Polhe3 optics

Optical Alignment

Yi and Xiaohui have a write-up here

Here is how it's done in a nut shell.

• use "cross laser aligner" to do initial alignment of the cube and mirrors,
• then use laser in low power mode (maybe 5-10na) to do fine tuning by looking at the spots on the mirror close to target. * Try to focus on aligning the main light spot, not many of the weaker reflections.
• Put the cell in and record the exact position of cell by drawing its shadow on a paper. then take the cell out and put the paper on, then fine tuning the mirrors to make the spots align with the cell shadow mark.
• check and make sure the reflection from the left line not going to laser fiber directly, try to guide it on side by adjusting mirrors to avoid burning the coating on the fiber ends. double check the alignment on cell as this could have affect that due to mirror adjustment.

• The light should going to the one side of the split cube. The right side has a dot on the corner.

Quarter waver plates calibration

The configuration is laser (light has no pol)-> split cube #1 (linear pol)-> quarter wave plate #1 (circular pol)-> quarter wave plate #2 (linear pol in another direction)-> split cube #2 (light deflected)-> light intensity detector.

quarter wave plate #1 need to be calibrated ahead, then adjust the #2 to have lowest light output so that wave plate #2 is calibrated well.

(copy the record on notebook here)

3/15/2010
COMET LASER (JLAB #1)
half power - 12.2 W
I=30A T=20C

1/4-Wave Plate	Angle	Residual Power
#101	286°	Reference
#102	214°	272 mW
#19	127°	256 mW
#16	330°	185 mW
#21	240°	165 mW
#2	76°	55 mW
#25	120°	164 mW
#20	225°	114 mW

Also #17 and #7 are identified as half wave plates.