共查询到20条相似文献,搜索用时 15 毫秒
1.
S. Suzuki H. Yamaguchi T. Ishigaki R. Sen H. Kataura W. Krätschmer Y. Achiba 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):369-372
Time evolution of emission by carbon nanoparticles generated with a laser furnace technique was investigated with a high-speed
video camera. Assuming blackbody radiation formula for small spherical particle, the internal temperature of these carbon
nanoparticles was determined as a function of time delay (Δt) after laser vaporization. It was found that the internal temperature of them drastically decreased at Δt < 400μs through collision with the surrounding rare gas inside the furnace. On the other hand, in particular laser vaporization
condition where yields of C60 and other higher fullerenes in the soot were found to be high, an increase in the blackbody emission intensity could be recognized
for longer wavelength ( 660 < λ < 830 nm) at Δt > 400μs. This finding suggests that a certain exothermic process related to the formation of C60 and other higher fullerenes should occur at Δt > 400μs inside the furnace. 相似文献
2.
D. M. Zashchirinskii L. I. Koroleva A. S. Morozov Yu. V. Dolzhenkova 《Physics of the Solid State》2011,53(2):316-319
The magnetocaloric effect ΔT has been studied by a direct method in two samples of the manganite Sm0.55Sr0.45MnO3, namely, a single crystal (sample A) and a ceramic sample (sample C). The temperature dependences of the ΔT effect of both samples exhibit a maximum at T
max = 143.3 K for the sample A and T
max = 143 K for the sample C. In these maxima, the values of the ΔT effect are 0.8 and 0.4 K in the magnetic field H = 14.2 kOe for the samples A and C, respectively. In addition, the ΔT(T) curve of the sample A has a minimum at T
min = 120 K, in which ΔT = −0.1 K. The maximum value of the ΔT effect increases with an increase in the magnetic field H in the range of magnetic fields up to 14.2 kOe, and the rate of this increase at H > 8 kOe is higher than that at H < 8 kOe. These features of the ΔT effect are explained by the presence of ferromagnetic and antiferromagnetic A- and CE-type clusters in the samples. 相似文献
3.
V. M. Svistunov V. Yu. Tarenkov A. I. D’yachenko R. Aoku H. Murakami M. Shirai 《Journal of Experimental and Theoretical Physics》1998,86(4):763-770
We study the energy spectrum of Bi2223 (Bi1.6Pb0.4Sr1.8Ca2.2Cu3Ox) at high hydrostatic pressures by Andreev-and tunneling-spectroscopy methods. We determine the gap anisotropy in the basal
ab plane and find the following values for the parameters Δ(ϕ): Δmax=42 mV, and Δmin=19.5 mV (T
c
=110 K and dT
c
/dP=0.16 K/kbar). We detect an increase in the ratio R=2Δmax/kT
c
with pressure P; for Bi2223 cuprate, dR/dP≈0.017 kbar−1. In the phonon-frequency region we detect a “softening,” due to pressure, of the high-frequency part of the phonon spectrum
corresponding to “breathing” modes of oxygen, as well as other optical modes of Cu-O. The characteristic frequencies of the
spectrum for ℏΩ>60 mV are found to decrease, with increasing pressure, at a rate d ln(ℏΩ)/dP≈−6.5±0.5×10−3 kbar−1. This result explains the observed increase in the ratio 2Δ/kT
c
(P) in the model of strong electron-phonon interaction.
Zh. éksp. Teor. Fiz. 113, 1397–1410 (April 1998) 相似文献
4.
The focal switch of cosine-Gaussian (CsG) beams passing through a system with the aperture and lens separated is studied analytically
and numerically. It is shown that the focal switch of CsG beams can appear not only for the apertured case, but also for the
unapertured case. The necessary condition for the focal switch is that truncation parameter α > αc and the beam parameter β > βc, αc, βc being the corresponding critical values. There exists a maximum of the relative transition height Δz
sw as α varies, and Δz
sw increases with increasing β and decreasing N
w. The normalized axial intensity minimum I
min / I
max decreases with an increase of α and β, and I
min / I
max remains unchanged as N
w varies. 相似文献
5.
Nonlinear optical gain modulation in an InGaAsP/InP bulk reflective semiconductor optical amplifier (RSOA) is studied. The differences of the optical properties between RSOAs and conventional SOAs are initially investigated. All-optical wavelength conversion based on nonlinear gain modulation in RSOAs is demonstrated at a bit rate of 2.488 Gbit/s. It is shown that a bit-error-rate of <10−9 can be achieved and an extinction ratio of >9 dB can be obtained at a bit rate of 2.488 Gbit/s with a 231-1 non-return-to-zero (NRZ) pseudorandom bit sequence (PRBS). In comparison with conventional SOAs, wavelength conversion by RSOAs shows much improved performances in high-speed all-optical wavelength conversions. 相似文献
6.
Jiangyong Jia 《Indian Journal of Physics》2011,85(1):149-154
We provide a detailed survey study of dihadron azimuthal angle (Δϕ) correlations in a broad range of transverse momentum (0.4 < p
T
< 10 GeV/c) and centrality (0–92%) in Au+Au collisions at 149-2 = 200 GeV. The evolution of the jet shape and yield with p
T
seems to suggest two distinct components at the away-side pairs: a suppressed jet fragmentation component around Δϕ ∼ π, and a medium-induced components around |Δϕ − π| ∼ 1.1. The former dominates p
T
> 5 GeV/c and the later dominates at p
T
< 4 GeV/c. 相似文献
7.
A Continuously Tunable Erbium-Doped Fibre Laser Using Tunable Fibre Bragg Gratings and Optical Circulator
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A continuously tunable erbium-doped fibre laser (TEDFL) based on tunable fibre Bragger grating (TFBG) and a three-port optical circulator (OC) is proposed and demonstrated. The OC acts as a 100%-reflective mirror. A strain-induced uniform fibre Bragger grating (FBG) which functions as a partial-reflecting mirror is implemented in the linear cavity. By applying axial strain onto the TFBG, a continuously tunable lazing output can be realized. The wavelength tuning range covers approximately 7.00nm in C band (from 1543.6161 to 1550.3307nm). The side mode suppression ratio (SMSR) is better than 50 dB, and the 3 dB bandwidth of the laser is less than 0.01 nm. Moreover, an array waveguide grating (AWG) is inserted into the cavity for wavelength preselecting, and a 50 km transmission experiment was performed using our TEDFL at a 10 Gb/s modulation rate. 相似文献
8.
N. Nagaraj M. C. Shastry P. G. Vaidya 《The European physical journal. Special topics》2008,165(1):73-83
The direct measurement of the gluon polarization in the nucleon at the COMPASS experiment is discussed. Three complementary
analyses are considered. All of them study ΔG/G using method based on selection of events originating from the Photon Gluon Fusion process. Most precise preliminary value
of ΔG/G is obtained from the high p
T
pair channel for the Q
2 < 1 (GeV/c)2 region: ΔG/G = 0.016 ± 0.058 (stat.) ± 0.055 (syst.).
on behalf of the COMPASS collaboration 相似文献
9.
