Correct relationships of ultrafst probe

[kara-mela]

While working on #479, we realized that there is something wrong with ultrafast probe.

Proposed Definition

ultrafast refers to duration of pulses not frequencies

Status

• ultrafast probe-based techniques is subclass of defined by experimental probe
• ultrafast probe is subclass of pulsed probe
• pulsed probe is subclass defined by beam characteristic

ultrafast should only have relations to beam characteristics, but not to probe.

Suggestion

• ultrafast probe-based techniques is subclass of defined by beam characteristic