Frequency-selective coupling in parallel dielectric waveguides

A formula for the efficiency of coupling of electromagnetic energy between dielectric waveguides which, in the absence of coupling, have unequal guided-mode propagation constants, is derived. This result is used in calculating the frequency dependence of coupling between non-identical slab waveguides.     

Analysis of coupling between two parallel dielectric waveguides

The coupling between two parallel dielectric waveguides with a finite coupling length is investigated. The ends of the waveguides are tapered in order to reduce the scattering losses. It is shown that the taper sections can be utilized to achieve an effective coupling which is insensitive to the coupling length, thus, providing a much greater tolerance for the design and manufacturing of coupling devices.     

Adiabatic coupling between conventional dielectric waveguides and waveguides with discrete translational symmetry

We study adiabatic transformation in optical waveguides with discrete translational symmetry. We calculate the reflection and transmission coefficient for a structure consisting of a slab waveguide that is adiabatically transformed into a photonic crystal waveguide and then back into a slab waveguide. The calculation yields high transmission over a wide frequency range of the photonic crystal waveguide band and indicates efficient coupling between the slab waveguide and the photonic crystal waveguide. Other applications of adiabatic mode transformation in photonic crystal waveguides and the coupled-resonator optical waveguides are also discussed.     

Geometrical theory of coupling errors in dielectric optical waveguides

The power losses due to coupling errors between source and fibre or two fibres are evaluated by means of a geometrical analysis of the coupling between an emitting and a detecting surfac. The theory is apllied to actual cases of separation, displacement and misalignment between a uniformly emitting lambertian source and fibre, and between two fibres. Good agreement is obtained with experimental results found in the literature.     

Analysis of the coupling of two non-parallel dielectric rod waveguides

In this paper the coupling between two closely spaced single mode dielectric rod waveguides is investigated when the corresponding propagation axes are not in the same plane. An approximate analysis is presented by assuming only first order interaction between the guided waves. For a given incident HE₁₁ mode (in one of the rod waveguides) the coupled wave amplitudes are computed in the other waveguide for both propagation directions. Numerical results are presented for several coupling geometries.     

Theory of A ϕ-periodic one-dimensional bundle of dielectric waveguides

Mogil' Division, Institute of Physics, Belorussian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 35, No. 2, pp. 200–204, February, 1992.     

Analysis of optical coupling between air-holes photonic crystal and tapered dielectric waveguides

Two types of structures for the optical coupling between photonic crystal waveguide (PCW) with triangular air-holes lattice and tapered dielectric waveguide (TDW) are investigated. The TDWs are coupled with PCW at the input and output connections of the PCW, which can constitute a unidirectional waveguide structure. The transmission efficiencies of the input and output coupling are analyzed theoretically for different coupling structures. It is found that the coupling efficiencies vary with the width and length of coupling region. When the light transmitted from TDW to PCW, the highest transmission efficiency is 92.6%, and it is 99.6% when the light transmitted from PCW to TDW. Then the total transmission efficiency of the entire waveguide is simulated and it can reach 92.3% for one type of structure and is a little lower for the other type of structure under the chosen optimal structure parameters. Considering the current processing accuracy, the structure mentioned above should be an effective coupling manner that can be easily realized.     

基于时域有限差分法分析等离子波导和介质波导耦合

使用Rsoft软件中的时域有限差分模块Fullwave分析二维介质波导和等离子波导耦合特性,利用软件仿真耦合结构并自动计算出光在介质波导和等离子波导中传输的耦合效率,进而测绘耦合效率随波导尺寸和光波长的变化曲线图,发现MDM导波结构的缝隙宽度和光通信质量密切相关,在确定尺寸下,传输损耗随传输距离成指数衰减.根据分析得到的耦合效率变化规律发现介质波导和等离子波导间距最佳点都应设为15 nm,进而优化波导的几何结构参数后,可以将耦合效率提高到83%.     

T-shaped dielectric slot waveguides for efficient control of birefringence and polarization independent directional coupling

A novel dielectric slot waveguide supporting strongly confined field in a T-shaped low-index slot region for both TE and TM polarizations is proposed and analyzed. Numerical simulations have demonstrated that quite different birefringent modal properties are achievable with tight optical confinement in the slot by tuning key geometrical parameters of the waveguide. Based on such a slot structure, the characteristics of directional couplers are investigated and the conditions for polarization independent coupling are also given. The presented T-shaped slot waveguide might be employed in integrated photonic systems as important building blocks enabling a number of potential applications.     

