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Message ID: 2398     Entry time: Wed Aug 14 16:07:57 2019
Author: Nathan Holland 
Type: DailyProgress 
Category: 2micronLasers 
Subject: New AOM Driver. 

After reproting phase noise issues with the VCO, here, I have changed the VCO for a high power RF amplifier - a mini circuits ZHL--5W==sma (ZHL-5W-1). It is being driven by thre Moku to provide the 80 MHz signal. Please note the following:

  • This is a high power amplifier so you should follow the correct high power amplifier turn on/off procedure.
  • The amplifier can output a maximum of 5W. However the AOM can only tolerate a maximum of 0.6 W. Ensure that an appropriately small signal is input into the amplifier, as to not break the AOM.

 

The new setup is shown in attachment 1. Attachment 2 show the phase noise of the LO arm. This is now a much more acceptable level, as compared to the previous VCO. I am outputting -19.2 dBm, and measuring 5.3 dBm on input 2. This means I am driving the AOM at 24.8 dBm, or 0.302 W.

 

With the greater drive on the AOM, as compared to previous incorrect useage of the VCO, the signal from the IFO arm is much more robust. Attachment 3 shows the phase time series of the IFO arm. You will notice the large jumps, which spoil the spectrum, not shown here. In attachment 4 I zoom into the largest of these jumps. You can see it is comprised of several linear transitions, which occur over a short time period.

 

Aidan has suggested that locking the laser is the best way to avoide these non-stationary noise sources. He suggests that these jumps could be mode hops of the laser.

Attachment 1: 20190814__Phase_Noise_Setup.pdf  56 kB  Uploaded Wed Aug 14 17:13:31 2019  | Hide | Hide all
20190814__Phase_Noise_Setup.pdf
Attachment 2: MachZehnder_measured_phase_noise-LO_path__20190814.pdf  23 kB  Uploaded Wed Aug 14 17:13:44 2019  | Hide | Hide all
MachZehnder_measured_phase_noise-LO_path__20190814.pdf
Attachment 3: MachZehnder_measured_phase-IFO_path__20190814.pdf  150 kB  Uploaded Wed Aug 14 17:17:00 2019  | Hide | Hide all
MachZehnder_measured_phase-IFO_path__20190814.pdf
Attachment 4: MachZehnder_measured_phase-IFO_path_zoom__20190814.pdf  75 kB  Uploaded Wed Aug 14 17:18:51 2019  | Hide | Hide all
MachZehnder_measured_phase-IFO_path_zoom__20190814.pdf
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