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######################################################################
# #
# Copyright 2009-2019 Lucas Heitzmann Gabrielli. #
# This file is part of gdspy, distributed under the terms of the #
# Boost Software License - Version 1.0. See the accompanying #
# LICENSE file or <http://www.boost.org/LICENSE_1_0.txt> #
# #
######################################################################
import numpy
import gdspy
def grating(period, number_of_teeth, fill_frac, width, position, direction, lda=1, sin_theta=0,
focus_distance=-1, focus_width=-1, tolerance=0.001, layer=0, datatype=0):
'''
Straight or focusing grating.
period : grating period
number_of_teeth : number of teeth in the grating
fill_frac : filling fraction of the teeth (w.r.t. the period)
width : width of the grating
position : grating position (feed point)
direction : one of {'+x', '-x', '+y', '-y'}
lda : free-space wavelength
sin_theta : sine of incidence angle
focus_distance : focus distance (negative for straight grating)
focus_width : if non-negative, the focusing area is included in
the result (usually for negative resists) and this
is the width of the waveguide connecting to the
grating
tolerance : same as in `path.parametric`
layer : GDSII layer number
datatype : GDSII datatype number
Return `PolygonSet`
'''
if focus_distance < 0:
p = gdspy.L1Path((position[0] - 0.5 * width,
position[1] + 0.5 * (number_of_teeth - 1 + fill_frac) * period),
'+x', period * fill_frac, [width], [], number_of_teeth, period,
layer=layer, datatype=datatype)
else:
neff = lda / float(period) + sin_theta
qmin = int(focus_distance / float(period) + 0.5)
p = gdspy.Path(period * fill_frac, position)
c3 = neff**2 - sin_theta**2
w = 0.5 * width
for q in range(qmin, qmin + number_of_teeth):
c1 = q * lda * sin_theta
c2 = (q * lda)**2
p.parametric(lambda t: (width * t - w,
(c1 + neff * numpy.sqrt(c2 - c3 * (width * t - w)**2)) / c3),
tolerance=tolerance, max_points=0, layer=layer, datatype=datatype)
p.x = position[0]
p.y = position[1]
sz = p.polygons[0].shape[0] // 2
if focus_width == 0:
p.polygons[0] = numpy.vstack((p.polygons[0][:sz, :], [position]))
elif focus_width > 0:
p.polygons[0] = numpy.vstack((p.polygons[0][:sz, :],
[(position[0] + 0.5 * focus_width, position[1]),
(position[0] - 0.5 * focus_width, position[1])]))
p.fracture()
if direction == '-x':
return p.rotate(0.5 * numpy.pi, position)
elif direction == '+x':
return p.rotate(-0.5 * numpy.pi, position)
elif direction == '-y':
return p.rotate(numpy.pi, position)
else:
return p
if __name__ == '__main__':
# Examples
# Negative resist example
width = 0.45
bend_radius = 50.0
ring_radius = 20.0
taper_len = 50.0
input_gap = 150.0
io_gap = 500.0
wg_gap = 20.0
ring_gaps = [0.06 + 0.02 * i for i in range(8)]
ring = gdspy.Cell('NRing')
ring.add(gdspy.Round((ring_radius, 0), ring_radius, ring_radius - width, tolerance=0.001))
grat = gdspy.Cell('NGrat')
grat.add(grating(0.626, 28, 0.5, 19, (0, 0), '+y', 1.55,
numpy.sin(numpy.pi * 8 / 180), 21.5, width,
tolerance=0.001))
taper = gdspy.Cell('NTaper')
taper.add(gdspy.Path(0.12, (0, 0)).segment(taper_len, '+y', final_width=width))
c = gdspy.Cell('Negative')
for i, gap in enumerate(ring_gaps):
path = gdspy.FlexPath([(input_gap * i, taper_len)], width=width,
corners='circular bend', bend_radius=bend_radius,
gdsii_path=True)
path.segment((0, 600 - wg_gap * i), relative=True)
path.segment((io_gap, 0), relative=True)
path.segment((0, 300 + wg_gap * i), relative=True)
c.add(path)
c.add(gdspy.CellReference(ring, (input_gap * i + width / 2 + gap, 300)))
c.add(gdspy.CellArray(taper, len(ring_gaps), 1, (input_gap, 0), (0, 0)))
c.add(gdspy.CellArray(grat, len(ring_gaps), 1, (input_gap, 0), (io_gap, 900 + taper_len)))
# Positive resist example
width = 0.45
ring_radius = 20.0
big_margin = 10.0
small_margin = 5.0
taper_len = 50.0
bus_len = 400.0
input_gap = 150.0
io_gap = 500.0
wg_gap = 20.0
ring_gaps = [0.06 + 0.02 * i for i in range(8)]
ring_margin = gdspy.Rectangle((0, -ring_radius - big_margin),
(2 * ring_radius + big_margin, ring_radius + big_margin))
ring_hole = gdspy.Round((ring_radius, 0), ring_radius, ring_radius - width, tolerance=0.001)
ring_bus = gdspy.Path(small_margin, (0, taper_len), number_of_paths=2,
distance=small_margin + width)
ring_bus.segment(bus_len, '+y')
p = gdspy.Path(small_margin, (0, 0), number_of_paths=2, distance=small_margin + width)
p.segment(21.5, '+y', final_distance=small_margin + 19)
grat = gdspy.Cell('PGrat').add(p)
grat.add(grating(0.626, 28, 0.5, 19, (0, 0), '+y', 1.55,
numpy.sin(numpy.pi * 8 / 180), 21.5, tolerance=0.001))
p = gdspy.Path(big_margin, (0, 0), number_of_paths=2, distance=big_margin + 0.12)
p.segment(taper_len, '+y', final_width=small_margin, final_distance=small_margin + width)
taper = gdspy.Cell('PTaper').add(p)
c = gdspy.Cell('Positive')
for i, gap in enumerate(ring_gaps):
path = gdspy.FlexPath([(input_gap * i, taper_len + bus_len)],
width=[small_margin, small_margin],
offset=small_margin + width, gdsii_path=True)
path.segment((0, 600 - bus_len - bend_radius - wg_gap * i), relative=True)
path.turn(bend_radius, 'r')
path.segment((io_gap - 2 * bend_radius, 0), relative=True)
path.turn(bend_radius, 'l')
path.segment((0, 300 - bend_radius + wg_gap * i), relative=True)
c.add(path)
dx = width / 2 + gap
c.add(gdspy.boolean(
gdspy.boolean(ring_bus, gdspy.copy(ring_margin, dx, 300), 'or', precision=1e-4),
gdspy.copy(ring_hole, dx, 300), 'not', precision=1e-4).translate(input_gap * i, 0))
c.add(gdspy.CellArray(taper, len(ring_gaps), 1, (input_gap, 0), (0, 0)))
c.add(gdspy.CellArray(grat, len(ring_gaps), 1, (input_gap, 0), (io_gap, 900 + taper_len)))
# Save to a gds file and check out the output
gdspy.write_gds('photonics.gds')
gdspy.LayoutViewer()
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