Enhanced Kerr nonlinearity in sub-wavelength diameter As_2Se_3 chalcogenide fiber tapers

Abstract

We experimentally demonstrate enhanced Kerr nonlinear effects in highly nonlinear As(2)Se(3) chalcogenide fiber tapered down to sub-wavelength waist diameter of 1.2 mum. Based on self phase modulation measurements, we infer an enhanced nonlinearity of 68 W(-1)m(-1). This is 62,000 times larger than in standard silica singlemode fiber, owing to the 500 times larger n(2) and almost 125 times smaller effective mode area. We also consider the potential to exploit the modified dispersion in these tapers for ultra-low threshold supercontinuum generation.

Small core optical waveguides are more nonlinear than expected: experimental confirmation

“…While the statistical fluctuations of attenuation values for fibers B, C, and D were similar to those owing to power and length measurements, they were significantly higher for fiber A-with the smallest core diameter (see Fig. 2 and [7][8][9] and numerical results of ␥ V and ␥ S versus core diameter for (a) bismuth, (b) SF57 suspended core, and (c) chalcogenide [10,11] tapered (nanowire) fibers. the inset)-and represent the main source of uncertainty.…”

“…Figures 1(a)-1(c) show the recorded experimental values of ␥ for a few bismuth [7] and SF57 [8,9] suspended core microstructured optical fibers (MOFs) and chalcogenide nanowires [10,11] Figs. 1(a)-1(c), respectively, with the theoretical calculations according to ␥ S and ␥ V expressions indicates that for the corresponding core diameters there are no distinguishable differences between the two theoretical models.…”

Optical microfibers and nanofibers

“…Owing to the miniaturized mode area [11,18] and engineerable dispersion [11,16,211], MNFs exhibit enhanced nonlinear effects such as supercontinuum generation [9,15,17,112,113,118,119,182], third-harmonic generation [183][184][185][186][187][188], bistability [46,160], two-photon absorption [189,190] with relatively low optical power. To obtain higher optical nonlinearity, many other materials with high nonlinearities (e.g., leadsilicate, bismuth-silicate, As 2 Se 3 chalcogenide) have been drawn into MNFs for various purposes [82,191]. In addition, sub-wavelength-diameter MNFs offer tightly confined evanescent field with high spatial gradients, which can be used to efficiently trap and guide atoms near the surface of the MNF [20,59,60,63,175,176] and couple radiation atoms to the guided modes of the MNF [61,62,177].…”

Optical microfiber passive components

“…1) The "self-modulated taper-drawing" [1] 2) The flame-brushing technique [2][3][4][5][6] 3) The modified flame-brushing technique [9,12,13] 4) Direct pull from bulk glass [14] The "self-modulated taper-drawing" [1,15] was the methodology firstly published in Nature in 2003. It is a twostep procedure: firstly, a taper with a diameter of few micrometers is drawn from an optical fibre using the conventional flame brushing technique; then, the manufactured taper is cut into two halves in the uniform waist region, and one of the microfibers is wrapped onto a hot sapphire rod and pulled to sub-micrometric diameters.…”

“…The modified flame-brushing technique is derived, as the name suggests, from the flame brushing technique and it replaces the flame with a different heat source: a microheater [12,13] or a sapphire capillary tube heated by a CO 2 laser beam [9]. In the last few years it has emerged as the technique of choice for the manufacture of OMFs from compound glass optical fibres.…”