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Optical Waveguiding
Published in Joachim Piprek, Handbook of Optoelectronic Device Modeling and Simulation, 2017
If the angle of incidence for a ray shown in Figure 4.4 is smaller than the critical angle, the ray will undergo refraction at the boundary between the core and the cladding. In Figure 4.9, we show three possible scenarios for a slab waveguide with nf > ns > nc. The case shown in Figure 4.9a corresponds to a guided mode that was already discussed in Section 4.2.1. The cases shown in Figures 4.9b and c correspond to radiation modes, i.e., modes that are not guided by the waveguide core. In fact, once the incidence angle is less than the critical angle, the ray may undergo refraction only at the interface between the core and substrate, which corresponds to a substrate radiation mode. If the ray undergoes refraction also at the cladding-core interface, the mode is referred to as free space radiation mode. Assuming that ∂/∂y = 0 ∂/∂y, the solutions of the Maxwell equation for both modes can be obtained by solving Equations 4.24 and 4.22 for TE and TM modes, respectively (Marcuse, 1972, 1974; Ebeling, 1993). Figure 4.10 shows calculated distributions of the Ey electromagnetic field component obtained by directly solving Maxwell equations for a guided mode and substrate and free space radiation modes.
Isolator and Circulator
Published in Kenichi Iga, Yasuo Kokubun, Encyclopedic Handbook of Integrated Optics, 2018
The cutoff condition is dependent on the propagation direction due to nonreciprocal phase shift. That is, lightwave is confined in the waveguide core in the case of forward propagation, while it is leaky in the backward direction. This can be utilized to construct an isolator [50]. In the channel waveguide, this is applicable to the nonreciprocal mode conversion to a transverse radiation mode (Figure 13) [51].
Light Attenuation in Optical Components
Published in Abdul Al-Azzawi, Photonics, 2017
In another class of modes, called radiation mode, power from these modes radiates into the cladding and increases the attenuation. In radiation mode, the electromagnetic energy is distributed in the core and the cladding; however, the cladding carries no light.
A wideband dual-mode complementary dipole antenna
Published in Electromagnetics, 2018
Yong Cheng, Ya-Dan Li, Wen-Jun Lu, Lei Zhu
In this letter, a wideband dual-mode complementary dipole antenna is proposed, analyzed and further experimentally validated. By introducing a pair of stubs symmetrically along the center slotline resonator, the one and a half-wavelength radiation mode could be excited and reallocated in proximity to its fundamental counterpart. As the dual-mode slotline radiator is combined with a one half-wavelength dipole, a wideband complementary dipole antenna can be formed up. The measured impedance bandwidth of 40.2% with two resonances has verified the operational principle and design approach. Meanwhile, unidirectional radiation pattern and an average gain of about 7 dBi are achieved within the operating bandwidth. The developed antenna prototype has well exhibited a simple structure, unidirectional radiation pattern, and dual-resonant, wideband operation. Although the resultant antenna can hardly be used as an integrable antenna directly, its configuration can be optimized and its height can be further shrunk by introducing an artificial magnetic conductor surface (Bell, Iskander, and Lee 2007) or incorporating other advanced technologies (Liu, Chen, and Qing 2014). It is expected that the proposed antenna and its design approach are promising to get applications in the antenna developments of future wireless communication.