Demonstration of UV-written waveguides, Bragg gratings and cavities at   780 nm, and an original experimental measurement of group delay
  We present direct UV-written waveguides and Bragg gratings operating at 780 nm. By combining two gratings into a Fabry-Perot cavity we have devised and implemented a novel and practical method of measuring the group delay of Bragg gratings. 
Guillaume Lepert, Michael Trupke, Ed A. Hinds, Helen Rogers, James C.   Gates and Peter G. R. Smith
physics.optics