Dispersion-shifted all-solid high index-contrast microstructured optical fiber for nonlinear applications at 1.55µm

We report the fabrication of an all-solid highly nonlinear microstructured optical fiber. The structured preform was made by glass extrusion using two types of commercial lead silicate glasses that provide high index-contrast. Effectively single-moded guidance was observed in the fiber at 1.55µm. The effective nonlinearity and the propagation loss at this wavelength were measured to be 120W/km respectively at 1.55µm. These predictions are consistent with the experimentally determined dispersion of +12.5ps/nm/km at 1.55µm. Tunable and efficient four-wave-mixing based wavelength conversion was demonstrated at wavelengths around 1.55µm using a 1.5m length of the fiber

Multichannel wavelength conversion of 40 Gbit/s NRZ DPSK signals in a highly nonlinear dispersion flattened lead silicate fibre

We experimentally demonstrate the wavelength conversion of three wavelength multiplexed 40 Gbit/s Differential Phase Shift Keyed (DPSK) signals in a 2.2m length of highly nonlinear, dispersion tailored W-type lead-silicate optical fibre

The hydrogen sulfide releasing molecule acetyl deacylasadisulfide inhibits metastatic melanoma

Melanoma is the most common form of skin cancer. Given its high mortality, the interest in the search of preventive measures, such as dietary factors, is growing significantly. In this study we tested, in vitro and in vivo, the potential anti-cancer effect of the acetyl deacylasadisulfide (ADA), a vinyl disulfide compound, isolated and purified from asafoetida a foul-smelling oleo gum-resin of dietary and medicinal relevance. ADA markedly suppressed proliferation of human melanoma cell lines by inducing apoptosis. Moreover, treatment of melanoma cells with ADA reduced nuclear translocation and activation of NF-κB, decreased the expression of the anti-apoptotic proteins c-FLIP, XIAP, and Bcl-2 and inhibited the phosphorylation and activation of both AKT and ERK proteins, two of the most frequently deregulated pathways in melanoma. Finally, the results obtained in vitro were substantiated by the findings that ADA significantly and dose-dependently reduced lung metastatic foci formation in C57BL/6 mice. In conclusion, our findings suggest that ADA significantly inhibits melanoma progression in vivo and could represent an important lead compound for the development of new anti-metastatic agents

New optical fibre based technologies and their application in highly nonlinear systems

This thesis investigates new fibre technologies and their application in nonlinear optical systems, designed mainly for telecommunications. The thesis includes a study of two different directions in achieving a high nonlinearity in a fibre system, namely holey fibres filled with nonlinear liquids and soft glass, small core microstructured fibres. The challenges arising from the development of liquid-filled structures have made soft glass microstructured fibres the technology of choice for the realisation of highly nonlinear systems.Amongst the various soft glasses, commercially available lead-silicate glasses are identified as the material for the development of highly nonlinear fibres. Small-core, leadsilicate fibres with different designs are considered within this thesis. A solid core holey fibre design as well as two all-solid designs, a multi-ring cladding and a simpler W-index profile, are characterised. The measurements confirm the advantages of the all-solid designs over the holey structures and reveal the possibility to achieve simultaneously a high nonlinear coefficient and a novel dispersion profile in such fibres. Some of the presented fibres are employed in all-optical wavelength conversion schemes based on four-wave-mixing. Numerical simulations and experimental results are combined to study the performance of the fibres and demonstrate their use in wavelength conversion devices. In particular, a lead-silicate W-index profile fibre, showing a high nonlinear coefficient of 820W-1km-1 with a near zero dispersion profile at telecoms wavelengths, is employed to demonstrate a flat conversion gain in the whole C-band. The same fibre is then employed in FWM-based systems to demonstrate multi-channel wavelength conversion, generation of high repetition rate pulses and all-optical demultiplexing. The experiments presented in this thesis clearly reveal the potential of small-core soft-glass fibres for nonlinear applications.The use of soft glass microstructured fibres in the mid-IR is also investigated. Tellurite holey fibres with different core sizes and hole arrangements are employed in a supercontinuum generation scheme

Four-wave mixing-based wavelength conversion in a short-length of a solid 1D microstructured fibre

We demonstrate a four-wave mixing based wavelength conversion scheme at 1.55µm in a 1.5m long highly nonlinear, dispersion tailored one-dimensional (1D) soft glass microstructured optical fibre

160-to-40Gbit/s time demultiplexing in a low dispersion lead-silicate W-index profile fiber

A 2.2m long sample of lead-silicate W-index profile fiber with nonlinear coefficient of 820W-1km-1 and exhibiting low and flat dispersion across the C-band is used in an all-optical 160-to-40Gbit/s demultiplexing scheme based on four-wave-mixing

Experimental investigation of a parabolic pulse generation using tapered microstructured optical fibres

It has been shown that the parabolic pulses can be generated under certain conditions within normally dispersive optical amplifiers by exploiting the interplay between gain, nonlinearity and dispersion. Passive means to generate parabolic pulses have also been exploited and in previous experiments it has been investigated e.g. in a comb-like profiled dispersion decreasing fibre or using single conventional dispersion decreasing optical fibres. Tapered microstructured optical fibres represent an alternative way to produce the required dispersion decreasing fibre. This method is ideal for producing metre-length tapers needed to efficiently generate parabolic pulses starting from femtosecond pulses.In this paper we experimentally and numerically demonstrate the possibility of parabolic pulse generation in a normally dispersive microstructured optical fibre taper. The microstructured optical fibre that was initially in the anomalous dispersion regime was tapered to achieve normal dispersion values. The fibre parameters were measured and the taper's parameters determined to obtain a desirable linear taper profile. Using novel tapering facility we fabricated 1.8m long taper. The experimental study of parabolic pulse generation has been compared with the numerical simulations. The pulse propagating through the taper was characterized using linear FROG method. A qualitative agreement between the results of experiment and simulation was demonstrated. The consistent convergence towards the parabolic pulse at the taper's output is observed with increasing in the input pulse power levels. The quality of the parabolic pulses was quantified using a misfit parameter, which reached value of 0.0032, when maximum power level has been applied. It has been shown that the initial pulse FWHM of 0.59ps has been shaped into a pulse of 1.22ps FWHM (which has a root mean square error against the parabolic fit of 0.0032). These results suggest the possibility of achieving better parabolic pulses if the optimum launching conditions can be achieved or longer taper fabricated

Single-mode tellurite glass holey fiber with extremely large mode area for infrared nonlinear applications

We report the fabrication of a large mode area tellurite holey fiber from an extruded perform, with a mode area of 3000µm2. Robust single-mode guidance at 1.55µm was confirmed by both optical measurement and numerical simulation. The propagation loss was measured as 2.9dB/m at 1.55µm. A broad and flat supercontinuum from 0.9 to 2.5µm with 6mW output was obtained with a 9cm length of this fiber

Dispersion controlled highly nonlinear fibers for all optical processing at telecoms wavelengths

We review our recent progress in the development of lead silicate glass fibers with high nonlinearity and tailored near-zero dispersion at telecommunication wavelengths, encompassing holey, all-solid microstructured and W-type fiber designs. The fabrication techniques and relative merits of each fiber design are described in detail. The optical properties of the fabricated fibers are assessed both experimentally and through accurate numerical simulations. The significant potential of lead silicate highly nonlinear fibers for all-optical signal processing at telecommunication wavelengths is shown via a number of key experimental demonstrators