Ring filter

Calculations

For a ring resonator we need to define:

Optical parameters:

• coupling coefficient: will define resonance extinction ratio for a particular ring loss.

• Free spectral range.

Electrical parameters:

• VpiL

• Resistance

import gdsfactory as gf
import numpy as np


def ring(
    wl: np.ndarray,
    wl0: float,
    neff: float,
    ng: float,
    ring_length: float,
    coupling: float,
    loss: float,
) -> np.ndarray:
    """Returns Frequency Domain Response of an all pass filter.

    Args:
        wl: wavelength in  um.
        wl0: center wavelength at which neff and ng are defined.
        neff: effective index.
        ng: group index.
        ring_length: in um.
        coupling: coupling coefficient.
        loss: dB/um.
    """
    transmission = 1 - coupling
    neff_wl = (
        neff + (wl0 - wl) * (ng - neff) / wl0
    )  # we expect a linear behavior with respect to wavelength
    out = np.sqrt(transmission) - 10 ** (-loss * ring_length / 20.0) * np.exp(
        2j * np.pi * neff_wl * ring_length / wl
    )
    out /= 1 - np.sqrt(transmission) * 10 ** (-loss * ring_length / 20.0) * np.exp(
        2j * np.pi * neff_wl * ring_length / wl
    )
    return abs(out) ** 2


if __name__ == "__main__":
    import matplotlib.pyplot as plt

    loss = 0.03  # [dB/μm] (alpha) waveguide loss
    neff = 2.46  # Effective index of the waveguides
    wl0 = 1.55  # [μm] the wavelength at which neff and ng are defined
    radius = 5
    ring_length = 2 * np.pi * radius  # [μm] Length of the ring
    coupling = 0.5  # [] coupling of the coupler
    wl = np.linspace(1.5, 1.6, 1000)  # [μm] Wavelengths to sweep over
    wl = np.linspace(1.55, 1.60, 1000)  # [μm] Wavelengths to sweep over
    ngs = [4.182551, 4.169563, 4.172917]
    thicknesses = [210, 220, 230]

    # widths = np.array([0.4, 0.45, 0.5, 0.55, 0.6])
    # ngs = np.array([4.38215238, 4.27254985, 4.16956338, 4.13283219, 4.05791982])

    widths = np.array([0.495, 0.5, 0.505])
    neffs = np.array([2.40197253, 2.46586378, 2.46731758])
    ng = 4.2  # Group index of the waveguides

    for width, neff in zip(widths, neffs):
        p = ring(
            wl=wl,
            wl0=wl0,
            neff=neff,
            ng=ng,
            ring_length=ring_length,
            coupling=coupling,
            loss=loss,
        )
        plt.plot(wl, p, label=f"{int(width*1e3)}nm")

    plt.title("ring resonator vs waveguide width")
    plt.xlabel("wavelength (um)")
    plt.ylabel("Power Transmission")
    plt.grid()
    plt.legend()
    plt.show()

Layout

gdsfactory easily enables you to layout Component with as many levels of hierarchy as you need.

A Component is a canvas where we can add polygons, references to other components or ports.

Lets add two references in a component.

c = gf.components.ring_single_heater(gap=0.2, radius=10, length_x=4)
c.plot()

scene = c.to_3d()
scene.show()

Lets define a ring function that also accepts other component specs for the subcomponents (straight, coupler, bend)

ring = gf.components.ring_single_heater(
    gap=0.2, radius=10, length_x=4, via_stack_offset=(2, 0)
)
ring_with_grating_couplers = gf.routing.add_fiber_array(ring)
ring_with_grating_couplers.plot()

port_names = ["l_e1", "r_e3"]
port_names = ["l_e4", "r_e4"]
c = gf.routing.add_pads_top(
    ring,
    port_names=port_names,
)
c = gf.routing.add_fiber_array(c)
c

Top reticle assembly

Once you have your components and circuits defined, you can add them into a top reticle Component for fabrication.

You need to consider:

• what design variations do you want to include in the mask? You need to define your Design Of Experiment or DOE

• obey DRC (Design rule checking) foundry rules for manufacturability. Foundry usually provides those rules for each layer (min width, min space, min density, max density)

• make sure you will be able to test te devices after fabrication. Obey DFT (design for testing) rules. For example, if your test setup works only for fiber array, what is the fiber array spacing (127 or 250um?)

