Yesterday with Aurélien, we try to make the laser modelock using the Smaract translation stages embedded inside the laser head.

unfortunately, we got some errors when we try to do the "calibration" and "reference" of both Smaract stages !
we contacted by email M. Nicoul to help us on this topic

Today, we removed the 33MHz and its controller and motors controller from the casemate to install it in the PLIC room.

with the help of M. Nicoul, we did a first check of the PZT capacitance of each stage (~ 60nF)
for channel 0 (Frep), the measured capacitance is 53nF on the laser head
for channel 2 (CEP), the measured capacitance is 63nF on the laser head
between pins 1 and 9 of the DB9 connector.

M. Nicoul says that these values are compatible with the reference values ~ 60nF, then the PZT translation stages are OK.
Then, the controler is maybe damaged.
One has to find a new one to test the stages.

This morning, with Aurélien and Daniele, we did the swap between the 33MHz and 133MHz oscillators.

now, the 33MHz oscillator is on ThomX inside the casemate.
it has been restarted and some laser is going out.
it has been screwed on the metal plate, roughly aligned with the Alphanov "fiber injection and strecher" box.
tomorrow, we will do the fine alignment with this box and check if the laser is properly modelocking.

the 133MHz oscillator is back in the PLIC optical room.
it has been restarted and some laser is going out.
it seems there are no pulses at the output... it seems we have to trigger the modelock.

We checked the Dichroic mirror we have : it is a DMSP1000 shortpass dichroic mirror as specified in this post.

The Arrow engraved on the edge of the mirror points on the AR surface !
not on the HR surface...

the AOI is 45°.

On the 8th of July, the SN2439 33MHz laser was returned from NKT to our lab, being repaired.

it stayed all the weekend to warm up in the optical room and has been turned on on Monday.

the mode-locking was not working (28mW output power and a CW line for the optical spectrum), thus I "kicked" the laser with 100µm moves on the motors.

now, the laser is mode-locked with 42mW output power and the expected optical spectrum.
 

This morning with Viktor, we opened the 2 vessels and removed the 4 FP-cavity mirrors.

all the mirrors have been put in plastic boxes with labels to indicate which mirror it is,

and with all the HR coatings face down.

the mirrors are in the PLIC room in the "THOMX MIRRORS" box.

Last Friday and this morning, with Bruno, we close the ring/cavity valves and put some dry air in the two vessels through a filter to avoid turbulences.

Now, the two vessels are at ambient pressure and ready for opening (to remove the mirrors).

One can let the ambient pressure in the vessels as long as we want, the ring/cavity valves have been chosen to be compatible with the high vacuum in the ring and the ambient pressure in the vessel for a long time.

last Friday with Manar, we took some thermal images of the Alpnavov compressor box.

I post a small document to summarize some points :

- the 2 mirrors used to make the CVBG injection are polarized thin-film mirrors... thus sensitive to the beam polarization.
there is also a half-wave plate on the input path...
are we sure that the beam polarization is properly set with the Onefive laser injecting the amplifier?
(Alphanov used their own seeder).

- the CVBG temperature seems normal without too much difference between profiles and values.

- the 2 thin-film mirrors seem quite hot (45°) compared to the rest of the setup.
a basic calculation of power thermally radiated gives an absorbed power of around 55mW which is equivalent to about 500ppm of absorption.
is this estimation correct? could it be the confirmation of some misalignment that traps some power inside the mirror substrate?
(document corrected to take into account the room temperature)

last Friday with Manar, we took some thermal images of the Alpnavov compressor box.

I post a small document to summarize some points :

- the 2 mirrors used to make the CVBG injection are polarized thin-film mirrors... thus sensitive to the beam polarization.
there is also a half-wave plate on the input path...
are we sure that the beam polarization is properly set with the Onefive laser injecting the amplifier ?
(Alphanov used their own seeder).

- the CVBG temperature seems normal without too much difference between profiles and values.

- the 2 thin-film mirrors seem quite hot (45°) compared to the rest of the setup.
a basic calculation about power thermally radiated gives an absorbed power of around 0.2W which is equivalent to more than 1000ppm of absorption.
is this estimation correct? could it be the confirmation of some misalignment that traps some power inside the mirror substrate?
 

For better comparison ,

the measurements done previously with 2 CVBGs was done at ~ 30 cm and the one done on Friday was for 1 CVBG is at 1 m

so we did additional measurement for 2 CVBGs at 1 m, for 20 , 50 and 70 % amplification 

we clearly see the similar deformation at high power.

Conclusion : the effect is most likely coming from the 2nd CVBG

At 70 % victor optimized the horizontal axis for the injection mirror into 2nd CVBG , we see an improvement in the Gaussian fit on Horizontal and vertical axis of ~ 2%

Victor, Ronic, Manar

Today  was dedicated to the study of the CVBG, and it's effect on the beam profile

we opened the box containing the 2 CVBGs : The 2CVBG are glued from the bottom on a copper surface .

Using the beam viwer, the beam line inside the two CVBG is not at the exact center but not at the edges too and not hitting the boarders.

From the sides you see two lines, one is reflection on the metal.

To observe the effect of the first CVBG by itself, we blocked the second reflection into the 2nd CVBG.

By placing the D-shaped mirror just at the entrance of the 2nd CVBG (there was just enough space to put it)

Beam Profiler + OD 10E + OD 30E + OD(not known) placed at ~ 1 m from the output of compressor.

We see clearly a much better circular shape of the beam and a better Gaussian fit,

only above 90% where we see the fit percentage going down to ~ 86% and on just the Horizontal Axis.

Pulse Duration FWHM = 12.9 ps

Measurement of the pulse was done at the end of the afternoon, Pulse Duration FWHM = 12.9 ps

After a long process of adjusting the alignment and angle of the crystal inside the device

The power input on the PulseCheck device should be above the sensitivity, in our case we had 1 mW input.

To reach it, we removed one of the wedge mirrors and used dielectric mirrors with an amplification of 20% ~ 25 W direct output power.

The input to the pulsecheck must be horizontally polarized, which is why we used a polarizing beam splitter (PBS).

For a better pulse shape, Victor adjusted the "beam distance" and  "beam focus" nobs on the device.

The pulse duration from the amplifier compressor output will be measured using PulseCheck autocorelator

a first alignment of the device was done, continuation in the afternoon.

YouTube link attached of the general operation of pulse check < 5 min :  https://www.youtube.com/watch?v=J1pNHYySSYg

Software Works well and is operational.

Just closing the log series!!!

This Morning, another reading was taken for the output of the amplifier after the compressor using 2 wedge mirrors.

In addition, a start of the calibration of a PulseCheck "Autocorrelator" to measure the pulse duration. 

note, the pulsed laser used is OneFive 133.33 MHz

Adding the readings  20% , 30% ,  40%  for output of amplifier after the compressor

Readings of the beam shape and fit at the output of the compressor

differance from previous reading is that here we used wedges instead of HR mirrors.

Similar to previous readings, the beam shape deforms and the Gaussian fit is bad after 50% amplification

Readings of the beam shape and horizontal (upper plot) and vertical (lower plot) axis fit at the direct output of the amplifier.

The beam shape relatively shaped like an egg.

Today a second reading of the beam profile was done , with Victor ,Ronic, Aurlien and Manar

an additional set-up was made using two 4 deg wedges instead of High reflecting (HR) and Anti-reflecting (AR) mirrors.

Two reading were taken:

• at the output of the compressor with a NE30A filter on the beam profiler
• at the output of the amplifier with NE30A + NE10A filter on beam profiler

Adding the fitted beam in 1D in Horizontal and vertical axis.

for 10%   to  60%