Phase-predictable tuning of single-frequency optical synthesizers
  We investigate the tuning behavior of a novel type of single-frequency optical synthesizers by phase comparison of the output signals of two identical devices. We achieve phase-stable and cycle slip free frequency tuning over 28.1 GHz with a maximum zero-to-peak phase deviation of 62 mrad. In contrast to previous implementations of single-frequency optical synthesizers, no comb line order switching is needed when tuned over more than one comb line spacing range of the employed frequency comb. 
Felix Rohde, Erik Benkler, Thomas Puppe, Reinhard Unterreitmayer,   Armin Zach, and Harald R Telle
physics.optics