On the analysis of single- and multiple-step discontinuities for ashielded three-layer coplanar waveguide

The mode matching procedure is employed to obtain the scattering (S) parameters of the discontinuities. The analysis is validated through a comparison of the calculated S-parameters of a single step discontinuity for a shielded single-layer CPW and those published previously. Calculated S-parameters for various single, double, and triple step discontinuities are presented. Effect of the modal orthogonality criterion on the discontinuity S-parameters is given. Extensive investigation of the numerical convergence of the S-parameters is also described     

FDTD analysis of CPW-fed folded-slot and multiple-slot antennas onthin substrates

Folded slot antennas are attractive for active arrays due to relatively large bandwidth, fabrication simplicity, and ease of integration with devices. Currently, there is little design information for these antennas, especially on thin substrates. The finite-difference time-domain (FDTD) method is applied to the analysis of CPW-fed folded-slot antennas. The paper describes the problems encountered in the analysis, compares the theoretical results and measured data, and provides some design information for folded slots. In addition, it explores the manipulation of input impedance through the use of additional slots, yielding antennas with a broadband 50 Ω input impedance     

表面等离子波导改进LED发光效率的研究

设计了在氮化镓材料上淀积周期光栅银薄膜的结构,利用SPPs增强作用提高LED的发光效率。理论上建立了增强LED的内部发光效率、SPPs辐射匹配以及SPPs辐射衰减模型。实验结果表明:淀积银薄膜的LED结构由于SPPs的增强可以显著提高出光效率;出射光的偏振模式对LED出光效率没有影响;金属光栅的吸收率在占空比达到0.87左右达到峰值;SPPs的增强作用可以显著改善弱光致发光的发光效率和非线性过程。这一研究对于LED发光效率的改进具有明显的理论和实际意义。     

A simple analysis of single- and double-V-groove guides

Single- and double-V-groove guides are analyzed by an approach based on a combination of the transverse resonance method and the numerical integration technique. Comparisons between the predicted results and available measured results for a single V-groove guide show good agreement. The new approach is simple and accurate. Numerical results for the coupling characteristics of a double-V-groove guide are also presented     

Determination of diffraction efficiency for a second-ordercorrugated waveguide

The diffraction from a second-order corrugated waveguide is analyzed to determine its efficiency as an element to redirect a guided wave. Using a rectangular grating, the efficiency is evaluated in an approximate closed form. The dependence upon grating thickness, waveguide thickness, and wavelength are investigated and the results indicate usefulness as a simulation tool for photonic integrated circuits     

Study of waveguide coupling efficiency in hybrid silicon lasers

This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel＇s.     

低阈值电流、高量子效率脊形波导激光器

研制了低阈值电流、高量子效率670nm压缩应变单量子阱GaInP/AIGalnP脊形波导激光器。测量解理成的激光器条,腔长为300μm时,阈值电流为12．8mA,双面外部量子效率之和达到94．6％。     

Study of waveguide coupling efficiency in hybrid silicon lasers

This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers.We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide.The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm.Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm.Therefore,our invariable coupling power technique is simpler than Intel's.     

Optimal design and characteristics analysis of a polymer electro-optic switch with seven vertical-turning serial-cou- pled microrings

A novel 1 x2 polymer electro-optic （EO） switch based on seven vertical-mining serial-coupled microrings is proposed for dropping crosstalk and obtaining fiat boxlike spectrum. The device structure, theory and formulation are presented, and the microring resonance order and coupling gaps are optimized. The switching voltage of the device for obtaining crosstalk lower than -30 dB under through state is decided to be about 1.86 V. Under the operation voltages of 0 V （drop state） and 1.86 V （through state）, the switching performance is characterized, and the output spectrum is ana- lyzed. The calculation results show that the crosstalk at through state and that at drop state are -30.2 dB and -53.2 dB, respectively, while the insertion losses are 0.86 dB and 3.18 dB, respectively. Owning to the seven serial-coupled mi- crorings resonance structure, the proposed switch reveals the favorable boxlike spectrum compared with the simple device with only one microring, and thus the crosstalk under drop state is improved from -26.8 dB to -53.2 dB. Due to the low crosstalk, this device can be used in optical networks-on-chip for signal switching and routing.     

Effect of multiple-modes on the switching efficiency of waveguide couplers

The switching efficiency of rectangular waveguide couplers is investigated for a case where multiple-modes exist in the waveguides perpendicular to the direction of coupling but only a single-mode exists in the direction of coupling. It is found that, given a reasonable distribution of input energy over the possible modes, the existence of multiple-modes perpendicular to the direction of coupling has only negligible effects on the performance of the couplers. These results, while applicable to planar waveguide couplers, are of particular interest for vertically arranged couplers.<>     

Coupling efficiency in grating tuned carbon dioxide waveguide lasers

The coupling efficiency in typical CO₂ waveguide lasers when the feedback element is a diffraction grating is investigated theoretically. A scalar diffraction integral approach is adopted, and the laser is assumed to operate on its lowest loss waveguide mode.     

