In an unstable or overpumped mode-locked laser, some intracavity power lases as a continuous wave alongside the pulses. On a spectrometer it appears as a sharp line on top of the smooth pulse spectrum, and on a fast photodiode as a raised baseline. It wastes power, adds noise and often precedes loss of mode locking, so operators adjust pump power or cavity alignment until it disappears.
There's CW breakthrough at 812 on the spectrometer, tweak the prism insertion before you hand the beam to the users.
Also heard as
- CW spike
Related terms
Mode locking
Fixing the phases of many longitudinal modes so they add up into a train of ultrashort pulses.
Lock
The stable locked state of a laser, either mode-locked pulsing or frequency-locked to a reference.
Kick
To start a Kerr-lens mode-locked laser by briefly disturbing the cavity so a pulse can form.
CW
Continuous Wave: laser operation with a steady output beam rather than pulses.
Double pulsing
A fault where a pulsed laser emits two pulses where it should emit one, from too much gain or bad switch timing.