• if you plan to package your device, make sure you follow your packaging guidelines from your packaging house (min pad size, min pad pitch, max number of rows for wire bonding …)

import gdsfactory as gf
import pandas as pd


@gf.cell
def spiral_gc(**kwargs):
    """Returns spiral with Grating Couplers."""
    c = gf.components.spiral(**kwargs)
    c = gf.routing.add_fiber_array(c)
    c.info["doe"] = "spirals_sc"  # strip Cband spirals
    c.info["measurement"] = "optical_spectrum"
    c.info["measurement_parameters"] = ""
    c.info["analysis"] = "[power_envelope]"
    c.info["analysis_parameters"] = "[]"
    c.info["ports_optical"] = 4
    c.info["ports_electrical"] = 0
    c.info.update(kwargs)
    return c


@gf.cell
def mzm_gc(length_x=10, **kwargs) -> gf.Component:
    """Returns a MZI with Grating Couplers.

    Args:
        length_x: length of the MZI.
        kwargs: additional settings.
    """
    c = gf.components.mzi2x2_2x2_phase_shifter(
        length_x=length_x, auto_rename_ports=False, **kwargs
    )
    c = gf.routing.add_pads_top(c, port_names=["top_l_e1", "top_r_e3"])
    c = gf.routing.add_fiber_array(c)
    c.info["doe"] = "mzm"
    c.info["measurement"] = "optical_spectrum"
    c.info["analysis"] = "[fsr]"
    c.info["analysis_parameters"] = "[]"
    c.info["measurement_parameters"] = ""
    c.info["ports_electrical"] = 2
    c.info["ports_optical"] = 6
    c.info["length_x"] = length_x
    c.info.update(kwargs)
    return c


def sample_reticle(grid: bool = False) -> gf.Component:
    """Returns MZI with TE grating couplers."""
    from gdsfactory.generic_tech.cells import (
        add_fiber_array_optical_south_electrical_north,
    )

    mzis = [mzm_gc(length_x=lengths) for lengths in [100, 200, 300]]
    spirals = [spiral_gc(length=length) for length in [0, 100, 200]]
    rings = []
    for length_x in [10, 20, 30]:
        ring = gf.components.ring_single_heater(length_x=length_x)
        c = add_fiber_array_optical_south_electrical_north(
            component=ring,
            electrical_port_names=["l_e2", "r_e2"],
        )
        c.name = f"ring_{length_x}"
        c.info["doe"] = "ring_length_x"
        c.info["measurement"] = "optical_spectrum"
        c.info["measurement_parameters"] = ""
        c.info["ports_electrical"] = 2
        c.info["ports_optical"] = 4
        c.info["analysis"] = "[fsr]"
        c.info["analysis_parameters"] = "[]"
        c.info["length_x"] = length_x
        rings.append(c)

    copies = 3  # number of copies of each component
    components = mzis * copies + rings * copies + spirals * copies
    if grid:
        return gf.grid(components)
    c = gf.pack(components)
    if len(c) > 1:
        c = gf.pack(c)[0]
    return c[0]


c = sample_reticle()
c.show()
c

gf.labels.write_test_manifest(c, csvpath="sample_reticle.csv")
df = pd.read_csv("sample_reticle.csv")
df

