An absorber that bleaches when intense light depletes its ground state, letting strong peaks through while still absorbing weaker light. In a cavity this favors pulses over continuous operation with no electronics. Cr:YAG crystals passively Q-switch Nd lasers; semiconductor saturable absorber mirrors, SESAMs, mode-lock many solid-state and fiber lasers. Recovery time and modulation depth decide which pulse regime it supports.
SESAM's got a burn spot, translate it half a millimeter to fresh area and the laser should self-start again.
Also heard as
- bleachable absorber
Related terms
Mode locking
Fixing the phases of many longitudinal modes so they add up into a train of ultrashort pulses.
Q-switching
Producing short, intense laser pulses by holding cavity losses high while energy builds up, then suddenly dropping them.
Lock
The stable locked state of a laser, either mode-locked pulsing or frequency-locked to a reference.
Damage threshold
The maximum fluence or power density an optic can take before it is permanently damaged.