共查询到20条相似文献,搜索用时 31 毫秒
1.
Xu Bingshe Han Peide Liu Xuguang Li Tianbao Hideki Ichinose 《Solid State Communications》2005,133(6):353-356
Theoretical calculations via a transfer matrix method (TMM) were performed to investigate the possibility of fullerene/AlN multilayer films acting as one-dimensional (1D) photonic band gap (PBG) crystals. The response within and out of the periodic plane of (C60, C70)/AlN multilayers was studied. (C60, C70)/AlN multilayer films presented incomplete PBG behavior in UV region. C60/AlN multilayers with two pairs of 49 nm-C60 and 21 nm-AlN layers exhibited a high reflectivity of 90.4% at a wavelength of about 200 nm. As a consequence, this photonic crystal may be important for achieving materials with an incomplete band gap in the UV region. 相似文献
2.
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4.
In this paper, a rigorous theoretical analysis has been made to study the dispersion relation of EM waves in periodic ternary one-dimensional photonic crystal having two different structures. In one case we have chosen glass-plasma and ZnS in one unit cell and in other case we have considered glass-plasma and MgF2 in one unit cell. Using Kronig-Penney model the dispersion relation for proposed structures has been obtained and numerical results are presented in the form of dispersion curves. The dependence of photonic band gap (PBG) characteristics on plasma frequency, plasma width and the width of dielectric media are discussed in the light of frequency gap and cutoffs of binary one-dimensional plasma photonic crystal. An attempt has been made to show how the PBG characteristic of a particular structure changes when the dielectric materials of its unit cell is changed by the other dielectric material. It is found that the structure having glass-plasma-ZnS in unit cell is more useful for broad band filtering and other plasma functioning devices compared to the structure having glass-plasma-MgF2 in one unit cell. 相似文献
5.
Khem B. Thapa S. K. Singh S. P. Ojha 《International Journal of Infrared and Millimeter Waves》2006,27(9):1257-1268
We have purposed the design of omnidirectional high reflectors with wide bandwidth (nearly 6300A0) for the infrared wavelength. Using translational matrix method for numerical calculation, it is found that a complete photonic
band gap high reflector covering the wavelength region 11500A0 to 17800A0 is obtained for the quarter wave stack air / (nL nH)7 / air by using the tellurium (n=4.60) and TiO2 (n=2.35) as material of high reflective index and SiO2(n=1.45) low refractive index. Due to high refractive index of contrast of the structure i.e. SiO2/tellurium, a large complete photonic band gap, omnidirectional high reflector, has been observed for the infrared wavelengths.
This type of omnidirectional high reflector can be used in telecommunication. Besides this, we have studied the effective
refractive indices (phase and group) of the proposed structures. It is observed that the effective refractive indices (phase
and group) of the high omnidirectional reflector band are largely changed near the band edges due to the high refractive index
of contrast, and the reflections from the internal interfaces of the structure. 相似文献
6.
In the present paper, a novel photonic crystal (PC) defect mode is designed by inserting a ferroelectric material layer (LiNbO3) into Si/C60 one-dimensional PCs. The band structure of the ferroelectric PCs is numerically analyzed by the transfer matrix method (TMM). The width of the photonic band gap increases by 80 nm and a defect mode appears at a central wavelength of 680 nm when a 150 nm LiNbO3 layer is inserted into the Si/C60 PC structure. The defect mode in the band gap shifts linearly with the change in electric field. The defect mode shifts by 11.2 nm toward shorter wavelengths when the thin film is subjected to a DC voltage of 1 KV. 相似文献
7.
This paper presents a design of sharp transmission filters using band edge resonance effects in a hetero-structure composed
of one-dimensional photonic crystals with different periods. Assuming that the photonic crystals are made of identical pairs
of transparent materials, the band-edge resonance occurs when the periods are distributed in a geometrical progression with
a common ratio, r=r
c
, where r
c
is a known function of refractive-index modulation, incident angle and the polarization of light. The band-edge resonance
results in sharp resonant peaks in the transmission spectrum, with the full width at half maximum of the peaks increasing
with an increase in the number of unit cells in each photonic crystal. Furthermore, if M photonic crystals are used to construct the hetero-structure, M−1 resonant peaks with the spacing between kth (1<k<M) and (k−1)th peaks equal to the band gap of the kth photonic crystal form in the transmission spectrum. 相似文献
8.
