Analysis of bistability at the coupling between waveguide and whispering gallery modes of a nonlinear hemicylinder

The optical bistability caused by the coupling between modes of the parallel-plate waveguide and a nonlinear hemicylindrical crystal is studied using theoretical and numerical analysis. In such a system a waveguide channel is parallelly coupled to whispering gallery modes of a hemicylindrical microresonator ensuring bistable behaviour at input intensities of the order of a few MW/cm2. The characteristic minimum switching time of the system (around 30 ps) can be controlled by varying the thickness of the metal layer which couples the waveguide and whispering gallery modes. This is conditioned by the change of the quality Q-factor, as well as the coupling coefficient of the resonator. The main advantages of the system are fabrication simplicity, small sizes of the order of 3 µm and the possibility of adjusting the processes by making use of the electro-optical effect.

The Water Drop Lens: Revisiting the Past to Shape the Future

This vision paper provides a brief overview on recent developments related to a new solution of quasi-optical beamformer, referred to as the water drop lens. This parallel plate waveguide beamformer, which is a revisited geodesic lens with a shaped profile, is attracting attention for applications in the millimetre-wave range, where more conventional dielectric lenses prove to be too lossy and standard geodesic lenses are still too bulky. On-going investigations include satellite and terrestrial communication systems, radar systems and imaging systems with wideband operation at centre frequencies ranging from about 20 GHz to over 120 GHz.

Temporal transition in parallel-plate waveguides: analysis of scattering and propagation at the temporal interface

In this contribution, we present the analysis and numerical verification of the scattering phenomenon from a temporal interface in a parallel-plate waveguide realized by suddenly modifying the dimensions of the waveguide while the wave is propagating. As it is well known in guided wave theory, at the interface between two different waveguides there exists a change of the effective refractive index and wave impedance perceived by the propagating wave within the device, which inevitably scatters at the interface into a reflected and refracted wave. In analogous way, by suddenly changing the effective material properties within the whole waveguide, it is possible to realize the so-called temporal interface, as well. Here, we theoretically and numerically investigate on the scattering from a waveguide temporal interface induced by the abrupt change of the waveguide dimension, which in turn realize a change of the effective material properties perceived by the wave.

A Low-Profile and Beam-tilted Continuous Transverse Stub Array Antenna at W-band

This paper presents a low-profile, high gain, beam-tilted continuous transverse stub (CTS) array antenna at W-band. The antenna compromises 32 radiating slots and is fed by a parallel plate waveguide (PPW) network with a linear source generator. To deflect the outgoing beam, the principle of linear array scanning is adopted to design inverted T-type structure in each stub to introduce wave path difference. PPW network allows the antenna to obtain lower profile compared to other transmission lines. The design procedure, and the antenna characterization are described. The main beam of the antenna is titled 12 degree in H-plane. The simulation and measured results show that this antenna achieves peak gain of 32.4 dB and a 12 degree beam tilt angle at 99GHz. S11 parameters of the antenna is less than -10 dB in a broadband from 96 GHz to 103 GHz. This antenna has an advantage of miniaturization over other high-gain antenna solutions. The promising performance of this proposed CTS antenna reveals the possible candidate for Millimeter wave (MMW) telecommunication applications.