We report on designing, fabrication and experimental characterization of highly nonlinear, tellurite glass photonic crystal fibers with engineered normal dispersion characteristics for coherent supercontinuum generation. Effectively single mode, air-hole lattice fibers, with measured, all-normal dispersion profiles as flat as -10 to -50 ps/mn/km over 1500-2400 nm wavelengths are developed and investigated. Supercontinuum spectra are measured for these fibers, with a spectral width covering 1100-2600 nm wavelengths under pumping with a robust, fixed-wavelength erbium fiber-based femtosecond laser, delivering 90 fs pulses, centered at 1560 nm with peak power below 40 kW. To the best of our knowledge, this is the first engineered microstructured fiber, which due to its high nonlinearity, enables a self-phase modulation and optical wave breaking-based supercontinuum pumped with a turnkey, 40 kW femtosecond laser at spectral widths obtainable with previous all-normal dispersion fiber designs only under pumping with systems delivering peak power in the MW range.

We report on near-infrared supercontinuum generation in a submeter-long single-mode, nanostructured core fiber. The fiber core is composed of few thousand pure silica and germanium-doped silica glass nanorods with diameter of 200 nm each. The nanorods' distribution is calculated based on the Maxwell-Garnett effective medium approach to mimic effective parabolic refractive index distribution in the fiber core. The standard stack-and-draw method was used to scale down the fiber structure and obtain subwavelength nanorods in the core. Size and distribution of individual nanorods are essential to determine modal and dispersion properties of the fiber without assistance of air holes in the fiber cladding. We study supercontinuum generation performance in this nanostructured core fiber pumping with low-cost microchip laser operating at 1550 nm with 1 ns pulse length and pulse energy of 0.4 µJ. A modulation instability-driven supercontinuum is generated in the fiber, covering a wavelength span of 1400-2300 nm. Due to possibility of dispersion engineering and all-solid structure the nanostructured fibers offer new possibilities for development of low-cost all-fiber supercontinuum light sources for the near-infrared range and cascaded ultrabroadband supercontinuum all-fiber systems.

