A back-formation from laser that lab people use constantly, both for a system that has crossed threshold and, in fiber and amplifier work, for unwanted lasing between stray reflections. Getting a new cavity to lase for the first time is a milestone in any build. Outside physics the word sounds odd, and machining people prefer to say a part is lasered or laser cut.
Finally got it to lase at 3 amps, faint and multimode, but now we can walk the mirrors and peak it up.
Parasitic lasing means the amplifier found its own cavity, often between a fiber end face and a flat surface, and it shows up as sharp spectral lines and erratic power.
Related terms
Lasing threshold
The pump level at which gain exactly balances resonator losses and laser output begins.
Resonator
The arrangement of mirrors that sends light back and forth through the gain medium to build up laser oscillation.
Peak up
To fine-tune alignment knobs while watching a power meter or signal until the reading reaches its maximum.
Walk the beam
To align a beam onto a path using two steering mirrors adjusted in turn against two targets or irises.