bunker temperature @ 22.5°C

today, Sebastien Pitrel improved its python software to manually control the laser peltier.
we were able to make to some test. unfortunately, doing only one step change the 500MHz relative frequency by ~400Hz (see the attached plot from 480Hz to 100Hz which is the laser harmonic @500MHz compared to the RF reference @500MHz), which is equivalent to a round trip length variation of 8µm !!!
the present PZT's ranges are equivalent to 400nm of the round trip length. the laser PZT range could be extended by a factor 10 if one drives it using 100V instead of 10V actually, but it would not be enough to be able to use the Peltier ! :-(

if the Peltier changes the inox baseplate of the laser, the relative length change is 1e-5 /K which is equivalent to 100µm/K of the round trip length.
it means the internal temperature steps, done by the peltier, are around 0.08K.
maybe we could try to have smaller steps by using an external thermal setup ?