Amplified spontaneous emission (ASE) and parasitic oscillations (PO) in disk lasers with unstable resonators
are investigated theoretically. The efficiency loss due to ASE/PO is essentially determined by the product of
disk diameter D and "self-maintain gain" of ASE/PO. Threshold to establish the laser oscillations in presence
of ASE/PO is explored as the self-maintain gain of ASE/PO is higher than threshold gain gt of the resonator.
The criterion to ignore ASE/PO in disk laser is given by gtD < 2.0 as an ASE absorber is clad, gtD < 0.55 as
the disk side is roughened, and gtD <0.8 as the effective ASE path is half reduced. The time evolution of laser
output exhibits a strenuous relaxation oscillation, in which ASE plays a role of strong damping, and consume
the energy before each of sub-pulses.
"Amplified spontaneous emission in thin-disk lasers", Proc. SPIE 8235, Solid State Lasers XXI: Technology and Devices, 82351Q (15 February 2012); doi: 10.1117/12.906358; https://doi.org/10.1117/12.906358