Adjustable Laser Beam Splitter with Dual Polarization-Maintaining Fiber-Couplers

Description

This assembly takes the beam from a 633 nm HeNe or other similar red laser, splits it 50:50, passes the resulting beams through Half WavePlates on rotation mounts, and couples them into separate single mode polarization-maintaining fibers on FC connectors.  It will mount directly on the output bezel of most 1.75" diameter cylindrical HeNe laser heads but can be easily adapted to other laser configurations.  The internal components are as follows:
1 5x5x5 mm Non-Polarizing Beam-Splitter cube.
1 Thorlabs FT-51X60-Multi-Axis FiberBench, 51x60 mm, 4 Ports, 16 Position.
2 OZ Optics HPUC-23AF-633-P-3.9AS-15 633 nm Fiber Couplers with FC connectors.
2 Thorlabs FBR FiberBench Rotation Mounts for Ø1/2" Optics with Half WavePlates.  One is secured with a FiberBench screw; the other needs to be glued.
1 HeNe 4 hole adapter plate (input side of case).
2 Mounting plates for the fiber couplers.
1 Blank side plate and cover (not shown).
This is in absolutely perfect condition except for one issue:
T
here
is a small spot inside the NPBS which may be in the beam path, though it didn't seem to affect either output
.
(How a <2 mW laser could damage the coating is not clear.)  If you buy the unit and that matters to you, I will reposition it so that the spot is safely out of the beam path.
Regardless, some adjustment will be necessary to tweak the coupling and polarization alignment.
The fiber couplers are fully adjustable and the NPBS cube can be rotated around its vertical axis and tilted.  Together, these provide all the degrees of freedom needed.
While intended for polarization-maintaining fiber, it should be possible to use other SM or MM fiber with FC connectors.
It can also be reconfigured or a PBS can be substituted for the NPBS (I can provide one) to separate the orthogonal modes of a typical random polarized HeNe laser.  And a different split ratio than 50:50 could be implemented.
Tested and guaranteed functional except as noted, but some adjustment required.  This hardware costs well over ,000 if purchased from Thorlabs and OZ Optics.
Thanks for looking,
--- sam