High efficiency grating coupling of THz pulse radiation intodielectric waveguide

First results of efficient frequency selective coupling of THz signals into a dielectric waveguide are presented. The coupling is performed through a grating engraved at the top of a highly resistive silicon waveguide. Coupling efficiencies higher than 90% are observed in the sub-millimetre range     

Exact polarised rib waveguide analysis

An exact Fourier operator transform method (F-OPT) is presented for finding the polarised mode propagation constants of a rib waveguide with any number of supporting layers and an arbitrary cladding. The implementation is of the order of one hundred times faster than the finite difference method for the same accuracy of the normalised propagation constant     

Computer-aided analysis and design of circular waveguide tapers

Two computer programs have been developed for the rigorous performance analysis of circular waveguide tapers. They are based on the direct integration of the coupled wave equations and on a mode-matching procedure applied to a step-ladder equivalent of the taper, respectively. Close agreement has been obtained between the predictions of these two approaches. The computer programs are utilized to examine the usefulness of existing taper design procedures. It has been found that a Dolph-Chebychev design is actually capable of predicting the level of the first unwanted mode, provided that the operational frequency is far above its cutoff. The spurious mode excitation can still be improved by taking into account the reconversion of power from the unwanted into the wanted modes. It has been verified by the computer analysis that the above design procedures are applicable even for frequencies near cutoff of the dominant spurious mode; however, that is at the expense of a certain degradation of the input reflection of the incident mode. A further improvement of the performance is possible only by direct computer optimization of the taper     

Mode-matching analysis of circular-ridged waveguide discontinuities

This paper describes a mode-matching algorithm for S-parameter computation of circular-ridged waveguide (CRW) discontinuities. The ridges are shaped like the cross section of a cone (pie-shaped) with a geometry that can he described in cylindrical coordinates. This idea avoids the use of a mixed-coordinate system in the analysis of the electromagnetic fields in the ridged sections, which can, therefore, be expressed in terms of modal functions. The resulting algorithm is fast and accurate and has been utilized to design and optimize a five-section double-ridge filter and a quadruple-ridge waveguide transformer. The measured response of the filter is in good agreement with the calculated data     

Modal analysis of open groove waveguide

A self-contained analysis for lower-order modes in the open groove waveguide is presented. By adopting an approximate form for the fields in the outer region of the guide and then performing the remainder of the analysis rigorously, closed-form results for the fields and modal equation are obtained. The analysis shows a simple transverse network representation that can be compared with that obtained by A.A. Oliner and P. Lampariello (ibid., vol.33, no.9, p.755-64, 1985). Universal dispersion curves, obtained numerically for the dominant mode, are presented     

Full-wave analysis of cross-aperture waveguide couplers

This paper presents a full-wave analysis of coupling between rectangular waveguides through a cross-aperture. The rigorous mode-matching method is used to derive the generalized scattering matrix of a waveguide T-junction having a crossed waveguide as the side arm. Two three-port T-junctions are then cascaded together to form a number of cross-aperture couplers. The analysis method can handle both broad-wall and narrow-wall, both parallel and crossed coupling structures. Our numerical results for a variety of couplers are in good agreement with those obtained by Ansoft's HFSS     

Finite-element analysis of leaky waveguide antennas

A finite-element method is described for the analysis of leaky modes of open uniform waveguides with arbitrary cross-section. The field is represented by a hybrid element in the infinite exterior region, and by conventional triangular elements inside and near the waveguide. Results are presented for channel waveguide, slotted square guide and slotted circular waveguide.     

Spectral and power efficiency investigation in single- and multi-line-rate optical wavelength division multiplexed (WDM) networks

In order to tackle the increasing heterogeneous global Internet traffic, mixed-line-rate (MLR) optical wavelength division multiplexed (WDM) networks have emerged as the cost- and power-efficient solution. In MLR WDM networks, channels are structured as sub-bands, each of which consists of wavelengths operating at a similar data rate. By reducing the (1) spacing within a sub-band, or (2) spacing between sub-bands operating at different data rates, spectral efficiency can be improved. However, owing to high physical layer impairment levels, decrease in sub-band spacing adversely affects transmission reach of the channels, which results in higher power consumption due to requirement of increased signal regeneration. In this work, we compare power efficiency of various MLR and single-line-rate (SLR) solutions, and also investigate the trade-off that exists between spectral and power efficiency in a WDM network. Simulation results indicate that (1) for high transmission capacities, a combination of 100 Gbps transponders and 40 Gbps regenerators will obtain the highest power efficiency; (2) for long connection distances, a point of merging occurs for various SLR and MLR designs, where power consumption is independent of the frequency band distribution; and (3) for MLR systems, both spectral and power efficiency can be improved by using either shorter links with higher bandwidth assignment to 100 Gbps wavelengths, or longer links with higher bandwidth assignment to 40 Gbps wavelengths. Finally, the results indicate that focusing on spectral efficiency alone results in extra power consumption, since high quality of transmission and spectral efficiency leads to increased regeneration.