Design and Analysis of High Power, Broadband Terahertz Vacuum Photomixer Device

Compact, cost-effective, high-power and broadband radiation sources are required for terahertz (THz) spectroscopy and communication applications. In this paper, we present a new terahertz photomixer using a planar antenna integrated vacuum photodiode. The photocathode of the photodiode can be excited to emit high-density THz electron beams corresponding to the illuminating laser beat frequency. The electron beams can be accelerated and transported through a micron scale vacuum channel to feed an integrated broadband antenna generating continuous THz radiation into free space. The vacuum channel enables high current density operation and carrier mobility, which makes the photomixer capable of radiating high output power of milliwatt level within 0.1-2.0 THz. The latest development in the schematic design of the vacuum photomixer, design and analysis of the vacuum transistor and the broadband antenna is reviewed and discussed. Further research works will be focused on the analytical framework of the photomixer that involves photocathode modeling, charged sheets transportation in the micron scale vacuum channel, and impedance match.