1,721,295 research outputs found
Design of an extra-low-loss broadband Y-branch waveguide splitter based on a tapered MMI structure
No full textAn optimal design for an extra-low loss buried waveguide Y-branch splitter is presented over a broadband wavelength range from 1500~1600 nm. A tapered multimode waveguide section, earlier used to reduce the excess loss, is optimized when the light distribution at the end of the multimode waveguide section is matched to the profile of the symmetric supermode for the structure of the two branching waveguides. An optimization that combines genetic algorithm and a gradient-based search method are used to obtain the optimal geometrical parameters for the multimode waveguide section as well as the widths for the input and branching waveguides. An excess loss of 0.015 dB @1550 nm was obtained after the proposed optimization. For these optimized parameters, even when packaging induces a typical offset between input standard singlemode fibre and waveguide, the wavelength dependence of the output ratio between the two branches is small (less than 0.03 dB)
Long period grating inscribed in multimode fibre interferometer and its application in refractive index sensing
Full text linkA long period grating (LPG) is inscribed by a femtosecond laser in the multimode region of a singlemode-multimode-singlemode fibre device to provide a compact refractive index sensor. An average sensitivity of 39 nm/RIU and a resolvable index change of 2.56×10-4 are obtained experimentally with a 44.4 mm long multimode fibre over a measured refractive index range of 1.33-1.35. Because of its compactness, ease of fabrication, linear response, high sensitivity, easy connectivity to other fiberized optical components and low cost, this refractometer could find various applications in chemical and biological sensing
A Review of Multimode Interference in Tapered Optical Fibers and Related Applications
Full text linkIn recent years, tapered optical fibers (TOFs) have attracted increasing interest and developed into a range of devices used in many practical applications ranging from optical communication, sensing to optical manipulation and high-Q resonators. Compared with conventional optical fibers, TOFs possess a range of unique features, such as large evanescent field, strong optical confinement, mechanical flexibility and compactness. In this review, we critically summarize the multimode interference in TOFs and some of its applications with a focus on our research project undertaken at the Optoelectronics Research Centre of the University of Southampton in the United Kingdom
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Packaged silica and chalcogenide microspheres and their applications for telecommunications
No full textObjective: To investigate, both theoretically and experimentally, packaged silica and chalcogenide microsphere and their potential applications in telecommunication
All-optical modulation in Black Phosphorus functionalized microfibre coil resonator
No full textAll-optical modulation is experimentally demonstrated in a microfibre coil resonator (MCR) functionalized with black phosphorus (BP) nanosheets (BP-MCR). The BP nanosheets is deposited onto microfibre and then microfibre is wrapped on a PMMA rod covered with UV-curable low refractive index polycarbonate (PC) resin. The BP-MCR modulation properties are regulated based on BP absorption, photo-thermal and optical Kerr effects. The resonance wavelength and extinction ratio responsivity to incident pump power can attain ∼0.033 nm mW-1 and ∼0.180 dBm mW-1, while the averaged rising/falling response time is ∼9.58/8.53 ms. The device could find applications as all-optical modulator, optical switch or tunable optical filter.</p
2.4 μm fluorescence of holmium doped fluoroaluminate glasses
No full textHo3+-doped fluoroaluminate glass samples were fabricated by melt-quenching. Intense 2.4 μm emission was observed under pumping of a 638 nm laser diode, which was ascribed to the Ho3+:5F5→5I5 transitions. The Judd-Ofelt (J-O) theory was applied to predict the radiative probabilities, radiative lifetimes, and branch ratios of Ho3+ transitions. The emission and absorption cross-sections were calculated, and the gain coefficients determined for a 1 mol% Ho3+ concentration. Our results indicate that Ho3+-doped fluoroaluminate glass has a potential for developing fiber lasers operating at 2.4 μm
Enhanced refractometer based on periodically tapered small core singlemode fiber
Full text linkAn all-fiber refractive index (RI) sensor with a simple configuration of periodical tapers is proposed and investigated experimentally. The proposed fiber RI sensor consists of a small core fiber sandwiched between two standard singlemode fibers, with tapers periodically fabricated along the small core fiber using a focused CO2 laser beam. Such a structure can be used for RI sensing by measuring the dip wavelength shift of the multimode interference within the small core fiber cladding. An average sensitivity of 226.6 nm/RIU (RI Unit) has been experimentally achieved in the RI range from 1.33 to 1.38. The refractometer is sensitive to temperature and an experimental investigation of this sensitivity is presented. It is found that the peak shift response has a linear variation with temperature; therefore, temperature dependence can be mitigated by a suitable RI correction process. The proposed RI sensor benefits from simplicity and low cost and achieves a competitive sensitivity compared with other existing fiber-optic sensors
Fiber-tip high-temperature sensor based on multimode interference
No full textA fiber-tip high-temperature sensor based on multimode interference is demonstrated both theoretically and experimentally. The temperature sensor presented can measure a broad temperature interval ranging from room temperature to 1089°C. An average sensitivity of 11.4 pm/°C is achieved experimentally
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