Ferrite resonance isolators in coaxial line and rectangular and planar waveguides with dielectric

A plane-parallel analog of a coaxial line, and a rectangular and planar waveguide with ferrite and dielectric slabs situated in the E-plane is considered. Transcendental equations for determining the propagation constants of an electromagnetic wave in these systems are obtained. Approximate solutions of these equations are given for small thicknesses of the ferrite plate.Analytical expressions for the isolation ratio in these systems are obtained. It is shown analytically that in all cases the maximum isolation ratio is obtained at the resonance magnetic field. For each system, analytical expressions are derived for the optimum value of ferrite magnetization for which the maximum possible isolation ratio should be observed. The value of the optimum magnetization depends on the frequency, the dielectric constant of the dielectric used and the geometry of the system. The values of maximum possible isolation ratio are the same for all three devices.     

Eigenmodes expansions in lossy open waveguides (fibres)

The properties of the radiation eigenmodes propagating in lossy open waveguides (fibres) are examined by the-operator method. The radiation eigenmode fields are demonstrated to be transversely unbounded at infinity. For these modes the orthogonal relationships are derived by regularization of divergent integrals.     

Mode conversion in dielectric waveguides

We have studied the effect of weakz-dependence of the dielectric constant on the propagation of modes in SELFOC fibres. We have also used the Green's function technique to study mode conversion due to weak irregularities in a waveguide.     

Midinfrared dielectric coated metallic waveguides

The transmission characteristics of planar dielectric coated metallic waveguides are investigated. In addition, the coupling of a gaussian beam into the normal modes of these devices and the far field radiated from an open end are discussed in detail.     

Analysis of third and one-third harmonic generation in lossy waveguides

A comprehensive study on the requirements for the highly efficient third harmonic generation(THG) and its inverse process, one-third harmonic generation(OTHG), in lossy waveguides is proposed. The field intensity restrictions for both THG and OTHG caused by loss are demonstrated. The effective relative phase ranges, supporting the positive growth of signal fields of THG and OTHG are shrunken by the loss. Furthermore, it turns out that the effective relative phase ranges depend on the intensities of the interacting fields. At last, a modified definition of coherent length in loss situation, which evaluates the phase matching degree more precisely, is proposed by incorporating the shrunken relative phase range and the nonlinear phase mismatch. These theoretical analysis are valuable for guiding the experimental designs for highly efficient THG and OTHG.     

Collocation calculations on dielectric waveguides

Physics Problems Institute, Academy of Sciences of the USSR. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 31, No. 1, pp. 93–102, January, 1988.     

Ferrite resonance isolators in coaxial,strip, and rectangular waveguides with a dielectric

An analysis is given of ferrite resonance isolators in coaxial and strip lines and in a rectangular waveguide containing a dielectric. The analysis is based on numerical calculations (using a computer) using the results obtained in [1]. The results enable us to estimate the influence of the thickness of the dielectric, its permittivity, the ferromagnetic resonance line width and other parameters, upon the bandwidth of the system and upon the optimum magnetization ensuring the maximum isolation for the chosen system parameters and center frequency of the band. In this paper the terminology used is the same as in [1].     

Coupled-mode analysis of periodic dielectric waveguides

The coupled-mode formalism is used to describe the behavior of a corrugated dielectric waveguide. Explicit expressions for the dispersion near the Bragg regime are given. These are compared with the results of an “exact” analysis.     

Low-loss surface modes and lossy hybrid modes in metamaterial waveguides

We show that waveguides with a dielectric core and a lossy metamaterial cladding (metamaterial-dielectric guides) can support hybrid ordinary-surface modes previously only known for metal-dielectric waveguides. These hybrid modes are potentially useful for frequency filtering applications as sharp changes in field attenuation occur at tailorable frequencies. Our results also show that the surface modes of a metamaterial-dielectric waveguide with comparable electric and magnetic losses can be less lossy than the surface modes of an analogous metal-dielectric waveguide with electric losses alone. Through a characterization of both slab and cylindrical metamaterial-dielectric guides, we find that the surface modes of the cylindrical guides show promise as candidates for all-optical control of low-intensity pulses.     

损耗电介质在镜像法测试装置中的应用

通过在校准头的耦合波导中填充介电常数为10,损耗角正切为0.6的损耗电介质材料,利用该介质对电磁波的损耗来近似测试头中的输入输出耦合环对电磁场能量的影响,以满足镜像法中测试头和校准头中电磁场分布一致这一要求。这一损耗介质材料的引入,改进了测试头和校准头的设计,使得测试头在取得较大耦合量的同时能保持与校准头的对称性,减小了以往测试装置低耦合量所引起的测试误差。     

FDTD analysis of point-defected periodical dielectric waveguides

In this paper, we utilize the finite-difference time-domain method to analyze the transmission characteristics of the point-defected periodical dielectric waveguides (point-defected PDWGs). Each point-defected PDWG contains a defected cylinder distinct from the others. It is found that the optical transmittance becomes worse due to the shorter defected cylinder but it is not affected by the longer one. Moreover, the optical transmission is very sensitive to the radius of the defected cylinder whatever it is larger or smaller than that of the other cylinders.