共查询到20条相似文献,搜索用时 15 毫秒
1.
An open cavity formed by three 60 degrees wedges of a photonic crystal with negative effective index is designed and studied. The quality factor of the open cavity can be larger than 2000. The influence of the interface termination on the resonant frequency and the quality factor is studied. 相似文献
2.
The resolution of imaging is limited by the missing of high-frequencies information. The superlens employing negative refraction can compensate for these components. But for the directional coupling of Bloch waves and the low coupling efficiency of large-angle waves, the resolution of subwavelength imaging is not satisfactory. However, the subwavelength metallic grating can produce high-order diffracted waves carrying a lot of high-frequencies information. Therefore, this structure is used to inhibit the zero-order diffraction and enhance the high-order diffraction to achieve super-resolution. 相似文献
3.
We report a systematic analysis of anomalous refractive effects at interfaces between two photonic crystal waveguide arrays. Discrete negative refraction can be easily predicted from the sign of the coupling coefficient between adjacent waveguides, regardless of handedness of propagation. 相似文献
4.
Nathalie Fabre 《Optics Communications》2008,281(13):3571-3577
We propose an optimization procedure for focusing operation in finite two dimensional photonic crystal slabs. The device consists of a triangular lattice air holes etched in a semiconductor matrix at a nanometer scale to operate at 1.55 μm. To reach simultaneously an effective refractive index equal to −1 along with a very high transmission coefficient whatever optical wave incidence, the parameters as the lattice period and/or filling factor are precisely adjusted depending on the slab thickness. The method relies on Fabry-Perot resonances engineering in the air/crystal/air cavity constituting the lens. 相似文献
5.
Shuai Feng Yuxi Li Bo Lei Jieying Hu Yiquan Wang Wenzhong Wang 《Solid State Communications》2012,152(11):929-932
Imaging properties and negative refraction of the two-dimensional metallic photonic crystal (PC) consisting of a triangular lattice of silver rods immersed in a dielectric is studied. It is found that good-quality image spots and negative refraction with an effective refractive index of ?1 can be achieved for the near-infrared frequency through the adjustment of the metallic PC's lattice constant and the permittivity of the background material together. Drude dispersion model is adopted to describe the silver rod and it is found that the influence of the metal's absorption is trivial to debase the quality of the image spot. 相似文献
6.
In this paper, a novel biosensor based on hetero photonic crystal (PC) structures is proposed. The biosensor consists of photonic crystals with negative refraction (PCNR) embedded between two ordinary PC structures. The PCNR is employed in order to produce an image that is as similar as the light source, which is located in the first ordinary PC. Significant enhancement of the image is achieved when a nanocavity is introduced into the PCNR. It is found that the transmission peak shifts when the nanocavity is filled with blood plasma, liquid and dry air. It is shown that by careful selection of the radius of the nanocavity, the sensitivity of the proposed biosensor can be enhanced. The presented PCNR biosensor is investigated by employing the finite-difference time-domain method (FDTD). 相似文献
7.
A three-dimensional bicontinuous photonic crystal of a bcc lattice with all-angle negative refraction that can be achieved at optical frequencies by interference lithography is proposed. A numerical simulation of the focusing imaging of a slab of this crystal was performed to verify the property of all-angle negative refraction. The dependence of the negative-refraction frequency range on the threshold of photoresist development and on the dielectric constant is also discussed. 相似文献
8.
K. Ren Z.Y. Li X. Ren B. Cheng D. Zhang 《Applied Physics A: Materials Science & Processing》2007,87(2):181-185
This paper describes a simple hydrothermal procedure for high-yield synthesis of single-crystalline ZnO hexagonal nanoplates in a surfactant-free system at 70 °C. The structures and morphologies of the synthesized ZnO nanoplates are derived from characterisation by X-ray diffraction, and scanning and transmission electron microscopy. Their optical properties are recorded by Raman and photoluminescence spectroscopy. These ZnO hexagonal nanoplates exhibit the enhanced photocatalytic activity of phenol photodecomposition, suggesting that they could be served as an active system for the treatment of the waste water, in addition to their common applications. PACS 81.10.Dn; 61.10.Nz; 68.37.Hk; 78.55.Hx 相似文献
9.
Based on transmission spectra, optical switching effect of equivalent negative refractive photonic crystals (PCs) composed of a triangular array of air cylinders in a GaAs matrix is studied by the finite-difference time-domain (FDTD) method in this paper. The mechanism of wave resonance is probed and the propagation of optical waves in the PCs is described in terms of effective refraction index and Bloch waves. Our numerical results show that the probability of spontaneous radiation would be enhanced extremely under the influence of Bloch resonance waves, stimulated emission and photon tunnel effect, resulting in the optical waves being localized greatly in the PCs at particular frequencies. In addition, we found that the position of transmission peaks, with values much greater than unit, can be controlled by tuning the central frequency of the waveguide source. It means that photon current in the PCs can also be controlled to optimize transmission properties of PCs, so as to meet the requirements of novel optical devices based on PCs, such as all-optical switches. 相似文献
10.
