Terry, Daniel, Nutsinee
Two weeks ago ISCT6 got craned over from the SQZ bay to HAM6 (alog40588). We hooked everything back up but was only able to check the alignment when the LVEA became laser Hazard on Thursday. Pretty much everything became misaligned, from small amount of misalignment into the SHG to catastrophic amount of misalignment into the fiber couplers. Below is a summary of the work we did to get the table back to the condition it once was.
SHG
Because we got rid of the extension cables the RF35 phase shifter needed some adjustment (now 193.88 deg) and a sign flip on the common mode board was required. I tweaked the alignment to get rid of a higher order mode. The mode matching is currently 98.6% (about as good as it gets). I took a transfer function to make sure that the UGF hasn't changed (~3kHz). We also took a measurement of shot noise, dark noise, and SHG length noise (weekend, when the LVEA is relatively quiet). These measurements will be posted in a different alog.
Alignment to fiber coupler
Alignment land is still work in progress. We got every thing back up to over 60% and 70% coupling efficiency as of Saturday. For a reference, this is what we were able to achieve before (alog40342) and should be able to get them back to at least the same efficiency given more time. The pump light now has 15.8mW coming out of the fiber. CLF has 10.2 mW coming out of the fiber (still a lot of room for improvement).
CLF AOMs
For a reference, this is what we used to have when the table was in the SQZ bay: alog40198.
We are now getting more RF power coming to the amplifier (extension cables were surprisingly lossy). The top RF amp that drives AOM1 used to not have any attenuator, now has 3dB attenuator at the input. RF power measured at the output to the AOM1 is now 34.29 dBm, or 2.68W. Maximum drive power allowed for this AOM is 2.9W.
The bottom RF amp that drives AOM2 used to have a 6dB attenuator, now has 10dB attenuator. RF power measured at the output to the AOM2 is now 32.83 dBm, or 1.9W (.2dBm less than what it used to be in the SQZ bay). Maximum drive power allowed for this AOM is 2.2W. Putting 9dB attenuator would have given 33.56 dBm (2.27 W) at the output. Which is slightly more than maximum drive power allowed.
AOM1 (IntraAction ATM-200) now has diffraction efficiency of 83%, AOM2 (AA Opto Electronic MT200) now has coupling efficiency of 69.7%.
Flippers
We found that CLF and Pump flipper wasn't working. We were able to open and close the shutter by hand which implies that these flippers were not getting any power. Turns out these DC plugs from Thorlabs are very dodgy. We unplugged the cables and plugged them back in that seems to solve our power issue.
Pump flipper still wasn't working then. It was not getting any signal from Beckhoff. Turns out the new cables from the EE shop we put in for I/O1 was bad (again, how? I have no clue). SQ_259-2 was removed then replaced with a temporary cable. I suspect these bad cables are acting like something of a high resistance. Which would explain the issue we once had with the cable at the output of an RF amplifier (the signal came out to be 30dB less than what it should be). But does that explain why we're not getting any DC signal to the flipper?
Motorized Rotation stages
All working fine.
Stray beams
We went around the table and hunt for any stray beams we could find. Several additional beam dumbs have been installed. There should be no stray beam higher than a milliwatt leaving the table at this point. In fact there should't be any stray beam leaving the table at all. Both red and green.
Nominal laser box settings
Current = 2.182 A
Crystal Temperature = 25.98 C
Diode Temperature = 20.22 C
