First steps in Characterizing Dark counts and Efficiencies for SNSPD's

I have been working in Maria's Lab with Boris and Andrew to get familiar and create updates for the new machines they have for measuring SNSPD characteristics.

Here are the details of our work so far and the first measurements we have done on the currently loaded SNSPD's.

 

Basic set of procedures:

First calibrating the fibers loss must be done Unplug from the SNSPD DIFF-2/3 fiber port

    Use:

          Python PhotonRateYokogawa.py -CAL

Then perform the fiber switches as directed in the code Follow on screen instructions to swap between fibers 3+ times Add the new "cfactor" variable to the yaml file (PhotonRate.yml) under "cfactor" Plug the cable back into the DIFF-2/3 fiber port To set a photon rate using the script

    Use:

         Python PhotonRateYokogawa.py -P

For PCR Measurements: Use PCR Yaml to setup the start and end bias ramp values Use the KEYSIGHT_55320A.yaml to setup the ramping threshold values Use the IsolatedVSourceServer.yaml to setup the diff output being used Set the min and max bias current levels and threshold levels in the yaml's by manually adjusting the bias current while checking the spikes on an oscilascope

     Once all setup Use:

        Python pcrCurveVarint.py

This will allow us to run the ramping threshold levels for the photon counter For Dark Count Measurements Keep almost all variables the same but we will take out the fiber for the laser and cap the SNSPD port, then we will increase the integration time for each bias voltage step Run the same code: Python pcrCurveVarint.py

Code for running these scripts will soon be uploaded to the gitlab as we finalize our changes.

 

Attachment 1: raw plots for readout from DIFF2 and DIFF3 for photon counts.

Attachment 2: Dark Count plot for DIFF2 and DIFF3 (port is covered with a cap)

Attachment 3: Efficiency plot (difference of counts - dark counts divided by total photon input)

Attachment 4: SNSPD pulse response from oscilloscope. Red line is the threshold used for triggering a count on the counter.

 

Next Steps:

1. Calculating uncertainties and measuring uncertainties for the new system (power meter, laser, attenuators and optical switch).

2. Redo the plots and add the uncertainties to the data.

3. Place GQuEST SNSPD into dark box and cryostat and take Dark Counts measurement

4. Characterize efficiency of the GQuEST SNSPD