V. D. Borman M. A. Pushkin V. N. Tronin V. I. Troyan 《Journal of Experimental and Theoretical Physics》2010,110(6):1005-1025
The electronic properties of nanoclusters of transition (Ni, Co, Cr) and noble (Au, Cu) metals deposited on the surface of
highly oriented pyrolytic graphite (HOPG) are studied using the method of X-ray photoelectron spectroscopy. The laws of variation
of a change ΔE
b in the binding energies of core-level electrons in the initial (ΔE
i) and final (ΔE
f) states of atoms in nanoclusters, the intrinsic widths γ of photoelectron lines, and their singularity indices α as functions
of the metal cluster size d are determined. A qualitative difference in behavior of the ΔE
i(d) and α(d) values in metals of the two groups (Ni, Cr versus Co, Cu) is found. The values of the final-state energy (ΔE
f < 0) and the line width (Δγ > 0) in the clusters of all metals studied vary in a similar manner. It is shown that a significant
contribution to E
i is due to a transfer of the valence-shell electrons at the cluster-substrate interface, which is caused by the contact potential
difference. The value of an uncompensated charge per nanocluster is determined as a function of the cluster size and the number
of atoms in the cluster. The behavior of ΔE
f(d) is controlled by the Coulomb energy of a charged cluster and by a decrease in the efficiency of electron screening, which
is different in the metals studied. The broadening of photoelectron lines is determined by a spread of the cluster sizes and
by lower electron screening in the final Fermi system. An asymmetry of the core-level electron spectra of nanoclusters can
be explained using notions about the electron-hole pair excitation near the Fermi level. The effect of the structure of the
density of electron states in the d band of transition metals on the asymmetry of photoelectron lines is considered and it is concluded that this structure near
the Fermi level qualitatively changes with a decrease in the nanocluster size. The obtained results indicate that the behavior
of the electron subsystem of clusters of the d-metals in a size range of 2–10 nm under consideration is close to the behavior of a normal Fermi system. 相似文献
10.
We have experimentally investigated supercontinuum generation in a conventional single-mode fiber pumped with a nanosecond
pulse source. The experimental results show that, when pump power increases, the spectral flatness is improved obviously and
the spectral broadening only occurs in a red-shifted radiation rather than a blue-shifted radiation. A supercontinuum source
is experimentally reported with a flatness of 4.7 dB over 180 nm (ranging from 1555 to >1735 nm) at pump power P
R
= 5 W and is predicted to have the flatness of less than 1 dB at P
R
> 8 W. The cascade of stimulated Raman scattering (SRS) together with soliton fission plays the key roles in supercontinuum
generation. 相似文献
11.
M. Sioli 《Physics of Atomic Nuclei》2006,69(11):1842-1846
The energy spectrum of neutrino-induced upward-going muons in MACRO has been analyzed in terms of effects of violating relativity
principles, keeping standard mass-induced atmospheric neutrino oscillations as the dominant source of ν
μ → ν
τ transitions. The data disfavor these exotic possibilities even at a subdominant level, and stringent 90% C.L. limits are
placed on the Lorentz invariance violation parameter |Δυ| < 6 × 10−24 at sin(2ϑυ) = 0 and |Δυ| < (2.5–5) × 10−26 at sin(2ϑυ) = ±1. These limits can also be reinterpreted as upper bounds on the parameters describing violation of the equivalence principle.
The text was submitted by the author in English. 相似文献
12.
According to equivalent external cavity approximation model, after taking into account the joint contribution of semiconductor laser, external cavity and fiber grating (FG) to the phase condition, the mode distribution of the fiber grating external cavity semiconductor laser (FGESL) can be determined. As a result, the effect of the FG external cavity length (L) on the side mode suppression ratio (SMSR) of the FGESL is investigated theoretically. The results show that with the injected current and the coupling efficiency increase of the SMSR has taken on rise at all. For strong feedback (R2 = 10?4), the SMSR become more flattened with more than 40 dB, but, for weak feedback condition, The SMSR have lesser than 35 dB by an oscillation during rising course. Under the condition of short external cavity, the SMSR is in deep relation to the external cavity length, but the SMSR of longer external cavity is smaller than the SMSR of shorter external cavity on the whole and for 8–11 mm of the external cavity length, the SMSR of the FGESL has better (SMSR > 40.8 dB), and the SMSR become more flattened. 相似文献
13.
Potential for micromachined actuation of ultra-wide continuously tunable optoelectronic devices 总被引:1,自引:0,他引:1
H. Hillmer J. Daleiden C. Prott F. Römer S. Irmer V. Rangelov A. Tarraf S. Schüler M. Strassner 《Applied physics. B, Lasers and optics》2002,75(1):3-13
Tailored scaling represents a principle of success that, both in nature and in technology, allows the effectiveness of physical
effects to be enhanced. Mutation and selection in nature are imitated in technology, e.g. by model calculation and design.
