Remarks about spectrum of bad-cavity laser

Technical notes.
"Spectrum via filter cavity and two-time correlation.pdf" describes correspondence between spectrum of a laser defined via filter cavities (as in https://doi.org/10.1103/PhysRevA.98.063837 ) and two-time correlation function of the cavity field.

"Stability of heterodyne phase locking" contain hand-written derivation about ultimate stability of a laser phase locked to some weak but high-stable master laser. Instability is connected with shot noise of the the photons emitted by the master laser.