1.3 Example 2 : a lossy 1D grating

In next example, we introduce a few new features.

• non-perpendicular incidence of the wave
• lossy materials (complex refractive index)
• slabs with a complicated structure

from rodis import * # rodis data set_lambda(1.0) set_N(10) set_alpha(0.1) set_delta(0.1) set_psi(0.9) # make device Alas = Material(2.9 - 0.1j) air = Material(1.0) start = Slab( Alas(1.2) ) bigrod = Slab( air(0.15) + Alas(0.9) + air(0.15)) smallrod = Slab( 2*(air(0.15) + Alas(0.3) + air(0.15))) end = Slab( air(1.2) ) cratch = Stack( start(1.) + bigrod(0.3) + smallrod(0.3) + end(1.)) # calculate cratch.calc() print cratch.field().R_TM(1) print abs(cratch.field().R_TE(2)) print cratch.field().T_TE(3).real print cratch.field().T_TM(4).imag

We add two variables which describe the angle of incidence of the field: alpha and delta. As can be seen in the script, both can be set using set_alpha(alpha) and set_delta(delta).

The use of delta comes with a change in defining the polarisation. We don't have to set TM or TE anymore, instead, we have to define psi as angle of polarisation. (set_psi())

Remark that the refractive index of the material Alas is complex. The negative imaginary part makes the material lossy. A positive imaginary part would provide the material of gain. Complex numbers are written in Python like a + bj. The output illustrates how to ask the real, imaginary part and absolute value of a Complex.

Instead of writing air(.15)+ Alas(.3)+ air(.3)+alas(.3)+air(0.15) to make a slab, you can write 2*(air(.15)+alas(0.3)+air(0.15)). Rodis wil stick materials with a same index togheter.