1,721,006 research outputs found
Method for improving the spectral flatness of the supercontinuum at 1.55 µm in tapered microstructured optical fibers
No full textWe propose a method for enhancing the flatness of a supercontinuum centered at 1.55 µm by the use of specially designed tapered microstructured optical fibers (MOFs). Based on the procedure presented one can determine the linear taper profile parameters and the optimum launching conditions needed to achieve the broadest supercontinuum spectra (SC) and the best spectra flatness. We quantify the maximally broad and flat SC using the calculated standard deviation of the spectra at the required wavelength range and show that it is possible to obtain significantly better results than those obtained by using an untapered fiber
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
Kerr nonlinear switching in silicon fibre-based microcylindrical resonators
Get PDFWe 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
Semiconductor filled microstructured optical fibres with single mode guidance
No full textMicrostructured optical fibre (MOF) technology has generated new opportunities for the implementation of optical fibres with novel properties and functions [1]. It has been shown that silica MOFs make excellent 3D templates for semiconductor material deposition inside the capillary voids [2]. Recently a silicon MOF was designed and fabricated that had a high refractive index micron sized core, but yet only supported two guided modes [3]. This structure was realised via the complete filling of a hollow core photonic bandgap fibre (PBGF) with silicon so that the original air guiding PBGF was converted to a total internal reflection guiding fibre. Here, we extend the investigation by using a finite element method to model the optical properties of semiconductor filled MOFs of similar structures, with the aim to achieve broadband single mode guidance. Strategies to achieve single mode guidance both through the MOF template design and the selective filling of the voids of the original PBGF with semiconductor materials of different indices (silicon, silicon nitride, germanium) are proposed and investigated numerically. In particular, by selectively filling MOF templates with cladding rods that have a slightly raised index over that of the core, index guiding single mode operation can be observed in high index micron sized cores. Small index differences are achievable by controlling the nitrogen content in SiNx and an example of a single mode semiconductor MOF is shown in Figure 1, where the confinement loss of the fundamental mode is ~106 lower than the lowest order cladding mode
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
Novel method for the fabrication of long optical fiber tapers
No full textWe report a novel fiber taper facility that allows the fabrication of fiber tapers between a few centimeters and tens of meters in length and that can be used for standard and microstructured optical fibers (MOFs). Efficient reduction of error in diameter variation is achieved using the velocity control feedback loop. The experimental results of the tapering of both the step index fiber and the MOF are presented. The observed outer diameter tracking error over the taper length was within 1%
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
Guiding properties of large mode area silicon microstructured fibers: a route to effective single mode operation
No full textNumerical simulations are used to investigate the guiding properties of large mode area silicon microstructured fibers. Modal analysis of the isolated high refractive index core and cladding rod inclusions will be applied to show that the guidance mechanism of the composite fiber can be well described via a hybrid of the total internal reflection and antiresonant reflecting optical waveguide models. It will be shown that by selectively filling the cladding holes with silicon, which has been modified to have a slightly raised index, the fiber can be designed to operate in an effectively single-mode regime over an extended wavelength range
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