HOME SBOX THOMX MINICAV Utilities
THOMX orders THOMX installation THOMX commissioning THOMX control command
  Status of commissioning, report also here plots are reports.  Not logged in ELOG logo
 List  |  Find  |  Login  |  Help 
Entry   Onefive 33MHz modelock loss, posted by Ronic Chiche at ThomX igloo about lasers and optics 
    Reply   Onefive 33MHz modelock loss, posted by Ronic Chiche at ThomX igloo about lasers and optics 
       Reply   Onefive 33MHz modelock loss, posted by Ronic Chiche at ThomX igloo about lasers and optics 
          Reply   Onefive 33MHz modelock loss, posted by Ronic Chiche at ThomX igloo about lasers and optics 
Message ID: 373     Entry time: Tue Oct 22 18:52:40 2024     In reply to: 372
 Author: Ronic Chiche 
 Status: Fixed 
 Type: issue 
 Category: lasers and optics 
 Location: ThomX igloo 
 Title: Onefive 33MHz modelock loss 

For the modulation/demodulation generator for the PDH signal,
after a power shutdown, on can :
1) restart the generator to get the correct parameters:
CH1:3Vrms on 50 ohms @ 8.4MHz (demod)
CH2: 100mVrms on 50 ohms @ 8.4MHz (modulation on EOM)

2) do an "Align phase" on the generator

3) put 270° on CH2 (0° on CH1) to get the max Error signal
and use a "positive" sign on the Laselock : cf https://elog.lal.in2p3.fr/FPC/THOMX+commissioning/365

Ronic Chiche wrote:

After the new Yvette flooding of the last week and the consecutive AC-shut down, I restarted this morning the laser with the same procedure (step of 1mm at 10mm/s with the Smaract motor on the rep rate channel (CH1)).

now, we have again 33.371MHz and 3.1mW input power as expected ! => OK

the last thing to do is to tune again the PDH demodulation frequency, as the generator has been shut off during the AC shut down.

Ronic Chiche wrote:

This morning, I verified the reason why the seeder frequency was not displayed on the amplifier software screen:

one needs to start the amplifier (even at 0%) to see the seeder frequency !!!
now, we have 33.371MHz as expected ! => OK

the last thing to do is to tune again the PDH demodulation frequency, as the generator has been shut off during the AC shut down.
 

Ronic Chiche wrote:

On Friday 11th of October, due to the Yvette flooding, all the AC power of ThomX have been shut down.
After the shutdown, I had to restart the Onefive oscillator but the laser modelock was lost.
I had to do a step of 1mm at 10mm/s with the Smaract motor on the rep rate channel (CH1)

After the step, the laser was mode-locking again, and I put it back in the original position at a much lower speed, ~10µm/s, to prevent a new modelock loss.
the power detected by the laser amplifier software is still above 3mW! => OK

Surprisingly, the laser amplifier software is not able to detect the oscillator frequency.
hopefully, the internal photodiode of the oscillator is sent to the CH4 of the R&S scope (192.168.229.21)
and we measured a correct 30ns of period, corresponding to 33MHz.

Because all the safety procedures are not fulfilled, the laser amplifier is not granted to start.
Maybe it is the Reason for the lack of measurement => to be verified later
 

 

 

 

ELOG V3.1.4-395e101