finesse.exceptions.LostLock

Overview

class finesse.exceptions.LostLock(message, **kwargs)[source]

Bases: FinesseException

Thrown when the lock is lost by the locking algorithm. This is typically an issue of:

  • the error signal has been lost (no longer linear, rotated into a different quadrature

  • The error signal slope has become too small (need more lock gain) or too large (need less lock gain)

  • multiple locks are competing and dragging the interferometer to an unstable state.

In such cases you can run the lock action with the flag exception_on_fail=False to ensure it returns a finesse.analysis.actions.locks.RunLocksSolution. This solution can then be used to diagnose the issue, plot_error_signals and plot_control_signals are useful for this to see which error signals are causing an issue.