This weekend I remounted the first calcite polarizer (CWP1) and re-optimized the extinction ratio of the system at low power.
The beam was initially not centered on the calcite polarizers (off-centered horizontally by ~3-4 mm on each in opposite directions). I released the posts holding the breadboard and rotated the breadboard CCW to center horizontally on both calcites. This misalignment probably happened when the granite block was moved to make room for the beam profile measurements.
I also centered the beam vertically inside the isolator (optics and magnet), but the beam is no longer centered on the two input/output irises, indicating that the breadboard is NOT parallel to the table, but sloped upward. I will check the sloping again on Monday.
At 2.2 mW power, the extinction of the first calcite polarizer was 56.43 dB.
Extinction measurements after CWP2:
|
Power s+p (mW) |
Power s-pol (uW) |
Extinction (dB) |
POWER TRAN (W) |
|
|
3.2 |
0.002 |
62.04 |
10.8 |
|
|
16.4 |
0.111 |
51.70 |
10.8 |
|
|
104 |
0.686 |
51.81 |
10.3 |
|
|
103 |
0.205 |
57.01 |
10.3 |
after finelly adjusting CWP2 pitch / yaw |
|
268 |
0.530 |
57.04 |
10.3 |
|
|
505 |
0.480 |
60.22 |
10.3 |
|
|
504 |
0.473 |
60.28 |
10.3 |
after finelly adjusting CWP2 pitch / yaw |
This should be checked at higher powers also.