finesse.analysis.actions.pseudolock.PseudoLockDRFPMI

Overview

class finesse.analysis.actions.pseudolock.PseudoLockDRFPMI(frequency=0, *, apply_tunings=True, name='operator_lock')

Bases: Action

Pseudo-locking is attempting to find an operating point for a LIGO like model without needing to use RF sidebands and readouts. Although it is not physically accurate it does provide a useful tool for analysing detectors from a more theoretical basis. This generates a PseudoLockDRFPMISolution solution containing various operators and results.

This action is hardcoded to work with a LIGO like model. Mirrors should be named with ITMX, ETMX, PRM, etc.

This currently action only really works for finding the lock points for the PRC, SRC, XARM, and YARM – which all have defined cavity roundtrips which allow eigendecomposition of roundtrip operators. The eigenvectors describe the HOM mix for each resonant mode in a cavity and the eigenvalues the roundtrip phase and loss of the mode. This code looks for eigenvectors with the largest HG00 content and then uses the eigenvalues to compute what cavity tunings need to make this mode resonant.

The corner is the most complicated here as the PRC and SRC are coupled via the beamsplitter. The eigendecomposition is performed on the 2x2 operator matrix for the PRC, SRC, and the coupling matrices between them. When the coupling is small the results are the same as performing the decomposition on each SRC and PRC separately.

Note that the only degree of freedom that this does not handle currently is MICH. MICH is awkward because it is not a cavity. It is essentially the beamsplitter position that makes the anti-symmetric port dark.

Parameters

frequencyfloat, optional

Frequency to use for calculating the operators

apply_tuningsbool, optional

When True the action will modify the model tunings

namestr, optional

Name of the solution generated by this action