共查询到19条相似文献,搜索用时 386 毫秒
1.
构造了由普通材料A(SiO2)和电单负材料B组成的(AB)N(BA)N型一维光子晶体.数值计算表明原禁带的1907.3 nm处出现了一个十分尖锐的隧穿模. 入射角增加,该隧穿模的透射率和半峰全宽度均保持不变,但位置发生蓝移, 入射角在15°-65°的区间内,移动率的绝对值 |dλ/dθ| 较大.当B介质的磁导率μB 从5增加到10时,只是隧穿模的位置发生了红移. 介质的几何厚度增加时,隧穿模的透射率不变,但其位置红移明显,半峰全宽略有增加. 相似文献
2.
光子晶体缺陷模的带宽与品质因子研究 总被引:22,自引:11,他引:11
利用光学传输矩阵法研究了结构参量对缺陷态光子晶体的缺陷模带宽和品质因子的影响.研究发现,当缺陷介质层厚度h0的值较小时,缺陷模的带宽很小且基本保持不变;当h0较大时,缺陷模的带宽随h0的增加而快速增加.另外发现,缺陷模的品质因子在某个h0处取最大值.但是总体上看,h0较小时的品质因子要远大于h0较大时的品质因子.此外,缺陷模的品质因子随光子晶体的周期数增加而急剧增加约4.788倍,而带宽则随周期数的增加而急剧减少约4.788倍.当周期数为13时就可以获得109以上的品质因子值和小于10-9的相对带宽值. 相似文献
3.
4.
对二维介质柱光子晶体耦合腔波导慢光结构进行了研究,发现随着缺陷腔之间晶格个数增多,群速度减小很快,选用7×7超胞单元时耦合腔波导结构的导模最大群速度νg-max只有光子晶体线缺陷波导的1/251.然后对7×7超胞单元的缺陷腔周围四个介质柱半径进行调整,发现新型结构导模的νg-max进一步减小,最小可达到589×10-4c,约为未调整之前的1/5.最后通过比较发现,当改变缺陷腔上下相邻两个介质柱半径时得到的结构具有更好的慢光特性. 相似文献
5.
6.
采用固相反应法制备了不同含氧量的BiFeOδ多晶陶瓷样品,利用HP4294A阻抗分析仪测量了样品的介电特性随频率和氧含量的变化,用正电子湮没寿命谱学的方法研究了样品中因氧含量的变化所引起的结构缺陷. 实验结果表明:引入氧空位和氧填隙离子缺陷都会使介电常数减小,而介电损耗则随氧含量的增加而增加,二者的变化范围均在10%—35%之间;对不同氧含量的BiFeOδ样品,介电常数和介电损耗随测量频率的增加而减小. 氧空位的引入使得局域电子密度变小,正电子平均寿命τm增加. 在氧含量δ=2.99时电子密度最大(ne=3.90×1023/cm3),继续增加氧含量对正电子寿命与局域电子密度的影响不大. BiFeOδ样品的介电常数和介电损耗随氧含量的变化可以在空间电荷限制电导的框架下来理解. 相似文献
7.
利用传输矩阵法,讨论了由单负材料组成的对称型一维光子晶体的偏振特性。结果表明:入射角较小时,TE、TM两波隧穿模的中心位置基本相同。入射角θ增加,两隧穿模均向短波方向移动,且其半峰全宽变窄。入射角θ>20°时,两隧穿模的蓝移量增加,且TM波的移动量大于TE的,入射角越大,这一变化越明显。周期数N增加时,两隧穿模的位置保持不变,半峰全宽变窄;TM波隧穿模的透射率保持为1,而TE波的有所下降。介质的几何厚度增加时,两隧穿模均向长波方向移动,隧穿模的透射率保持不变。两介质几何厚度的变化量相同,两隧穿模的移动量也分别相同。 相似文献
8.
混合应变多量子阱有源材料及其增益偏振特性 总被引:1,自引:1,他引:0
采用MOCVD外延交替生长了压应变、张应变InxGa1-xAsyP1-y多量子阱材料,对应1.3 μm波段.平均应变量-0.16%,周期11 nm.采用三个周期外延材料的芯片制作的LD,实现了TE和TM双偏振模激射. 相似文献
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第Ⅴ类两态叠加多模叠加态光场的等阶N次方H压缩特性研究 总被引:39,自引:23,他引:16
本文构造了由多模真空态|{Oj}〉q和多模虚相干态的相反态|{-iZj}〉q这两者的线性叠加所组成的第Ⅴ类两态叠加多模叠加态光场ψ5(2)〉q,利用多模压缩态理论详细研究了态 ψ5(2)〉q的广义非线性等阶N次方H压缩特性.结果发现:1)态ψ5(2)〉q是一种典型的多模非经典光场;无论腔模总数q与压缩阶数N这两者之积q·N取奇还是取偶,只要各模的初始相位之和 、态间的初始相位之差(θnq(I)-θoq(o))等满足一定的量子化条件,态ψ5(2)〉q总可分别呈现出周期性变化的、任意的奇数模-奇数阶、奇数模-偶数阶、偶数模-偶数阶和偶数模-奇数阶这四种不同形式的等阶N次方H压缩效应.2)上述四种不同形式的等阶N次方H压缩效应,其态间压缩条件完全相同,但模间压缩条件完全不同,结果使其压缩幅度、压缩结果和压缩特性等各不相同.3)无论q·N取奇还是取偶,态ψ5(2)〉q的第一和第二这两个正交分量的等阶N次方H压缩效应总是呈现周期性的互补关系. 相似文献
11.