The propagation of an electromagnetic wave through a barrier with a periodic structure is considered. An interesting manifestation
of electromagnetic wave tunneling through a barrier with a periodic structure is revealed. Specifically, it is theoretically
and experimentally shown that, when an electromagnetic wave passes through a medium with a periodic structure in the diffraction
mode within a photonic band gap, the field in the medium is localized near its boundaries. Theoretical calculations have been
performed for a cholesteric liquid crystal layer of finite thickness and for a 1D photonic crystal. The experiment was carried
out with perfect Si single crystals in reflection from the $
(2\bar 20)$
(2\bar 20)
and $
(4\bar 40)$
(4\bar 40) planes using MoK
α X rays. 相似文献
9.
GK Johri Akhilesh Tiwari Saumya Saxena Rajesh Sharma Kuldeep Srivastava Manoj Johri 《Pramana》2002,58(3):563-567
Calculations for the relative width (Δω/ω0) as a function of refractive index and relative radius of the photonic band gap for the fcc closed packed 3-D dielectric
microstructure are reported and comparison of experimental observations and theoretical predictions are given. This work is
useful for the understanding of photonic crystals and occurrence of the photonic band gap. 相似文献
10.
The existence and properties of photonic band gaps was investigated for a square lattice of dielectric cylinders in air. Band structure calculations were performed using the transfer matrix method as function of the dielectric constant of the cylinders and the cylinder radius-to-pitch ratio r/a. It was found that band gaps exist only for transverse magnetic polarization for a dielectric contrast larger then 3.8 (index contrast >1.95). The optimum r/a ratio is 0.25 for the smallest index contrast. For silicon cylinders (n = 3.45) the widest gap is observed for r/a = 0.18. Band structure calculations as function of r/a show that up to four gaps open for the silicon structure. The effective index was obtained from the band structure calculations and compared with Maxwell–Garnett effective medium theory. Using the band structure calculations we obtained design parameters for silicon based photonic crystal waveguides. The possibility and limitations of amorphous silicon, silicon germanium and silicon-on-insulator structures to achieve index guiding in the third dimension is discussed. 相似文献
11.
S. Roshan Entezar A. MadaniA. Namdar H. Tajalli 《Journal of magnetism and magnetic materials》2012,324(9):1739-1744
The effect of anisotropy on the photonic band structure and surface polaritons of a one-dimensional photonic crystal made of uniaxially anisotropic epsilon-negative (ε<0,μ>0) and mu-negative (ε>0,μ<0) metamaterials is theoretically investigated. Two different cases of uniaxially anisotropic epsilon-negative and mu-negative metamaterials are considered. It is found out that for one case of anisotropy, one-dimensional photonic crystal does not have any single-negative band gap. As a result, it can not support the surface polaritons. While, for another case, the structure shows single-negative band gaps. So, the surface polaritons can be excited at the interface of such a photonic crystal. However, these surface polaritons, unlike the isotropic case, are not omnidirectional and they are restricted to a limited rang of the propagation constant. 相似文献
12.
In this paper, we study the asymptotic behavior of solutions of semilinear abstract differential equations (*) u′(t) = Au(t) + t
n
f(t, u(t)), where A is the generator of a C
0-semigroup (or group) T(·), f(·, x) ∈ A for each x ∈ X, A is the class of almost periodic, almost automorphic or Levitan almost periodic Banach space valued functions ϕ: ℝ → X and n ∈ {0, 1, 2, ...}. We investigate the linear case when T(·)x is almost periodic for each x ∈ X; and the semilinear case when T(·) is an asymptotically stable C
0-semigroup, n = 0 and f(·, x) satisfies a Lipschitz condition. Also, in the linear case, we investigate (*) when ϕ belongs to a Stepanov class S
p-A defined similarly to the case of S
p-almost periodic functions. Under certain conditions, we show that the solutions of (*) belong to A
u:= A ∩ BUC(ℝ, X) if n = 0 and to t
n
A
u ⊕ w
n
C
0 (ℝ, X) if n ∈ ℕ, where w
n(t) = (1 + |t|)n. The results are new for the case n ∈ ℕ and extend many recent ones in the case n = 0.
Dedicated to the memory of B. M. Levitan 相似文献
13.
István Lagzi 《Pramana》2005,64(2):291-298
Formation of 1D Liesegang patterns was studied numerically in precipitation and reversible complex formation of precipitate
scenarios in an electric field. The Ostwald’s supersaturation model reported by Buki, Kárpáti-Smidróczki and Zrínyi (BKZ model)
was extended further. In the presence of an electric field the position of the first and the last bands (X
n) measured from the junction point of the outer and the inner electrolytes can be described by the functionX
n =a
1τ
n
1/2
+a
2τn +a
3, where τn is the time elapsed until the nth band formation,a
1,a
2 anda
3 are constants. The variation of the total number of bands with different electric field strengths (ε) has a maximum. For
higher ε one can observe a moving precipitation zone that becomes wider due to precipitation and reversible complex formation. 相似文献
14.
