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projects:optics:log [2026/09/14 20:31] – 2026-09-14 rahixprojects:optics:log [2026/10/03 23:41] (current) – [Day 2026-10-03 (rahix, guest)] rahix
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 > //This page is a lab notebook. It documents the work done in the lab and our thoughts, theories, and findings related to it. Everything you read here is work in progress and not final results. We believe it is best to have our lab notes out in the open, because it gives more detailed insight into what worked for us and what didn't. Of course you can also use this page to follow our progress!// > //This page is a lab notebook. It documents the work done in the lab and our thoughts, theories, and findings related to it. Everything you read here is work in progress and not final results. We believe it is best to have our lab notes out in the open, because it gives more detailed insight into what worked for us and what didn't. Of course you can also use this page to follow our progress!//
  
 +==== Day 2026-10-03 (rahix, guest) ====
 +More attempts at alignment with the Open Micro-Manipulator. Managed to get quite consistent coupling efficiency again. Working towards automatic alignment optimization.
 +
 +For this, we pointed the collimated fiber output at the camera-branded camera. After quite a bit of fiddling with the camera, managed to get it to fixed exposure at an acceptable level (Something about using the ''Auto AWB'' feature I think??).
 +
 +Truly an experiment setup:
 +
 +{{:projects:optics:20261003_fiber-alignment-experiment-overview.jpg?400|}}
 +
 +On the camera, we never see a stable beam, it always looks extremely wobbly:
 +
 +{{:projects:optics:20261003-beam-01.png?200|}}
 +{{:projects:optics:20261003-beam-02.png?200|}}
 +{{:projects:optics:20261003-beam-03.png?200|}}
 +{{:projects:optics:20261003-beam-04.png?200|}}
 +
 +We placed the fiber output and camera on the vibration-isolated optics breadboard. A bit better, but still significant (pictures above were afterwards). We are very certain the remaining wobbles is vibration in the fiber alignment part, as you can excite it easily by hand. The missing vibration isolation is very noticeable, even floor vibrations have a visible effect. By eye, you cannot see these fast intensity fluctuations in the output intensity.
 +
 +Built a proxy server for allowing network-access to the motion controller and the measured intensity. See [[https://git.fa-fo.de/rahix/FiberCoupledLaserModule/src/commit/b50cc51a03df2bef308efaaff5ec270d6712547a/alignment/control-proxy|alignment/control-proxy]] for details.
 +
 +Started working on a tool to sweep areas around the focus region to automatically improve alignment. In a dry run, we already see the expected intensity profiles along the sweep.
 +
 +With how things are aligned in the diode case right now, we are always very close to hitting the fiber on the casing/brass rod. This makes alignment in the Z direction quite annoying.
 +
 +==== Day 2026-09-27 (anuejn, rahix) ====
 +Now using the [[..:micromanipulator:start|Open Micro-Manipulator]] for attempting fiber alignment.
 +
 +{{:projects:optics:20260927_mm_fiber_alignment.jpg?600|}}
 +
 +Once the setup is done: Works amazingly well! The speed and large range of motion of the micro-manipulator make the process much faster. So far, best case light output was compareable to the openflexure. But we still lack a good way to quantify it...
 +
 +Tried setting up a camera with a microscope objective for getting a better look at the fiber end. Unfortunately that didn't work out with the hardware we have in the lab. Switched back to the original setup with the soldering microscope.
 +
 +The fiber end was re-cleaved for todays alignment. Unfortunately ran out of time before we could do another attempt at glueing the fiber...
 ==== Day 2026-09-14 (rahix, guest) ==== ==== Day 2026-09-14 (rahix, guest) ====
 Installed the commercial ND filter in front of the microscope. It does, in fact, not fit the thread. But nothing that some adhesive tape can't fix... With the ND filter, we can dim the picture enough to see some more structure on the fiber end, without overexposing everything. Installed the commercial ND filter in front of the microscope. It does, in fact, not fit the thread. But nothing that some adhesive tape can't fix... With the ND filter, we can dim the picture enough to see some more structure on the fiber end, without overexposing everything.
 +
 +{{:projects:optics:20260914_ndfilter.jpg?400|}}
  
 Managed to use this to quickly get alignment much better and significant light output. Managed to use this to quickly get alignment much better and significant light output.
  
-Re-installed the brass rod in preparation for gluing the fiber. So far it is not secured with loctite (recommended is loctite 603).+Re-installed the brass rod in preparation for gluing the fiber. We filed down the end of the brass rod because it gets too close to the focus of the laser.  So far the rod is not secured with loctite (recommended is loctite 603).
  
 Final alignment using microscope and visual intensity estimate. Final alignment using microscope and visual intensity estimate.
  
 +First attempt at glueing but we just made a big mess. Also no good coupling with wet glue applied, maybe we dirtied the fiber end... Will try again next time.
 ==== Day 2026-09-05 (rahix, guest) ==== ==== Day 2026-09-05 (rahix, guest) ====
 Re-did alignment without vibration isolation but without great results. Started thinking about instrumenting the openflexure with more software to automate large parts of the alignment sweep. Re-did alignment without vibration isolation but without great results. Started thinking about instrumenting the openflexure with more software to automate large parts of the alignment sweep.