We report on successful synthesis of ZBLAN glass. Different purity of zirconium tetrafluoride used for synthesis and fluorinating agents were analyzed to obtain high optical quality glass. Among fluorinating agents we used ammonium bifluoride, xenon difluoride and sulfur hexafluoride. The best results in form of synthetized glasses have transmission window extending from 0.2 to 8.0 um, which allows to fabricate fibers for mid-infrared applications. Full Text: PDF ReferencesR. Stępień, J. Cimek, D. Pysz, I. Kujawa, M. Klimczak, and R. Buczyński, Soft glasses for photonic crystal fibers and microstructured optical components, Opt. Eng. 53, 071815 (2014). CrossRef D. Pysz, I. Kujawa, R. Stępień, M. Klimczak, A. Filipkowski, M. Franczyk, L. Kociszewski, J. Buźniak, K. Haraśny, R. Buczyński, Stack and draw fabrication of soft glass microstructured fiber optics, Bull. Pol. Acad. Sci.-Tech. Sci., 62(4), 667-683 (2014). CrossRef R. Kasztelanic, I. Kujawa, R. Stępień, K. Haraśny, D. Pysz and R. Buczyński, Molding of soft glass refraction mini lens with hot embossing process for broadband infrared transmission systems, Infrared Phys. Technol. 61, 299-305 (2013). CrossRef Moynihan C.T. (1987) Crystallization Behavior of Fluorozirconate Glasses. In: Almeida R.M. (eds) Halide Glasses for Infrared Fiberoptics. NATO ASI Series (Series E: Applied Sciences), 123, Springer, Dordrecht. CrossRef M. R. Majewski, R. I. Woodward, S. D. Jackson, Dysprosium-doped ZBLAN fiber laser tunable from 2.8?m to 3.4?m, pumped at 1.7?m, Opt. Lett. 43, 971-974 (2018). CrossRef G Bharathan, R. I. Woodward, M. Ams, D. D. Hudson, S. D. Jackson, A. Fuerbach, Direct inscription of Bragg gratings into coated fluoride fibers for widely tunable and robust mid-infrared lasers, Opt. Express 25, 30013-30019 (2017). CrossRef Y. Shen, Y. Wang, H. Chen, K. Luan, M. Tao, J. Si, Wavelength-tunable passively mode-locked mid-infrared Er3+-doped ZBLAN fiber laser, Sci. Rep. 7, 14913 (2017). CrossRef J. Méndez-Ramos, P. Acosta-Mora, J. C. Ruiz-Morales, T. Hernández, M. E. Borges, P. Esparza, Heavy rare-earth-doped ZBLAN glasses for UV?blue up-conversion and white light generation, J. Lumin. 143, 479-483 (2013). CrossRef X. Jiang, N. Y. Joly, M. A. Finger, F. Babic, G. K. L. Wong, J. C. Travers, P. St. J. Russell, Deep-ultraviolet to mid-infrared supercontinuum generated in solid-core ZBLAN photonic crystal fibre, Nat. Photonics 9, 133?139 (2015). CrossRef X. Jiang, N. Y. Joly, M. A. Finger, F. Babic, M. Pang, R. Sopalla, M. H. Frosz, S. Poulain, M. Poulain, V. Cardin, J. C. Travers, P. St. J. Russell, Supercontinuum generation in ZBLAN glass photonic crystal fiber with six nanobore cores, Opt. Lett. 41, 4245-4248 (2016). CrossRef A. Medjouri, E. B. Meraghni, H. Hathroubi, D. Abed, L. M. Simohamed, O. Ziane, Design of ZBLAN photonic crystal fiber with nearly zero ultra-flattened chromatic dispersion for supercontinuum generation, Optik 135, 417?425 (2017). CrossRef D. C. Tee, N. Tamchek, C. H. Raymond Ooi, Numerical Modeling of the Fundamental Characteristics of ZBLAN Photonic Crystal Fiber for Communication in 2?3 ?m Midinfrared Region, IEEE Photon. J. 8, 4500713 (2016) . CrossRef Y. Dai, K. Takahashi, I. Yamaguchi, Thermal oxidation of fluorozirconate glass and fibres, J. Mater. Sci. Lett. 12, 1648?1651 (1993). CrossRef P. Hlubina, White-light spectral interferometry with the uncompensated Michelson interferometer and the group refractive index dispersion in fused silica, Opt. Commun. 193, 1-7 (2001). CrossRef F. Gan, Optical properties of fluoride glasses: a review, J. Non Cryst. Sol. 184, 9-20 (1995). CrossRef A. Filipkowski, B. Piechal, D. Pysz, R. Stepien, A. Waddie, M. R. Taghizadeh, and R. Buczynski, Nanostructured gradient index micro axicons made by a modified stack and draw method, Opt. Lett. 40, 5200-5203 (2015). CrossRef R. Kasztelanic, A. Filipkowski, D. Pysz, R. Stepień, A. J. Waddie, M. R. Taghizadeh, and R. Buczynski, High resolution Shack-Hartmann sensor based on array of nanostructured GRIN lenses, Opt. Express 25, 1680-1691 (2017). CrossRef

Fabrication of graded index (GRIN) fibers is for a long time limited to ion‐exchange, modified chemical vapour deposition (MCVD) or other deposition techniques. Recently, the nanostructuring of an all‐solid core in fibers has proven to be a versatile and low cost alternative for the production of gradient index optical fibers. Herein, high purity chalcogenide glasses in the Ge‐As‐Se glass system, synthesized in‐house, are used for stacking and drawing chalcogenide nanostructured GRIN fibers designed using the Maxwell‐Garnett effective medium theory, simulated annealing and genetic algorithms. The successful generation of a supercontinuum spanning the mid‐infrared from 3 to 6 μm, pumping at a central wavelength of 4 μm using an Optical Parametric Oscillator with femtoseconds pulses, is also reported.