In this article, the reflection properties in one-dimensional dielectric-dielectric photonic band gap (PBG) structure have
been studied. We have used SiO2 as material of low refractive index and Te as a high refractive index material. Reflectivity of proposed PBG structure is
plotted as a function of wavelength and angle of incidence and omni-directional PBGs are computed theoretically. To obtain
reflectance, we used transfer matrix method for solving Maxwell’s equations for electromagnetic wave in PBG structures. For
a large range of frequency, the PBG structure is found to exhibit omni-directional reflection which can be exploited in devices
such as optical resonators, mirrors, etc. 相似文献
15.
The finite-difference time-domain method was used to analyze band structures in two-dimensional Kerr-nonlinear photonic crystal slabs. A triangular lattice of circular air rods was considered. Results show red-shifting of the band structure due to the nonlinearity and the incident intensity. The red-shift of the band gap between the first and the second bands is maximal when the air rod radius is in the range 0.2a to 0.25a, where a is the period. 相似文献
16.
The reversibility problem for linear cellular automata with null boundary defined by a rule matrix in the form of a pentadiagonal
matrix was studied recently over the binary field ℤ2 (del Rey and Rodriguez Sánchez in Appl. Math. Comput., 2011, doi:). In this paper, we study one-dimensional linear cellular automata with periodic boundary conditions over any finite field
ℤ
p
. For any given p≥2, we show that the reversibility problem can be reduced to solving a recurrence relation depending on the number of cells
and the coefficients of the local rules defining the one-dimensional linear cellular automata. More specifically, for any
given values (from any fixed field ℤ
p
) of the coefficients of the local rules, we outline a computer algorithm determining the recurrence relation which can be
solved by testing reversibility of the cellular automaton for some finite number of cells. As an example, we give the full
criteria for the reversibility of the one-dimensional linear cellular automata over the fields ℤ2 and ℤ3. 相似文献
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18.
A. V. Balakin V. A. Bushuev B. I. Mantsyzov P. Masselin I. A. Ozheredov A. P. Shkurinov D. Boucher 《JETP Letters》1999,70(11):725-729
A new property of a one-dimensional periodic structure — amplification of the sum-frequency signal arising under the simultaneous
action of two laser pulses on this structure with radiation frequencies corresponding to the edges of the fixed Bragg band
gap — is experimentally observed and described.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 11, 718–721 (10 December 1999) 相似文献
19.
Detection of periodic structures, hidden in random surfaces has been addressed by us for some time and the ‘extended matched
filter’ method, developed by us, has been shown to be effective in detecting the hidden periodic part from the light scattering
data in circumstances where conventional data analysis methods cannot reveal the successive peaks due to scattering by the
periodic part of the surface. It has been shown that if r
0 is the coherence length of light on scattering from the rough part and Λ is the wavelength of the periodic part of the surface,
the extended matched filter method can detect hidden periodic structures for (r
0/Λ) ≥ 0.11, while conventional methods are limited to much higher values ((r
0/Λ) ≥ 0.33). In the method developed till now, the detection of periodic structures involves the detection of the central
peak, first peak and second peak in the scattered intensity of light, located at scattering wave vectors v
x
= 0, Q, 2Q, respectively, where Q = 2Gp/Λ, their distinct identities being obfuscated by the fact that the peaks have width Δv
x
= 2Gp/r
0 ≫ Q. The relative magnitudes of these peaks and the consequent problems associated in identifying them is discussed. The Kolmogorov-Smirnov
statistical goodness test is used to justify the identification of the peaks. This test is used to ‘reject’ or ‘not reject’
the null hypothesis which states that the successive peaks do exist. This test is repeated for various values of r
0/Λ, which leads to the conclusion that there is really a periodic structure hidden behind the random surface.
相似文献
20.
Within the Maxwell framework and using the transfer-matrix method, we have determined an exact expression that governs the photonic band structure and the density of states (the group velocity) of one-dimensional superlattices composed of three alternate layers (quasi-sandwiching periodic structure) characterized by three different refractive indexes. We begin by giving the band gap of the quasi-sandwiching period structure. Owing to the advantage of the quasi-sandwiching periodic structure, we develop a specific formula that gives the N-period mode density in terms of the complex transmission coefficient of a unit cell. The specific example of a quarter-wave stack is analyzed. 相似文献