This paper introduces a new type of microwave isolator. The operation is based on the two phenomena; the ferrite edge-mode and the photo-generated plasma on silicon substrate. Conventional ferrite edge-mode isolator has been made of the ferrite and the resistive material. The later is used to absorb the reverse-propagating wave of the isolator. An inadequate choice of the resistive body leads to the imperfect absorption; the isolation ratio decreases. In this paper, the isolation-variable isolator is introduced by using this change of isolation. The control is realized by the change of the surface resistance on the silicon. On this isolator, the frequency response is investigated both experimentally and numerically. The numerical analysis is conducted by FDTD method. The experiment is carried out on the prototype isolator. Both experimental and numerical results have shown that the isolation ratio can be controlled for 39 dB at 12 GHz by the irradiation.

In this paper, an optical signal processing beam forming network (BFN) for two-dimensional (2-D) beam steering is proposed and experimentally demonstrated. Two lightwaves, called the signal and reference, are both Fourier transformed, combined, and then down-converted into RF signals using an optical heterodyne technique. A simple combination of orthogonal one-dimensional position scannings of the signal and reference lightwaves generates RF signals with phase distributions for 2-D beam steering. The system operation and optical losses are theoretically analyzed. Using graded index fiber (GIF) lensed single mode fibers (SMFs), total optical loss of the sampling fiber array is evaluated to be 4.5 dB from the fiber to fiber loss measurements. Using an experimental optical signal processing BFN at 25 GHz, 2-D beam steering is demonstrated at 0, 10, 20, and 30through the measured amplitudes and phases of RF signals for 16 position sets of the signal and reference fibers. The proposed method has the potential to provide ultra-fast beam scanning by utilizing optical switching technologies.

This paper presents scattering characteristics of a TE electromagnetic plane wave by a photo-induced plasma strip grating in a semiconductor slab at millimeter wave frequencies. The characteristics are analyzed by using the moment method and estimated numerically over a frequency band from 30-50 GHz. It is shown that the resonance anomaly in the grating can be controlled by changing not only the periodic light illumination pattern but also the plasma density.

This paper presents the scattering characteristics of a TE electromagnetic plane wave by metallic strip gratings on an optically plasma-induced silicon slab at millimeter wave frequencies. The characteristics were analyzed by using the spectral domain Galerkin method and estimated numerically. We examined to control the resonance anomaly by changing the optically induced plasma density, and the metallic strip grating structures were fabricated on highly resistive silicon. The optical control characteristics of the reflection, and the forward scattering pattern by the grating structures, were measured at Q band and are discussed briefly with theory.

This letter proposes a microstrip band elimination filter having an optically controlled small gap on a resonant section for the shift of the eliminated frequency range using the semiconductor plasma. The basic characteristics of this filter are analized theoretically utilizing the (FD)2TD method.

For the effective control of microwaves in the frequency domain, we propose a new method utilizing current distributions of standing waves on the terminated microstrip line. We analized a short ended microstrip line using the (FD)2TD method to indicate the effectiveness of our proposal. Further we proposed an optically controlled microstrip filter as an application of this method.

In this letter, the effectiveness of the quasi-TEM approximation is studied for the microstrip line including optically induced semiconductor plasma region. This approximation is considered to be efficient under several restrictions such as the upper limit of the microwave frequency and the plasma density.

This letter discusses a microstrip line with an open-end termination in which the reflected microwaves can be optically controlled by a laser illumination. The frequency characteristics are emphasized rather than the time domain ones. The reflection characteristics have been demonstrated experimentally and theoretically for the frequency range of 24 GHz. In the theoretical treatment both the conductance and the capacitance are considered in the equivalent circuit model of the open end of the strip.

The various propagation characteristics of millimeter waves in silicon rib and image guides containing the optically induced plasma region have been investigated. Phase shift and attenuation properties resulting from the presence of plasma are evaluated using the effective dielectric constant method. Experiments have been carried out to demonstrate the optical control of millimeter waves at frequencies ranging from 3350 GHz using high-resistivity silicon illuminated by a high-power Xenon arc lamp and light emitting diodes. Optical control of millimeter wave attenuation of 20dB has been confirmed for a guide of length 90 mm and plasma density of 1021/m3 with average plasma thickness of 20 µm. To increase the sensitivity of optical control, Bragg reflection filter characteristics are studied and its stop band characteristics have been calculated using the transmission line model, and confirmed experimentally. To further develop the Bragg reflection filter, a Mach-Zehnder interferometer guide with one of the arms periodically corrugated is newly proposed and its optical control performance is confirmed by experiments. Finally the field distributions of the Mach-Zehnder configuration of rib waveguides are measured by a simple optical probing technique using the focused laser spot.