Andrey D. Pryamikov

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 CO 2 -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.

Single-mode all-silica photonic bandgap fiber with 20-μm mode-field diameter

An all-silica photonic bandgap fiber with a cladding index difference of approximately 2 % and diameter-to-pitch ratio (d/Λ) of 0.12 was fabricated and studied. To our knowledge, this is the first report on the properties of photonic bandgap fiber with such a small d/Λ. The fiber is single-mode in the fundamental bandgap. The mode field diameter in the 1000-1200 nm wavelength range is 19-20 μm. The minimum loss in the same range is 20 dB/km for a 30-cm bending diameter. In our opinion, all-silica photonic bandgap fiber can serve as a potential candidate for achieving single-mode propagation with a large mode area.

Highly dispersive large mode area photonic bandgap fiber.

An all-silica photonic bandgap fiber composed of a low-index core surrounded by alternating high- and low-index rings allows us to achieve a large mode area (500 microm(2)) and large chromatic dispersion. Sharp resonances from the even Bragg mode to odd ring modes theoretically lead to 20,000 ps/(nm km) chromatic dispersion when large bends are applied. By nature, sharp resonances are sensitive to inhomogeneities along the fiber length. Under experimental conditions, the resonances are broadened and the dispersion coefficient is decreased to 1000 ps/(nm km). However, to the best of our knowledge, this is the largest dispersion coefficient reported using a large mode area fiber.

Hollow-core revolver fibre with a double-capillary reflective cladding

We report the fabrication of the first hollow-core revolver fibre with a core diameter as small as 25 μm and an optical loss no higher than 75 dB km-1 at a wavelength of 1850 nm. The decrease in core diameter, with no significant increase in optical loss, is due to the use of double nested capillaries in the reflective cladding design. A number of technical problems pertaining to the fabrication of such fibres are resolved.

Parametric frequency conversion in photonic crystal fibres with germanosilicate core

Numerical analysis of dispersion and nonlinear characteristics of photonic crystal fibres (PCFs) with a small number of hole rings and large (>20 mol%) concentrations of GeO2 in the core is performed. It is shown that by proper choice of the fibre design and, in particular, the diameter of a doped core and the GeO2 concentration, it is possible to obtain a high nonlinearity coefficient simultaneously with the desired dispersion characteristic and to realize efficient parametric frequency conversion with large Stokes shifts at a pump in the vicinity of 1.1 µm.

Very-large-mode-area photonic bandgap Bragg fiber polarizing in a wide spectral range

A design of a polarizing all-glass Bragg fiber with a microstructure core has been proposed for the first time. This design provides suppression of high-order modes and of one of the polarization states of the fundamental mode. The polarizing fiber was fabricated by a new, simple method based on a combination of the modified chemical vapor deposition (MCVD) process and the rod-in-tube technique. The mode field area has been found to be about 870 μm² near λ=1064 nm. The polarization extinction ratio better than 13 dB has been observed over a 33% wavelength range (from 1 to 1.4 μm) after propagation in a 1.7 m fiber piece bent to a radius of 70 cm.

Polarization-maintaining photonic bandgap Bragg fiber

The possibility of fabricating a polarization-maintaining Bragg fiber has been studied. It is shown that violation of the cylindrical symmetry of a Bragg mirror in most cases results in a sharp increase in optical loss, which is caused by resonance transmission through the Bragg mirror at wavelengths near the cutoffs of the modes of the high-index rings with a nonzero azimuthal index. It is shown that placing stress-applied parts or air holes inside the Bragg fiber core allows one to avoid this effect. A polarization-maintaining Bragg fiber with perfect light confinement in the core is demonstrated for the first time to our knowledge.

All-solid photonic bandgap fiber with large mode area and high order modes suppression

We present all-solid bandgap fiber design with the small ratio of cladding elements diameter to pitch (0.24), with MFD of 36 m at 1 m wavelength and higher order mode suppression caused by the propagation loss difference.

Four-wave mixing with large stokes shifts in heavily Ge-doped silica fibers.

Four-wave mixing (FWM) in nonlinear germanosilicate fibers with GeO2 concentrations as high as 67 mol.% in the core is studied theoretically and experimentally. Large frequency shifts of 1875-3829 cm(-1) are observed in the mixed-mode pump parametric process. The dependence of FWM phase matching on the GeO2 concentration, core diameter, and index profile is demonstrated. The 2.5% conversion efficiency of an 887 nm signal to a 1.3 microm communication band is obtained at a 2 W cw pump power inside the fiber.