Fabrication of a variable diffraction efficiency phase mask by multiple dose ion implantation

Abstract

Apodized fiber Bragg gratings show reductions in the unwanted sidebands from those of uniform Bragg grating. A phase mask whose diffraction efficiency varied from the center to the ends was fabricated by implanting a grating pattern in a SiO2 substrate with Si++ and wet etching in diluted HF. The phase mask diffraction efficiency vs ion dose was measured. Using this phase mask, apodized Bragg gratings were photoimprinted into fibers. The sidebands of the apodized fiber gratings were 26 dB below the peak of the central resonance compared to 12 dB for the uniform Bragg grating. The modeled values were 29 and 13.2 dB, respectively.