Two mirrors on a vertical post, the lower one sending the beam up or down and the upper one sending it back horizontal at the new height. Used when equipment on the table has different beam heights. If the upper mirror also turns the beam 90 degrees sideways, the polarization rotates by 90 degrees, a feature when it is wanted and a puzzle when it is not.
Amplifier input is 30 mm higher than the seed, build a periscope and check the polarization after it.
Related terms
Walk the beam
To align a beam onto a path using two steering mirrors adjusted in turn against two targets or irises.
Waveplate
A birefringent plate that shifts the phase between two polarization components to rotate or convert polarization.
Kinematic mount
An adjustable optic holder that uses three-point contact and fine screws to set tip and tilt repeatably.
Breadboard
A rigid, flat plate drilled with a grid of threaded holes on which optics are mounted, smaller than a full optical table.