Proper scaling of dimensions in natural photonic crystals and our fabricated artificial 1D photonic crystals (DBRs, distributed
Bragg reflectors) enable efficient diffractive interaction in a specific spectral range. For our optical microsystems we illustrate
that tailored miniaturization may also increase the mechanical stability and the effectiveness of spectral tuning by thermal
and electrostatic actuation, since the relative significance of the fundamental physical forces involved considerably changes
with scaling. These basic physical principles are rigorously applied in micromachined 1.55-μm vertical-resonator-based devices.
We modeled, implemented and characterized 1.55-μm micromachined optical filters and vertical-cavity surface-emitting laser
devices capable of wide, monotonic and kink-free tuning by a single control parameter. Tuning is achieved by mechanical actuation
of one or several air-gaps that are part of the vertical resonator including two ultra-highly reflective DBR mirrors of strong
refractive index contrast: (i) Δn=2.17 for InP/air-gap DBRs (3.5 periods) using GaInAs sacrificial layers and (ii) Δn=0.5
for Si3N4/SiO2 DBRs (12 periods) with a polymer sacrificial layer to implement the air-cavity. In semiconductor multiple air-gap filters,
a continuous tuning of >8% of the absolute wavelength is obtained. Varying the reverse voltage (U=0–5 V) between the membranes
(electrostatic actuation), a tuning range of >110 nm was obtained for a large number of devices. The correlation of the wavelength
and the applied voltage is accurately reproducible without any hysteresis. In two filters, tuning of 127 and 130 nm was observed
for about ΔU=7 V. The extremely wide tuning range and the very small voltage required are record values to the best of our
knowledge. For thermally actuated dielectric filters based on polymer sacrificial layers, Δλ/ΔU=-7 nm/V is found.
Received: 10 May 2002 / Published online: 8 August 2002 相似文献
14.
C.-T. Zheng C.-S. Ma X. Yan Z.-C. Cui D.-M. Zhang 《Applied physics. B, Lasers and optics》2011,105(2):343-352
We proposed a kind of polymer arc-type Mach–Zehnder interferometer (MZI) optical filter by employing two parallel cascaded
Nth-order phase-generating couplers (PGCs). To realize periodic spectrum response with low insertion loss, a nonlinear least
square method was investigated for optimizing PGC structure to satisfy periodic phase compensation (PPC) and insertion loss
compensation (ILC) conditions. With the needed wavelength period of 24 nm, design and simulation on five Nth-order PGCs-based filters were performed as N changes from 0 to 4. When N=3, the optimized filter exhibits the most favorable uniform periodic response with the maximum period shift less than 0.3 nm,
which is about 1/10 times of that of the traditional filter when N=0, and the insertion loss at the central wavelength of each channel is 1.39–9.98 dB. The PGC’s order N should be properly selected for low optical loss, uniform wavelength period, and feasible optimization complexity. The proposed
technique can also be used to design such PGCs-based arc-type MZI filters with any other uniform wavelength period by altering
the radius-difference between two arc-type MZI waveguides for CWDM networks. 相似文献
15.
We investigate the application of the Migdal-Kadanoff bond-moving renormalization group (RG) approach to fractal lattices.
We find the following two results: first, for inhomogeneous interaction lattice models, bond moving involving inequivalent
bonds is unsuitable because it violates the condition <Δ>=0 (Δ is the perturbation potential resulting from moving the bonds); second, the condition <Δ>=0 does not uniquely determine the way to move bonds; different choices of bond moving yield different RG recursion relations
and corresponding fixed points, which makes the conclusions concerning the phase transition quite uncertain. 相似文献
16.
A single-longitudinal-mode of 0.25 mm Tm,Ho:GdVO4 Microchip Laser was reported. The maximal continuous wave (CW) output power was 26.4 mW and the threshold of 118 mW. The
Tm,Ho:GdVO4 Microchip Laser output wavelength was centered at 2039.7598 nm with bandwidth of about 57.1 pm. The beam quality factor was
M
2 ∼ 1.52 ± 0.03 measured by knife-edge method. The Longitudinal-Mode was scanned by a FPI and the transverse mode was monitored
by an infrared vidicon camera. 相似文献
17.
