Angle dependent condensing efficiency of Winston cone in terahertz region

The condensing performance of Winston cone has been examined in the optical and terahertz (THz) regions by geometrical and wave optics simulations and the measurement of visible light. We have confirmed that the Winston cone possesses a sharp cutoff of incidence angle in condensing efficiency as expected; however we have found the condensing efficiency decreases at around normal incident, which is due to many times of reflection losses inside the condenser.

► We evaluate the condensing efficiency of Winston cone in the THz region.
► The optical experiment, 2D and 3D ray-tracing, and EM simulation are performed.
► The condensing efficiency of the cone decreases at the vicinity of normal incidence.
► The THz condensing efficiency at low temperature can achieve the ideal performance.