Generation of pure two-beam interference grating structures in an optical fiber with a femtosecond infrared source and a phase mask

Abstract

Fiber Bragg gratings were fabricated in all-silica core fiber by focusing 125-fs 800-nm pulses with an 80-mm lens through a phase mask with 4.28-microm pitch onto a fiber sample. When the phase-mask-fiber separation was 5 mm the observed structure was clearly the result of two-beam interference between the +/- 1 orders. The elimination of the remaining 9 orders is a consequence of the walk-off experienced by the mask orders and the short duration of the femtosecond pulse. This effect is unique to the fabrication of Bragg gratings with femtosecond sources and would not be observed with a longer pulse duration or incoherent UV sources.

Achieving pattern uniformity in plasmonic lithography by spatial frequency selection

“…In both cases, deep subwavelength periodic patterns are used, not only because dense line and spacing patterns have traditionally been used as a gold standard for evaluating lithography performance, but also because they have numerous applications in microelectronics, photonics and in other related fields [25][26][27][28][29]. The broad optical transfer function (OTF) of smooth superlens enables a wide range of high wavevector evanescent waves to pass through; meanwhile, the broad OTF also causes the superlens to suffer severely from the roughness of the thin film and isolated defects on the mask.…”

Reflective Optical Fiber Sensors Based on Tilted Fiber Bragg Gratings Fabricated With Femtosecond Laser

“…The 2.5 mm radius with 0.45 mJ pulse energy at 100 Hz repetition rate was focused using a cylindrical lens (focal length, 40 mm) through a phase mask (pitch, 3.33 m) into the fiber (Corning SMF-28). The phase mask was positioned 3 mm away from the fiber to generate pure interference between the st-order diffractive 0733-8724/$31.00 © 2012 IEEE laser beams [23]. The average light power intensity in the focal line was about W/cm .…”

Phase-shifted fiber Bragg grating inscription by fusion splicing technique and femtosecond laser

“…The half-width of the focal line ω is 2.5 μm according to ω¼λf/(πω 0 ) , where λ is the wavelength of incident laser, f is the focal length of the cylindrical lens, and ω 0 is the incident beam radius. The coating stripped SMF is cleaved and spliced, and then it is positioned behind the PM at a distance of about 2 mm in order to produce two-pure interference [20]. The PM is designed for 800 nm radiation with a period Λ m of 2142 nm (Ibsen Photonics) which is twice of the period Λ g of inscribed PS-FBG.…”