2020

• Record 433 of
  
  Title:VSe2 nanosheets for ultrafast fiber lasers
  
  Author(s):Li, Lu(1); Pang, Lihui(2); Zhao, Qiyi(1); Liu, Wenjun(3); Su, Yulong(4)
  Source: Journal of Materials Chemistry C  Volume: 8  Issue: 3  DOI: 10.1039/c9tc06159b  Published: 2020  
  Abstract:In this work, we investigate VSe2 for generating femtosecond and large energy mode-locked laser pulses for the first time. Two types of VSe2 based saturable absorbers (SAs), microfiber-VSe2 and VSe2/polyvinyl alcohol (PVA), are prepared, which exhibit strong nonlinear optical characteristics with a modulation depth (ΔT) of 22.5% and 1.849%, respectively. In contrast to other transition metal dichalcogenides (TMDCs), theoretical calculations show that VSe2 is a metallic TMDC SA. With the implementation of microfiber-VSe2, conventional soliton mode-locking Er-doped fiber (EDF) laser is demonstrated with an ultrashort pulse duration of 910 fs. Based on VSe2/PVA, a large energy EDF laser is established. The maximum single pulse energy is 25.57 nJ. This study suggests that VSe2 possesses application potential in ultrafast photonics and provides a valuable strategy for the development of TMDC based devices with desirable optoelectronic properties. This journal is © The Royal Society of Chemistry.
  Accession Number: 20200508102238
• Record 434 of
  
  Title:Wavelength locking in a large-smile diode-laser array using dual-beam transformation systems
  
  Author(s):Liu, Bin(1,2); Liu, Hui(1); Chen, Fenning(3); Li, Haiyan(3); Liu, Xingsheng(3)
  Source: Applied Optics  Volume: 59  Issue: 11  DOI: 10.1364/AO.388241  Published: April 10, 2020  
  Abstract:Dual-beam transformation systems (dualBTSs) are used to obtain a wide wavelength-locking range for high-power large-smile diode-laser arrays. The collimating residual divergence angle can be reduced from 9 mrad to less than 6.5 mrad using a set of two angled BTSs that are located in front of a diode-laser array with about a 2μmsmile.Due to the reduced collimating residual divergence angle, the external cavity with a set of two angled BTSs and a volume Bragg grating achieved a wide wavelength-locking range for temperatures ranging from 20°Cto 30°C. In addition, the side-mode suppression ratio exceeds 30 dB. © 2020 Optical Society of America.
  Accession Number: 20201608421676
• Record 435 of
  
  Title:Reduction of beam divergence angle in laser-diode arrays with large smiles using a dual-beam transformation system
  
  Author(s):Liu, Bin(1,2); Liu, Hui(1); Chen, Fenning(3); Li, Haiyan(3); Gao, Lei(3); Zhu, Pengfei(3); Liu, Xingsheng(3)
  Source: Optics Communications  Volume: 462  Issue:   DOI: 10.1016/j.optcom.2020.125279  Published: 1 May 2020  
  Abstract:Two new angled half-beam transformation systems (BTSs) for the reduction of the beam-divergence problem in laser-diode arrays with large smiles are investigated. Both simulations and experiments show that the angle of divergence of laser-diode arrays with the parabola-shaped smile and the S-shaped smile can be reduced by more than 37% and 23% respectively, when two angled half-BTSs are used in front of the laser-diode array. Furthermore, a fiber-coupling module, with a 400μm core-fiber and two angled half-BTSs, is fabricated. The optical/optical coupling efficiency increases to more than 85%, which is an improvement by more than 4% over laser diodes that use a full-BTS. © 2020 Elsevier B.V.
  Accession Number: 20200308059066
• Record 436 of
  
  Title:Photoluminescence of Yb3+/Ce3+ co-doped aluminosilicate glasses under ultraviolet irradiation
  
