The Development of High-Power and Wide-Bandwidth Photonic Transmitter for Millimeter-Wave over Fiber Wireless Communications Based on Orbital Angular Momentum Modes(3/3)

Microwave or millimeter-wave (MMW) orbital angular momentum (OAM) multiplexing technique, which has been treated as one of the most effective ways to increase the bandwidth capacity in next generation wireless transmission system, have attracted lots of attentions. As compared to the traditional wireless communication systems, OAM technique can generate multiple orthogonal spatial modes by use of special antenna design. By use of these modes in free space, OAM can thus offer one extra dimension (space other than frequency and time) for multiplexing to increase the total bandwidth capacity in wireless transmission. Nevertheless, just like any kinds of MMW wireless transmission systems, the quality of communication in OAM MMW systems also limits by the large propagation loss of MMW signal through free space. By combing the radio-over-fiber (RoF) technique with the high-speed and high-power photodiode to broadcast such special OAM MMW signal through low-loss optical fiber is one important trend in the development of OAM. In this project, we will develop a novel high-speed and high-power photodiode (PD). By combing such novel PD with a new kind of OAM antenna, we will realize the key front end of photonic MMW transmission system: OAM photonic transmitter module. Through the use of such module, we will generate OAM modes at W (75-110 GHz) and Y (170-260 GHz) bands and demonstrate the 100 Gbit/sec point-to-point wireless transmission based on OAM modes multiplexing. Regarding with the responsivity and high-power performance of ultrafast photodiode, it can be improved by type-II hybrid absorber and multiple etched mesa structures for increasing the heat-sink area, respectively. With respect to the OAM antenna excitation, it can be further optimized by re-design the impedance matching circuit between photodiode chips and waveguide to minimize the coupling loss between them. The success of such project will have revolutionary influence on the development of next generation 6G wireless communication system at Taiwan.