We fitted shutter and ringdown functions to the ringdown data. It is not perfectly clear how the power change due to the shutter is handed over to the power change due to ringdown. The fit suggests that the ringdown starts at a later time, but this does not necessarily make sense. It could be that the slow power decrease when the shutter starts clipping the TEM00 beam is followed by the cavity, but then the power decrease becomes too fast when the shutter reaches the optical axis and the ringdown takes over. Also, the next measurement should be taken with adjusted DC offset.