186,994 research outputs found
Novel applications of fibre tapers
No full textIn this talk we will discuss new applications for fibre tapers ranging from femtosecond pulse manipulation to optical clock generation in micro-coil resonators. Fundamental to these interactions is the enhanced nonlinearity arising from the smaller cores making compact optical devices possible
Optical properties of long photonic crystal fibre tapers
No full textIn this thesis I investigate optical properties of metre - long tapers. Microstructured optical fibre technology has created new opportunities in a broad range of science and technology. In the work presented in this thesis I have combined the microstructured optical fibre technology with a novel tapering facility in order to develop new applications in the field of nonlinear optics. This thesis concerns development of a novel tapering facility, capable of achieving intermediate length (few tens of cm to ~10 m) tapers. In comparison with systems presented to date, the novel system has the advantage of the increased control over the desired taper profile and enables efficient fabrication of intermediate taper lengths of potentially arbitrary profiles. During the fabrication the fibre diameter exhibits significant variations, due to various disturbances. A design of the feedback loop for the enhanced control of the output diameter variation is proposed. The system capabilities have been tested and demonstrated in many different examples. The presented results show that the variation of the fibre diameter is within ~1%, which offers possibilities to use the system in various applications. As an example of the intermediate taper length design and application, parabolic pulse generation was investigated. It represents a very attractive pulse shape, since it can propagate at high peak powers while avoiding wave-breaking effect and have a flat and broad spectrum, which could lead to pulse compression applications. This thesis presents numerical modelling and experimental results (restricted to a set of parameters of fibres available from ’stock’) concerning this phenomena. Supercontinuum generation is an area of research that has been attracting scientific interest over several decades. This thesis shows results of a study of supercontinuum generation in intermediate length tapered microstructured optical fibres. A simulation tool has been developed and the procedure to efficiently determine optimum conditions for improving flatness of the supercontinuum spectra has been proposed. The proposed method concerns a ’standard’ microstructured optical fibre, but generally can be extended to different fibre designs
Kerr nonlinear switching in silicon fibre-based microcylindrical resonators
No full textWe investigate the Kerr nonlinearity in a a-Si:H microcylindrical resonator fabricated from the silicon fibre platform. The large resonant wavelength shift observed for pulsed excitation is used to demonstrate ultrafast all-optical switching
Characterization of thermal induced nonlinear effects in silicon microcylindrical resonators
No full textWe explore the thermal nonlinearity in hydrogenated amorphous silicon microcylindrical resonators that are fabricated from the silicon optical fiber platform. In particular, we use a pump/probe technique to experimentally determine the thermal response time from which we can infer the material absorption coefficient
Whispering gallery modes in semiconductor optical fibres and optical bottle microresonators
No full textWe explore the optical properties of whispering gallery modes (WGMs) in silicon optical fibres and optical bottle microresonators. In particular, a pump-probe technique is used to experimentally demonstrate thermally induced all-optical modulation. High quality (Q) factors and small mode volumes are utilized to demonstrate ultrafast Kerr effect based modulation and switching. Q factors exceeding ~107 are demonstrated for novel microbottle resonators (MBRs), fabricated from standard telecommunications fibres
Supplemental material for this article is available online.
No full textSupplemental Material for Nexus of Bank Income Structure and Risk: Evidence from Balkans by Dusko Ranisavljevic, Darko B. Vukovic and Moinak Maiti, in Global Business Review</p
Nonlinear optics in silicon fibre micro structures
No full textSilicon photonic devices are becoming an increasingly popular platform for nonlinear optical applications owing to the high Kerr nonlinearity and tight optical confinement. Although typically these devices are fabricated from silicon planar wafers using standard photolithographic and etching techniques, more recently alternative fiber-based platforms have emerged [1]. In this paper we will review methods to fabricate novel micro-scale devices from our silicon fiber platform using standard fiber post-processing techniques. Fig. 1 shows two geometries that are unique to the fiber platform; microcylindrical silicon resonators [2] and tapered silicon core waveguides [3]. The ability to arbitrarily tailor the dimensions in these devices to manipulate the light confinement is of particular interest for low power, high speed nonlinear optical processing. For example, we will show that the ultra-small mode volume of the resonators can be exploited for ultrafast Kerr optical switching and modulation, whilst the longitudinally varying waveguide parameters of the tapers can be used for nonlinear pulse shaping at modest power levels
Demonstration of Kerr nonlinearity in silicon microcylindrical resonators
No full textWe investigate the Kerr nonlinearity in a-Si:H based microcylindrical resonators. The large resonant wavelength shift observed for pulsed excitation is used to demonstrate ultrafast alloptical switching
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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