F. Ouerghi F. AbdelMalek S. Haxha M. Mejatty H. Bouchriha 《Optical and Quantum Electronics》2012,44(15):691-699
We report a novel design of an ultracompact sensor consisting of two-dimension photonic crystal with negative refraction coupled to a taper ended by multicavity structure. It is shown that this system exhibits promising properties in the area of sensing. The presence of nanocavities enables the detection of small amount of analytes. By controlling their radii, a large quality factor, Q is reached. It is demonstrated that the quality factor is a key parameter in determining the sensitivity to the analytes. 相似文献
11.
Polarization beam splitters based on a two-dimensional photonic crystal of negative refraction 总被引:1,自引:0,他引:1
A two-dimensional metallo-dielectric photonic crystal of negative refraction was designed for the application of polarization beam splitters. To match the refractive index of air, the effective refractive index of the designed photonic crystal is -1 for TE polarization and +1 for TM polarization. Two types of polarization beam splitter are presented. 相似文献
12.
Kurt H Hao R Chen Y Feng J Blair J Gaillot DP Summers C Citrin DS Zhou Z 《Optics letters》2008,33(14):1614-1616
We present the design of realistic annular photonic-crystal (APC) structures of finite thickness aiming to obtain a complete photonic bandgap (PBG). The APC is composed of dielectric rods and circular air holes in a triangular lattice such that each rod is centered within each hole. The optical and geometrical values of the structure are studied, and the interplay between various design parameters is highlighted. The coupled role of the inner-dielectric-rod radius, material types, and slab thickness is investigated. It is shown that the slab thickness is vital to obtain a complete photonic bandgap below the light line, and the specific value of the inner-dielectric-rod radius to sustain the maximum PBG if the hole radius is fixed at proper value is found. 相似文献
13.
The electromagnetic wave propagation in a two-dimensional (2D) circular photonic crystal (CPC) is investigated. The CPC structure is composed of air holes in the dielectric background material. The finite element method is used to study the optical and propagating properties of the CPC slab. Numerical simulations show that negative refraction and near-field imaging can appear in a 2D CPC slab. We also find that the high-symmetry CPC slab possesses an optics axis along the vertical direction intersecting the symmetric center. As a result, the CPC slab can exhibit an excellent imaging performance when a source is placed on the optical axis. 相似文献
14.
15.
Cheng-Yang Liu Nai-Wen Zhang Hung-Wen Wang Lien-Wen Chen 《Physica B: Condensed Matter》2009,404(21):4060-4070
Photonic crystals (PCs) have many potential applications because of their ability to control light-wave propagation. We have investigated the electromagnetic wave propagation inside an elliptic rod PC slab by means of finite-difference time-domain simulations. The band structure of the PC composed of elliptic rod in the square and triangular lattices is studied by solving Maxwell's equations using the plane wave expansion method. Numerical simulations show that the refractive angle can be tuned greatly by rotating the directors of elliptic rod in the PC slab. Furthermore, an optical switch based on elliptic rod PC structures with nematic liquid crystals was proposed. In the on/off switching system, the partial band gap can be controlled when the normalized operation frequency is 0.28. The modulation induced by liquid crystals created a sharp switching in the photonic devices. Such a mechanism of negative refraction PCs should open up a new application for designing components in photonic integrated circuits. 相似文献
16.
Optical properties of the direct-coupled Y-branch filtersby using photonic crystal slabs 总被引:1,自引:0,他引:1
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We fabricated a new type of two-dimensional photonic crystal slab filter. The
resonant cavities were directly put into the waveguide arms. The optical
transmissions of the filters were measured and the results show that the optimized
two-channel filters give good intensity distribution at the output ports of the
waveguide. A minimum wavelength spacing of 5~nm of the filter outputs isrealized
by accurately controlling the size of the resonant cavities. 相似文献
17.
Existing conditions of full bandgaps and absolute negative refraction in metallic-dielectric photonic crystal 总被引:1,自引:0,他引:1
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This paper has theoretically studied the characteristic frequencies
of band structures in two-dimensional metallic-dielectric photonic
crystals. It is demonstrated that a large filling fraction benefits
the existence of absolute photonic band gap, while a smaller filling
fraction benefits an absolute negative refraction band. In addition,
it also finds that the relation between the cut-off frequency of
E-polarized wave and the filling fraction exceeding 10{\%} is content
with a linear increasing function, whose coefficients are exponential
to the normalized lattice constant. These investigations have
significant implications for tuning the operational frequencies to
desired applications and manufacturing photonic crystals. 相似文献
18.
A method to realize absolute negative refraction index -1 with a two-dimensional (2D) photonic crystal is presented by introducing dielectric anisotropy in the photonic crystal material. The band structures of E-polarization mode and H-polarization mode can be adjusted by changing the parameters of materials. Thus the two modes with different polarizations have the same negative refraction index -1 for the same frequency. The results are demonstrated by numerical simulation based on the finite-difference time-domain (FDTD) method. 相似文献
19.
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
20.
A theoretical study of cavity modes in one-dimensional photonic crystal slabs embedded in Silicon-on-Insulator structures is reported. Three different methods are employed, namely a guided-mode expansion in which the coupling to radiative modes is treated by perturbation theory, a grating or scattering-matrix method for calculating the surface reflectance, and a Fourier modal expansion for in-plane transmission calculations. It is shown that all methods lead to the same values for the quality factors of cavity modes for both first- and second-order Bragg mirrors. We conclude that the quality factor of a cavity mode can be determined with optical reflectance from the surface of the slab. 相似文献