User:Steven J. Koch/Notebook/Kochlab/2009/07/14/Power modulation

Steve Koch 18:20, 14 July 2009 (EDT): Power modulator looks very promising. Only thing I don't know about yet is speed. But it seems to have a great range. Settings now, for example

• ND filter "in" (3rd position: I think we should leave it like this from now on)
• 10.31 amps on laser (0.56 W)
• Not sure of "internal setpoint voltage" on modulator.
  • Mod input voltage:
  • -1.8 V = 347.6 mW
  • -1V = 258.9 mW
  • 0V = 148 mW
  • 1V = 36.9 mW
  • 1.23V = 11.48 mW
  • (no connection) = 147.8 mW (it's at about 38.3%)

So, that's a range of over a factor 30, which I think should easily be sufficient for us. Great! As for speed, I can check that by modulating the power with a sine wave and monitoring the sum signal.

• 1 Hz: looks OK (0 Volt center, 1.2 V amplitude sine wave) (looking at detector sum signal and mod in on oscilloscope)
• 2 Hz: looks OK
• 3 Hz: looks OK (I think "error" light begins to flicker at this frequency)
• 4 Hz: starts to look bad