Fig. 4: Performance characterization.
From: Experimental observation of topological Dirac vortex mode in terahertz photonic crystal fibers
a The group delay of the DVM is determined by measuring the time delay between pulses propagating through an equal distance (1 cm) in air and the PCF. b DVM dispersion extracted from the data in Fig. 3c, exhibiting a perfectly linear dispersion and a group velocity of 0.5848c as compared with the light line in free space. c Effective area for the mode confinement and numerical aperture. d Total loss, material loss, and confinement loss
