Femtosecond pulse written fiber gratings: a new avenue to integrated fiber technology

Abstract

The use of ultrashort laser pulses for fiber grating inscription has many advantages in comparison to continuous wave and long pulse lasers. The most important one is that it allows inscription in nonphotosensitive fiber materials. In this paper the principal inscription techniques and the physical properties of femtosecond (fs) pulse written in-fiber gratings are reviewed. The role of focusing and order walk-off on the inscribed structures is emphasized. A fs pulse written fiber Bragg grating (FBG) also has a unique coupling behavior, due to a refractive index change that is independent from the fiber geometry. Selected applications of such gratings for sensing and fiber lasers are discussed.

Switchable dual-wavelength erbium-doped fibre laser utilizing two-channel fibre Bragg grating fabricated by femtosecond laser

“…To relieve the need of photosensitation, femtosecond laser has emerged as a powerful tool for FBG inscription [23]. Gratings inscribed by femtosecond laser can be highly localized in the fibre core with a width of ~0.3 m and depth of ~1.9 [24], rather small compared with the core of single mode fibre (SMF), so two gratings co-located parallel, e. g. two-channel fibre Bragg grating (TC-FBG), can be inscribed in the core of SMF as previously reported [25].…”

“…Compared with other techniques mentioned above, this method requires only one section of grating, needs no special fibre except EDF, and is easily switchable by simply adjusting the polarization controller apart from the intrinsic advantages of FBG. Moreover, as no photosensitivity is required for femtosecond laser inscription [23], TC-FBG can be written into gain fibre directly, making it promising candidate for more compact dual-wavelength fibre laser.…”

Fabricating waveguide Bragg gratings (WBGs) in bulk materials using ultrashort laser pulses

“…The manuscript concentrates only on WBGs created via multiphoton, nonlinear excitation processes and not on those created using two-photon routes, namely, we focus on laser writing pulses in infrared and visible as opposed to UV. Moreover, we concentrate on WBGs fabricated inside bulk materials and point the reader to other review articles on the field of fibre-based ultrafast laser-written gratings [8,16]. After outlining the various fabrication techniques in the next section, we then dedicate a section to describing how to tailor WBG characteristics.…”

Variable period change of femtosecond written fiber Bragg gratings with a deformed wavefront

“…However, conventional UVinscription techniques reach their limits as they require photosensitive fibers. This drawback can be overcome by using femtosecond laser pulses for the inscription [1]. Thus, monolithic fiber laser concepts without splicing can be realized.…”