[Daniel, Torrey]
Talking with Sander this morning he pointed out that the amount of power on the 1550 camera from both beams should be approximately the same. Attached pics with the camera show that while locked on 775 and attenuating 1550 light, and blocking the 1550 beam, the majority of light is 775 leaking through. This was done for 2.2 mW input power for 1550. I have increased the power to 15.7 mW input for 1550 so that the amount of leakage of 775 through the mirror will be negligible.
Below are a brief description of each image.
- "1550 blocked low power mode" and "both beams low power mode" are 2 mW input power, unknown exposure time (these are looking for 775 leakage, which they do)
- "lowpower-increased input.bmp" is 15.7 mW input power with an exposure time of 29859 us, gain = 0db.
- "highpower - increased input.bmp" is 15.7mW input power with an exposure time of 16 us, gain = 0db.
- "1550 blocked lowpower-increased input.bmp" is 15.7 mW input power with exposure time of 26163 us, gain = 0db; 1550 blocked
- "highpower - increased input ND 2 filter" is 15.7mW input power with an exposure time of 70 us, gain = 0db; ND 2 filter applied in front of camera (used so that we can fit Gaussian to high power beam without a saturated image)
With these measurements and this script I'm getting 8 * 10^4 suppression. I think the low power measurement method needs to be improved for this to be reliable.
The thorlabs NENIR20A-C 2.0 ND filter is actually rated for 1.91 @ 1550 nm. This adjusts it to 7 * 10 ^ 4 suppression. This also makes the two methods of fitting a saturated Gaussian and fitted a Gaussian to the filtered beam very consistant.
Accounting for the 775 light that is leaking through the 1550 HR mirror I am getting closer to 3 * 10^5 suppression of the 1550 light. This is a very rough subtraction method. I am going to increase the power to the 1550 path as much as possible now that I have a clean ND filter and the saturation method working so that the amount of 775 light will be negligible. at 15.7 mW input it is not.
-1550 increased to 57 mW input. Only increase to be gained from here is amplifier pump current.
-Redo high and low power transmission pictures.
- low exposure time - 12649 us
- high exposure time - 16 us
-Additionally i've set up a flip mount with an ND filter on the 1550 camera path. Please refer to 11370 on how to controll them. The physical button is on the bottom left corner of the breadboard.
These values above yield ~2 * 10^5 suppression.