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61.
The paper presents simulation studies targeting high-power narrow-linewidth emission from semiconductor distributed feedback (DFB) lasers. The studies contain analytic and numerical calculations of emission linewidth, side mode suppression ratio and output power for DFB lasers without phase shifts and with \(1\times \lambda /4\) and \(2\times \lambda /8\) phase shifts, taking into account the grating and facets reflectivities, the randomness of the spontaneous emission and the longitudinal photon and carrier density distributions in the laser cavity. Single device structural parameter optimization is generally associated with a trade-off between achieving a narrow linewidth and a high output power. Correlated optimization of multiple structural parameters enables the evaluation of achievable ranges of narrow linewidth and high power combinations. Devices with long cavities and low grating coupling coefficients, \(\kappa\) (keeping \(\kappa L\) values below the levels that promote re-broadening), with AR-coated facets and with a distributed phase-shift have the flattest longitudinal photon and carrier density distributions. This flatness enables stable single-longitudinal-mode operation with high side-mode-suppression ratio up to high injection current densities, which facilitates narrow linewidths and high output powers. The results reported in the paper indicate that Master-Oscillator Power-Amplifier laser structures are needed for achieving W-level high-powers with sub-MHz linewidths because most single-cavity DFB laser structural variations that reduce the linewidth also limit the achievable output power in single-mode operation. 相似文献
62.
Butler PA Humphreys RD Greenlees PT Herzberg RD Jenkins DG Jones GD Kankaanpää H Kettunen H Rahkila P Scholey C Uusitalo J Amzal N Bastin JE Brew PM Eskola K Gerl J Hammond NJ Hauschild K Helariutta K Hessberger FP Hürstel A Jones PM Julin R Juutinen S Keenan A Khoo TL Korten W Kuusiniemi P Le Coz Y Leino M Leppänen AP Muikku M Nieminen P Ødegård SW Page T Pakarinen J Reiter P Sletten G Theisen Ch Wollersheim HJ 《Physical review letters》2002,89(20):202501
The spectrum of prompt conversion electrons emitted by excited 254No nuclei has been measured, revealing discrete lines arising from transitions within the ground state band. A striking feature is a broad distribution that peaks near 100 keV and comprises high multiplicity electron cascades, probably originating from M1 transitions within rotational bands built on high K states. 相似文献
63.
A. Hürstel Y. Le Coz E. Bouchez A. Chatillon A. Görgen P. T. Greenlees K. Hauschild S. Juutinen H. Kettunen W. Korten P. Nieminen M. Rejmund Ch Theisen J. Wilson A. N. Andreyev F. Becker T. Enqvist P. M. Jones R. Julin H. Kankaanpää A. Keenan P. Kuusiniemi M. Leino A.-P. Leppänen M. Muikku J. Pakarinen P. Rahkila J. Uusitalo 《The European Physical Journal A - Hadrons and Nuclei》2004,21(3):365-368
Prompt and delayed gamma-ray spectroscopy of very neutron-deficient bismuth isotopes 187, 189Bi has been performed using the recoil decay tagging method. A rotational band has been observed in 189Bi and is interpreted as a complete decoupling of a single proton from the deformed lead core. The results for 187Bi suggest a similar structure and coupling scheme. This study gives the first evidence for a prolate band in a light bismuth nucleus and confirms the prolate character of the low-lying rotational band observed in the core nuclei 188Pb and 186Pb.Received: 21 July 2004, Published online: 21 September 2004PACS:
23.20.Lv
transitions and level energies - 27.70. + q
K. Hauschild: Present address: CSNSM, Orsay, France.P. Nieminen: Present address: ANU, Canberra, Australia.M. Rejmund: Present address: GANIL, Caen, France.J. Wilson: Present address: LPSC, Grenoble, France.A.N. Andreyev: Present address: TRIUMF, Vancouver, Canada.F. Becker: Present address: GSI, Darmstadt, Germany.M. Muikku: Present address: RNSA, Helsinki, Finland. 相似文献
64.
