Parabolic lens

Collimation and focusing using parabolic lenses

In the examples/ example, we create a collimated phonon flux by reflecting phonons from a parabolic surface. The figure below illustrates the concept:

We place the parabolic boundary at the bottom and move the hot spot that emits the phonon to y = 300 nm, as shown in the input file:

# Hot and cold sides:

# Phonon source:
PHONON_SOURCES = [Source(y=300e-9, size_x=100e-9,  size_y=100e-9, size_z=THICKNESS, angle_distribution="uniform")]

# Parabolic mirror:
HOLES = [ParabolaBottom(tip=0, focus=300e-9)]

Note that angle_distribution="uniform" because we need to emit phonons in all directions evenly. This model produces the following structure, which collimates phonons after reflection from the parabolic boundary:

The parabolic lens can also be inverted and placed at the top as follows

# Phonon source:
PHONON_SOURCES = [Source(x=0, y=0, z=0, size_x=WIDTH,  size_y=0, size_z=THICKNESS, angle_distribution="directional")]

# Parabolic boundary:
HOLES = [ParabolaTop(tip=1000e-9, focus=100e-9)]

Here, the source is place in the bottom, while parabola at the top.


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