Noise Reduction

• Auxiliary length loops: a change in philosophy

  • Reduced sensing noise: more power, thermal compensation
  • High gain -> reduced nonlinear upconversion
  • Off-diagonal correction paths (“feed-forward”)

• Angular controls noise => apparent cavity length

  • Coupling: spot mis-centering or coil/magnet gain imbalance
  • Output of software 'lock-in' used to servo coil gains
  • Automated procedure (easy to modify shell scripts)

• Photodetector saturation at 2 x fmod

  • Circuit modified with an 'active' notch

• RF oscillator phase noise

  • Dedicated crystal oscillator
  • Coupling reduced through differential thermal lensing

Notes: