"""DBR gratings.
wavelength = 2*period*neff
period = wavelength/2/neff
dbr default parameters are from Stephen Lin thesis
https://open.library.ubc.ca/cIRcle/collections/ubctheses/24/items/1.0388871
Period: 318nm, width: 500nm, dw: 20 ~ 120 nm.
"""
from __future__ import annotations
import gdsfactory as gf
from gdsfactory.cell import cell
from gdsfactory.component import Component
from gdsfactory.components.straight import straight
from gdsfactory.snap import snap_to_grid
from gdsfactory.typings import CrossSectionSpec
period = 318e-3
w0 = 0.5
dw = 50e-3
w1 = w0 - dw / 2
w2 = w0 + dw / 2
@cell
def dbr_cell(
w1: float = w1,
w2: float = w2,
l1: float = period / 2,
l2: float = period / 2,
cross_section: CrossSectionSpec = "xs_sc",
**kwargs,
) -> Component:
"""Distributed Bragg Reflector unit cell.
Args:
w1: thin width in um.
l1: thin length in um.
w2: thick width in um.
l2: thick length in um.
n: number of periods.
cross_section: cross_section spec.
.. code::
l1 l2
<-----><-------->
_________
_______|
w1 w2
_______
|_________
"""
l1 = snap_to_grid(l1)
l2 = snap_to_grid(l2)
w1 = snap_to_grid(w1, 2)
w2 = snap_to_grid(w2, 2)
xs = gf.get_cross_section(cross_section, **kwargs)
xs1 = xs.copy(width=w1)
xs2 = xs.copy(width=w2)
c = Component()
c1 = c << straight(length=l1, cross_section=xs1)
c2 = c << straight(length=l2, cross_section=xs2)
c2.connect(port="o1", destination=c1.ports["o2"], allow_width_mismatch=True)
c.add_port("o1", port=c1.ports["o1"])
c.add_port("o2", port=c2.ports["o2"])
return c
[docs]
@cell
def dbr(
w1: float = w1,
w2: float = w2,
l1: float = period / 2,
l2: float = period / 2,
n: int = 10,
cross_section: CrossSectionSpec = "xs_sc",
**kwargs,
) -> Component:
"""Distributed Bragg Reflector.
Args:
w1: thin width in um.
l1: thin length in um.
w2: thick width in um.
l2: thick length in um.
n: number of periods.
cross_section: cross_section spec.
kwargs: cross_section settings.
.. code::
l1 l2
<-----><-------->
_________
_______|
w1 w2 ... n times
_______
|_________
"""
c = Component()
l1 = snap_to_grid(l1)
l2 = snap_to_grid(l2)
cell = dbr_cell(w1=w1, w2=w2, l1=l1, l2=l2, cross_section=cross_section, **kwargs)
c.add_array(cell, columns=n, rows=1, spacing=(l1 + l2, 100))
s = gf.c.straight(length=l1, cross_section=cross_section, **kwargs)
sl = c << s
sr = c << s
p1 = cell.ports["o2"].copy()
p1.center = [(l1 + l2) * n, 0]
sl.connect(port="o2", destination=cell.ports["o1"], allow_width_mismatch=True)
sr.connect(
port="o1",
destination=p1,
allow_width_mismatch=True,
)
c.add_port("o1", port=sl.ports["o1"])
c.add_port("o2", port=sr.ports["o2"])
return c
if __name__ == "__main__":
# c = dbr(w1=0.5, w2=0.6, l1=0.2, l2=0.3, n=10)
c = dbr(n=10)
# c = dbr_cell()
# c.assert_ports_on_grid()
c.show(show_ports=True)
