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Experimental Observation of Bright and Dark Solitons mode-Locked with Zirconia-Based Erbium-Doped Fiber Laser

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chinese Physics Letters 2018年第2期35卷 25-28页

作者： A.m.markom S.J.Tan H.Haris m.c.paul A.Dhar S.Das S.W.Harun Faculty of Electrical Engineering Universiti Teknologi MARAMasai 81750Malaysia School of Engineering KDU University CollegeUtropolis GlenmarieShah Alam 40150Malaysia Department of Electrical Engineering University of MalayaKuala Lumpur 50603Malaysia Fiber Optics and Photonics Division CSIR-Central Glass and Ceramic Research InstituteKolkata 700032India

We demonstrate the generation of dark and bright solitons with our homemade zirconia-based erbium-doped fiber and graphene oxide（GO） saturable absorber in anomalous dispersion *** GO is fabricated using an abridged Hummer＇s method,which is combined with polyethylene oxide to produce a composite *** film is sandwiched between two optical ferrules and embedded in the laser cavity to enhance its birefringence and *** self-starting bright soliton is easily generated at pump power of 78 mW with the whole length cavity of 14.7 *** laser produces the bright pulse train with repetition rate,pulse width,pulse energy and central wavelength being 13.9 mHz,0.6 ps,2.74 p J and 1577.46 nm,***,by adding the 10 m of single mode fiber into the laser cavity,dark soliton pulse is *** the formation of dark pulse train,the measured repetition rate,pulse width,pulse energy and central wavelength are 8.3 mHz,20 ns and 4.98 p J and1596.82 nm,*** pulses operate in the anomalous region.

关键词： Zr EDF Experimental Observation of Bright and Dark Solitons mode-Locked with Zirconia-Based Erbium-Doped Fiber Laser

mode-locked 2 μm fiber laser with a multi-walled carbon nanotube as a saturable absorber

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chinese Optics Letters 2015年第3期13卷 10-13页

作者： S.m.Azooz F.Ahmad H.Ahmad S.W.Harun B.A.Hamida S.Khan A.Halder m.c.paul m.Pal S.K.Bhadra Department of Electrical Engineering Faculty of Engineering University of Malaya Photonics Research center University of Malaya Department of Electrical and computer Engineering International Islamic University MalaysiaJalan Gombak Fiber Optics and Photonics Division Central Glass & Ceramic Research InstituteCSIR

We propose and demonstrate a passively mode-locked fiber laser operating at 1951.8 nm using a commercial thulium-doped fiber （TDF） laser, a homemade double-clad thulium-ytterbium co-doped fiber （TYDF） as the gain media, and a multi-walled carbon nanotube （mWcNT） based saturable absorber （SA）. We prepare the mWcNT composite by mixing a homogeneous solution of mWcNTs with a diluted polyvinyl alcohol （PVA） polymer solution and then drying it at room temperature to form a film. The film is placed between two fiber connectors as a SA before it is integrated into a laser ring cavity. The cavity consists of a 2 m long TDF pumped by a 800 nm laser diode and a 15 m long homemade TYDF pumped by a 905 nm multimode laser diode. A stable mode-locking pulse with a repetition rate of 34.6 mHz and a pulse width of 10.79 ps is obtained when the 905 nm multimode pump power reaches 1.8-2.2 W, while the single-mode 800 nm pump power is fixed at 141.5 mW at all times. To the best of our knowledge, this is the first reported mode-locked fiber laser using a mWcNT-based SA.

关键词： mWcNTs mode mode-locked 2 m fiber laser with a multi-walled carbon nanotube as a saturable absorber

A Tm-Bi co-Doped Fiber Laser with Dual Pumping Operation

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chinese Physics Letters 2013年第3期30卷 71-74页

作者： N.Saidin S.W.Harun S.S.A.Damanhuri S.m.m.Ali H.Ahmad A.Halder m.c.paul S.Das m.Pal S.K.Bhadra Department of Electrical Engineering Faculty of EngineeringUniversity of Malaya50603 Kuala LumpurMalaysia Photonics Research centre University of Malaya50603 Kuala LumpurMalaysia Fiber Optics and Photonics Division CSIR-Central Glass&Ceramic Research InstituteKolkataIndia

We demonstrate an efficient fiber laser operating at 1901.6 nm using a newly developed thulium bismuth co-doped fiber(TBF)with dual pumping at 792 nm and 1552 *** fiber was fabricated using modified chemical vapor deposition and solution doping *** dopant concentrations(wt%)and compositions inside the core are 0.15 Bi_(2)O_(3),0.3 Tm_(2)O_(3),1.0 Al_(2)O_(3) and 12.0 GeO_(2).The TBF laser operates at 1901.6 nm with a lasing efficiency of 33.2%and pump power threshold of 85 mW using a 2-m-long TBF in a linear cavity with two fiber Bragg gratings(FBGs).The high efficiency is attributed to the use of additional 1552 nm pump to complement 792 nm *** maximum output power of 225 mW is achieved at the pump power of 820 mW with the optimum length of 2 m.

