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projects:optics:log [2026/04/01 17:41] – [Lab Notes for Optics Experiments] rahixprojects:optics:log [2026/04/14 08:22] (current) – [Day 2026-04-04 (k8ik, rahix, many guests)] rahix
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 ====== Lab Notes for Optics Experiments ====== ====== Lab Notes for Optics Experiments ======
  
 +==== Day 2026-04-04 (k8ik, rahix, many guests) ====
 +We presented our low-cost optics and the interferometer at EH23!  Watch our talk here: [[https://media.ccc.de/v/eh23-budget-beams-laser-experiments-in-a-hacker-lab|Budget Beams – Laser Experiments in a Hacker Lab]]
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 +{{:projects:optics:2026-04-04-interferometer-eh23.jpg?600|}}
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 +During the event, our laser diode broke (well, rahix fed it too much voltage really) so we scrambled to disassemble a DVD drive and extract the red 650nm diode from it. We kept the collimation optics from the DVD drive and hot-glued the entire subassembly to an optics mount.  It took 3 attempts (3 DVD drives) to not immediately kill the new diode again.
 +
 +We managed to demonstrate the fringe movement from the piezo quite a few times.  We borrowed a different power supply to drive it.  This one seems to lead to a slow ramp-up of voltage (fringes move slowly when turning on) and an abrupt cutoff (fringes fall back very quickly when turing off).
 +
 +Stability was quite alright with the reduced isolation setup as long as nobody touched the table.
 ==== Day 2026-04-01 (k8ik, rahix) ==== ==== Day 2026-04-01 (k8ik, rahix) ====
 Set up the interferometer experiment again, but with "analog" readout (i.e. just a viewing screen where the pattern is enlarged). Set up the interferometer experiment again, but with "analog" readout (i.e. just a viewing screen where the pattern is enlarged).
  
-Tried driving the Z-axis piezo of the STM head with +20V.  We can see movement!  Eyeballed to be somewhere below λ/2, so <300nm.+Tried driving the Z-axis piezo of the STM head with +20V.  We can see movement!  When turning on the voltage, the pattern immediately jumps.  When turning it back off, it slowly drifts back to its original state. 
 + 
 +Eyeballed the movement to be somewhere below λ/2, so <300nm.  But for any proper measurement, we need to do digital readout again.
  
 Getting the laser stable enough to see the movement without noise is not easy. The mechanics hold up plenty fine. Getting the laser stable enough to see the movement without noise is not easy. The mechanics hold up plenty fine.