tesla500 | HP 5518A Interferometry Laser head @tesla500 | Uploaded December 2015 | Updated October 2024, 23 hours ago.
A look at a HP(/Agilent/Keysight) Interferometry laser head, a partial teardown and some info on interferometry applications and operation of Zeeman split lasers.

Links to relevant sections of Sam's Laser FAQ

Sam's Laser FAQ:
repairfaq.org/sam/laserfaq.htm

General Overview of HP Interferometry Lasers:
repairfaq.org/sam/laserhst.htm#hstgohp

HP/Agilent Laser Principles of Operation:
repairfaq.org/sam/laserhst.htm#hsthppoo

Explanation of Axial Zeeman HeNe Laser Behavior
repairfaq.org/sam/laserhst.htm#hstsazlb

PIC32 based measurement display:
http://repairfaq.cis.upenn.edu/Misc/uMD1/#umd1twi