关键词： pump fiber pumping

A Flat-Gain Double-Pass Amplifier with New Hafnia-Bismuth-Erbium codoped Fiber

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chinese Physics Letters 2018年第5期35卷 52-55页

作者： Alabbas A.Al-Azzawi Aya A.Almukhtar P.H.Reddy D.Dutta S.Das A.Dhar m.c.paul U.N.Zakaria S.W.Harun Photonics Engineering Laboratory Department of Electrical Engineering University of Malaya Department of computer Techniques Engineering Al-Esra'a University College Fiber Optics and Photonics Division CSIR-Central Glass and Ceramic Research Institute Academy of Scientific and Innovative Research CSIR-CGCRI Campus

An efficient and compact double-pass optical fiber amplifier is demonstrated using a newly developed hafnia bismuth erbium co-doped fiber（HBEDF） as a gain medium. The HBEDF is fabricated using a modified chemical vapor deposition in conjunction with solution doping. The fiber has an erbium ion concentration of 12500 *** the optimum length of 0.5 m, the HBEDF amplifier（HBEDFA） achieves a flat gain of 26 d B with a gain variation of less than 1.5 d B within a wavelength region from 1530 to 1560 nm when the input signal and pump power are fixed at-30 d Bm and 140 m W, respectively. On the other hand, at the input signal power of-10 d Bm,the HBEDFA also achieves a flat gain of 14.2 d B with a gain variation of less than 2.5 d B within a wide wavelength region from 1525 to 1570 nm. compared with the conventional zirconia erbium co-doped fiber based amplifier,the proposed HBEDFA obtains a more efficient gain and lower noise figure. For an input signal of-30 d Bm, the gain improvements of 6.2 d B and 4.8 d B are obtained at 1525 nm and 1540 nm, respectively.

关键词： length A Flat-Gain Double-Pass Amplifier with New Hafnia-Bismuth-Erbium codoped Fiber

Self-starting harmonic mode-locked Tm-Bi co-doped germanate f iber laser with carbon nanotube-based saturable absorber

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chinese Optics Letters 2013年第6期11卷 81-83页

作者： N.Saidin D.I.m.Zen S.S.A.Damanhuri S.W.Harun H.Ahmad F.Ahmad K.Dimyati A.Halder m.c.paul m.Pal S.K.Bhadra Photonics Research centre University of Malaya50603 Kuala LumpurMalaysia Department of Electrical Engineering Faculty of EngineeringUniversity of Malaya50603 Kuala LumpurMalaysia Department of Electrical and Electronic Engineering National Defense University of MalaysiaKem Sungai Besi57000 Kuala LumpurMalaysia Fiber Optics and Photonics Division Central Glass and Ceramic Research InstituteCSIRKolkataIndia

We report a ring cavity passively harmonic mode-locked fiber laser using a newly developed thulium- bismuth co-doped fiber （TBF） as a gain medium in conjunction with a carbon nanotube （cNT）-based saturable absorber. The TBF laser generates a third harmonic mode-locked soliton pulse train with a high repetition rate of 50 mHz and a pulse duration of 1.86 ps. The laser operates at 1 901.6 nm with an average power of 6.6 mW, corresponding to a pulse energy of 0.132 nJ, at a 1 552 nm pump power of 723.3 roW.

关键词： mode Self-starting harmonic mode-locked Tm-Bi co-doped germanate f iber laser with carbon nanotube-based saturable absorber cNT Tm Bi

Improving Heat Transfer in Parabolic Trough Solar collectors by magnetic Nanofluids

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Energy Engineering 2024年第4期121卷 835-848页

作者： Ritesh Singh Abhishek Gupta Akshoy Ranjan paul Bireswar paul Suvash c.Saha Department of Applied mechanics Motilal Nehru National Institute of Technology AllahabadPrayagrajIndia Department of mechanical and mechatronic Engineering University of Technology SydneySydneyAustralia

A parabolic trough solar collector(PTSc)converts solar radiation into thermal ***,low thermal efficiency of PTSc poses a hindrance to the deployment of solar thermal power *** performance of PTSc is enhanced in this study by incorporating magnetic nanoparticles into the working *** circular receiver pipe,with dimensions of 66 mm diameter,2 mm thickness,and 24 m length,is exposed to uniform temperature and velocity *** working fluid,Therminol-66,is supplemented with Fe3O4 magnetic nanoparticles at concentrations ranging from 1%to 4%.The findings demonstrate that the inclusion of nanoparticles increases the convective heat transfer coefficient(HTc)of the PTSc,with higher nanoparticle volume fractions leading to greater heat transfer but increased pressure *** thermal enhancement factor(TEF)of the PTSc is positively affected by the volume fraction of nanoparticles,both with and without a magnetic ***,the scenario with a 4%nanoparticle volume fraction and a magnetic field strength of 250 G exhibits the highest TEF,indicating superior thermal *** findings offer potential avenues for improving the efficiency of PTScs in solar thermal plants by introducing magnetic nanoparticles into the working fluid.

