Bragg gratings made in reverse proton exchange lithium niobate waveguides with a femtosecond IR laser and a phase mask

Three-decibel reflecting Bragg gratings were made in buried reverse proton exchange lithium niobate waveguides with high-power femtosecond infrared radiation from a regenerative Ti : sapphire amplifier and a phase mask. Two superposed gratings were observed: a relief grating on the surface of the crystal with a 300-nm corrugation depth and a subsurface grating in phase with the surface grating. Atomic force and optical microscopy were used to characterize the grating's physical structure.