Browsing by Author "Yang, Tzong-Jer"

Now showing 1 - 18 of 18

50/50 beam splitter using a one-dimensional metal photonic crystal with parabolalike dispersion
(2007-06-18)
Shen, Linfang
;
Yang, Tzong-Jer
;
Chau, Yuan-Fong
;
電子物理學系
;
Department of Electrophysics
The spatial dispersion properties of a one-dimensional metal photonic crystal have been analyzed and five types of dispersion curves have been shown at a normalized frequency less than 1. It is demonstrated that by exploiting a parabolalike dispersion behavior, a metal photonic crystal slab can be used to realize an exactly 50/50 beam splitter. (c) 2007 American Institute of Physics.
Analysis of effective plasma frequency in a superconducting photonic crystal
(2013-02-01)
Hu, Chung-An
;
Wu, Chien-Jang
;
Yang, Tzong-Jer
;
Yang, Su-Lin
;
電子物理學系
In this work, a theoretical analysis on the effective plasma frequency (EPF) for a one-dimensional superconductor dielectric photonic crystal is made. First, the EPF is extracted from the first photonic band calculated within the framework of transfer matrix method together with Bloch theorem in a periodic multilayer structure. We investigate the EPF as a function of the filling factor and the permittivity of the dielectric layer, and the operating temperature as well. Then, the EPF is comparatively studied by the analytical expression derived from the effective medium theory. It is found that both results are in fairly good agreement. (C) 2013 Optical Society of America
Analysis of optical properties in cylindrical dielectric photonic crystal
(2013-03-15)
Hu, Chung-An
;
Wu, Chien-Jang
;
Yang, Tzong-Jer
;
Yang, Su-Lin
;
電子物理學系
In this work, theoretical formulas for the H-polarization electromagnetic propagation in a cylindrical multilayer structure (CMS) are given. The relationships between two modes, H- and E-polarization are pointed out. With the derived formulae, we present the numerical results for three model structures such as the single cylindrical interface, the single cylindrical slab, and the cylindrical photonic crystal (CPC). In the single cylindrical interface, it is found that there exists a Brewster starting radius at which a minimum reflectance is attained in H-polarization. In the single cylindrical slab, the result illustrates that the reflectance response in the wavelength domain contains the oscillating and nonoscillating regions. As for the CPC, we find the PBG structure at zero azimuthal mode number is very similar to that of planar photonic crystal. The PBG, however, can be strongly influenced by increasing the azimuthal mode number in a CPC. (C) 2012 Elsevier B.V. All ights reserved.
Coherent Coupling Between a Three-Level Atom and a Structured Reservoir
(2008-12-01)
Wu, Jing-Nuo
;
Yang, Tzong-Jer
;
Cheng, Szu-Cheng
;
光電工程學系
;
Department of Photonics
We study the spontaneous emission (SE) spectra of a three-level A-type atom in photonic crystals. The air-band, the dielectric-band and the free-space vacuum reservoirs coupled with the atom are considered. With the consideration of the phase difference between the air-band and the dielectric-band fields, two band reservoirs become coherent and can interfere with each other. This interference effect depends on the embedded position of the atom and the band-gap width and can affect the SE spectrum. The effect of this interference on the SE spectrum is shown.
Dynamic structure factor of liquid Ga close to the melting point: spectral linewidth at high momentum transfer
(2007-05-23)
Tsai, K. H.
;
Wu, Ten-Ming
;
Tsay, Shiow-Fon
;
Yang, Tzong-Jer
;
電子物理學系
By simulating an interatomic pair potential obtained from the first-principles generalized energy-independent nonlocal model-pseudopotential (GEINMP) theory, we have reproduced the high-wavevector shoulder in the static structure factor and the recently observed anomaly in the linewidth of the dynamic structure factor of liquid Ga close to the melting point. Our results indicate that the two anomalies have the same physical origin, which is associated with the Friedel oscillations induced by conduction electrons. The anomaly in the dynamics can be well described by the revised Enskog theory for the hard-sphere (HS) system, with the effective HS diameter determined by the position at the first peak of the radial distribution function. We interpret the occurrence of the anomaly in the dynamics by the physical picture of cage diffusion.
