Inscription of phase-shifted gratings with ultrashort pulses using defocusing and phase-mask shifting
Two slightly shifted wavelength gratings are inscribed one over the other in a single mode fiber by shifting the phasemask between two positions. The inscription setup includes a NIR femtosecond laser, a phase-mask, a defocusing spherical lens and a cylindrical focusing lens. A first fiber Bragg grating (FBG) is inscribed, while the second overlapping FBG is inscribed only after a slight shift of the phase-mask, enabling a slight wavelength shift. The transmission spectrum of the complex structure is like that of a phase shifted grating, while the inscription process is very fast and simple compared to other standard methods. A high-quality phase shifted grating with two −20 dB transmission dips, a 15 dB transmission peak with a 30 pm transmission bandwidth at 3 dB is achieved. It is also observed that this phase shifted grating structure is birefringent.
Ben-Gurion Univ. of the Negev (Israel)
Aviran Halstuch is a Postdoctoral researcher at Ben-Gurion University of the Negev working with Prof. Amiel Ishaaya. Aviran received his B.Sc. and B.A. in Mechanical Engineering and Physics respectively from the Technion (both cum laude). Aviran earned his M.Sc. in Electro-Optical Engineering (summa cum laude) and PhD in Electrical and Computer Engineering from Ben-Gurion University of the Negev, Israel. His research focuses on femtosecond inscription and material processing, and specifically on fiber Bragg grating's inscription in various fibers and materials.