Highly birefringent optical microfibers

Abstract

Abstract:Highly birefringent (Hi-Bi) air-clad silica microfibers (MFs) with wavelength and sub-wavelength scale transverse dimensions are studied theoretically and experimentally. Hi-Bi MFs are taper-drawn from the standard SMF-28 single mode fibers that are "pre-processed" by "cutting away" parts of the silica cladding on opposite sides of the fiber with a femtosecond infrared laser. Such Hi-Bi MFs have approximately elliptical cross-sections and are approximated by a three-layer model comprising a small central Ge-doped region surrounded by an elliptical silica region and an air-cladding. Theoretical modeling shows that phase and group birefringence of the order 10 −2 can be achieved with such air-clad Hi-Bi MFs. Experiments with an air-clad elliptical fiber with a major diameter of 0.9µm and a minor/major diameter ratio of 0.9 demonstrated a group birefringence of ~ 0.015, agreeing well with the theoretical predictions. The Hi-Bi MFs are useful for micron/nanoscale polarization maintaining transmission and phase-sensitive interferometric sensors. Express 12(9), 1916-1923 (2004). 24. R. B. Dyott, Elliptical fiber waveguides (Artech House, boston.london, 1995). 25. C. Yeh, "Elliptical dielectric waveguides," J. Appl. Phys. 33(11), 3235-3243 (1962 2359-2371 (1995). 27. S. C. Rashleigh, "Measurement of fiber birefringence by wavelength scanning: effect of dispersion," Opt. Lett. ©2010 Optical Society of America

Optical microfibers and nanofibers

“…In addition, by measuring optical transmission via standard fiber at both ends, it is possible to in-situ monitoring the waveguiding properties of the MNF during the pulling process in terms of propagation loss, multi-mode interference and group velocity delay [73,74]. Based on the taper-drawing process mentioned above, in recent years, a number of improvements on this technique have been reported for fabricating MNFs with various parameters including ultra-small diameters [10], reduced propagation losses [15,75], optimized tapering profiles and controllable cross-section geometries [76,77].…”

Tunable comb filters and refractive index sensors based on fiber loop mirror with inline high birefringence microfiber

“…The upper and lower curves are, respectively, for the microfiber placed in air and in water. From the upper curve birefringence of the microfiber is estimated to be about 8.5 × 10 −3 [11] (at wavelength of 1550 nm). Because of the higher RI of water than air, the comb spacing is larger when the microfiber is immersed in water.…”

“…One incorporates a single piece of twisted Hi-Bi microfiber in a Sagnac loop, while the other includes two pieces of Hi-Bi microfibers cascaded along a fiber with a rotation of their birefringence axes. This work on microfibers may result in novel applications, such as wavelengthscale light transmission and interconnection, which are useful for photonic integration, computing, and nanoscale sensing.The Hi-Bi microfiber is made from a commercial SMF-28 (outer diameter D ∼ 125 μm, core diameter d ∼ 8.2 μm, Δn ∼ 0.36%) [11]. The SMF-28 fiber is first "processed" by use of a femtosecond IR laser system (Fig.…”

“…The Hi-Bi microfiber is made from a commercial SMF-28 (outer diameter D ∼ 125 μm, core diameter d ∼ 8.2 μm, Δn ∼ 0.36%) [11]. The SMF-28 fiber is first "processed" by use of a femtosecond IR laser system ( Fig.…”

“…The "processed" SMF is then taper-drawn to micrometer size by use of a flame-brushing technique. The cross-sectional shape of the "processed" region is well preserved during the initial taper-drawn process and eventually turns to an approximately elliptical shape when the fiber diameter is reduced down to wavelength scale, which generates a high birefringence of the order of 10 −2 [11], much bigger than conventional polarization maintaining fibers. The insertion loss of the tapered microfibers with diameter above 2 μm is in general considerably smaller than 0.2 dB.…”