  Author(s):Feng, Wei(1,2); She, Shengfei(1,2); Wang, Pengfei(1); Liu, Yongsheng(3); Chang, Chang(1,2); Hou, Chaoqi(1); Li, Weinan(1)
  Source: Journal of Non-Crystalline Solids  Volume: 528  Issue:   DOI: 10.1016/j.jnoncrysol.2019.119540  Published: 15 January 2020  
  Abstract:The photoluminescence and decay properties of Yb3+/Ce3+ co-doped aluminosilicate glasses were investigated under ultraviolet irradiation. A strong excitation band was ascribed to 4f → 5d transitions of Ce3+ ions. A broad ultraviolet-visible emission band belonged to 5d → 4f transitions of Ce3+ ions and oxygen-deficient centers (ODCs) in the host matrix, and the visible-near infrared emission band was attributed to non-bridging oxygen hole centers. Comparative tests of the core composition were performed. The results showed Yb2O3 and the ODCs played a crucial role on ultraviolet-visible emission band. ODCs rather than Ce3+ ions were responsible for the 1–35 μs lifetime decay of the ultraviolet-visible emission, but had no contribution to the longer decay lifetimes (77.58 μs) for Ce-free Yb3+-doped glasses. A complex schematic energy-level diagram including the electron transfer mechanism such as Ce3+-Yb3+ → Ce4+-Yb2+, the cooperative up- and down-conversion processes was proposed to describe different luminescence mechanisms UV-expose. © 2019 Elsevier B.V.
  Accession Number: 20193607401713
• Record 437 of
  
  Title:Efficient Optical Angular Momentum Manipulation for Compact Multiplexing and Demultiplexing Using a Dielectric Metasurface
  
  Author(s):Li, Siqi(1,2); Li, Xingyi(1,2); Zhang, Lei(3); Wang, Guoxi(1,2); Zhang, Lingxuan(1,2); Liu, Mulong(1,2); Zeng, Chao(1,2); Wang, Leiran(1,2); Sun, Qibing(1,2); Zhao, Wei(1,2); Zhang, Wenfu(1,2)
  Source: Advanced Optical Materials  Volume: 8  Issue: 8  DOI: 10.1002/adom.201901666  Published: April 1, 2020  
  Abstract:Angular momentum (AM), one of the most basic physical properties of light, has attracted great interest of the scientific community due to its significant values in high-capacity optical communication. To realize AM multiplexing and demultiplexing, the methods based on metallic metasurface are proposed, which suffers from huge Ohmic losses. Besides, additional coupling elements are necessary for coupling the output light into single-mode waveguides. Here, an efficient and focused AM multiplexing and demultiplexing system based on dielectric metasurfaces are proposed and investigated. Employing the off-axis technique and spin photonic Hall effect, the orbital angular momentum (OAM) and spin angular momentum (SAM) multiplexing/demultiplexing can be achieved. A 10-channel AM multiplexing/demultiplexing system based on the proposed method is demonstrated. The demultiplexing efficiencies for all AM stats are above 8% and the maximum crosstalk among all AM states is −12.8 dB, which exhibits an excellent performance of the proposed metasurface for the AM demultiplexing. Furthermore, the output light is focused at the focal plane, which can be directly coupled into the single-mode waveguides and improve the compactness of the system. The proposed method provides an effective way for AM multiplexing and demultiplexing, which possess a crucial potential for high-capacity optical communication applications. © 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
  Accession Number: 20200808199661
• Record 438 of
  
  Title:Improving performance of semipolar (202¯1) light emitting diodes through reduction of threading dislocations by AlGaN/GaN superlattice interlayer
  
  Author(s):Song, Jie(1,2); Choi, Joowon(2); Han, Jung(2)
  Source: Journal of Crystal Growth  Volume: 536  Issue:   DOI: 10.1016/j.jcrysgro.2020.125575  Published: 15 April 2020  
  Abstract:We report reducing the density of threading dislocations (TDs) in stacking-fault-free semipolar (202¯1) GaN grown on sapphire by inserting an AlGaN/GaN superlattice (SL). We have studied the influence of AlGaN/GaN SL on the reduction of TDs and found that the density of TDs decreases by more than a factor of three with increasing the number of AlGaN/GaN SL pairs up to 10. Furthermore, blue light emitting diodes (LEDs) have been grown on semipolar (202¯1) GaN/sapphire templates with inserted 10 pairs of AlGaN/GaN SL showing doubled light output power in comparison with the LEDs grown without AlGaN/GaN SL. © 2020 Elsevier B.V.
  Accession Number: 20200908236603
• Record 439 of
  