	cell	x	y	info	ports	settings	doe	analysis	analysis_parameters	measurement	measurement_parameters	ports_optical	ports_electrical
0	mzm_gc_LX100	250.020	153.225	{"length_x": 100}	{"in_o1": {"name": "in_o1", "center": [145.02,...	{"length_x":100}	mzm	[fsr]	[]	optical_spectrum	NaN	6	2
1	mzm_gc_LX200	200.020	419.775	{"length_x": 200}	{"in_o1": {"name": "in_o1", "center": [145.02,...	{"length_x":200}	mzm	[fsr]	[]	optical_spectrum	NaN	6	2
2	mzm_gc_LX300	150.020	686.325	{"length_x": 300}	{"in_o1": {"name": "in_o1", "center": [145.02,...	{"length_x":300}	mzm	[fsr]	[]	optical_spectrum	NaN	6	2
3	mzm_gc_LX100	250.020	952.876	{"length_x": 100}	{"in_o1": {"name": "in_o1", "center": [145.02,...	{"length_x":100}	mzm	[fsr]	[]	optical_spectrum	NaN	6	2
4	mzm_gc_LX200	200.020	1219.426	{"length_x": 200}	{"in_o1": {"name": "in_o1", "center": [145.02,...	{"length_x":200}	mzm	[fsr]	[]	optical_spectrum	NaN	6	2
5	mzm_gc_LX300	150.020	1485.976	{"length_x": 300}	{"in_o1": {"name": "in_o1", "center": [145.02,...	{"length_x":300}	mzm	[fsr]	[]	optical_spectrum	NaN	6	2
6	mzm_gc_LX100	250.020	1752.526	{"length_x": 100}	{"in_o1": {"name": "in_o1", "center": [145.02,...	{"length_x":100}	mzm	[fsr]	[]	optical_spectrum	NaN	6	2
7	mzm_gc_LX200	200.020	2019.076	{"length_x": 200}	{"in_o1": {"name": "in_o1", "center": [145.02,...	{"length_x":200}	mzm	[fsr]	[]	optical_spectrum	NaN	6	2
8	mzm_gc_LX300	820.960	153.225	{"length_x": 300}	{"in_o1": {"name": "in_o1", "center": [815.96,...	{"length_x":300}	mzm	[fsr]	[]	optical_spectrum	NaN	6	2
9	ring_10	884.460	367.151	{"length_x": 10}	{"o1": {"name": "o1", "center": [815.96, 300.6...	{}	ring_length_x	[fsr]	[]	optical_spectrum	NaN	4	2
10	ring_20	889.460	707.151	{"length_x": 20}	{"o1": {"name": "o1", "center": [815.96, 640.6...	{}	ring_length_x	[fsr]	[]	optical_spectrum	NaN	4	2
11	ring_30	894.460	1047.151	{"length_x": 30}	{"o1": {"name": "o1", "center": [815.96, 980.6...	{}	ring_length_x	[fsr]	[]	optical_spectrum	NaN	4	2
12	ring_10	884.460	1387.151	{"length_x": 10}	{"o1": {"name": "o1", "center": [815.96, 1320....	{}	ring_length_x	[fsr]	[]	optical_spectrum	NaN	4	2
13	ring_20	889.460	1727.151	{"length_x": 20}	{"o1": {"name": "o1", "center": [815.96, 1660....	{}	ring_length_x	[fsr]	[]	optical_spectrum	NaN	4	2
14	ring_30	1311.400	367.151	{"length_x": 30}	{"o1": {"name": "o1", "center": [1232.9, 300.6...	{}	ring_length_x	[fsr]	[]	optical_spectrum	NaN	4	2
15	ring_10	1301.400	707.151	{"length_x": 10}	{"o1": {"name": "o1", "center": [1232.9, 640.6...	{}	ring_length_x	[fsr]	[]	optical_spectrum	NaN	4	2
16	ring_20	1306.400	1047.151	{"length_x": 20}	{"o1": {"name": "o1", "center": [1232.9, 980.6...	{}	ring_length_x	[fsr]	[]	optical_spectrum	NaN	4	2
17	ring_30	1311.400	1387.151	{"length_x": 30}	{"o1": {"name": "o1", "center": [1232.9, 1320....	{}	ring_length_x	[fsr]	[]	optical_spectrum	NaN	4	2
18	spiral_gc_L200	1395.179	140.351	{"length": 200}	{"o1": {"name": "o1", "center": [1551.179, 34....	{"length":200}	spirals_sc	[power_envelope]	[]	optical_spectrum	NaN	4	0
19	spiral_gc_L200	1141.179	1766.901	{"length": 200}	{"o1": {"name": "o1", "center": [1297.179, 166...	{"length":200}	spirals_sc	[power_envelope]	[]	optical_spectrum	NaN	4	0
20	spiral_gc_L200	1141.179	1950.451	{"length": 200}	{"o1": {"name": "o1", "center": [1297.179, 184...	{"length":200}	spirals_sc	[power_envelope]	[]	optical_spectrum	NaN	4	0
21	spiral_gc_L100	759.960	2106.901	{"length": 100}	{"o1": {"name": "o1", "center": [815.96, 2000....	{"length":100}	spirals_sc	[power_envelope]	[]	optical_spectrum	NaN	4	0
22	spiral_gc_L100	1593.840	323.901	{"length": 100}	{"o1": {"name": "o1", "center": [1649.84000000...	{"length":100}	spirals_sc	[power_envelope]	[]	optical_spectrum	NaN	4	0
23	spiral_gc_L100	1593.840	507.451	{"length": 100}	{"o1": {"name": "o1", "center": [1649.84000000...	{"length":100}	spirals_sc	[power_envelope]	[]	optical_spectrum	NaN	4	0
24	spiral_gc_L0	1693.840	680.751	{"length": 0}	{"o1": {"name": "o1", "center": [1649.84000000...	{"length":0}	spirals_sc	[power_envelope]	[]	optical_spectrum	NaN	4	0
25	spiral_gc_L0	1693.840	854.051	{"length": 0}	{"o1": {"name": "o1", "center": [1649.84000000...	{"length":0}	spirals_sc	[power_envelope]	[]	optical_spectrum	NaN	4	0
26	spiral_gc_L0	1693.840	1027.351	{"length": 0}	{"o1": {"name": "o1", "center": [1649.84000000...	{"length":0}	spirals_sc	[power_envelope]	[]	optical_spectrum	NaN	4	0