Waveguide

About: Waveguide is a research topic. Over the lifetime, 28522 publications have been published within this topic receiving 375461 citations.

First‐order quasi‐phase matched LiNbO3 waveguide periodically poled by applying an external field for efficient blue second‐harmonic generation

Abstract: A novel method of fabricating a periodic domain structure with ideal laminar domains in LiNbO3 by applying an external field at room temperature is proposed. The method allows a high blue beam power of 20.7 mW and a high conversion efficiency of 600%/W cm2 to be obtained.

Plasmon-polariton waves guided by thin lossy metal films of finite width: Bound modes of asymmetric structures

Abstract: The purely bound electromagnetic modes of propagation supported by asymmetric waveguide structures, comprised of a thin lossy metal film of finite width on a dielectric substrate and covered by a different dielectric superstrate, have been characterized at optical wavelengths. The dispersion of the modes with film thickness and width has been assessed and the effects caused by varying the difference between the superstrate and substrate dielectric constants on the characteristics of the modes have been determined. The modes are quite different from those supported by corresponding slab structures or similar finite-width symmetric waveguides. Unlike these limiting cases, the dispersion with film thickness can exhibit an unusual oscillatory character which is explained by a switching or swapping of the constituent interface modes. In addition, the four fundamental modes supported can evolve such that none has a diminishing attenuation with diminishing film thickness. This rather complex evolution of modes is unique to asymmetric finite-width structures. Under certain conditions, a long-ranging mode having a field distribution that is suitable to excitation using an end-fire technique can be supported. The long-ranging mode has a cutoff thickness below which it is no longer propagated, and its attenuation near cutoff decreases very rapidly, much more so than the attenuation related to the long-ranging mode in a comparable symmetric waveguide. Furthermore, its cutoff thickness is larger than that of the ${s}_{b}$ mode in the corresponding asymmetric slab waveguide, which implies that decreasing the film width increases the sensitivity of the mode to the asymmetry in the structure. This result is interesting and potentially useful in that the propagation characteristics of the mode can be affected by a smaller change in the dielectric constant of the substrate or superstrate compared with the ${s}_{b}$ mode guided by the corresponding slab structure.

Accurate modeling, wave mechanisms, and design considerations of a substrate integrated waveguide

Abstract: A new method of analysis is presented in this paper for the determination of complex propagation constants in substrate integrated waveguides (SIWs) This method makes use of the concept of surface impedance to model the rows of conducting cylinders, and the proposed model is then solved by combining a method of moments and a transverse resonance procedure The proposed method is further applied to extract results in terms of parametric curves and graphs which demonstrate fundamental and interesting wave guidance and leakage properties of this type of periodic waveguide Useful design rules are extracted from this analysis, suggesting that appropriate design parameters and regions should be carefully selected for practical applications In addition, comprehensive review and comparisons with published results are also presented to show the performance and accuracy of the proposed modeling technique Practical measurements of fabricated samples with different levels of loss have confirmed the accuracy of this new method and validity of design rules

Local Metamaterial-Based Waveguides in Gaps Between Parallel Metal Plates

Abstract: This letter presents a new metamaterial-based waveguide technology referred to as ridge gap waveguides. The main advantages of the ridge gap waveguides compared to hollow waveguides are that they are planar and much cheaper to manufacture, in particular at high frequencies such as for millimeter and sub- millimeter waves. The latter is due to the fact that there are no mechanical joints across which electric currents must float. The gap waveguides have lower losses than microstrip lines, and they are completely shielded by metal so no additional packaging is needed, in contrast to the severe packaging problems associated with microstrip circuits. The gap waveguides are realized in a narrow gap between two parallel metal plates by using a texture or multilayer structure on one of the surfaces. The waves follow metal ridges in the textured surface. All wave propagation in other directions is prohibited (in cutoff) by realizing a high surface impedance (ideally a perfect magnetic conductor) in the textured surface at both sides of all ridges. Thereby, cavity resonances do not appear either within the band of operation. The present letter introduces the gap waveguide and presents some initial simulated results.

High dielectric constant microwave probes for sensing soil moisture

Abstract: Implantable soil moisture sensors suitable for long-term monitoring of moisture in highway subgrades and for similar applications are needed. Two candidate designs of microwave sensors (operating range 4 to 6 GHz) have been investigated for such applications. One design uses the fringing field of a low-loss dielectric slab waveguide (relative dielectric constant of 25) to obtain good resolution for finely divided soil such as bentonite clay with moisture ranging from 10 to 50 percent by dry weight for effective sample volumes of 20 to 40 cm2. The response of the dielectric waveguide sensor has been calculated in terms of the effective dielectric constant of the soil-water mixture. A model based on index of refraction yields an effective dielectric constant in reasonable agreement with experiment when effects of ionic conduction are accounted for. Another sensor design, better adapted for coarse materials, such as crushed limestone aggregate, uses waves launched from a tapered dielectric slab. By using either frequency or spatial averaging methods, the launched wave sensor accommodated aggregate particles passed by a 0.63-cm mesh sieve, and was found to have satisfactory resolution for the range of 0- to 10-percent moisture by dry weight.