We demonstrate that commercially available poly(D,L-lactic acid) (PDLLA) is a suitable material for the fabrication of biodegradable optical fibers with a standard heat drawing process. To do so we ...report on the chemical and optical characterization of the material. We address the influence of the polymer processing on the molecular weight and thermal properties of the polymer following the preparation of the polymer preforms and the fiber optic drawing process. We show that cutback measurements of the first optical fibers drawn from PDLLA return an attenuation coefficient as low as 0.11 dB/cm at 772 nm, which is the lowest loss reported this far for optical fibers drawn from bio-resorbable material. We also report on the dispersion characteristics of PDLLA, and we find that the thermo-optic coefficient is in the range of -10 -4 °C -1 . Finally, we studied the degradation of PDLLA fibers in vitro, revealing that fibers with the largest diameter of 600 μm degrade faster than those with smaller diameters of 300 and 200 μm and feature more than 84% molecular weight loss over a period of 3 months. The evolution of the optical loss of the fibers as a function of time during immersion in phosphate-buffered saline indicates that these devices are potential candidates for use in photodynamic therapy-like application scenarios.
We present a new approach for the development of structured optical fibers. It is shown that fibers having an effective gradient index profile with designed refractive index distribution can be ...developed with internal nanostructuring of the core composed of two glasses. As proof-of-concept, fibers made of two soft glasses with a parabolic gradient index profile are developed. Energy-dispersive X-ray spectroscopy reveals a possibility of selective diffusion of individual chemical ingredients among the sub-wavelength components of the nanostructure. This hints a postulate that core nanostructuring also changes material dispersion of the glasses in the core, potentially opening up unique dispersion shaping possibilities.
We present composition development of borosilicate glasses for fabrication of high refractive index contrast, all-solid photonic crystal fibers. An oxide system composed of SiO2B2O3Al2O3Li2ONa2OK2O ...was adjusted to match thermal properties of selected highly nonlinear, lead bismuth gallium silicate glass. A high difference of refractive index of 0.376 is achieved at a wavelength of 1550 nm. We proved experimentally that the developed pair of glasses enables to draw optical fibers, and we propose a design of a photonic crystal fiber structure for broadband supercontinuum generation.
•A new pair of multicomponent silicate glasses for fabrication all-solid photonic crystal fibers is proposed.•Obtained refractive index difference is equal to 0.376 at 1550 nm wavelength.•Proposed all-solid photonic crystal fiber generates supercontinuum spanning from 900 nm to 2500 nm.
•Low-dispersion silica PCF for high-power short pulse delivery has been demonstrated.•The investigated PCF has low dispersion −20 to 60 ps/nm/km near 1300 nm wavelength.•The investigated silica PCF ...can resist up to tested 9.1 W of QCW power.•The investigated PCF can transmit 5.5 kW signal without distorting the pulse in time.
A low-dispersion and low-nonlinearity silica photonic crystal fiber is designed and developed. The investigated fiber is effectively single-mode and has low dispersion −20 to 40 ps/nm/km in the 1–1.7 μm wavelength range. The silica PCF can withstand a 1017 nm QCW laser beam with a maximum tested power of 9.1 W. The investigated PCF with NA = 0.15 is suggested as a promising medium for a high-power femtosecond undistorted pulse delivery in the near-infrared region.
We propose a new approach to developing of graded-index chalcogenide fibers. Since chalcogenide glasses are incompatible with current vapor deposition techniques, the arbitrary refractive index ...gradient is obtained by means of core nanostructurization by the effective medium approach. We study the influence of graded-index core profile and the core diameter on the fiber dispersion characteristics. Flat, normal dispersion profiles across the mid-infrared transmission window of the assumed glasses are easily obtained for the investigated core nanostructure layouts. Nonlinear propagation simulations enable to expect 3.5-8.5 µm spectrum of coherent, pulse preserving supercontinuum. Fabrication feasibility of the proposed fiber is also discussed.
We investigate coupling tolerances of selected designs of negative-curvature anti-resonant fibers (NC-ARFs) with open- and closed-boundary types of structure under linear and angular misalignment of ...the input near-infrared laser beam. The coupling tolerances of NC-ARFs are compared with those of a commercially available step-index fiber. The expected coupling efficiency for the step-index fiber is calculated using scalar diffraction theory and directly compared with measured profiles. We show that the analyzed NC-ARFs can provide lower sensitivity to input beam misalignment than the step-index fiber, despite having a numerical aperture approximately half of that of the step-index fiber (0.044 compared to 0.07, respectively). In particular, a nodeless design is only half as sensitive to input linear misalignment as the step-index fiber, whilst having an almost identical sensitivity to tilt. A 3.5-μm linear shift and 22 mrad tilt result in 10% decrease in total output power of the beam. The good match between experiment and calculations suggests that the profiles measured for NC-ARFs are correct.
The ability to shape the index profile of optical fibers holds the key to fully flexible engineering of their optical properties and future applications. We present a new approach for the development ...of a graded index fused silica fiber based on core nanostructurization. A graded index core is obtained by means of distribution of two types of subwavelength glass rods. The proposed method allows to obtain arbitrary graded distribution not limited to the circular or any other symmetry, such as in the standard graded index fibers. We have developed a proof of concept fiber with parabolic refractive index core and showed a perfect match between its predicted, designed and measured properties. The fiber has a core composed of 2107 rods of 190 nm of diameter made of either pure fused silica or Ge-doped fused silica with 8.5% mol concentration. The proposed method breaks the limits of standard fabrication approaches used in fused silica fiber technology.
Hollow core negative curvature fibres (NCFs) are a relatively new class of microstructured optical fibre with potential applications in areas such as the delivery of high power laser light and gas ...sensing. For sensing, it is necessary for the measurand to interact with the guided mode. To facilitate this, a novel femtosecond laser-based machining protocol has been developed that allows the precision sculpting of access slots into the NCF core along the length of the fibre. The process is a direct-write process using a digitally defined scanning strategy with no need for physical masks or additional processing such as wet etchants and/or focussed ion beam machining. Due to the inherent flexibility of the machining strategy and the high level of control over the depth of material removal, it is likely that this new technique will be transferable to a wide range of microstructured fibres.
Two all-solid glass photonic crystal fibers with all-normal dispersion profiles are evaluated for coherent supercontinuum generation under pumping in the 2.0 μm range. In-house boron-silicate and ...commercial lead-silicate glasses were used to fabricate fibers optimized for either flat dispersion, albeit with lower nonlinearity, or with larger dispersion profile curvature but with much higher nonlinearity. Recorded spectra at the redshifted edge reached 2500-2800 nm depending on fiber type. Possible factors behind these differences are discussed with numerical simulations. The fiber enabling the broadest spectrum is suggested as an efficient first stage of an all-normal dispersion cascade for coherent supercontinuum generation exceeding 3000 nm.
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