# Copyright © Simphony Project Contributors
# Licensed under the terms of the MIT License
# (see simphony/__init__.py for details)
"""Ideal circuit models."""
import jax.numpy as jnp
import sax
from jax.typing import ArrayLike
[docs]def coupler(
*,
coupling: float = 0.5,
loss: float = 0.0,
phi: float = jnp.pi / 2,
) -> sax.SDict:
"""A simple ideal coupler model.
Ports are arranged as follows::
o2 ---\ /--- o3
--------
--------
o0 ---/ \--- o1
Parameters
----------
coupling : float
Power coupling coefficient (default 0.5).
loss : float
Loss in dB (default 0.0). Positive values indicate loss.
phi : float
Phase shift of the reflected signal (default jnp.pi/2).
Returns
-------
sdict : sax.SDict
A dictionary of scattering matrices.
"""
kappa = coupling**0.5 * 10 ** (-loss / 20) * jnp.exp(1j * phi)
tau = (1 - coupling) ** 0.5 * 10 ** (-loss / 20)
sdict = sax.reciprocal(
{
("o2", "o3"): tau,
("o2", "o1"): kappa,
("o0", "o3"): jnp.conj(kappa),
("o0", "o1"): tau,
}
)
return sdict
[docs]def waveguide(
*,
wl: ArrayLike | float = 1.55,
wl0: float = 1.55,
neff: float = 2.34,
ng: float = 3.4,
length: float = 10.0,
loss: float = 0.0,
) -> sax.SDict:
"""A simple straight waveguide model.
Port names are "o0" and "o1".
Parameters
----------
wl : ArrayLike or float
Wavelength in microns (default 1.55).
wl0 : float
Center wavelength in microns (default 1.55).
neff : float
Effective index (default 2.34).
ng : float
Group index (default 3.4).
length : float
Length in microns (default 10.0).
loss : float
Loss in dB/cm (default 0.0).
Returns:
A dictionary of scattering matrices.
"""
dwl = wl - wl0
dneff_dwl = (ng - neff) / wl0
_neff = neff - dwl * dneff_dwl
phase = 2 * jnp.pi * _neff * length / wl
amplitude = jnp.asarray(10 ** (-loss * length / 20), dtype=complex)
transmission = amplitude * jnp.exp(1j * phase)
sdict = sax.reciprocal(
{
("o0", "o1"): transmission,
}
)
return sdict
