Soluble Fluorinated Cardo Copolyimide as an Effective Additive to Photopolymerizable Compositions Based on Di(meth)acrylates: Application for Highly Thermostable Primary Protective Coating of Silica Optical Fiber.

The development of photocurable compositions is in high demand for the manufacture of functional materials for electronics, optics, medicine, energy, etc. The properties of the final photo-cured material are primarily determined by the initial mixture, which needs to be tuned for each application. In this study we propose to use simple systems based on di(meth)acrylate, polyimide and photoinitiator for the preparation of new photo-curable compositions. It was established that a fluorinated cardo copolyimide (FCPI) based on 2,2-bis-(3,4-dicarboxydiphenyl)hexafluoropropane dianhydride, 9,9-bis-(4-aminophenyl)fluorene and 2,2-bis-(4-aminophenyl)hexafluoropropane (1.00:0.75:0.25 mol) has excellent solubility in di(met)acrylates. This made it possible to prepare solutions of FCPI in such monomers, to study the effect of FCPI on the kinetics of their photopolymerization in situ and the properties of the resulting polymers. According to the obtained data, the solutions of FCPI (23 wt.%) in 1,4-butanediol diacrylate (BDDA) and FCPI (15 wt.%) in tetraethylene glycol diacrylate were tested for the formation of the primary protective coatings of the silica optical fibers. It was found that the new coating of poly(BDDA-FCPI23%) can withstand prolonged annealing at 200 °C (72 h), which is comparable or superior to the known most thermally stable photo-curable coatings. The proposed approach can be applied to obtain other functional materials.

Light transmission in negative curvature hollow core fiber in extremely high material loss region.

In this paper we demonstrate the light transmission in a spectral range of 2.5 to 7.9 µm through a silica negative curvature hollow core fiber (NCHCF) with a cladding consisting of eight capillaries. A separation between the cladding capillaries was introduced to remove the additional resonances in the transmission bands. The measured optical loss at 3.39 µm was about 50 dB/km under a few modes waveguide regime.

Demonstration of a waveguide regime for a silica hollow--core microstructured optical fiber with a negative curvature of the core boundary in the spectral region > 3.5 µm.

We present a numerical and experimental demonstration of a waveguide regime in a broad band spectral range for the hollow core microstructured optical fibers (HC MOFs) made of silica with a negative curvature of the core boundary. It is shown that HC MOFs with the cladding consisting only of one row of silica capillaries allows to guide light from the near to mid infrared despite of high material losses of silica in this spectral region. Such result can be obtained by a special arrangement of cladding capillaries which leads to a change in the sign of the core boundary curvature. The change in the sign of the core boundary curvature leads to a loss of simplicity of boundary conditions for core modes and to "localization" and limitation of their interaction with the cladding material in space. Such HC MOFs made of different materials can be potential candidates for solving problem of ultra high power transmission including transmission of CO and CO2 laser radiation.

Demonstration of CO2-laser power delivery through chalcogenide-glass fiber with negative-curvature hollow core.

A technologically simple optical fiber cross-section structure with a negative-curvature hollow-core has been proposed for the delivery of the CO2 laser radiation. The structure was optimized numerically and then realized using Te20As30Se50 (TAS) chalcogenide glass. Guidance of the 10.6 µm СО2-laser radiation through this TAS-glass hollow-core fiber has been demonstrated. The loss at λ=10.6 µm was amounted ~11 dB/m. A resonance behavior of the fiber bend loss as a function of the bend radius has been revealed.

Broadband wavelength conversion in a germanosilicate-core photonic crystal fiber.

A photonic crystal fiber with a germanosilicate core having a nonlinear coefficient of 40 (W km)(-1) near the single dispersion zero at 1.09 microm is fabricated and studied. Broadband parametric wavelength conversion of the Ti:sapphire laser output tunable at 0.8 microm to the 1.55 microm band is obtained at 1.064 microm cw pump. The tuning of the converted signal in the 300 nm range was first realized without variation of the pump wavelength.