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A Q-Switched Erbium-Doped fiber Laser with a Carbon Nanotube Based Saturable Absorber

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Chinese Physics Letters 2012年第11期29卷 67-69页

作者： S.W.Harun m.A.ismail f.Ahmad m.f.ismail R.m.Nor N.R.Zulkepely H.Ahmad Department of Electrical Engineering University of Malaya 50603 Kuala LumpurMalaysia Photonics Research Center Department of PhysicsUniversity of Malaya50603 Kuala LumpurMalaysia Department of Physics University of Malaya50603 Kuala LumpurMalaysia

We demonstrate a simple,compact and low cost Q-switched erbium-doped fiber laser(EDfL)using single-wall carbon nanotubes(CNTs)as a saturable absorber for possible applications in metrology,sensing,and medical *** EDfL operates at around 1560 nm with repetition rates of 16.1 kHz and 6.4 kHz with saturable absorbers SA1 and SA2 at a pump power of 120 *** absorbers are constructed by optically driven deposition and normal deposition *** is observed that the optical deposition method produces a Q-switched EDfL with a lower threshold of 70 mW and better Q-switching performance compared to that of the normal deposition *** EDfL also has pulse energy of 90.3 nJ and pulse width of 11.6μs at 120 mW pump power.

关键词： pump switched Erbium

Optically modulated Tunable O-Band Praseodymium-Doped fluoride fiber Laser Utilizing multi-Walled Carbon Nanotube Saturable Absorber

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Chinese Physics Letters 2019年第10期36卷 32-35页

作者： H.Ahmad m.f.ismail S.N.Aidit Photonics Research Center University of MalayaKuala Lumpur 50603Malaysia Physics Department Faculty of ScienceUniversity of Malaya50603 Kuala LumpurMalaysia

A tunable and optically modulated fiber laser utilizing a multi-walled carbon nanotube based saturable absorber is demonstrated for operation in the O-band region.A praseodymium-doped fluoride fiber is used as the gain medium and the system is capable of generating modulated outputs at 1300 *** output is observed at pump powers of 511 mW and above,with repetition rates and pulse widths that can be tuned from 41 kHz and 3.4μs to 48 kHz and 2.4μs,respectively,at the maximum pump power available.A maximum average output power of 100μW with a corresponding single pulse energy of 2.1 nJ is measured,while the tunability of the proposed laser is from 1290 nm to 1308 *** output is stable,with peak power fluctuations of^4 dB from the average value.

关键词： pump fiber Optically

Antimonene-based saturable absorber for a soliton mode-locked and Q-switched fiber laser in the 2 μm wavelength region

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Chinese Physics B 2023年第6期32卷 259-269页

作者： H Ahmad B Nizamani m Z Samion N Yusoff m f ismail Photonics Research Centre Universiti Malaya50603 Kuala LumpurMalaysia Physics Department Faculty of ScienceUniversiti Malaya50603 Kuala LumpurMalaysia Distinguished Visiting Professor Universiti Kuala Lumpur British Malaysian Institute(UniKL BMI)Batu 8Jln Sungai Pusu53100SelangorMalaysia

We demonstrate antimonene as a saturable absorber(SA) to generate an ultrafast mode-locked and Q-switched laser in the 2 μm wavelength region. The two antimonene-based SAs were prepared and inserted separately in a thulium–holmiumdoped fiber laser to produce the pulsed laser. Antimonene was coated onto a tapered fiber to generate soliton mode-locked pulses and used in thin-film form for the generation of Q-switched pulses. The mode-locking was stable within a pump power of 267 m W–511 m W, and the laser operated at a central wavelength of 1897.4 nm. The mode-locked laser had a pulse width of 1.3 ps and a repetition rate of 12.6 mHz, with a signal-to-noise ratio of 64 d B. Q-switched laser operation was stable at a wavelength of 1890.1 nm within a pump power of 312 m W–381 m W. With the increase in pump power from 312 m W to 381 m W, the repetition rate increased to a maximum of 56.63 k Hz and the pulse width decreased to a minimum value of 2.85 μs. Wide-range tunability of the Q-switched laser was also realized within the wavelength range of1882 nm–1936 nm.

