enter Mon Jan 25 13:02:47 2021
cantilever Q materials
I moved the following materials to measure cantilever Qs from cryo lab to QIL. The are located in bins labelled 'cantilever Q' in a cabinet on the S wall of the QIL lab (see photos).
- cantilevers
- HeNe laser and power
- QPD from the GeNS setup, and power
- What I think are the clamps Zach was using for cantilever Q measurements.
I also identified in QIL the IR labs cryostat that was used for cantilever Qs, and is now set up for PD measurements. I tried lifting out the cold plate, but felt resistance while opening and stopped. Probably the electrical connections are keeping the cold plate in place, and I would like to check with the user of this cryostat before proceeding.
three corner hat
I am recording spectra of the beat note between three lasers: PSOMA north laser, PSOMA south laser, and cryo cavities East laser. I unplugged the E laser from its fiber-to-free launch (after Faraday isolator), and instead send it to the PSOMA table by fiber. Without changing settings on the cryo cavs TEC or laser driver, the E laser is 8.1 mW when it reaches PSOMA table. When measuring the beat note between the cryo cavs E laser and PSOMA north (south) laser, I send the E laser through the south (north) 90-10 pickoff BS in place of the PSOMA laser. Before recording spectra, I tune the current of the PSOMA N and S lasers until all beat notes are < 20 MHz (there is a few MHz drift during the measurements).
Summary of the measurements, all taken at the FC 1611 (AC measurements on the Moku):
- acquisition speed: 125 kHz
- phaselock bandwidth: 10 kHz
- coupling: AC, 50 Ohm
- Moku input range: 1 Vpp
- Measurement time: 1 m 40 s
- freewheeling: yes
| Pair of lasers |
DC intensity mon (mW) |
beat note power (dBm) |
beat frequency (MHz) |
| PSOMA north and south |
6.0 |
3 |
18 |
| PSOMA north, cryo cavs east |
4.3 |
-1 |
24 |
| PSOMA south, cryo cavs east |
3.5 |
-2 |
5 |
I notice that the FC 1611 has a UPC connector on its face... but the rest of our components have APC connectors. I'll watch out for effects from this, and order an adapting fiber. I also see sidebands at the harmonics of the beat note when the note is > 0 dBm (linear regime of 1611 is only 1mW).
The rate-limiting step is transferring data from Moku RAM to the ipad over the Wifi... should set up the Moku on ethernet, and check out ctn-scripts for automating the process.
exit Mon Jan 25 16:10:59 2021 |