关键词： Parabolic trough solar collector(PTSc) magnetic nanofluid(mNF) heat transfer convective heat transfer coefficient(HTc) thermal enhancement factor(TEF)

combining neural progenitor cell transplant and rehabilitation for enhanced recovery after cervical spinal cord injury

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Neural Regeneration Research 2024年第7期19卷 1433-1434页

作者： camila m.Freria paul Lu Department of Neurosciences University of CaliforniaSan DiegoLa JollaCAUSA Veterans Administration San Diego Healthcare System San DiegoCAUSA

Efforts to promote recovery of function after human spinal cord injury(ScI) will likely require interventions to rgeting the corticospinal tract(cST) motor system:the most important pathway for voluntary motor control in *** system has historically been the most refractory to regenerative efforts after *** "nonregeneration" of the cST changed when robust regeneration of the cST into spared tissue was demonstrated by the inactivation of phosphatase and tensin homolog and delivery of inosine.

关键词： cervical progenitor injury

Post-fire recovery of Puya raimondii, vegetation and birds in the puna of Huascarán National Park, Perú

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Journal of mountain Science 2024年第1期21卷 20-32页

作者： mery L.SUNI Giovana P.VADILLO césar ARANA Enoc JARA-PENA Letty SALINAS m.Estela PONcE paul m.RAmSAY Plant Physiology Laboratory Faculty of Biological SciencesUniversidad Nacional Mayor de San MarcosLima 15081Peru Natural History museum Universidad Nacional Mayor de San MarcosLima 15072Peru Applied Phytology Laboratory Faculty of Biological SciencesUniversidad Nacional Mayor de San MarcosLima 15081Peru Department of Statistics Faculty of Mathematical SciencesUniversidad Nacional Mayor de San MarcosLima 15081Peru Department of chemical and Biological Sciences Universidad de las Américas PueblaSan Andrés Cholula CP Cholula CP 72810Mexico

A large fire of 233 ha in Huascarán National Park in Peru provided an opportunity to compare plant and bird responses in burned and nearby unburned zones of the puna. Heights and live diameters of flagship Puya raimondii rosettes(assigned to four broad developmental phases), plant communities(66 species in 24 families and nine growth forms) and bird communities(77 species in six trophic guilds) were monitored after the fire. Although no mortality was observed, Puya raimondii plants were affected by the fire, losing approximately 60% of their photosynthetic area across all developmental phases, but recovered quickly during the first two years after fire. The comparison of Puya rosette recovery after fire was complicated by the changes in live rosette diameter for unburned plants, which showed plasticity of photosynthetic area linked to seasonal and annual fluctuations in precipitation in this relatively dry environment(decreased by 26% for mature adult plants over the study period). Fire caused an immediate change in the density, biomass and composition of vegetation. Although the species present remained similar, their abundances changed significantly immediately after the fire, with notable reductions in dominant tussock grasses. This provided opportunities for other plants, resulting in higher postfire diversity of plant species, genera, families and growth forms. In turn, the changes in vegetation after fire affected the composition of birds according to their trophic guild. Granivores largely disappeared,generalists were mostly unaffected, and other guilds showed a more complex response. As the vegetation recovered, most displaced birds returned within approximately one year.

关键词： Burning Plant biomass Trophic guilds Andes Giant rosette plants

Pressurized environments directly influence friction and wear of dry steel contacts—Investigations in a novel high fluid pressure tribometer

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Friction 2024年第7期12卷 1599-1617页

作者： paul REIcHLE Jakob BARZ Georg UmLAUF Günter E.m.TOVAR Institute of Interfacial Process Engineering and Plasma Technology(IGVP) University of StuttgartStuttgart 70569Germany Fraunhofer Institute for Interfacial Engineering and Biotechnology(IGB) Stuttgart 70569Germany

To reduce the usage of classical lubricants in deep drawing,a new tribological system based on volatile lubricants was ***,a volatile medium is injected under high pressure into the interstice between drawing tool and sheet *** on temperature and pressure,the temporary lubricant may exist in its gaseous or liquid *** this study,a novel high fluid pressure tribometer was designed to investigate the friction and wear of dry steel contacts under comparable conditions like in dry deep ***,a new ball-on-disc tribometer was designed and integrated into a high-pressure *** specifically investigate the effects of different environments(technical air,liquid and gaseous carbon dioxide,nitrogen,argon)at atmospheric and high pressure(0.1 mPa,6 mPa)on tribology,the specimens and all components were operating *** the experiments,the friction was measured *** show that the highest friction occurs in air and the lowest in carbon dioxide *** to the experiments,the wear of the specimens was assessed along with changes in surface chemistry related to tribochemical ***,the tribology of the dry sliding contacts is correlated to changes of the surface *** differences as well as similarities regarding the different fluid environments are *** the results show,the differences between the media used are most pronounced at elevated ***,this work gives clear indications on the suitability of volatile lubricants in dry friction or rather gas lubrication,especially for dry deep drawing.

关键词： dry friction and dry wear gas lubrication carbon dioxide tribo-layer dry metal forming