关键词： mode-locking Q-switched fiber laser optical saturable absorber

Targeting oral-gut microbial transmission in diabetic coronary heart disease:unveiling key pathogenic mechanisms

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Science China(Life Sciences) 2024年第10期67卷 2287-2288页

作者： ismail Cimen Aab Cardiovascular Research Institute Department of MedicineUniversity of Rochester School of Medicine and DentistryRochester 14642USA

Diabetes significantly exacerbates the occurrence and adverse prognosis of coronary heart disease(CHD),emphasizing the importance of focusing on the prevention and management of diabetesrelated *** study identifies and verifies for the first time a distinctive oral-gut microbiota profile in patients with diabetic coronary heart disease(DCHD),marked by an increased abundance of oral fusobacterium nucleatum and gut Lactobacillus.

关键词： coronary prevention diabetic

Spatiotemporal landscape pattern changes and their effects on land surface temperature in greenbelt with semi-arid climate:A case study of the Erbil City,Iraq

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Journal of Arid Land 2024年第9期16卷 1214-1231页

作者： Suzan ismail Hamid mALIKI Department of Architecture College of EngineeringSalahaddin UniversityErbil 44002Iraq

Urban expansion of cities has caused changes in land use and land cover(LULC)in addition to transformations in the spatial characteristics of landscape *** alterations have generated heat islands and rise of land surface temperature(LST),which consequently have caused a variety of environmental issues and threated the sustainable development of urban *** are employed as an urban planning containment policy to regulate urban expansion,safeguard natural open spaces,and serve adaptation and mitigation *** they are regarded as a powerful measure for enhancing urban environmental *** the fact that,the relation between landscape structure change and variation of LST has been examined thoroughly in many studies,but there is a limitation concerning this relation in semi-arid climate and in greenbelts as well,with the lacking of comprehensive research combing both ***,this study investigated the spatiotemporal changes of landscape pattern of LULC and their relationship with variation of LST within an inner greenbelt in the semi-arid Erbil City of northern *** study utilized remote sensing data to retrieve LST,classified LULC,and calculated landscape metrics for analyzing spatial changes during the study *** results indicated that both composition and configuration of LULC had an impact on the variation of LST in the study *** Pearson's correlation showed the significant effect of Vegetation 1 type(VH),cultivated land(CU),and bare soil(BS)on LST,as increase of LST was related to the decrease of VH and the increases of CU and BS,while,neither Vegetation 2 type(VL)nor built-up(BU)had any ***,the spatial distribution of LULC also exhibited significant effects on LST,as LST was strongly correlated with landscape indices for VH,CU,and ***,for BU,only aggregation index metric affected LST,while none of VL metrics had a *** study provides insights for landscape pla

关键词： land use and land cover change landscape pattern land surface temperature greenbelt remote sensing

Assembly of functional carboxymethyl cellulose/polyethylene oxide/anatase TiO_(2) nanocomposites and tuning the dielectric relaxation, optical, and photoluminescence performances

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Journal of Semiconductors 2024年第7期45卷 26-38页

作者： Asmaa m.ismail Abeer A.Reffaee fawzy G.El Desouky Spectroscopy Department Physics Research InstituteNational Research CentreGizaCairo 12622Egypt microwave Physics and Dielectrics Department National Research CentreDokkiCairoEgypt Solid State Physics Department Physics Research InstituteNational Research CentreGizaCairo 12622Egypt

Nanocomposite films consisting of carboxymethyl cellulose,polyethylene oxide(CmC/PEO),and anatase titanium diox-ide(TO)were produced by the use of sol-gel and solution casting ***2 nanocrystals were effectively incorporated into CmC/PEO polymers,as shown by X-ray diffraction(XRD)and attenuated total reflectance fourier transform infrared(ATR-fTIR)*** roughness growth is at high levels of TO nanocrystals(TO NCs),which means increasing active sites and defects in CmC/*** differential scanning calorimetry(DSC)thermograms,the change in glass transition temperature(Tg)val-ues verifies that the polymer blend interacts with TO *** increment proportions of TO NCs have a notable impact on the dielectric performances of the nanocomposites,as *** electrical properties of the CmC/PEO/TO nanocomposite undergo significant *** nanocomposite films exhibit a red alteration in the absorption edge as the concentration of TO NCs increases in the polymer *** decline in the energy gap is readily apparent as the weight percentage of TO NCs *** photoluminescence(PL)emission spectra indicate that the sites of the luminescence peak maximums show slight variation;peaks get wider,while their intensities decrease dramatically as the concentration of TO *** nanocomposite materials show potential for multifunctional applications including optoelectronics,antireflection coatings,pho-tocatalysis,light emitting diodes,and solid polymer electrolytes.

