finesse.analysis.actions.lti.FrequencyResponse4

Overview

class finesse.analysis.actions.lti.FrequencyResponse4(f, inputs, outputs, *, name='frequency_response4')[source]

Bases: Action

Computes the frequency response of a signal injected at an electrical or mechanical port. This differs from FrequencyResponse in the way the inputs and outputs are prescribed. For FrequencyResponse4 you specify signal input nodes and optical output nodes.

This action does not alter the model state. This action will ignore any currently defined signal generator elements in the model.

Produces an output transfer matrix from each signal node to each HOM at a particular frequency and optical node. The shape of the output matrix is:

[frequencies, outputs, inputs, HOMs]

It should be noted that when exciting a lower signal sideband frequency it will actually return the operator for propagating the conjugate of the lower sideband. This is because FINESSE is internally solving for the conjugate of the lower sideband to linearise non-linear optical effects.

To inject into optical nodes please see FrequencyResponse2 and FrequencyResponse3. To readout mechanical and electrical nodes please see FrequencyResponse and FrequencyResponse2.

Parameters
farray, double

Frequencies to compute the transfer functions over

inputsiterable[str or Element]

Mechanical or electrical node to inject signal at

outputsiterable[tuple[str or Node, Frequency]]

Optical node and frequency tuple to measure output at. A symbolic reference to the model’s fsig.f parameter should always be used when defining a frequency to look at.

namestr, optional

Solution name

Examples

It is advisable to use always use a reference to the symbolic reference to the signal frequency model.fsig.f.ref instead of a fixed number incase it changes. This action will look for an initial frequency bin of X Hz to track during the frequency response analysis. A symbolic reference will always ensure the right bin is used, in cases such as looking at RF signal sidebands, 10e6+model.fsig.f.ref and 10e6-model.fsig.f.ref will always look at the upper and lower signal sideband around the +10MHz sideband.

>>> sol = model.run(
...     FrequencyResponse(
...         [1, 10, 100],
...         [model.ETM.mech.z],
...         [
...             (model.ITM.p2.o, +model.fsig.f.ref),
...             (model.ITM.p2.o, -model.fsig.f.ref)
...         ]
...     )
... )