  Title:1D Solitons in Saturable Nonlinear Media with Space Fractional Derivatives
  
  Author(s):Shi, Jincheng(1,2,3); Zeng, Jianhua(1,2)
  Source: Annalen der Physik  Volume: 532  Issue: 1  DOI: 10.1002/andp.201900385  Published: January 1, 2020  
  Abstract:Two decades ago, standard quantum mechanics entered into a new territory called space-fractional quantum mechanics, in which wave dynamics and effects are described by the fractional Schrödinger equation. Such territory is now a key and hot topic in diverse branches of physics, particularly in optics driven by the recent theoretical proposal for emulating the fractional Schrödinger equation. However, the light-wave propagation in saturable nonlinear media with space fractional derivatives is yet to be clearly disclosed. Here, such nonlinear optics phenomenon is theoretically investigated based on the nonlinear fractional Schrödinger equation with nonlinear lattices—periodic distributions of either focusing cubic (Kerr) or quintic saturable nonlinearities—and the existence and evolution of localized wave structures allowed by the model are addressed. The model upholds two kinds of one-dimensional soliton families, including fundamental solitons (single peak) and higher-order solitonic structures consisting of two-hump solitons (in-phase) and dipole ones (anti-phase). Notably, the dipole solitons can be robust stable physical objects localized merely within a single well of the nonlinear lattices—previously thought impossible. Linear-stability analysis and direct simulations are executed for both soliton families, and their stability regions are acquired. The predicted solutions can be readily observed in optical experiments and beyond. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
  Accession Number: 20195007813900
• Record 440 of
  
  Title:Temperature distribution induced spectral broadening of high-power diode lasers
  
  Author(s):Wu, DI-Hai(1,2,3); Zhang, Pu(1); Liu, Bin(1,2,3); Zah, Chung-En(2); Liu, Xingsheng(2)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 11261  Issue:   DOI: 10.1117/12.2547159  Published: 2020  
  Abstract:High-power diode lasers are widely used in solid-state and fiber laser pumping. The spectral power distribution (SPD) of diode lasers should be perfectly matched with the absorption peak of gain materials. Spectral broadening would lead to a low optical-optical efficiency for the pump lasers. In this paper, a mathematical model based on multiple Gaussian functions was introduced to characterize the SPD of high-power diode lasers. The effect of temperature and the distribution on laser spectrum was specially included in this model. Temperature distribution in high-power diode lasers was calculated via an analytical three-dimensional thermal model. The temperature difference within the active region for diode lasers with different package structures and under different heat dissipation conditions was demonstrated. The intrinsic SPD for diode lasers with uniform junction temperature distribution was obtained from the experimental measurements in which a cold pulse current was injected into the diode lasers. SPDs for diode lasers under different injected currents were illustrated by this spectrum model, and compared to the experimental results for model validation. SPDs for the diode lasers with different chip architectures and packaging structures was calculated by coupling the analytical temperature fields into the spectrum model. Laser spectrum was verified to be independent of current density, but mainly depend on the junction temperature distribution in the experiments by comparing the spectra of the epi-up and epi-down packaged F-Mount single-emitters at same injected current. © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.
  Accession Number: 20201708569520
• Record 441 of
  
  Title:Flexible Plasmonic Tapes with Nanohole and Nanoparticle Arrays for Refractometric and Strain Sensing
  
