Alex and Daniel

We checked a Noliac NAC2125-H08 for shorts and found none. We measured the capacitance to be 2.4641 uF. The expected capacitance is 2.4 uF. We also measured a resistance of 3.5082 kOhm. When we pressed on the piezo, we noticed a voltage. We flagged one of the wires for polairty. See attached photos. We also noticed that the nylon tipped set screws that hold the piezo in place provide a voltage.

Boris has succesfully mounted in the SNSPD that we have been wokring on putting together. The SNSPD is in the ICE cryo chamber in Downs 123, and we will soon begin our testing of the PCR curves and dark count rate tests. See images for a close up view of the mounted SNSPD. 

I have now succesfully done some first tests on the 75V regulator circuit, first piece of the 5V reference circuit, and the Bias voltage circuit (5V reg >> 70, 65, 60, 50 volts). I have been experiencing some issues getting the +-5V clean references to work as well as the +-15V linear regulators, but this should all be fixed in the coming week! See the attatched images for the bias voltage outputs (check out my 3 power supplies haha).

I should be able to soon test the APD next week then begin developing the first PCB for the APD. 

I used to the Moku:Pro laser lockbox to maintain the small Michelson IFO in B102 at an ajustable point on the fringe. The Moku input is a photodiode signal at the output, and the Moku output goes to the piezo controller's external input, which in turn drives a ring piezo on one of the end mirrors. 

On the attached photos you see the Moku setup, photodiode signal (red), error signal (blue), and scanning signal (green) used to acquire the lock. The second photo shows the system in lock. I have not optimised the control loop, so it is not very robust. Next step will be to measure transfer functions for the piezo actuator.

Retook beam profile coming out of SHG with everything in place. SHG Profile data can be found at Nextcloud/GQuEST/B102/SHG/SHG\ Beam\ 20Profile/SHG_Profile.ipynb. Will use this to match to the fiber inputs at the end of the SHG farm. All 4 paths on the SHG farm should be within an inch of each other so 1 MM solution before the first 50:50 should be sufficient. Will also post a solution for the two lens on either side of the AOM.

[Sander, Ian, and Daniel]

The three of us set up a Michelson Interferometer to test the Noliac NAC2125-H08 (Ring Piezo) with 1550 nm laser light. See attached photo. The alignment was optimized to maximize the contrast.

The piezo is rated for 200 V and the MDT693B (Thorlabs Open-Loop Piezo Controllers) is rated for 150 V, but we decided to linearly sweep the data from 0 V to 150 V over 20 s. We saw the interferometer go through 8 fringes, exactly what we expect.

Free stroke = 12.6 μm , so there is a length change of 63 nm/V. Applying 100 V gives 6300 nm. A fringe is every 775 nm (the path length changes 2x the piezo change). Fringes = length change / (length/fringe) = 8.1 fringes, pretty much exactly what we observe. See attached graph and data.

[Torrey, Sander]

As described in entry 11348, the SHG was found to be producing much less 775 nm light than the SHG spec sheet predicts. We put a half-waveplate in front of the input fibre coupler upstream of the SHG to test the polarisation dependence of the SHG's output power. We found a strong dependence; we optimised the waveplace orientation and found SHG output powers at or slightly above spec.  

We tried to rotate the fibre in the collimator mount to try to send the optimal polarisation to the SHG, but this optimisation process was very laborious and not very succesful (as the fibre collimator mounting is quite finicky), so we decided to leave the half-waveplate in place. 

I put one Newport Dielectric Mirror, Laser Line, 25.4 mm, λ/10, 1520-1580 nm (10D20DM.8) each in the crusher and piezo bowtie subassemblies. The piezo subassembly also has a Clean Room Viton Fluoroelastomer O-Rings, Chemical-Resistant, 1/16 Fractional Width, Dash Number 020, 1309N22, from McMaster. After compressing the piezo and the o-ring by threading in the SM1 ring, I backed off the screws that hold the piezo.

The subassemblies themselves are mounted to test. I set up a Michelson Interferometer to test the piezo. The piezo leads are connected to a BNC, with the positive lead in the center of the BNC and the negative lead to ground. A Thorlabs MDT693B - 3-Channel, Open-Loop Piezo Controller is also ready to be used. The output port of the Michelson is a 1550 nm photodiode.

