from __future__ import annotations
import gdsfactory as gf
from gdsfactory.component import Component
from gdsfactory.components.bend_euler import bend_euler
from gdsfactory.components.coupler_straight import coupler_straight
from gdsfactory.typings import ComponentFactory, CrossSectionSpec
[docs]
@gf.cell
def coupler_broadband(
w_sc: float = 0.5, # width of waveguides in the symmetric coupler section
gap_sc: float = 0.2, # gap size between the waveguides in the symmetric coupler section
w_top: float = 0.6, # width of the top waveguide in the phase control section
gap_pc: float = 0.3, # gap size in the phase control section
legnth_taper: float = 1.0, # length of the tapers
bend: ComponentFactory = bend_euler,
coupler_straight: ComponentFactory = coupler_straight,
length_coupler_straight: float = 12.4, # optimal L_1 from the 3d fdtd analysis
lenght_coupler_big_gap: float = 4.7, # optimal L_2 from the 3d fdtd analysis
cross_section: CrossSectionSpec = "xs_sc",
radius: float = 10.0,
) -> Component:
"""Returns broadband coupler component.
https://docs.flexcompute.com/projects/tidy3d/en/latest/notebooks/BroadbandDirectionalCoupler.html
proposed in Zeqin Lu, Han Yun, Yun Wang, Zhitian Chen, Fan Zhang, Nicolas A. F. Jaeger, and Lukas Chrostowski,
"Broadband silicon photonic directional coupler using asymmetric-waveguide based phase control,"
Opt. Express 23, 3795-3808 (2015), DOI: 10.1364/OE.23.003795.
Args:
w_sc: width of waveguides in the symmetric coupler section.
gap_sc: gap size between the waveguides in the symmetric coupler section.
w_top: width of the top waveguide in the phase control section.
gap_pc: gap size in the phase control section.
legnth_taper: length of the tapers.
bend: bend factory.
coupler_straight: coupler_straight factory.
length_coupler_straight: optimal L_1 from the 3d fdtd analysis.
lenght_coupler_big_gap: optimal L_2 from the 3d fdtd analysis.
cross_section: cross_section of the waveguides.
radius: bend radius.
"""
c = gf.Component()
xs = gf.get_cross_section(cross_section)
layer = gf.get_layer(xs.layer)
L_t = legnth_taper
c = Component()
L_2 = lenght_coupler_big_gap
L_1 = length_coupler_straight
y_coupler = -w_sc + xs.width / 2 + gap_pc / 2
coupler = coupler_straight(length=L_1, cross_section=cross_section, gap=gap_sc)
coupler1 = c << coupler
coupler1.xmin = -L_2 / 2 - L_t - L_1
coupler1.y = y_coupler
_bend = bend(radius=radius, cross_section=cross_section)
bend_lt = c << _bend
bend_lb = c << _bend
bend_lt.mirror()
bend_lb.connect("o1", coupler1.ports["o1"])
bend_lt.connect("o1", coupler1.ports["o2"])
# define vertices of the top waveguide
vertices_top = [
(L_2 / 2 + L_t + L_1, 0),
(L_2 / 2 + L_t + L_1, w_sc),
(L_2 / 2 + L_t, w_sc),
(L_2 / 2, w_top),
(-L_2 / 2, w_top),
(-L_2 / 2 - L_t, w_sc),
(-L_2 / 2 - L_t - L_1, w_sc),
(-L_2 / 2 - L_t - L_1, 0),
]
c.add_polygon(vertices_top, layer=layer)
# define vertices of the bottom waveguide
vertices_bot = [
(L_2 / 2 + L_t + L_1, -gap_sc - w_sc),
(L_2 / 2 + L_t + L_1, -gap_sc),
(L_2 / 2 + L_t, -gap_sc),
(L_2 / 2, -gap_pc),
(-L_2 / 2, -gap_pc),
(-L_2 / 2 - L_t, -gap_sc),
(-L_2 / 2 - L_t - L_1, -gap_sc),
(-L_2 / 2 - L_t - L_1, -gap_sc - w_sc),
]
c.add_polygon(vertices_bot, layer=layer)
coupler2 = c << coupler
coupler2.xmax = L_2 / 2 + L_t + L_1
coupler2.y = y_coupler
_bend = bend(radius=radius, cross_section=cross_section)
bend_rt = c << _bend
bend_rb = c << _bend
bend_rt.mirror()
bend_rb.connect("o1", coupler2.ports["o3"])
bend_rt.connect("o1", coupler2.ports["o4"])
c.add_port("o1", port=bend_lb.ports["o2"])
c.add_port("o2", port=bend_lt.ports["o2"])
c.add_port("o3", port=bend_rt.ports["o2"])
c.add_port("o4", port=bend_rb.ports["o2"])
return c
if __name__ == "__main__":
c = coupler_broadband(cross_section="xs_sc")
c.show(show_ports=True)