Hollow cathode (HC) lasers usually operate in a single axial mode without any optical selection. This is attributed to the
large homogeneous linewidth of the gain curve due to the relatively high filling pressure of these lasers. Collisional and
Doppler broadening (ΔνC and ΔνD) of the Cd+ 636 nm and Cd+ 538 nm lines (laser transitions of the HeCd+ laser) excited in a HC discharge tube were determined using a Fabry–Perot interferometer technique. It was found that in
the pressure range 7–25 mbar ΔνD was nearly constant, while, as expected, ΔνC increased linearly with pressure. The broadening constants were α(636 nm)= (47±2) MHz/mbarand α(538 nm)=(11.8±0.5) MHz/mbar.
The first constant is large enough to explain single-mode operation of the red HeCd+ laser; but in the case of the green laser, the exact reason for the single-mode operation remained unclear.
Received: 23 November 2000 / Revised version: 30 March 2001 / Published online: 7 June 2001 相似文献
18.
Ya. G. Ponomarev S. A. Kuzmichev M. G. Mikheev M. V. Sudakova S. N. Tchesnokov T. E. Shanygina O. S. Volkova A. N. Vasiliev Th. Wolf 《Journal of Experimental and Theoretical Physics》2011,113(3):459-467
Current-voltage characteristics (CVCs) of Andreev superconductor-constriction-superconductor (ScS) contacts in polycrystalline
samples of FeSe with the critical temperature T
C = (12 ± 1) K have been measured using the break-junction technique. In Sharvin-type nanocontacts, two sets of subharmonic
gap structures were detected due to multiple Andreev reflections, indicating the existence of two nodeless superconducting
gaps Δ
L
= (2.75 ± 0.3) meV and Δ
S
= (0.8 ± 0.2) meV. Well-shaped CVCs for stacks of Andreev contacts with up to five contacts were observed due to the layered
structure of FeSe (the intrinsic multiple Andreev reflections effect). An additional fine structure in the CVCs of Andreev
ScS nanocontacts is attributed to the existence of a Leggett mode. A linear relation between the superconducting gap Δ
L
and the magnetic resonance energy E
magres ≈ 2Δ
L
is found to be valid for layered iron pnictides. 相似文献
19.
Summary The spin-orbit structure ofF
A centres in KCl:Li and KCl:Na have been studied by means of the magnetic circular dichroism. Due to theirC
4V symmetry theF
A centres have two different spin-orbit parameters, Δ‖ and Δ⊥, which only in the KCl:Li case follow the relation: Δ‖ < ΔF < Δ⊥ as expected from the theory. For a close comparison we have also reported our measurement of the spin-orbit coupling ofF centre in KCl. The spin-orbit parameters of theF andF
A centres have been determined using the method of moment. 相似文献
20.
V. K. Balkhanov Yu. B. Bashkuev 《Journal of Experimental and Theoretical Physics》2010,110(3):469-472
The temperature dependences of the ac resistivity R and ac capacitance C of arsenic selenide were measured more than four decades ago [V. I. Kruglov and L. P. Strakhov, in Problems of Solid State Electronics, Vol. 2 (Leningrad Univ., Leningrad, 1968)]. According to these measurements, the frequency dependences are R ∝ ω−0.80±0.01 and ΔC ∝ ω−0.120±0.006 (ω is the circular frequency and ΔC is measured from the temperature-independent value C
0). According to fractal-geometry methods, R ∝ ω1−3/h
and ΔC ∝ ω−2+3/h
, where h is the walk dimension of the electric current in arsenic selenide. Comparison of the experimental and theoretical results
indicates that the walk dimensions calculated from the frequency dependences of resistivity and capacitance are h
R
= 1.67 ± 0.02 and h
C
= 1.60 ± 0.08, which are in agreement with each other within the measurement errors. The fractal dimension of the distribution
of conducting sections is D = 1/h = 0.6. Since D < 1, the conducting sections are spatially separated and form a Cantor set. 相似文献