3.3 (newest) and see if this issue persists?