The crusher is mounted on a bowtie cavity and the beam profiler is ready to be used there.

Right now, I am waititng on a Thorlabs order I placed today to get fiber outputs mounted into SM1 rings.

I have dissasembled the axetris - EMIRS50 AT06V BR25M thermal source such that the reflective can was desoldered. Next, to properly mount the thermal source into the previously described lens tube assembly (11334) the thermal source was soldered onto a brass washer using thermal paste and the PCB oven. The end results are shown bellow in attachments 1-3. The parts for the assembly will be here on monday to be machined and assembled.

The source was placed as closely to the center of the washer as possible, but a custom washer may need to be designed such that minimum alignment is needed when assembling the fiber coulped device. 

The SNSPD will undergo a PCR test and be placed in the fridge monday as well. 

While cleaning the Newport AJS254-0.5K-NL Adjustment Screw, I sonicated three Newport AJS254-0.5K-NL Adjustment Screws in isopropyl alcohol at 30°C for 20 minutes. When I came back, I discovered the tip had dissolved. I thought the tip was stainless steal like the body, but it might not be. I reached out to Newport for clarification. If the crusher does work (we at least one screw on hand), we will need 3 more replacements.

[Daniel Torrey]

One of the low power paths in the power distribution center (See "C:\Users\gques\Nextcloud\GQuEST\Layout_Mockups\B102_starting_setup_pwr_dist.svg" for updated layout) is aligned with 84% efficiency through the fiber. We have light available for readout filter cavity science.

[Daniel Torrey]

Profiled the output of the SHG, data for which can be found at Nextcloud/GQuEST/B102/SHG/SHG Beam Profile/ .See attached. Note the output for the SHG fiber has a collimator, very easy to change the beam profile.

Set current to 2.3 amps. This corresponds to 3.96 W out of the amplifier. The beam goes through a PBS, 50:50, 90:10, and PBS. The waveplates before the PBS can be optimized to give <1% loss in the S pol. Assuming minimal loss at the 50:50 and 90:10 this gives 1.75 W into the fiber. With 85% efficiency through the fiber my best guess is we have ~1.48W going into the SHG. The readout on the power meter shows 38 mW. This can be adjusted by the ratios in responsivities of the power meter at 775 and 830 so 38mW * 207.1/146.77 = 54 mW of 775 nm light. If we believe the covesion data sheet it predicts ~350 mW for similiar inputs. Could our SHG be that much more inefficient? Based on the power we ARE getting out of the SHG, according to the data sheet, you would think were feeding in approximately 500 mW, which I don't think is the case. Don't want to stick the power meter in there though.

2.3 A on the amplifier was the previously calculated acceptable operating point to not damage the faraday isolator at the amplifier output. I'm assuming 50 mW of 775 nm light is not sufficient for all of gquest, although I don't have a good sense for this number.

https://wiki.mccullerlab.com/Main/NoliacPiezoInfo

SHG and temperature controller turned on and we are seeing 775 nm light (probably). Couple of things:

1) The thorlabs power meter doesn't have a 775 nm light calibration, if we want to detect 775 we may want to find another power meter. The closest it has is 830 nm. 

2) SHG temp controller takes ~350 seconds to stablize to within .005 of a degree. Set it to 50.461 C for maximum 775 effeciency.

3)The SHG cavity it wildly inefficient at low input powers, it produces 38.5 uW of 775 with an input of 28 mW (.13% effeciency, also for the record 4 uW measured at 1550 as well). I ramped the current on the amplifier to 1A. This corresponds to an input power of 93 mW which yields an output of 150uW (.16% effeciency). The SHG has been assigned the serial number S2300012, see that link for specs and manual for this which has an efficiency curve as a function of input power. Similarly for the temperature controller S2300013.

We also need a more permanent way to mount it to a breadboard if anyone wants to 3D print something for it.

[Torrey Daniel]

Began initial set up of the power distribution center. We have all the parts according to the diagram. Things are roughly aligned up until the first 50:50 BS. Will do alignment into input fiber couplers tomorrow. Torrey will attach photos and diagrams in a comment on this post.

We also put all of the laser initialization on one breadboard. This includes the seeder, polarization paddles, fiber PBS, and amplifier. The amplifier output is mounted on the power distribution center.