Photonic microfibre devices based on carbon nanotubes

Abstract

Photonic fibre devices based on the interaction of evanescent fields with materials possessing high Kerr nonlinearity such as carbon nanotubes are promising as an efficient, low loss and low cost devices to be employed in all-optical system applications. Specifically, this report encompasses the work toward addressing the basic key parameters to design and fabricate sufficient all-optical fibre devices based on coated CNTs. Thus, the fundamental concepts of optical fibres; fibre Bragg gratings (FBG), Optical nonlinear (ONL) properties and their effects, CNTs characteristics have been explored. Experimentally, an etch method by utilizing HF acid has been proposed to reduce cladding diameter of the optical fibre and to extend the overlapped evanescent waves to the outer-cladding, thus gaining an efficient interaction with the nonlinear effect of CNTs. And we probed a numerical model for SMF-28 fibre to estimate the fraction of evanescent field coupling within outer-cladding. In addition, real-time monitoring of etching process for both standard fibre SMF-28 and uniform FBG have been applied to demonstrate the influence of etching cladding diameter on the insertion loss of both fibre simultaneously. An optical deposition technique has been proposed to fabricate all-optical fibre devices by CNTs dispersed in DMF solution to be coated on the etched fibre. Moreover, Four wave mixing (FWM) has been performed experimentally and numerically to optimize the fabricated devices. A numerical study has been propped for the effective nonlinear coefficient of the fabricated all-optical fibre devices where it reported on interested results. With the purpose of controlling the losses, the extended fraction of the evanescent field in the etched optical fibre, a simple technique based on measuring, in-situ, the differential relative shifts of the Bragg resonances between the fundamental mode LP01 and the higher-order modes; LP11, LP02, LP21, LP12, LP31 in an etched FBG with accuracy precision ~0.2μm. Furthermore, we determine the refractive index of buffered Hydrofluoric (BHF) acid to be 1.36± 0.005 at 1.55μm. The experimental results were compared with simulations and exhibited excellent agreement. Adding to that, we applied this technique experimentally as a sensor for detecting the change of water salinity and as detector of thermal change based on the relative shifts of between the LP01 and first higher-order mode LP11. This it came matched with the simulations results. A Bragg wavelength shift has been observed about 3.3nm from complete etched cladding of the FBG and has been confirmed simultaneously. In additional work, for thinned FBG the evanescent field of the propagating mode within outer-cladding and the effect of surrounding refractive index on effective refractive index, Bragg wavelength shift for LP01, LP02 and LP03 have been simulated.

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