Inscription of polymer optical fiber Bragg grating at 962 nm and its potential in strain sensing

Author name used in this publication: Zhi Feng ZhangAuthor name used in this publication: Xiao Ming TaoAuthor name used in this publication: Guang Feng Wang2010-2011 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Asymmetric long period fiber gratings fabricated by use of CO₂laser to carve periodic grooves on the optical fiber

Author name used in this publication: Peng, Gang-DingAuthor name used in this publication: Wang, Yi-Ping2006-2007 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Improving broadband emission within Bi/Er doped silicate fibres with Yb co-doping

© 2015 Optical Society of America. We present Bi/Er/Yb co-doped silicate fibre (BEYDF) which is fabricated by co-doping with Yb2O3 into Bi/Er doped silicate fibre (BEDF), and investigate its properties associated with Yb co-doping. Spectral absorption, emission, emission lifetime, ESA and gain characteristics of BEYDF are experimentally investigated and compared with those of BEDF to reveal particular impacts of Yb on the broadband spectral characteristics. We measured Yb3+ emissions at 980 nm and 1040 nm in BEYDF, and emissions related to Bi active centres (BACs, at 1100 nm and 1420 nm) and Er3+ (1530 nm) in BEYDF and BEDF under 830 nm pumping. Evidences of Yb3+→BAC energy transfer process, in addition to the normal Yb3+→Er3+ energy transfer process are noticed. Compared with BEDF, BEYDF has shown both broadened and enhanced emissions and gain. In particular, the overall emission bandwidth within a 4 dB intensity is attained over Δλ = (1000-1590) nm in BEYDF, and just over Δλ = (1250-1590) nm in BEDF. The overall emission intensity is enhanced by a factor of 2.5 in BEYDF over that of BEDF. Furthermore, Er3+ gain at 1530 nm is increased and BAC linked ESA at 1400 nm is reduced in BEYDF. Yb3+ related emissions and energy transfers from the excited Yb3+ to both the Er3+ and BACs can explain the improvements of emission and gain. These results indicate that Yb3+ co-doping can be used to expand and enhance broadband emissions and gain in BEYDFs

Enhanced broadband near-IR luminescence and gain spectra of bismuth/erbium co-doped fiber by 830 and 980 nm dual pumping

© 2017 Author(s). A dual 830 and 980 nm pumping scheme is proposed aiming at broadening and flattening the spectral performance of bismuth/erbium codoped multicomponent fiber (BEDF). The spectral properties of distinct Bi active centers (BACs) associated with germanium (BAC-Ge), aluminium (BAC-Al), phosphorus (BAC-P) and silicon (BAC-Si) are characterized under single pumping of 830 and 980 nm, respectively. Based on the emission slope efficiencies of BAC-Al (∼1100 nm) and BAC-Si (∼1430 nm) under single pumping of 830 and 980 nm, the dual pumping scheme with the optimal pump power ratio of 25 (980 nm VS 830 nm) is determined to achieve flat, ultrabroadband luminescence spectra covering the wavelength range 950-1600 nm. The dual pumping scheme is further demonstrated on the on-off gain performance of BEDF. It is found under the pump power ratio of ∼8 (980 VS 830 nm), The gain spectrum has been flattened and broadened over 300 nm (1300-1600 nm) with an average gain coefficient of ∼1.5 dBm-1. The spectral coverage is approximately 1.5 and 3 times wider compared to single pumping of 830 and 980 nm pumping, respectively. The energy level diagrams of 830 and 980 nm are also constructed separately in view of the optical characteristic, which further clarifies the advantage for dual pumping. The proposed dual 830 and 980 nm pumping scheme with the multicomponent BEDF shows great potential in various broadband optical applications such as uniform ASE source, broadband amplifier and tuneable laser in NIR band

