The basic alignment technique with two mirrors and two irises along the desired path. Use the first mirror to center the beam on the near iris, then the second mirror to center it on the far iris, and repeat; done in that order the error shrinks each pass. Walking the beam also means deliberately stepping both mirrors together to translate the beam sideways while keeping its angle, for example to peak up fiber coupling.
Walk the beam through both irises again, the cavity won't lase if you're even a millimeter off at the far one.
If each pass makes the error worse, you are using the mirrors in the wrong order: the upstream mirror goes with the near iris.
Also heard as
- beam walking
- walking the mirrors
Related terms
Peak up
To fine-tune alignment knobs while watching a power meter or signal until the reading reaches its maximum.
Kinematic mount
An adjustable optic holder that uses three-point contact and fine screws to set tip and tilt repeatably.
IR card
A small card coated with phosphor that glows visibly where an invisible infrared beam hits it, used for alignment.
Periscope
A pair of stacked mirrors that changes a laser beam's height above the table, and optionally rotates its polarization.