  Author(s):Jia, Peipei(1,2,3); Kong, Depeng(1,2,3); Ebendorff-Heidepriem, Heike(1,2,3)
  Source: ACS Applied Nano Materials  Volume: 3  Issue: 8  DOI: 10.1021/acsanm.0c01673  Published: August 28, 2020  
  Abstract:Realization of plasmonic nanostructures on flexible and stretchable substrates have attracted considerable attention because such integration provides novel functionalities for sensing applications. Here, we present a plasmonic tape by achieving metal nanostructures on the transparent tape with a simple transfer technique. Examples include the tapes with nanohole and nanoparticle arrays for refractive index and strain sensing, respectively. These continuing and discrete structures on tapes feature characteristic plasmonic resonances and excellent flexibility. The tape with the nanohole array shows higher sensitivity in the refractive index sensing than that on the rigid substrate. The nanoparticle array used in strain sensing discloses two plasmonic modes with different responses. This plasmonic tape offers a new flexible platform for plasmonic sensing and may open new application possibilities in scenarios inaccessible by conventional plasmonic sensors. © 2020 American Chemical Society.
  Accession Number: 20204209339126
• Record 442 of
  
  Title:Development of an ultra-thin active mirror based on carbon fiber composite
  
  Author(s):Xu, Liang(1); Wang, Yongjie(1); Wu, Xiaoge(1); Ding, Jiaoteng(1); Ma, Zhen(1); Shen, Le(1)
  Source: Optik  Volume: 207  Issue:   DOI: 10.1016/j.ijleo.2020.164463  Published: April 2020  
  Abstract:Aiming at the application requirements of large synthetic aperture for light-weighted mirrors, a kind of ultra-thin active mirrors based on carbon fiber composites proposed. The structure of the mirror is a four-layer laminated structure, and the total thickness is only about 3mm.Using parallel actuation scheme, it has the advantages of low weight, rapid manufacturing, low cost, and smart surface adjustment ability. The design, numeral calculation, manufacture and surface correction test of this kind active mirror discussed in this article. A Φ85mm aperture, 19-channel active mirror prototype developed, and surface correction test shows that the surface accuracy RMS can be corrected from 1.4 λ to 0.15λ, about 10 times improved. © 2020 Elsevier GmbH
  Accession Number: 20200908228988
• Record 443 of
  
  Title:Pencil-beam scanning catheter for intravascular optical coherence tomography
  
  Author(s):Kang, Jiqiang(1); Zhu, Rui(2); Sun, Yunxu(1); Li, Jianan(1); Wong, Kenneth K.Y.(1)
  Source: 2020 Asia Communications and Photonics Conference, ACP 2020 and International Conference on Information Photonics and Optical Communications, IPOC 2020 - Proceedings  Volume:   Issue:   DOI: null  Published: October 2020  
  Abstract:A structure-simplified pencil-beam scanning probe is demonstrated for intravascular optical coherence tomography catheters. In vivo imaging capability of this catheter is verified by a clinical system with a stent-implanted beating porcine heart as the sample. © 2020 The Author(s)
  Accession Number: 20211210116292
• Record 444 of
  
  Title:Thermal design for the package of high-power single-emitter laser diodes
  
  Author(s):Wu, Di-Hai(1,2,3); Zah, Chung-En(3); Liu, Xingsheng(3)
  Source: Optics and Laser Technology  Volume: 129  Issue:   DOI: 10.1016/j.optlastec.2020.106266  Published: September 2020  
  Abstract:An analytical three-dimensional thermal model is employed to perform the thermal design for the package of high-power single-emitter laser diodes. Thermal design curves for the heat sink and submount are presented in detail, for laser diodes subjected to several convective heat transfer conditions on the bottom of the heat sink. An effective heat spreading angle is proposed to characterize thermal design for the heat sink. A differential heat spreading angle is proposed to clearly manifest heat flow in the packages. Full width and length at 90% energy are introduced to reveal the requirement of submount width and length, respectively. The impact of coefficient of thermal expansion (CTE)-matched sandwiched submount on total heat dissipation is studied. Special discussion is presented for a commercial F-Mount laser diode, and it is found that current heat sink design leads to a 27.4% increase in thermal resistance relative to a free lateral diffusion package. © 2020 Elsevier Ltd
  Accession Number: 20201608460737