This morning with Ronic, using a pickup mirror, we measured the power in different locations along the path of the stretcher box
Output power from oscillator : ~35mW
After the isolator : ~ 35 mW
just before the CVBG : ~ 35 mW
just before the fiber injection : 3 mW
After improving on the mirrors directly correlated to the first line in CVBG and the second reflection line (mirror 4 and 6 on the Alphanov documentation)
we managed to increase the power output just before the fiber to 5.7 mW
To confirm it is indeed the second reflection we see, when cutting the second line and the power drops to almost sero (~70 uW)
We will check the CVBG documentation if it is the maximum power we can obtain after the it due to it's bandwidth !!!!
for the fiber injection :
First without connecting the fiber we checked power after Schafter+Kirchhoff mount we measure 5.5 mW (all power pass through)
when connecting the fiber, we get 300 uW after a quick alignment on the power meter + OD2.
The issue of being too much sensitive arises from the Schafter+Kirchhoff mount, after adjusting the tilt screws and Black knob we got 1.05mW in the fiber for a quick moment.
we had at one point a stable 811 uW into the fiber, but when fixing the mount screws the power drops significantly to 150 uW and it is very difficult to reproduce.
The Schafter+Kirchhoff mount is very difficult to align, waiting on advice from Guillaume Machinet.
| Ronic Chiche wrote: |
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In preparation for tomorrow morning, I did a test with a 45° mount to have a power pickup inside the injection box.
I used the 133MHz laser.
output power measured with the powermeter : 45mW
output power measured with the powermeter + OD2 : 2mW
output power measured with the 45° mount with BB1-E03 mirror with the powermeter + OD2 : 2mW
as expected the BB1-E03 mirrors have a very good reflectance for AOI=45°
the specs give >99% @ 1030nm for both S and P polarizations.
| Ronic Chiche wrote: |
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This morning with Viktor, we started the alignment of the CVBG and fiber.
we did a better alignment of the 2-pass CVBG.
we are able to the see a spot after PBS (after the 2 CVBG pass) which means the alignment is OK even if it can be improved.
then, we started the fiber injection alignment with the 2 last mirrors (7 & 8 on Alphanov documentation).
we saw that if we unswcrew the fiber to play on the focal position, we are able to improve a lot the power in the fiber.
2-3µW with the fiber screwed => 500µW with the fiber unscrewed.
it means the beam is not enough focused.
I will ask Guillaume Machinet his advice when injecting the 33MHz... do we need to replace the long focal lens just after the Isolator ?
and with which value approximatively ?
we played also with the Schafter+Kirchhoff mount of the fiber colimator (see attached documentation).
we loosen the 2 screws around the eccentric key which adjust the focal position + play on this eccentic key + tighten the 2 screws again.
now, we reached 330µW with the fiber properly screwed.
we have to check the available power before the fiber injection but we have very few place to place the powermeter.
maybe with a small mirror ?
| Ronic Chiche wrote: |
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Today, after laser was modelocked, we checked the power inside the fiber coming from the Alphanov Strecher box.
it was almost zero, at the nW level.
after doing some very rough alignment, we clearly saw some power (with the powermeter) correlated with the position of mirrors, when turning the alignment knobs.
this is a first step but the output power in the fiber is still very low, about 20nW !
an additionnal 2mm L-shaped hex key is needed to do some walking alignment on the mounts.
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