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.

In this paper, we report the recent progress in visible light positioning and communication systems using light-emitting diodes (LEDs). Due to the wide deployment of LEDs for indoor illumination, visible light positioning (VLP) and visible light communication (VLC) using existing LEDs fixtures have attracted great attention in recent years. Here, we review our recent works on visible light positioning and communication, including image sensor-based VLP, photodetector-based VLP, integrated VLC and VLP (VLCP) systems, and heterogeneous radio frequency (RF) and VLC (RF/VLC) systems.