stencil.apodized_focused_grating

apodized_focused_grating(
    teeth_gaps,
    teeth_widths,
    n_eff,
    n_sin,
    focal_length,
    width=None,
    angle=None,
    input_width=None,
)

Create an apodized focused grating.

The geometry is based on the work by F. Van Laere et al., “Compact Focusing Grating Couplers for Silicon-on-Insulator Integrated Circuits,” in IEEE Photonics Technology Letters, vol. 19, no. 23, pp. 1919-1921, Dec.1, 2007, doi: 10.1109/LPT.2007.908762.

Args

• teeth_gaps (float | Sequence[float]): Spacing between grating teeth edges.
• teeth_widths (float | Sequence[float]): Width of the grating teeth along the horizontal line from focal point. If value is negative, this teeth is not created.
• n_eff (float | Sequence[float]): Effective index of the cylindrical wave in the broad waveguide with the grating.
• n_sin (float): Product $n_0 \sin\theta$ between the free-space index and the sine of the input wave angle measured from the grating surface normal (such that a value of 0 indicates normal grating illumination).
• focal_length (float): Distance between the focal point and the start of the grating.
• width (float | None): If set, a rectangular-shaped grating is created with the specified width. Only one of width and angle must be set.
• angle (float | None): If set, the grating is created with the shape of a circular section with the specified angle. Only one of width and angle must be set.
• input_width (float | None): If set, the input taper region is added to the grating terminating with this dimension.

Returns

list[Circle | Polygon]: Grating structures.

Note

Arguments teeth_gaps, teeth_widths, and n_eff can be a single number or a sequence. The largest sequence among them will define the number of teeth created. Smaller sequences will be increased to the largest length by repeating their last element.

Example

>>> # Pie-slice with gaps and n_eff variations
>>> grating1 = pf.stencil.apodized_focused_grating(
...     teeth_gaps=np.linspace(0.2, 0.4, 20),
...     teeth_widths=0.2,
...     n_eff=np.linspace(1.8, 1.6, 20),
...     n_sin=np.sin(np.pi / 18),
...     focal_length=12.5,
...     angle=60,
...     input_width=0.5,
... )
>>> # Rectangular-shaped with gaps and widths variations
>>> grating2 = pf.stencil.apodized_focused_grating(
...     teeth_gaps=np.linspace(0.2, 0.4, 20),
...     teeth_widths=np.linspace(0.4, 0.2, 20),
...     n_eff=1.8,
...     n_sin=np.sin(np.pi / 18),
...     focal_length=12.5,
...     width=16,
...     input_width=0.5,
... )
>>> grating2 = [s.translate((30, 0)) for s in grating2]
>>> component = pf.Component().add(*grating1, *grating2)