Phase-Locked, Low-Noise, Frequency Agile Titanium: Sapphire Lasers for   Simultaneous Atom Interferometers
  We demonstrate phase lock of two >1.6W Titanium:sapphire lasers with a phase noise of -138dBc/Hz at 1MHz from the carrier, using an intra-cavity electro-optic phase modulator. The residual phase variance is 2.5 10^(-8)rad^2 integrated from 1Hz to 10kHz. Instantaneous offset frequency steps of up to 4MHz are achieved within 200ns. Simultaneous atom interferometers can make full use of this ultra-low phase noise in differential measurements by suppressing common influences from vibration of optics. 
Holger Mueller, Sheng-wey Chiow, Quan Long, and Steven Chu