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Entry  Mon Nov 30 11:28:30 2020, aaron, Noise Hunting, Laser, pll IMG_0195.jpg
    Reply  Tue Dec 1 10:59:49 2020, aaron, Noise Hunting, Laser, pll 
       Reply  Wed Dec 2 13:37:55 2020, aaron, Noise Hunting, Laser, W laser oscillating 
          Reply  Thu Dec 3 10:18:07 2020, aaron, Noise Hunting, Laser, pll 
          Reply  Thu Dec 3 11:57:52 2020, rana, Noise Hunting, Laser, W laser oscillating 
             Reply  Fri Dec 4 10:36:18 2020, aaron, Noise Hunting, Laser, pll IMG_0015.PNG
                Reply  Sun Dec 6 19:22:10 2020, rana, Noise Hunting, Laser, pll 
                   Reply  Thu Dec 10 10:05:03 2020, aaron, Noise Hunting, Laser, pll IMG_0016.PNG
       Reply  Wed Feb 10 12:39:08 2021, rana, Noise Hunting, Laser, pll 
          Reply  Thu Feb 11 09:59:31 2021, aaron, Noise Hunting, Laser, pll 
          Reply  Thu Feb 11 17:24:41 2021, rana, Noise Hunting, Laser, pll PXL_20210212_000327036~2.jpg
             Reply  Mon Feb 15 14:57:25 2021, aaron, Noise Hunting, Laser, pll 
Message ID: 2601     Entry time: Thu Dec 10 10:05:03 2020     In reply to: 2600
Author: aaron 
Type: Noise Hunting 
Category: Laser 
Subject: pll 

enter Thu Dec 10 10:04:54 2020

Quote:

Doesn't the phase meter just read out the noise even with no locking? I thought that was going to be the magic.

For locking, the mixer readout is in units of phase and the laser current modulation gives a proportional frequency modulation with no frequency wiggles until > 1 MHz. So it should phase lock with no integrator, but I'm not sure if the free running noise will drive it out of the phase lock or not. I wonder if its possible to use the phase meter as an error signal. It would be much easier to lock frequency instead of phase via a mixer.

Hm, hadn't tried the phasemeter application. I'll check it out now... if I understand your second comment, you're saying because

f = \frac{d\phi}{dt} \\ \implies \int f dt = \Delta \phi

an error signal proportional to phase is already integrating the frequency error. Makes sense, but does 'easier to lock frequency instead of phase via a mixer' follow, or is that unrelated? 

The Moku phasemeter does produce a nice power spectrum. Here it is up to 200 Hz, I'm working with Anchal's ctn-scripts and pymoku to get the higher frequencies. 

Still odd that the beat amplitude is so small. Let's check:

quantity Power of E beam @ 1611 (power meter) Power of W laser @ 1611 (power meter) 1611 DC voltage from E beam 1611 DC voltage from W beam DC voltage gain responsivity @ 1550 (approx) Expected DC voltage due to E beam Expected DC voltage due to W beam
value 307.8 uW 65.7 uW  -1.55 V  -400 mV 10 V/mA 1 A/W -3.08 V -660 mV

Looks like neither beam is producing the expected photocurrent, but because the error is not the same factor for both beams I suspect alignment / beam size. I'm aligning with some apertures to avoid smearing the beam on lenses. Aligning each beam led to more power, but my procedure doesn't simultaneously align both beams. 

exit Thu Dec 10 15:11:30 2020

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