Fig. 5: Theoretical model with the evanescent wave coupling.
a Theoretical model with a y-polarized dipole in each nanobeam as an approximation of the y-polarized nanobeam cavity in Fig. 1a. Due to the total internal reflection of GaAs, evanescent field dominates near the nanobeam (within 500 nm), whilst the emission field dominates far away from the nanobeam. This essential feature is the same as that of the real nanobeam cavity in Fig. 1a. b Calculated polarization degree and angle as functions of gap dqual and shift squal. White dashed lines denote the threshold dqual of 500 nm for the evanescent wave coupling. c Theoretical model with dipoles in a homogeneous medium. No evanescent field exists in this case. d Calculated polarization degree and angle for the case of homogeneous medium
