40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  40m Log  Not logged in ELOG logo
Entry  Wed Dec 11 15:01:57 2019, Jon, Summary, PSL, PMC cavity ringdown measurement IMG_0101.jpg
    Reply  Thu Dec 12 19:20:43 2019, Yehonathan, Update, PSL, PMC cavity ringdown measurement IMG_0105.jpegTEK00001.PNG20191212_151642.jpg
       Reply  Fri Dec 13 12:28:43 2019, Yehonathan, Update, PSL, PMC cavity ringdown measurement Ringdown_InitialProcess.pdf
          Reply  Tue Dec 17 20:45:30 2019, rana, Update, PSL, PMC cavity ringdown measurement 
          Reply  Fri Dec 27 15:01:02 2019, Yehonathan, Update, PSL, PMC cavity ringdown measurement PDAOMResponse.pdfPMCTransmission.pdfRingdownsAndRefs.pdfTwoExponentialFitAOM0.3V.pdf
             Reply  Tue Dec 31 03:03:02 2019, gautam, Update, PSL, PMC cavity ringdown measurement 
       Reply  Mon Dec 16 18:19:42 2019, shruti, Update, PSL, PMC cavity ringdown measurement : beat-note disruption IMG_0040.jpg
Message ID: 15105     Entry time: Fri Dec 27 15:01:02 2019     In reply to: 15097     Reply to this: 15107
Author: Yehonathan 
Type: Update 
Category: PSL 
Subject: PMC cavity ringdown measurement 

I measured PMC ringdowns for several input powers. I change the input power by changing the DC voltage to the AOM.

First, I raise the DC voltage to the AOM from 0V and observe the signal on the picked off PD. I see that at around 0.6V the signal stops rising. The signal on the PD is around 4V at that point so it is not saturated.

Up until now, we provided 1.5V to the AOM, which means it was saturated.

I measured ringdowns at AOM voltages of 0.05, 0.1, 0.3, 0.5, 1 volt by shutting off the DC voltage to the AOM and measuring the signal at the PMC transmission PD and the picked off PD simultaneously for reference.

Attachment 1 shows the reference measurement for different AOM voltages. For low AOM DC voltages, the response of the AOM+PD is slower.

Attachment 2 shows the PMC transmission PD measurements which barely change as a function of AOM voltage but shows the same trend. I believe that if the AOM+PD response was much faster there would be no observable difference between those measurements.

Attachment 3 shows PMC transmissions and references for AOM voltages 0.05V and 1V. It seems like for low AOM voltages we are barely fast enough to measure the PMC ringdown.

I fitted the 0.3V ringdown and reference to a sum of two exponentials (Attachment 4).

The fitting function is explicitly a * nm.exp(-x/b) +c* nm.exp(-x/d) +e

For the PMC transmission I get:

a = 0.21
b = 3.64 (us)
c = 0.69, 
d = 39.62 (us)
e = 2.0e-04

For the reference measurement:

a = 0.34
b = 4.97 (us)
c = 0.58
d= 31.22 (us)
e = 1.11e-03

I am still not able to do deconvolution of the ref from the measurement reliably. I think we should do a network analyzer measurement.

Shruti, the PD is again in your beam path.

Attachment 1: PDAOMResponse.pdf  69 kB  | Hide | Hide all | Show all
PDAOMResponse.pdf
Attachment 2: PMCTransmission.pdf  103 kB  | Hide | Hide all | Show all
PMCTransmission.pdf
Attachment 3: RingdownsAndRefs.pdf  78 kB  | Hide | Hide all | Show all
RingdownsAndRefs.pdf
Attachment 4: TwoExponentialFitAOM0.3V.pdf  27 kB  Uploaded Fri Dec 27 16:20:52 2019  | Show | Hide all | Show all
ELOG V3.1.3-