TraMNet - Transition Matrix Network for Efficient Action Tube Proposals

Current state-of-the-art methods solve spatiotemporal action localisation by extending 2D anchors to 3D-cuboid proposals on stacks of frames, to generate sets of temporally connected bounding boxes called \textit{action micro-tubes}. However, they fail to consider that the underlying anchor proposal hypotheses should also move (transition) from frame to frame, as the actor or the camera does. Assuming we evaluate $n$ 2D anchors in each frame, then the number of possible transitions from each 2D anchor to the next, for a sequence of $f$ consecutive frames, is in the order of $O(n^f)$, expensive even for small values of $f$. To avoid this problem, we introduce a Transition-Matrix-based Network (TraMNet) which relies on computing transition probabilities between anchor proposals while maximising their overlap with ground truth bounding boxes across frames, and enforcing sparsity via a transition threshold. As the resulting transition matrix is sparse and stochastic, this reduces the proposal hypothesis search space from $O(n^f)$ to the cardinality of the thresholded matrix. At training time, transitions are specific to cell locations of the feature maps, so that a sparse (efficient) transition matrix is used to train the network. At test time, a denser transition matrix can be obtained either by decreasing the threshold or by adding to it all the relative transitions originating from any cell location, allowing the network to handle transitions in the test data that might not have been present in the training data, and making detection translation-invariant. Finally, we show that our network can handle sparse annotations such as those available in the DALY dataset. We report extensive experiments on the DALY, UCF101-24 and Transformed-UCF101-24 datasets to support our claims.Comment: 15 page

Transition of lasing modes in disordered active photonic crystals

Author name used in this publication: K. C. KwanAuthor name used in this publication: X. M. TaoAuthor name used in this publication: G. D. Peng2007-2008 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Air-structured optical fiber drawn from a 3D-printed preform

© 2015 Optical Society of America. A structured optical fiber is drawn from a 3D-printed structured preform. Preforms containing a single ring of holes around the core are fabricated using filament made from a modified butadiene polymer. More broadly, 3D printers capable of processing soft glasses, silica, and other materials are likely to come on line in the not-so-distant future. 3D printing of optical preforms signals a new milestone in optical fiber manufacture

Polarization mode coupling and related effects in fiber Bragg grating inscribed in polarization maintaining fiber

©2016 Optical Society of America. Polarization mode coupling (PMC) and related effects from writing fiber Bragg gratings in polarization maintaining fiber (FBGs-in- PMF) are observed experimentally for the first time by optical fiber coherence domain polarimetry (OCDP) using a broadband light source. PMC is another useful aspect of FBG-in-PMF besides Bragg wavelength and its possible potential is evaluated and discussed. A localized and long range temperature measurement based on the PMC and Bragg wavelength is given as an example

Spun High Birefringence Bismuth/Erbium Co-Doped Photonic Crystal Fibre with Broadband Polarized Emission

© 2018 IEEE. Spun Hi-Bi bismuth/erbium co-doped photonic optical fibre (SHB-BEPCF) has been fabricated using preform stacking and draw tower self-pressurization. Results demonstrate broadband and partially elliptical polarized NIR emission under un-polarized 830 nm pumping spanning Δλ ~ 520 nm centred at 1430 nm

Percolation diffusion into self-assembled mesoporous silica microfibres

© 2014 by the authors. Percolation diffusion into long (11.5 cm) self-assembled, ordered mesoporous microfibres is studied using optical transmission and laser ablation inductive coupled mass spectrometry (LA-ICP-MS). Optical transmission based diffusion studies reveal rapid penetration ( 80 μm2·s−1) of Rhodamine B with very little percolation of larger molecules such as zinc tetraphenylporphyrin (ZnTPP) observed under similar loading conditions. The failure of ZnTPP to enter the microfibre was confirmed, in higher resolution, using LA-ICP-MS. In the latter case, LA-ICP-MS was used to determine the diffusion of zinc acetate dihydrate, D~3 × 10−4 nm2·s−1. The large differences between the molecules are accounted for by proposing ordered solvent and structure assisted accelerated diffusion of the Rhodamine B based on its hydrophilicity relative to the zinc compounds. The broader implications and applications for filtration, molecular sieves and a range of devices and uses are described