Effect of atomic position on the spontaneous emission of a three-level atom in a coherent photonic-band-gap reservoir
(2009-01-01)
Cheng, Szu-
;
Wu, Jing-Nuo
;
Yang, Tzong-Jer
;
Hsieh, Wen-Feng
;
光電工程學系
The effect of atomic position on the spontaneous emission and optical spectra of a three-level atom embedded in a photonic crystal was studied by considering the coherent two-band photonic-band-gap (PBG) reservoir. With the definite phase difference between the fields of the air band and dielectric band in this coherent PBG reservoir, we found that this coherent property grows stronger and results in the spectrum shift and the appearance of dark lines and kinks as the width of band gap gets smaller; and the variation of the atomic position leads to large shift of spectral peak. The averaged spectra of the system with an ensemble of atoms embedded in the dielectric region are blueshifted while those of atoms in the air region are redshifted. The spectra peaks can even shift more than 75% of the half width at half maximum. The feasible experimental systems composed of an ensemble of molecules (quantum dots or fluorescence dye) in photonic crystals are discussed.
Effect of internal period on the optical dispersion of indefinite-medium materials
(2008-05-01)
Shen, Linfang
;
Yang, Tzong-Jer
;
Chau, Yuan-Fong
;
電子物理學系
;
Department of Electrophysics
The effect of internal period on the optical dispersion of indefinite medium material (IDMM) is analytically studied under the condition of the period much smaller than the operating wavelength, based on a simplified dipole model for the material. Interesting phenomena associated with the internal period, such as upper cutoff for wave vector, additional propagating mode, and parabolic dispersion in a limiting case are demonstrated in detail. However, for the normal wave vector (k) region, where vertical bar k vertical bar similar to k(0) or vertical bar k vertical bar << k(0) (k(0) is the free-space wave number), the hyperbolic dispersion behavior can still be realized by IDMM as long as its internal period is small enough. Our analysis also shows that unlike the homogeneous indefinite medium, there exists no special boundary for IDMM, on which the refraction problem cannot be physically solved. Finally, the dispersion properties obtained from the dipole model are verified by using a real example of layered IDMM.
Effects of superconducting film on the defect mode in dielectric photonic crystal heterostructure
(2013-03-01)
Hu, Chung-An
;
Liu, Jia-Wei
;
Wu, Chien-Jang
;
Yang, Tzong-Jer
;
Yang, Su-Lin
Effects of superconducting thin film on the defect mode in a dielectric photonic crystal heterostructure (PCH) are theoretically investigated. The considered structure is (12)S-N(21)(N), in which both layers 1 and 2 are dielectrics, layer S is a high-temperature superconducting layer, and N is the stack number. The defect mode is analyzed based on the transmission spectrum calculated by using the transfer matrix method. It is found that, in the normal incidence, the defect mode existing in the host PCH of (12)(N)(21)(N) will be blue-shifted as the thickness of layer S increases. In addition, the defect mode is also blue-shifted for both TE and TM modes in the case of oblique incidence. The embedded superconducting thin film plays the role of tuning agent for the defect mode of PCH. As a result, the proposed structure can be designed as a tunable narrowband transmission filter which could be of technical use in the optoelectronic applications. (c) 2013 Elsevier Ltd. All rights reserved.
Engineering the bandgap of a two-dimensional photonic crystal with slender dielectric veins
(2007-10-01)
Liu, Wen-Long
;
Yang, Tzong-Jer
;
電子物理學系
;
Department of Electrophysics
This study proposes the double-hybrid-rods structure of two-dimensional (2D) photonic crystals of a square lattice. A square dielectric rod connected with slender rectangular dielectric veins on the middle of each side,of dielectric square rod. Some specific modes are found to be sensitive to certain structural parameters, such as the length, the dielectric constant and the shift of the position of the veins, etc., and giving rise to a new complete PBG at lower index bands. These results could be understood by the use of band structure point of view. In particular, by carefully adjusting the structural parameters, the band structure of the photonic crystal can be substantially engineered to achieve large bandgaps. (C) 2007 Elsevier B.V.. All rights reserved.
