A nanostructured core silica fiber with active and photosensitive areas implemented within the fiber core is demonstrated. The photosensitivity, active and passive properties of the fiber can be ...independently shaped with this new approach. We show that discrete local doping with active ions in form of nanorods allow to obtain effective laser action as in case of continuous distribution of the ions in the core. Co-existing discrete photosensitive nanostructure of germanium doped silica determine single-mode performance and allow inscription of highly efficient Bragg grating over the entire core area. Each nanostructure do not degrade performance of other one since physical interaction between active and photosensitive areas are removed. As a proof of concept, we have designed and fabricated the nanostructured, ytterbium single-mode silica fiber laser with the Bragg grating inscribed in the entire core area. We demonstrated fiber laser with good quality of generated laser beam (M
=1.1) with lasing efficiency of 44% and inscribed Bragg grating with 98.5% efficiency and -18 dB contrast.
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.
The development of gradient index free-form micro-optic components dedicated to the mid-infrared range is challenging due to the lack of appropriate technology. We propose a method for developing ...gradient index components for broadband infrared range beyond the transmission window of silicate glass based on nanostructurization using a stack-and-draw fiber drawing technique. A proof-of-concept microlens is developed and verified experimentally in the wavelength range 1.5-4.3 µm. The microlenses are composed of a set of nanorods with a diameter of 940 nm made of a pair of SiO
-PbO-Bi
O
-Ga
O
based glasses ordered into the preliminary calculated binary pattern. The pattern forms effectively continuous parabolic refractive index distribution for infrared range according to Maxwell-Garnett effective medium model. The development of individual microlenses with a diameter of 118 µm and focal length of 278 µm at the wavelength of 3.75 µm are reported. A large array of 737 microlenses with an individual diameter of 125 µm and focal length of 375 µm is also presented and analyzed.
We report on experimental characterization of butt-coupling between a quantum cascade laser operating around the wavelength of 4.5 μm and a silica hollow core anti-resonant fiber. The used fiber has ...a single ring of non-touching capillaries surrounding a 42.5 μm dimeter air core and a mid-infrared transmission window in the wavelength range of 2.8 to 4.7 μm. A lens-less butt-coupling interconnection is established and coupling efficiency of 22% is achieved with over 100 mW of power at the fiber output. Bending losses in this test-bed system are verified depending on radius with the loss remaining below 1 dB/m for 20 mm loops, while bend losses exceeding 10 dB/m are observed when the fiber is bent down to a 5-mm radius. The presented coupling dramatically improves the output beam quality of the quantum cascade laser with a measured NA = 0.45. The beam at the fiber output has a circular shape, measured M 2 = 1.04 and uniform numerical aperture of NA = 0.13. Together with the hollow core fiber geometry, the proposed system would be suitable for simple implementations of absorption spectroscopy of popular atmospheric agents, like N 2 O.
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•New fabrication process of D-shape fibers for massive volumes is established.•Direct D-shape preform drawing results in 100 m long uniform parameters sensing fibers.•Direct drawing ...of D-shape fiber from modified preform gives very good surface quality.•Proof-of-concept lossy-mode resonant sensor with a sensitivity of 550 nm/RIE is shown.•New D-shape fiber can be a platform for chemical or biological sensing applications.
We verified experimentally a new method of development of well know D-shape fibers. Instead of mechanical or chemical postprocessing of standard fibers, we have developed a D-shaped preform and further processed it on a fiber drawing tower Inversion of the fabrication process allows to obtain hundreds of meters of uniform sensing fiber with a thermodynamically flattened sensing surface. We have developed fibers with a core of 7 by 8 µm, a 2 µm distance between the core and sensing surface, and its roughness of RMS = 40 nm. As a proof-of-concept, we have developed a lossy-mode resonant sensor with a 320 nm ITO layer and demonstrated its sensitivity of 550 nm/RIE.
We report on modeling, development, and optical characterization of fused silica photonic crystal fiber with germanium doped microinclusion placed in the middle of the core. The fiber is designed to ...efficiently couple and guide LP
mode. It offers high optical density in the center region, large mode separation, low losses, and small dispersion with relatively flat profile for both LP
and LP
modes in 1-1.6 µm wavelength range. We demonstrate that by changing geometrical and material parameters of the inclusion partially independent tuning of propagation constants of individual modes is possible, what might be found is a variety of potential applications, e.g., in nonlinear optics. We also show that diffraction-limited propagation of LP
mode in free space can be exploited in microscopy or lab-on-a-chip systems, where the proposed fiber can be used for light delivery.
We present the pedestal-free thulium doped silica fiber with a large nanostructured core optimized for fiber lasers. The fiber is composed of over 6 thousand thulium doped silica nanorods with a ...diameter of 71 nm each which form a nanostructured step-index core. We study the influence of non-continuous distribution in nanoscale active areas on gain, beam quality, and fiber laser performance. The proof-of-concept fiber is effectively single mode for wavelength above 1.8 µm. We demonstrate the performance of the fiber in a laser setup pumped at 792 nm. Single mode laser emission with a slope efficiency of 29% at quasi-continuous output power of 4 W with M2 = 1.3 at the emission spectrum 1880-1925 nm is achieved.
We report on the first step-index biodegradable polymer optical fiber (bioPOF) fabricated using commercially available polyesters, with a core made from poly(D,L-lactic-co-glycolic acid) and a ...cladding made from poly(D,L-lactic acid). We prepared the preforms with a rod-in-tube technique and the fibers with a standard heat drawing process. We discuss the chemical and optical properties of the polyesters along the fabrication process from polymer granulates to optical fiber. More specifically, we address the influence of the processing steps on the molecular weight and thermal properties of the polymers. Cutback measurements return an attenuation of 0.26 dB/cm at 950 nm for fibers with an outer diameter of 1000 ± 50 μm, a core of 570 ± 30 μm, and a numerical aperture of 0.163. When immersed in phosphate-buffered saline (PBS), bioPOFs degrade over a period of 3 months, concurrent with a 91% molecular weight loss. The core decomposes already after three weeks and features 85% molecular weight loss. There is no any additional optical loss caused by immersion in PBS during the first 30-40 min for a bioPOFs with a diameter of about 500 μm. Our result demonstrates that bioPOF can be suitable for applications requiring light delivery, deep into living tissue, such as photodynamic therapy.
We report on the multidimensional characterization of femtosecond pulse nonlinear dynamics in a tellurite glass graded-index multimode fiber. We observed novel multimode dynamics of a quasi-periodic ...pulse breathing which manifests as a recurrent spectral and temporal compression and elongation enabled by an input power change. This effect can be assigned to the power dependent modification of the distribution of excited modes, which in turn modifies the efficiency of involved nonlinear effects. Our results provide indirect evidence of periodic nonlinear mode coupling occurring in graded-index multimode fibers thanks to the modal four-wave-mixing phase-matched via Kerr-induced dynamic index grating.
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