Optically tunable millimeter-wave attenuator based on layered structures

A new type of optically controllable, millimeter‐wave (MMW) attenuator based on high‐resistivity (high‐R) silicon (Si) wafers and a layered structure is developed. A high‐R float‐zone Si wafer is a lossless dielectric material at microwave frequency without optical excitation. When an Si wafer is optically excited, free carriers are generated, and the Si wafer becomes a lossy dielectric. This property is combined with a layered structure to develop a simple optically tunable MMW attenuator. A more than 20 dB attenuation with a 10% bandwidth of the center frequency is obtained at W‐band. The proposed structure is useful for developing low‐cost attenuators and switches in the MMW region. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 27: 9–13, 2000.