Fig. 2.

Reflectance and bandstructure of a woodpile photonic crystal with a_xy = 350 nm, a_z = 614 nm. a Top view (top) and side view (bottom) reflection-mode optical micrographs of the woodpile photonic crystal. b Reflectance of the woodpile photonic crystal measured with top-down illumination (top) and side illumination (bottom). c First Brillouin zone and photonic bandstructure of the woodpile photonic crystal in the Γ–K and Γ–X directions. Stars indicate slow light modes and dots indicate stopbands. d, e Reflectance spectra and reflection-mode micrographs of woodpiles under top-down illumination conditions for a_xy = 300–350 nm (d) and a_xy = 350–672 nm (e), respectively. f Plot of reflectance-peak positions as a function of the lattice constant