from finesse.components.general import Connector, InteractionType
from finesse.components.node import NodeDirection, NodeType
from finesse.exceptions import FinesseException
from finesse.parameter import float_parameter
from finesse.utilities import refractive_index
[docs]@float_parameter("fc", "Central frequency", units="Hz")
@float_parameter("bandwidth", "Bandpass bandwidth", units="Hz")
class OpticalBandpassFilter(Connector):
"""An idealised optical bandpass filter that will transmit an optical frequency
around some central frequency with a 3dB bandwidth.
Notes
-----
Currently this is a classical component. No quantum noise losses are applied to
any filtered fields or modes, which means no additional vaccum noise is injected
back into the system for this lost information.
Parameters
----------
name : str
Name of element
fc : float, symbol
Central frequency
bandwidth : float, symbol
Filter 3dB bandwidth
filter_hom : [tuple | None], optional
Individual higher order modes can be filtered and transmitted by setting this
to a tuple of (n, m). If ``None`` then no mode filtering is done. This cannot
be changed during a simulation.
"""
def __init__(self, name, fc=0, bandwidth=1000, filter_hom=None):
super().__init__(name)
self.fc = fc
self.bandwidth = bandwidth
self.filter_hom = filter_hom
self._add_port("p1", NodeType.OPTICAL)
self.p1._add_node("i", NodeDirection.INPUT)
self.p1._add_node("o", NodeDirection.OUTPUT)
self._add_port("p2", NodeType.OPTICAL)
self.p2._add_node("i", NodeDirection.INPUT)
self.p2._add_node("o", NodeDirection.OUTPUT)
# optic to optic couplings
self._register_node_coupling(
"P1i_P2o",
self.p1.i,
self.p2.o,
interaction_type=InteractionType.TRANSMISSION,
)
self._register_node_coupling(
"P2i_P1o",
self.p2.i,
self.p1.o,
interaction_type=InteractionType.TRANSMISSION,
)
def _get_workspace(self, sim):
from finesse.simulations.basematrix import CarrierSignalMatrixSimulation
if isinstance(sim, CarrierSignalMatrixSimulation):
_, is_changing = self._eval_parameters()
refill = (
sim.is_component_in_mismatch_couplings(self)
or len(is_changing)
or sim.carrier.any_frequencies_changing
or (sim.signal.any_frequencies_changing if sim.signal else False)
)
from .modal.optical_bandpass import (
optical_bandpass_carrier_fill,
optical_bandpass_signal_fill,
OpticalBandpassWorkspace,
)
hom_filter_index = None
if self.filter_hom is not None:
if sim.is_modal:
try:
hom_filter_index = sim.model.mode_index_map[
tuple(self.filter_hom)
]
except KeyError:
raise FinesseException(
f"No HG mode {self.filter_hom} was found in this model."
)
else:
hom_filter_index = 0 # planewave
ws = OpticalBandpassWorkspace(self, sim, hom_filter_index)
# This assumes that nr1/nr2 cannot change during a simulation
ws.nr1 = refractive_index(self.p1)
ws.nr2 = refractive_index(self.p2)
# TODO ddb refractive index should be equal on
# both sides of the lens as we are using the thin
# lens approximation
assert ws.nr1 == ws.nr2
ws.carrier.add_fill_function(optical_bandpass_carrier_fill, refill)
ws.signal.add_fill_function(optical_bandpass_signal_fill, refill)
if sim.is_modal:
# Set the coupling matrix information
# ABCDs are same in each direction
ws.set_knm_info(
"P1i_P2o",
nr_from=ws.nr1,
nr_to=ws.nr2,
is_transmission=True,
)
# TODO nr reversed here for now until it's forced to be same on both sides
ws.set_knm_info(
"P2i_P1o",
nr_from=ws.nr2,
nr_to=ws.nr1,
is_transmission=True,
)
return ws
else:
raise Exception(
f"Optical bandpass filter does not handle a simulation of type {sim}"
)