关键词： anatase TiO_(2) CmC/PEO nanocomposites optical photoluminescent electrical optoelectronics

Investigation of ellipticity and pump power in a passively mode-locked fiber laser using the nonlinear polarization rotation technique

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Chinese Optics Letters 2017年第5期15卷 45-49页

作者： H. Ahmad S. I. Ooi m. Z. A. Razak S. R. Azzuhri A. A. Jasim K. Thambiratnam m. f. ismail m. A. ismail photonics Research Centre University of Malaya Kuala Lumpur Malaysia Institute of microengineering and Nanoelectronics Research Complex University Kebangsaan Malaysia 43600 Bangi Selangor Malaysia

An elliptical initial polarization state is essential for generating mode-locked pulses using the nonlinear polarization rotation technique. In this work, the relationship between the ellipticity ranges capable of maintaining mode-locked operation against different pump power levels is investigated. An increasing pump power, in conjunction with minor adjustments to the polarization controller＇s quarter waveplate, results in a wider ellipticity range that can accommodate mode-locked operation. Other parameters such as noise, pulsewidth, and average output power are also observed to vary as the ellipticity changes.

关键词： mode Investigation of ellipticity and pump power in a passively mode-locked fiber laser using the nonlinear polarization rotation tec

High resolution sequence stratigraphy of the mishrif formation(Cenomanian-Early Turonian)at zubair oilfield(al-rafdhiah dome),southern Iraq

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Petroleum Research 2024年第1期9卷 61-71页

作者： Aymen A.Lazim maher J.ismail maher m.mahdi Geoscience Department Zubair Field Operation DivisionBasra Oil CompanyIraq Basrah Oil Company WQ1 FODBasrahIraq University of Basrah College of ScienceGeology Dept.BasrahIraq

The mishrif formation(Cenomanian-E Turonian)is one of the most important geological formations in the middle East and Iraq because it contains enormous petroleum *** is considered to be the first reservoir in the region,and is still being studied because of its economic *** carbonate of the mishrif formation derives from a variety of depositional settings,including mid-ramp,shoal,lagoon,and *** five main microfacies discussed in this paper are wackestone,packstone,grainstone,floatstone,and *** most frequent fossilised components found in the mishrif formation are rudists,benthic foraminifera,echinoderms,burrows molluscs,and *** to the microfacies and analysed wireline log data,the sequence stratigraphy of the studied formation is composed of two regression *** parasequences of transgressive-regressive cycles make up the depositional sequence of the mishrif *** standard depositional environments seem to demonstrate a gradual regression,beginning with a short period of the outer ramp,then a steady period of the mid-ramp,and ending in the intertidal ***,the study recorded two regional maximum flooding surfaces:K-135 and *** former is present in the lowermost part of the formation,while the other lies in the *** study shows a close relationship between facies(environments)and hydrocarbon *** increased accumulation focuses on the lower part of the studied formation,and seems to be lower in the upper part of the formation as a result of changes in the environment of deposition.

关键词： mishrif formation Cenomanian Sequence stratigraphy Zubair oilfield Iraq

Titanium dioxide-based Q-switched dual wavelength in the 1 micron region

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Chinese Optics Letters 2016年第9期14卷 48-52页

作者： H.Ahmad m.A.m.Salim Z.A.Ali m.f.ismail K.Thambiratnam A.A.Latif N.Nayan S.W.Harun Photonics Research Centre(PRC) University of Malaya Department of Physics University Putra Malaysia faculty of Electrical and Electronic Engineering Universiti Tun Hussein Onn Malaysia

In this work a passively Q-switched dual-wavelength ytterbium-doped fiber laser using a titanium dioxide-based saturable absorber is proposed and proven. The system also utilizes a side-polished fiber in a ring cavity configuration to obtain the desired pulse train. A stable dual-wavelength pulse output is obtained at 1034.7and 1039.0 nm, with a maximum pulse energy of 2.0 n J, and a shortest pulse width of 3.2 μs. The generated pulse train is stable, and has a pulse repetition rate from 31.2 to 64.5 kHz.

关键词： Titanium dioxide-based Q-switched dual wavelength in the 1 micron region