Infrared absorption and Raman study ofβ-Ni(OH)2 has been carried out up to 25 GPa and 33 GPa, respectively. The frequency ofA
2u
internal antisymmetric stretching O-H mode decreases linearly with pressure at a rate of −0.7 cm−1/GPa. The FWHM of this mode increases continuously with pressure and reaches a value of ∼ 120 cm−1 around 25 GPa. There was no discernible change observed in the frequency and width of the symmetric stretchingA
1g
O-H Raman mode up to 33 GPa. The constancy of the Raman mode is taken as a signature of the repulsion produced by H-H contacts
in this material under pressure. Lack of any discontinuity in these modes suggests that there is no phase transition in this
material in the measured pressure range. 相似文献
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13.
Xin-Hai Liu Xue-Hua Wang Ben-Yuan Gu 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(1):37-41
The collective charge density excitations in asymmetric double-quantum-well (DQW) structures with different tunneling strengths
are systematically studied. In particular, the damping properties of the plasmon modes in various tunneling strengths are
investigated in detail. It is shown that plasmon modes in asymmetric DQW structures are quite different from those in symmetric
DQW systems. In weak tunneling regime, an intra-subband mode ω
- with an acoustic-like dispersion relation which is damped in symmetric DQW structures arises and coexists with the optical-like
mode ω
+ while the inter-subband mode ω
10 is highly damped. With the tunneling strength being increased, the ω
10 branch gradually becomes undamped and emerges out of the (1-0) single-particle continuum, whereas the ω
- branch gradually approaches the (0-0) single-particle continuum. In intermediate coupling regime, these three branches of
modes coexist undamped. In strong tunneling regime, ω
- enters the (0-0) single-particle continuum and becomes damped. Consequently, only the ω
+ and ω
10 modes exist in this regime.
Received 10 July 2001 and Received in final form 17 September 2001 相似文献
14.
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
15.
V.?Yu.?Tarenkov A.?I.?D’yachenko S.?L.?Sidorov V.?A.?Bo?chenko D.?I.?Bo?chenko ?.?Chromik V.??trbík ?.?Ga?i M.??panková ?.?Beňa?ka 《Physics of the Solid State》2009,51(9):1778-1784
The specific features of the phonon spectrum of the MgB2 compound (T
c
= 38 K) are investigated by tunneling spectroscopy. It is demonstrated that both the position and the energy width of the
fundamental optical mode E
2g
in the phonon spectrum are in good agreement with inelastic X-ray spectroscopy data but differ substantially from Raman spectroscopy
results. Among possible factors responsible for this discrepancy, the anharmonic and nonadiabatic effects that are characteristic
of the MgB2 system are discussed. 相似文献
16.
Recombination zone and efficiency in bipolar single layer light-emitting devices: a numerical study 总被引:1,自引:0,他引:1
Ying-Quan Peng Qing-Sen Yang Hong-Wei Xing Xun-Shuan Li Jian-Ting Yuan Chao-Zhu Ma Run-Sheng Wang 《Applied Physics A: Materials Science & Processing》2008,93(2):559-564
The efficiency of organic light-emitting devices (OLEDs) is closely related to the position and width of recombination zone
(RCZ) in the emission layer. Based on the drift–diffusion theory of carrier motion in semiconductors, we developed a numerical
model for the position and width of the RCZ in bipolar single layer OLEDs. The calculation results show that for a given operation
voltage, the position and width of the RCZ are determined by the mobility difference of electrons and holes, and the energy
barrier at the two contacts. When the anode and cathode contact are both ohmic, then RCZ will be near the electrode, from
which the low-mobility carriers are injected, and the smaller the mobility difference, the wider the RCZ, and the width of
RCZ will be maximal when the mobility of holes and electrons are equal. When the anode contact is Schottky, while the cathode
contact is ohmic, then the position and width of RCZ will be determined by both the mobility difference and hole–injection
energy barrier. When μ
p<μ
n, the RCZ will be at the anode side. When μ
p>μ
n, then RCZ will move away from the anode and become wider, with the increase of the hole injection barrier. For a given hole–injection
barrier and mobility of holes and electrons, the position and width of RCZ change with the applied voltage. 相似文献
17.
The absorption spectra of gold–silica–gold nanoshells have been investigated by using Mie theory with variation of the geometry.
With an increase in core radius the plasmon resonance for the lower energy mode ω
−− shows a distinct redshift while for the high-energy mode ω
−+ shows a blueshift. It is surprising that with increasing middle layer thickness the resonance of ω
−− mode blueshifts first and then redshifts. In addition, an increase of the dielectric constant of the middle layer is found
to reduce the resonance energies of the particle. The tunable near-infrared optical properties are discussed in terms of plasmon
hybridization theory. 相似文献
18.
The temperature dependence of the line width and the peak position of theE
g
librational mode (of nominal frequency 285 cm−1) and theE
g
translational mode (of nominal frequency 155 cm−1) in calcite (CaCO3) have been studied by laser-Raman spectrometry. The role of orientational relaxation as a possible process contributing to
the line width has been evaluated. It is concluded that reorientations do not play a major part in relation to the present
observations. It is further shown that the latter can be understood on the basis of cubic and quartic anharmonic processes.
The data also suggest that certain phonon interactions earlier considered insignificant for peak shift in calcite, do contribute
significantly. 相似文献
19.
Using the Dirac-Bogoliubov-de Gennes equation, we study the electron transport in a graphene-based superconductor-normal(graphene)-superconductor
(SNS) junction. We consider the properties of tunneling conductance through an undoped strip of graphene with heavily doped
superconducting electrodes in the dirty limit l
def ≪ L ≪ ξ. We find that the spectrum of Andreev bound states is modified in the presence of a single localized defect in the bulk.
The minimum tunneling conductance remains the same, and this result is independent of the actual location of the imperfection. 相似文献