High birefringence photonic crystal fiber with a complex unit cell of asymmetric elliptical air hole cladding
(2007-08-01)
Sun, Yuh-Sien
;
Chau, Yuan-Fong
;
Yeh, Han-Hsuan
;
Shen, Lin-Fang
;
Yang, Tzong-Jer
High birefringence induced by elliptical air hole photonic crystal fibers (EHPCFs) is analyzed numerically using the finite-element method. Statistical correlations between the birefringence and the various parameters are obtained. We found that the complex elliptical air hole is better than that of a circular one to obtain high birefringence in photonic crystal fibers. Our suggested structures can considerably enhance the birefringence in EHPCFs and show that the birefringence can be as high as 1.1294 x 10(-2), which is higher than the birefringence obtained from conventional step-index fiber (5 X 10(-4)), circular air holes PCF (3.7 X 10(-3)), and elliptical hollow PCF (2.35 x 10(-3)). (C) 2007 Optical Society of America.
Optical properties of a superconducting annular periodic multilayer structure
(2009-11-01)
Chen, Mei-Soong
;
Wu, Chien-Jang
;
Yang, Tzong-Jer
;
電子物理學系
;
Department of Electrophysics
The optical properties of a superconducting annular Bragg reflector (SABR) are theoretically investigated based on the transfer matrix method for the cylindrical waves. For TM wave at an azimuthal mode number, in >= 1, it is found that there exist some novelties compared with the usual superconducting planar Bragg reflector (SPBR). An additional high-reflectance band is seen and some reflection dips near the threshold wavelength of a superconductor are generated as well. These two special results arising from the higher order azimuthal mode of the cylindrical waves are not found in the SPBR. The results suggest that the SABR could be used to design a narrowband transmission Filter or an annular resonator without introducing any physical defect layer in the structure. (C) 2009 Elsevier Ltd. All rights reserved.
Photonic band gaps in a two-dimensional photonic crystal with open veins
(2006-10-01)
Liu, Wen-Long
;
Yang, Tzong-Jer
;
電子物理學系
;
Department of Electrophysics
We report two-dimensional (2D) photonic crystals of a square lattice with square dielectric rods growing slender veins on the middle side of each square dielectric rod in air. The complete photonic band gap (PBG) is found in higher index bands. Then extending the length of veins substantially shrinks this PBG, and for an appropriate vein length creates the new complete PBG at lower index bands. But the greatest complete PBG can be gotten where the veins are not fully closed at the lattice unit cell boundary. The photonic band gap is the result of considering the effects of Mie scattering due to the slender veins and interference of electromagnetic waves. Our results may provide a new direction for designing PBG of 2D photonic crystals. (c) 2006 Elsevier Ltd. All rights reserved.
Spontaneous emission of a three-level atom in a coherent photonic band gap reservoir
(2009)
Wu, Jing-Nuo
;
Yang, Tzong-Jer
;
Cheng, Szu-Cheng
;
Hsieh, Wen-Feng
;
光電工程學系
The optical spectra of a three-level atom embedded in a photonic crystal is studied by considering the coherent two-band photonic reservoir We find that the spectrum is shifting with respect to the atomic position.
Subwavelength optical imaging through a silver nanorod
(2007-03-01)
Chau, Yuan-Fong
;
Tsai, Din Ping
;
Hu, Guang-Wei
;
Shen, Lin-Fang
;
Yang, Tzong-Jer
We numerically investigated subwavelength imaging in a silver nanorod of 50-nm height and 20-nm diam buried in dielectric background (SiO2)with a finite-difference time-domain (FDTD) method in the three dimensions. The near-field components of the Gaussian incident beam were plasmonically transferred through the input end of a silver nanorod to reproduce the light distributions of the incident wave at the output end. The field distributions were calculated at the different sectional planes of the rods, and it was found that the spatial resolution was less than 40 nm given by the rod size, which is much beyond the diffraction limit of the conventional imaging system. The field intensity in the image plane was well resolved due to the collection of surface plasmon polaritons. The behaviors of the three components of field distribution at entrance and exit from the nanorod and the influences of the optical field distribution generated by some factors are also discussed in detail. The proposed structure possesses a deep transfer of superresolution image and can be used with image transfer. (C) 2007 Society of Photo-Optical Instrumentation Engineers.
