Extended Data Fig. 4: Mode field maps near the FW quasi-BIC.
From: Directive giant upconversion by supercritical bound states in the continuum
Main components Ey, Ez of the vector fields of mode 1 (dark, ω−) and mode 2 (bright, ω+) in the xy plane at z = 0, together with the intensity map I1, I2 in the yz cross-section for both modes 1 and 2 at the indicated incidence angle θ, as shown in Extended Data Fig. 3c. The colour map of their components (amplitude in modulus, divided by E0 = 1 V m–1, in logarithmic scale), on the right, indicates the change from TE (Ey) character to TM (Ez) character with varying momentum, k = ko(sinθcosϕ, sinθsinϕ), at fixed ϕ.