First-order fiber Bragg grating inscription in indium fluoride fiber using a UV/Vis femtosecond laser and two-beam interferometry

Abstract

Fiber gratings are among key components in fiber-based photonics systems and, particularly, laser cavities. In the latter, they can play multiple roles, such as those of mirrors, polarizers, filters, or dispersion compensators. In this Letter, we present the inscription of highly reflective first-order fiber Bragg gratings (FBGs) in soft indium fluoride-based ( I n F 3 ) fibers using a two-beam phase-mask interferometer and a femtosecond laser. We demonstrate an enhanced response of I n F 3 -based fiber to a visible (400 nm) inscription wavelength compared to ultraviolet irradiation at 266 nm. In this way, FBGs with a reflectivity > 99.7 % were inscribed at around 1.9 µm with the bandwidth of 2.68 nm. After thermal annealing at 393K, the Bragg wavelength demonstrates stable thermal shift of 20 pm/K in the temperature range 293–373K. These observations suggest a potential extension of I n F 3 fiber-based laser components to an operational range of up to 5 µm.

Controllable Light Scattering on Fiber Bragg Gratings in Multimode Fibers: Tailoring Angular Emission for Advanced Fiber-Based Light Sources

“…This corresponds to a grating pitch of Λ = λ 0 /(2n co ) = 647 nm at a refractive index of n co = 1.51. 36 Angular Scattering Pattern. The FBGs far-field scattering pattern shows discrete broken bands for the three different laser colors (red, green, and blue), which can be seen in Figure 2 for one azimuth fiber orientation for FBG1 in (e) and for FBG2 in (f).…”

“…This is in good agreement with the measured values from the transmission spectral measurement which gave a transmission minimum at λ 0 = 1953 nm. This corresponds to a grating pitch of Λ = λ 0 /(2 n co ) = 647 nm at a refractive index of n co = 1.51 …”

“…The Fiber Bragg Grating inscription was conducted in connection with the investigation of soft indium fluoride (InF) glass fibers for use in Mid-IR fiber-based photonic systems . The gratings were produced with a two-beam phase-mask interferometer and a 266 nm femtosecond laser.…”

“…The Fiber Bragg Grating inscription was conducted in connection with the investigation of soft indium fluoride (InF) glass fibers for use in Mid-IR fiber-based photonic systems. 36 The gratings were produced with a two-beam phasemask interferometer and a 266 nm femtosecond laser. The passive fiber was based on an indium fluoride glass matrix (Le Verre Fluore) with a core diameter of d co = 2r co = 7.5 μm, a cladding diameter of 125 μm, and a numerical aperture (NA) of 0.31.…”

Direct Femtosecond Laser Inscription of High-Order Bragg Gratings in Fluoroaluminate Glass Fiber

“…The split peaks at Ep ~3.15 µJ, 3.6 µJ, 4.05 µJ and 4.5 µJ were attributed to the defocusing of the lens due to the flow of index-matching oil during writing induced by heating of the oil at higher Ep values. As the grating planes deviated from perpendicularity to the core longitudinal direction along the laser focus point direction, in a few-mode fiber they induce cross-coupling, because of asymmetry [19]. The shortwavelength side of the Bragg peak has a side peak for Ep ~3.15 µJ, 3.6 µJ, while it is minimal for Ep ~4.05 µJ, possibly because of more symmetrical structure of the test fiber.…”