Terahertz surface plasmon polaritons on periodically corrugated metal surfaces
(2008-03-03)
Shen, Linfang
;
Chen, Xudong
;
Yang, Tzong-Jer
;
電子物理學系
;
Department of Electrophysics
Based on a modal expansion of electromagnetic fields, a rigorous method for analyzing surface plasmon polaritons (SPPs) on a periodically corrugated metal surface has been formulated in this paper. This method takes into account the finite conductivity of the metal as well as higher-order modes within the grooves of the surface structure, thus is able to accurately calculate the loss of these spoof SPPs propagating along the structured surface. In the terahertz (THz) frequency range, the properties of the dispersion and loss of spoof SPPs on corrugated Al surfaces are analyzed. For spoof SPPs at THz frequencies, the strong confinement of the fields is often accompanied with considerable absorption loss, but the performance of both low-loss propagation and subwavelength field confinement for spoof SPPs can be achieved by the optimum design of surface structure. (C) 2007 Optical Society of America.
The plasmon and distribution effects between incident light and active layer in PtOx-type super-resolution near-field structure
(2008-03-01)
Chau, Yuan-Fong
;
Tsai, Din Ping
;
Shen, Lin-Fang
;
Yang, Tzong-Jer
;
Sun, Yuh-Sien
The plasmon and distribution effects of collective localized surface plasmons between incident light and active layer of PtOx-type super resolution near-field structure (super-RENS) have been studied using finite-difference time-domain method. Four types of distribution of Pt nanoparticles, i.e., type A, B, C, and D in active layer are investigated. We find that type C and D in active layer can provide higher field intensity in a wider range of particle size when the particle sizes are varied, and the out-going filed emerging from the active layer exhibit smaller spot size than those of type A and B. Type B, C and D also provide the additional path longer than that of type A, and excite more evanescent field which located in the far edge of the bubble from the optical axis of the incident beam. Results show that the type C structure is the best choice in the view point of designing the PtOx-type super-RENS. This study provides new information to design a super-RENS with superior resolution as well as other applications in nano photonic devices. (C) 2007 Elsevier B.V. All rights reserved.
Variation in the Absolute Photonic Band Gap of Rods Ranging from Square to Octagonal in Square Lattices
(2011-07-01)
Hu, Chung-An
;
Chang, Kuo-Pin
;
Yang, Su-Lin
;
Shen, Lin Fang
;
Wu, Jin-Jei
The band structures and field patterns of dielectric rods in square lattices are calculated using the plane-wave method. The rods with various cross-sectional shapes from square to octagonal at a fixed filling-factor are constructed to assess the geometry effect of photonic crystals to their band gap properties. Analytical results indicate that the corner profiles of rods significantly affect the E- and H-polarization bands in resonance frequency and field distribution. The absolute photonic band gap is closed in the square lattice when square dielectric rods are replaced with octagonal dielectric rods. (C) 2011 The Japan Society of Applied Physics
Wave properties of an annular periodic multilayer structure containing the single-negative materials
(2009-09-21)
Chen, Mei-Soong
;
Wu, Chien-Jang
;
Yang, Tzong-Jer
;
電子物理學系
;
Department of Electrophysics
The optical properties of an annular periodic multilayer structure containing two kinds of single-negative materials are theoretically investigated based on the transfer matrix method of the cylindrical waves. At the azimuthal mode number m >= 1 and near the magnetic plasma frequency and the electronic plasma frequency for the TE wave and TM wave, respectively. we find that there is an additional high-reflectance band and some reflection dips exist when the plasma frequency is located in the photonic band gap. These two special features arising from the higher order azimuthal mode of the cylindrical waves are not seen in the planar one-dimensional Bragg reflector consisting of the single-negative materials. Such filtering responses provide a feasible way of designing a narrowband resonator without physically introducing any defect layer in the structure. (C) 2009 Elsevier B.V. All rights reserved.