Evanescent resonant mode for a T-shaped cavity in a terahertz parallel-plate waveguide.

The evanescent resonant modes are proposed for a T-shaped cavity in a terahertz (THz) parallel-plate waveguide (PPWG) to understand the essence of the resonant phenomenon. The theoretical modal field and the resonant frequency of the TE-like evanescent resonant mode show agreement with the simulated ones through the whole THz region. The modal field consists of three evanescent fields outside the cross region and one propagation field inside the cross region.

Laboratory demonstration of a broadband six-level phase mask coronagraph.

The six-level phase mask (SLPM) can be used in a focal plane as an efficient coronagraph [Opt. Express 22, 1884 (2014)]. It has several advantages: high-contrast imaging in broadband with small inner working angle; easy fabrication at low cost by photolithography and reactive ion etching processes; easy implementation with no need of pupil apodization.