AnalyticDirectionalCouplerModel

class photonforge.AnalyticDirectionalCouplerModel(*, interaction_length, coupling_length, propagation_length=one, cross_phase=90, insertion_loss=0.0, isolation=0.0, reflection=0.0, n_eff=0.0, n_group=None, reference_frequency=None, ports=None)[source]

Analytic model for a 4-port directional coupler.

The S matrix for the directional coupler for each mode is given by:

\[\begin{split}S = \begin{bmatrix} r & i & t & c \\ i & r & c & t \\ t & c & r & i \\ c & t & i & r \\ \end{bmatrix}\end{split}\]

with coefficients:

\[ \begin{align}\begin{aligned}t &= \sqrt{1 - c_r} A e^{j \phi}\\c &= \sqrt{c_r} A e^{j (\phi + \Delta\phi)}\\c_r &= \sin^2\left(\frac{\pi l_i}{2 l_c}\right)\\A &= 10^{-\frac{L_\text{dB}}{20}}\\\phi &= \frac{2 \pi l_p}{c_0} [n_\text{eff} f_0 + n_\text{group} (f - f_0)]\end{aligned}\end{align} \]
Parameters:

  • interaction_length (float) – Interaction length \(l_i\).

  • coupling_length (Annotated[float | Sequence[float] | Sequence[Sequence[float]], units='μm']) – Beat length \(l_c\).

  • propagation_length (Annotated[float | Sequence[float] | Sequence[Sequence[float]], units='μm'] | None) – Propagation length \(l_p\). If None, the value of interaction_length is used.

  • cross_phase (Annotated[float | Sequence[float] | Sequence[Sequence[float]], units='°']) – Cross-port phase shift \(\Delta\phi\).

  • insertion_loss (Annotated[complex | Sequence[complex] | Sequence[Sequence[complex]], units='dB']) – Insertion loss \(L_\text{dB}\).

  • isolation (complex | Sequence[complex] | Sequence[Sequence[complex]] | Interpolator) – Leakage (isolation) coefficient \(i\).

  • reflection (complex | Sequence[complex] | Sequence[Sequence[complex]] | Interpolator) – Reflection coefficient \(r\).

  • n_eff (complex | Sequence[complex] | Sequence[Sequence[complex]] | Interpolator) – Effective refractive index.

  • n_group (float | Sequence[float] | Sequence[Sequence[float]] | None) – Group index. If None, the value of n_eff is used.

  • reference_frequency (Annotated[float, minimum=0, units='Hz'] | None) – Reference frequency \(f_0\) for dispersion calculation. If None, the frequency average is used.

  • ports (Annotated[Sequence[str], maxItems=4, minItems=4] | None) – List of port names. If not set, the sorted list of port names from the component is used.

Notes

For multimode ports, a sequence of coefficients must be used, and mixed-mode coefficients are 0. Dispersion can be included in the model by setting the coefficients to an Interpolator (with multiple values for multimode ports), or a 2D array with shape (M, N), in which M is the number of modes, and N the length of the frequency sequence used in the S matrix computation.

Methods

black_box_component([port_spec, technology, ...])

Create a black-box component using this model for testing.

estimate_cost(*args, **kwargs)

Estimate the cost for S matrix computation.

s_matrix(component, frequencies[, ...])

Compute the S matrix for a component using this model.

setup_time_stepper(component, time_step[, ...])

Obtain a time stepper for a component using this model.

start(component, frequencies, **kwargs)

Start computing the S matrix response from a component.

update(*args, **kwargs)

Update this model.

Attributes

parametric_function

Function used to update a parametric component.

parametric_kwargs

Keyword arguments used to update a parametric component.

properties

Object properties.

random_variables

Random variables associated to this modles's parameters.

time_stepper

Time stepper associated with this model.
black_box_component(port_spec=None, technology=None, name=None)[source]

Create a black-box component using this model for testing.

Parameters:

  • port_spec (str | PortSpec | None) – Port specification used in the component. If None, look for "port_spec" in config.default_kwargs.

  • technology (Technology | None) – Component technology. If None, the default technology is used.

  • name (str | None) – Component name. If None a default is used.

Returns:

Component with ports and model.

Return type:

Component

start(component, frequencies, **kwargs)[source]

Start computing the S matrix response from a component.

Parameters:

  • component (Component) – Component from which to compute the S matrix.

  • frequencies (Sequence[float]) – Sequence of frequencies at which to perform the computation.

  • **kwargs (Any) – Unused.

Returns:

Model result with attributes status and s_matrix.

Return type:

SMatrix