Experimental, numerical and analytical studies of the staggered double vane structure for THz application

In our prior work, PIC simulation analysis predicted that half-period-staggered (HPSed) double grating arrays, the so-called ldquoBarnett-Shin (BS) circuitrdquo, can produce a few hundred watts at 0.22 THz with greater than 12 dB/cm growth rate. Also, the saturated conversion efficiency is predicted to be 3 to 5.5% corresponding to an output power of 150 to 275 W, assuming a beam power of 5 kW. Subsequent study of this circuit structure has shown that experimental measurements are in good agreement (within 2%) with both a theoretical model and simulation analysis and that this periodic phase shift supports a dynamic bandwidth exceeding 25% with attenuation of less than 0.15 dB~cm (at Ka-band). FDTD analysis revealed that this low dispersion and low-loss optical response can be ascribed to point-contact hopping motion of widespread resonant waveguide modes with the same phase velocity. The external coupler of our design provides more than 90% (63 GHz) matching coverage of intrinsic bandwidth. This planar circuit has a simple, two-dimensional geometry which is thermally and mechanically robust as well as being compatible with various MEMS fabrication techniques. The LIGA-fabricated G-band (0.22 THz) circuit will be characterized by signal transmission and dispersion test and fabrication accuracy and surface roughness measurement.