H. Kettunen T. Enqvist M. Leino K. Eskola P.T. Greenlees K. Helariutta P. Jones R. Julin S. Juutinen H. Kankaanpää H. Koivisto P. Kuusiniemi M. Muikku P. Nieminen P. Rahkila J. Uusitalo 《The European Physical Journal A - Hadrons and Nuclei》2003,16(4):457-467
The low-energy nuclear structure and decay properties of the neutron-deficient isotopes 195At and 191Bi have been studied. 195At was produced in the reaction 142Nd(56Fe,p2n)195At and 191Bi as the daughter activity of 195At. The activities were implanted in a position-sensitive silicon detector after being separated from the primary beam by
a gas-filled recoil separator. The 1/2+ intruder state was determined to be the ground state in 195At with an alpha-decay energy of E
α = 6953(3) keV and a half-life T
1/2 = 328(20) ms. Another state with an alpha-decay energy E
α = 7075(4) keV and a half-life T
1/2 = 147(5) ms was found to decay to a 148.7(5) keV excited state in 191Bi for which a spin and parity of 7/2- were deduced. Consequently, the same 7/2- character was assigned to the initial state at 32(7) keV in 195At on the basis of unhindered alpha-decay. The 9/2- state, being the ground state in heavier odd-mass astatine isotopes, was not observed.
Received: 16 September 2002 / Accepted: 19 December 2002 / Published online: 25 March 2003
RID="a"
ID="a"e-mail: heikki.kettunen@phys.jyu.fi
RID="b"
ID="b"Present address: Laboratory of Radiochemistry, P.O. Box 55, FIN-00014, University of Helsinki, Finland.
RID="c"
ID="c"Present address: Radiation and Nuclear Safety Authority, P.O. Box 14, FIN-00881 Helsinki, Finland.
Communicated by W. Henning 相似文献
65.
Seweryniak D Woods PJ Ressler JJ Davids CN Heinz A Sonzogni AA Uusitalo J Walters WB Caggiano JA Carpenter MP Cizewski JA Davinson T Ding KY Fotiades N Garg U Janssens RV Khoo TL Kondev FG Lauritsen T Lister CJ Reiter P Shergur J Wiedenhöver I 《Physical review letters》2001,86(8):1458-1461
Rotational bands feeding the ground state and the isomeric state in the proton emitter (141)Ho were observed using the recoil-decay tagging method. This constitutes direct evidence that (141)Ho is deformed. A quadrupole deformation of beta(2) = 0.25(4) was deduced for the ground state from the extracted dynamic moment of inertia. Based on observed band crossings and signature splittings the 7/2(-)[523] and 1/2(+)[411] configurations were proposed for the ground state and the isomeric state, respectively. Comparison with particle-rotor calculations for beta(2) = 0.25 indicates, however, that (141)Ho may have significant hexadecapole deformation and could be triaxial in the 7/2(-)[523] ground state. 相似文献
66.
Sandzelius M Hadinia B Cederwall B Andgren K Ganioğlu E Darby IG Dimmock MR Eeckhaudt S Grahn T Greenlees PT Ideguchi E Jones PM Joss DT Julin R Juutinen S Khaplanov A Leino M Nelson L Niikura M Nyman M Page RD Pakarinen J Paul ES Petri M Rahkila P Sarén J Scholey C Sorri J Uusitalo J Wadsworth R Wyss R 《Physical review letters》2007,99(2):022501
Gamma-ray transitions have been identified for the first time in the extremely neutron-deficient (N=Z+2) nucleus (110)Xe, and the energies of the three lowest excited states in the ground-state band have been deduced. The results establish a breaking of the normal trend of increasing first excited 2(+) and 4(+) level energies as a function of the decreasing neutron number as the N=50 major shell gap is approached for the neutron-deficient Xe isotopes. This unusual feature is suggested to be an effect of enhanced collectivity, possibly arising from isoscalar n-p interactions becoming increasingly important close to the N=Z line. 相似文献
67.
Jönsson S Uusitalo T van Bavel B Gustafsson IB Lindström G 《Journal of chromatography. A》2006,1111(1):71-75
A gas chromatography-high-resolution mass spectrometry (GC-HRMS) method using solid-phase microextraction (SPME) for the determination of 2,4,6-trichloroanisole (TCA) and 2,4,6-tribromoanisole (TBA) in wine at low ng L(-1) levels was developed. A robust SPME method was developed by optimizing several different parameters, including type of fiber, salt addition, sample volume, extraction and desorption time. The quantification limit for TCA and TBA in wine was lowered substantially using GC-HRMS in combination with the optimized SPME method and allowed the detection of low analyte concentrations (ng L(-1)) with good accuracy. Limits of quantification for red wine of 0.3 ng L(-1) for TCA and 0.2 ng L(-1) for TBA with gas chromatography-negative chemical ionization mass spectrometry and 0.03 ng L(-1) for TCA and TBA were achieved using GC-HRMS. The method was applied to 30 wines of which 4 wines were sensorically qualified as cork defected. TCA was found in three of these wines with concentrations in the range 2-25 ng L(-1). TBA was not detected in any of the samples. 相似文献