1,720,997 research outputs found
Microfiber devices based on evanescent field coupling
No full textMicrofiber (MF) devices are increasingly becoming attractive building blocks for numerous applications. This is attributed to a combinations of enabling properties including large evanescent field, compactness, low insertion loss and, most importantly, their configurability. This thesis describes the evanescent field coupling in MF devices in different forms and applications, such as microresonators for sensing, modal couplers for mode conversion and nonlinear frequency conversion.Micro-resonators are devices based on evanescent field coupling between turns of adjacent segments of the MF. Light inside these devices is confined within the resonator structure and trapped inside its cavity. Light, therefore, follows a longer path before passing to the output and this is wavelength dependent. A new type of resonator was successfully designed and manufactured: the multiport MF coil resonator. This structure has excellent features such as high extinction ratio, multiple resonance peaks and high stability.Novel modal couplers were also analysed and fabricated with high conversion efficiencies, high modal purity and low insertion loss. Modal couplers were manufactured to convert the launched input LP01 mode, into any of the higher order modes supported by the fiber. High conversion efficiencies were demonstrated for the LP11,LP21 and the LP02 modes.A MF coupler was successfully used for the detection of DNA by exploiting hybridisation on the surface of the MF coupler. The large evanescent field of the MF allows to detect the refractive index change that occurs when DNA attaches to the surface. Detection limits in the range of 10-6 per Refractive Index Unit (RIU) and sensitivities as high as 200nm/RIU were obtained.Nonlinearities were investigated both in straight MF and MF resonators, with particular stress on the second and third harmonic generation. While the conversion efficiency remained relatively low for straight MFs, by using a loop resonator, the circulation of pump power (at resonance) inside the loop allowed for a conversion efficiency enhancement of 7.7 dB for the Third harmonic generation (THG) and 7.6 dB for the Second Harmonic Generation(SHG). Knot resonators were also used and provided larger enhancement of 14.2 dB for the SHG signal
Dataset for Removing the directional degeneracy of LP11 mode in a fused-type mode selective coupler
No full textDataset to support:
Ismaeel, R. and Brambilla, G. (2016) Removing the Directional Degeneracy of LP11 Mode in a Fused-Type Mode Selective Coupler. Journal of Lightwave Technology, 34, (4), 1242-1246</span
Direct extrusion of hollow-core microstructured polymer optical fiber from 3D printer
No full textA novel technique for the fabrication of a hollow-core antiresonant polymer optical fiber is proposed. The fiber is directly extruded and drawn from a 3D printer in a single step procedure using a nozzle with inverted micro-structure. The possibility of exploiting fibers made from acrylonitrile butadiene styrene (ABS) for guiding CO2 laser (λ ~ 10.6 µm) is assessed analyzing the profile of the confinement loss
Magnetic field sensor based on multi-port microcoil resonator
No full textA multi-port microcoil resonator magnetic field sensor based on a microfiber coupler coil resonator (MMCR) is presented. The microfiber coupler coil is fabricated by coiling a four-port microfiber coupler with a uniform waist region around a low index support rod. The MMCR is embedded in a low refractive index polymer to increase the robustness and operation stability. The enhanced sensor response to the magnetic field is ascribed to the diverse MMCR response to the light polarization state. The MMCR magnetic field sensor is compact and low cost, and exhibits a magnetic field sensitivity of 37.09 dB/T with an estimated minimum detection limit (DL) of ~ 27 µT
A nano-fiber coupler thermometer
No full textOptical fiber couplers with ~300nm waist diameter are used as compact temperature sensors from room temperature to 661oC, showing an average temperature sensitivity of 55 pm/ºC and a maximum sensitivity of 60pm/ºC at the highest temperature
Fast-response and High sensitivity nanofiber coupler thermometer
No full textWe report a high speed optical fibre thermometer based on a nanofiber coupler (NFC) working in the spectral region close to the odd supermode cut-off. The ~300 nm waist diameter nanofiber coupler was fabricated from two standard telecom fibres (Corning SMF-28) and was used as a compact temperature sensor from room temperature to 661 ℃. Due to its small size and the close proximity to the odd supermode cut-off, the NFC had a response time of ~ 7.2 ms and a temperature sensitivity of 55 pm/℃
All-fiber fused directional coupler for highly efficient spatial mode conversion
Full text linkWe model and demonstrate a simple mode selective all-fiber coupler capable of exciting specific higher order modes in two- and few-mode fibres with high efficiency and purity. The coupler is based on inter-modally phase-matching the propagation constants in each arm of the asymmetric fused coupler, formed by dissimilar fibres. At a specific coupler diameter, the launched fundamental LP01 mode is coupled into the higher order mode (LP11, LP21, LP02) in the other arm, over a broadband wavelength range around 1550 nm. Unlike other techniques, the demonstrated coupler is composed of a multimode fiber that is weakly fused with a phase matched conventional single mode telecom fiber (SMF-28). The beating between the supermodes at the coupler waist produces a periodic power transfer between the two arms, and therefore, by monitoring the beating while tapering, it is possible to obtain optimum selection for the desired mode. High coupling efficiencies in excess of 90% for all the higher order modes were recorded over 100 nm spectral range, while insertion losses remain as low as 0.5 dB. Coupling efficiency can be further enhanced by performing slow tapering at high temperature, in order to precisely control the coupler cross-section geometry
Optical fibers for bio-sensing applications
No full textHere we discuss several different pathways of exploiting optical fibers for sensing applications. We demonstrate that fused optical fiber couplers can operate as a sensitive refractometers and thermometers. Their potential for bio-sensing applications is also discussed. We also discuss application of plastic fibers for accessing mid-IR spectral region for optical sensing.</p
Polarization maintaining mode selective coupler
No full textSimple all-fiber coupler is presented as solution to the missing MDM component in the future all fiber networks. It is capable of exciting specific higher order mode at the required spatial direction with high efficiency
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